[Federal Register Volume 82, Number 137 (Wednesday, July 19, 2017)]
[Notices]
[Pages 33106-33122]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-15182]



[[Page 33106]]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OAR-2014-0609; FRL-9965-08-OAR]


Criteria for the Certification and Recertification of the Waste 
Isolation Pilot Plant's Compliance With the Disposal Regulations; 
Recertification Decision

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice; recertification decision.

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SUMMARY: With this notice, the Environmental Protection Agency (EPA or 
the Agency) recertifies that the U.S. Department of Energy's (DOE) 
Waste Isolation Pilot Plant (WIPP) continues to comply with the 
``Environmental Standards for the Management and Disposal of Spent 
Nuclear Fuel, High-Level and Transuranic (TRU) Radioactive Waste.''
    This action represents the Agency's third periodic evaluation of 
the WIPP's continued compliance with the disposal regulations and WIPP 
Compliance Criteria. The WIPP Compliance Criteria implement and 
interpret the disposal regulations specifically for the WIPP. As 
directed by Congress in the WIPP Land Withdrawal Act (WIPP LWA), this 
``recertification'' process is required every five years following the 
WIPP's initial receipt of TRU waste on March 26, 1999 (e.g., March 
2004, March 2009), until the end of the decommissioning phase. For each 
recertification--including the one being announced with this action--
the DOE must submit documentation of the site's continuing compliance 
with the disposal regulations to the EPA for review.
    This recertification decision is based on a thorough review of 
information submitted by the DOE, independent technical analyses, and 
public comments. The Agency has determined that the DOE continues to 
meet all applicable requirements of the WIPP Compliance Criteria, and 
with this action, recertifies the WIPP facility. This recertification 
decision does not otherwise amend or affect the EPA's radioactive waste 
disposal regulations or the WIPP Compliance Criteria. In addition, 
recertification is not subject to rulemaking or judicial review, nor is 
it linked to the resumption of disposal activities at the WIPP 
facility. The EPA has also identified areas in which the DOE's 
technical analyses and justifications could be improved for the next 
recertification application.

FOR FURTHER INFORMATION CONTACT: Ray Lee, Radiation Protection 
Division, Mail Code 6608T, U.S. Environmental Protection Agency, 1200 
Pennsylvania Avenue Washington, DC 20460; telephone number: (202) 343-
9463; fax number: (202) 343-2305; email address: [email protected]. 
Copies of the Compliance Application Review Documents (CARDs) 
supporting this action and all other recertification-related 
documentation can be found in the Agency's electronic docket found at 
www.regulations.gov (Docket ID No. EPA-HQ-OAR-2014-0609).

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. General Information
II. What is the WIPP?
    A. Background
    B. Impacts of the February 2014 Incidents on the Repository
III. Compliance Certification History
    A. 1998 Certification Decision
    B. 2006 Recertification Decision
    C. 2010 Recertification Decision
IV. With which regulations must the WIPP comply?
    A. Compliance with Radioactive Waste Disposal Regulations & the 
WIPP Compliance Criteria
    B. Compliance with Other Environmental Laws and Regulations
V. Continuing Compliance with the WIPP Compliance Criteria
    A. Annual Change Reports
    B. Monitoring the Conditions of Compliance
    1. Panel Closure Rulemaking
    2. Quality Assurance
    3. Waste Characterization
    4. Passive Institutional Controls
    C. Inspections
V. What is the EPA's 2017 Recertification Decision?
    A. Performance Assessment and the EPA's Standards
    B. Summary of the EPA's Review
    C. What information did the Agency examine to make the final 
decision?
    D. Content of the Compliance Recertification Application 
(Sec. Sec.  194.14 and 194.15)
    1. Changes to the Disposal System Identified by the DOE
    a. Update to the Drilling Rate and Borehole Plugging Patterns
    b. Replacement of Option D Panel Closure System With Run-of-Mine 
Salt Panel Closure Design
    c. Modeling of Open Areas in the Repository
    d. The DOE's Revised Estimate of the Probability of Encountering 
Pressurized Brine
    e. Revised Corrosion Rate of Steel
    f. Revised Effective Shear Strength of the WIPP Waste
    g. Revised Repository Water Balance
    h. Variable Brine Volume
    i. Revised Colloid Parameters
    j. New Actinide Solubility Code (EQ3/6)
    2. Other Key Issues Identified by the EPA During Review
    a. Actinide Solubilities
    b. Solubility Uncertainty Distribution
    c. Plutonium Oxidation States
    E. Performance Assessment: Modeling and Containment Requirements 
(Sec. Sec.  194.14, 194.15, 194.23, 194.31 through 194.34)
    1. Overview
    2. Sensitivity Studies
    a. The SEN1 Study
    b. The SEN2 Study
    c. The SEN3 Study
    d. The SEN4 Study
    i. Overview
    ii. Cumulative Effects of the Changes Evaluated by Release 
Pathway
    aa. Direct Brine Releases
    bb. Spallings Releases
    cc. Cuttings and Cavings Releases
    dd. Releases From the Culebra
    ee. Insights from the SEN4 Study
    3. How the Four Sensitivity Studies Affect the WIPP Compliance
    F. Additional Requirements
    1. Waste Characterization (Waste Inventory (Sec.  194.24)
    2. Peer Review (Sec.  194.27)
    G. Individual and Groundwater Protection Requirements 
(Sec. Sec.  194.51 Through 194.55)
VII. How has the public been involved in the EPA's WIPP 
Recertification activities?
    A. Public Information
    B. Stakeholder Meetings
    C. Public Comments on Recertification
VIII. Where can I get more information about the EPA's WIPP-related 
activities?
    A. Supporting Documents for Recertification
    B. The WIPP Web site & WIPP-NEWS Email Listserv
    C. Dockets
IX. What is the EPA's role in future WIPP activities?

Abbreviations

CARD Compliance Application Review Document
CFR Code of Federal Regulations
DOE U.S. Department of Energy
EPA U.S. Environmental Protection Agency
FR Federal Register
NMED New Mexico Environment Department
OAR Office of Air and Radiation
Pa Pascal
PBRINE Parameter: Probability Distribution of Encountering Brine
RCRA Resource Conservation and Recovery Act
SEN Sensitivity Study
TRU Transuranic
TSD Technical Support Document
WIPP Waste Isolation Pilot Plant
WIPP LWA WIPP Land Withdrawal Act

I. General Information

A. How can I get copies of this document and other related information?

    1. Docket. The EPA has established a docket for this action under 
Docket ID No. EPA-HQ-OAR-2014-0609. Publicly available docket materials 
are available either electronically at http://www.regulations.gov or in 
hard copy at the Air and Radiation Docket in the EPA

[[Page 33107]]

Docket Center, (EPA/DC) EPA West, Room B102, 1301 Constitution Ave. 
NW., Washington, DC. The EPA Docket Center Public Reading Room is open 
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 
holidays. The telephone number for the Public Reading Room is (202) 
566-1744, and the telephone number for the Air and Radiation Docket is 
(202) 566-1742. As provided in the EPA's regulations at 40 CFR part 2, 
and in accordance with normal EPA docket procedures, if copies of any 
docket materials are requested, a reasonable fee may be charged for 
photocopying.
    2. Electronic Access. You may access this Federal Register document 
electronically through the U.S. Government Publishing Office Web site 
at https://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR.

II. What is the WIPP?

A. Background

    The Waste Isolation Pilot Plant (WIPP) is a disposal system for 
defense-related transuranic (TRU) radioactive waste. The WIPP Land 
Withdrawal Act (WIPP LWA) of 1992 defines TRU waste as materials 
containing alpha-emitting radioisotopes, with half-lives greater than 
twenty years, in concentrations greater than 100 nanocuries per gram 
(nCi/g), except for (A) high-level radioactive waste; (B) waste that 
the Secretary has determined, with the concurrence of the 
Administrator, does not need the degree of isolation required by the 
disposal regulations; or (C) waste that the Nuclear Regulatory 
Commission has approved for disposal on a case-by-case basis in 
accordance with part 61 of title 10, Code of Federal Regulations (CFR). 
Developed by the U.S. Department of Energy (DOE), the WIPP is located 
near Carlsbad in southeastern New Mexico. At the WIPP, the DOE disposes 
of radioactive waste 655 meters (2,150 feet) underground in an ancient 
salt layer which will eventually creep and encapsulate the waste. The 
WIPP has a total capacity to dispose of 6.2 million cubic feet of 
waste.
    Congress initially authorized the development and construction of 
the WIPP in 1980 ``for the express purpose of providing a research and 
development facility to demonstrate the safe disposal of radioactive 
wastes resulting from the defense activities and programs of the United 
States.'' \1\ To further facilitate the development and operation of 
the WIPP, Congress passed the WIPP LWA in 1992 and amended it in 1996. 
The WIPP LWA only allows TRU radioactive waste generated by defense 
activities associated with nuclear weapons to be emplaced in the WIPP 
and explicitly prohibits high-level waste or spent nuclear fuel from 
being disposed of at the WIPP.
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    \1\ Department of Energy National Security and Military 
Applications of Nuclear Energy Authorization Act of 1980, Pub. L. 
96-164, section 213.
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    Most TRU waste proposed for disposal at the WIPP consists of items 
that have become contaminated as a result of activities associated with 
the production of nuclear weapons or with the clean-up of weapons 
production facilities, e.g., rags, equipment, tools, protective gear 
and organic or inorganic sludges. Some TRU waste contains hazardous 
chemicals used during weapons production, research and development and 
cleaning/maintenance/deactivation activities. Some of the waste 
proposed for disposal at the WIPP is known as legacy waste and has been 
stored for decades at various federal facilities across the United 
States, including major generator sites such as the Idaho National 
Laboratory, Los Alamos National Laboratory and Oak Ridge National 
Laboratory, and smaller generators such as Argonne National Laboratory 
and Lawrence Livermore National Laboratory. These facilities continue 
to generate small quantities of TRU waste. All TRU waste which the DOE 
plans to ship to the WIPP is subjected to the EPA's WIPP waste 
characterization requirements at 40 CFR 194.24.
    The WIPP LWA provides the EPA the authority to oversee and regulate 
the WIPP. The WIPP LWA requires the EPA to conduct three main tasks, to 
be completed sequentially, to reach an initial compliance certification 
decision. First, the WIPP LWA requires the EPA to finalize general 
regulations for the disposal of highly-radioactive waste.\2\ The EPA 
published these disposal regulations, located at subparts B and C of 40 
CFR part 191, in the Federal Register in 1985 and 1993.\3\
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    \2\ WIPP LWA, section 8(b).
    \3\ 50 FR 38066-38089 (September 19, 1985) and 58 FR 66398-66416 
(December 20, 1993).
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    Second, the WIPP LWA requires the EPA to develop criteria, via 
rulemaking, to interpret and implement the general radioactive waste 
disposal regulations specifically as they apply to the WIPP. In 1996, 
the Agency issued the WIPP Compliance Criteria (40 CFR part 194).\4\
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    \4\ 61 FR 5224-5245 (February 9, 1996).
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    Third, the WIPP LWA requires the EPA to review the information 
submitted by the DOE every five years to demonstrate continued 
compliance with the disposal regulations and determine whether or not 
the WIPP continues to be in compliance.\5\ The Agency issued the 
initial certification decision on May 18, 1998 (63 FR 27354-27406).
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    \5\ WIPP LWA, section 8(d).
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B. Impacts of February 2014 Incidents on the Repository

    Since the EPA's initial certification, operation of the WIPP 
proceeded without substantial interruption until 2014. However, two 
events took place at the WIPP in February 2014 that led the DOE to 
suspend emplacement of additional waste in the facility for nearly 
three years. On February 5, a salt haul truck caught fire. Workers were 
evacuated, and the underground portion of the WIPP was shut down. On 
February 14, a second event occurred when a continuous air monitor 
alarmed during the night shift, signaling a detection of radiation. The 
continuous air monitor was measuring exhaust from waste panel 7, where 
waste emplacement had recently begun. Radiological contamination of the 
underground caused an indefinite suspension of waste handling 
activities.
    After implementing numerous corrective actions, the DOE resumed 
limited waste emplacement on January 4, 2017, and also resumed limited 
shipments from waste generator sites. Resumption of waste emplacement 
at the WIPP is unrelated to the EPA's recertification decision, which 
is primarily concerned with compliance with the EPA's long-term 
disposal requirements. However, the DOE has acknowledged that recovery 
from the radiological release will result in design changes to the 
repository, which will need to be considered from that longer-term 
perspective. These changes include installation of a new ventilation 
shaft and modification of the waste panel layout to accommodate the 
premature closure of planned waste emplacement capacity in panel 9. The 
DOE is still reviewing options and has not provided any specific plans 
to the EPA. The EPA will review these changes as more information 
becomes available and they are incorporated into future recertification 
applications. The EPA recognizes that the current recertification 
decision is based on a repository design that is likely to change, but 
the current application contains the information necessary to reach a 
decision without knowing the details of the future changes. It is not 
unprecedented for the EPA to conduct a recertification review with the 
knowledge that the DOE will submit a request to change an aspect of the 
disposal system design.

[[Page 33108]]

    The EPA expects that any issues associated with repository design 
changes will be appropriately addressed in responding to change 
requests from the DOE and in subsequent recertification applications. 
However, because these design changes are likely to be substantial, the 
EPA believes it is necessary for the DOE to ensure that future 
compliance recertification applications are as robust and technically 
defensible as possible. To that end, the EPA discusses in Section VI.D 
specific aspects of future compliance recertification applications that 
the Agency believes would benefit from independent technical review, or 
otherwise from thorough consideration of more recent scientific 
information and understanding of chemical processes anticipated to take 
place within the repository. The EPA strongly believes that 
incorporating such reviews and information into future applications 
will increase public confidence in the DOE's compliance demonstrations 
and facilitate the Agency's review.

III. Compliance Certification History

A. 1998 Certification Decision

    The WIPP LWA, as amended, required the EPA to evaluate whether the 
WIPP complied with the EPA's standards for the disposal of radioactive 
waste. On May 18, 1998 (63 FR 27354-27406), the EPA determined that the 
WIPP met the standards for radioactive waste disposal. This decision 
allowed the DOE to begin placing radioactive waste in the WIPP, 
provided that all other applicable health and safety standards, and 
other legal requirements, were met. The WIPP received the first 
shipment of TRU waste on March 26, 1999. The complete record and basis 
for the EPA's 1998 certification decision can be found in Air Docket A-
93-02.
    Although the EPA determined that the DOE met all of the applicable 
requirements of the WIPP Compliance Criteria in the original 
certification decision, the EPA also found that it was necessary for 
the DOE to take additional steps to ensure that the measures actually 
implemented at the WIPP (and thus the circumstances expected to exist 
there) were consistent with the DOE's compliance certification 
application and with the basis for the EPA's compliance certification. 
As a result, the EPA included four explicit conditions in the WIPP 
certification of compliance (see 40 CFR part 194, Appendix A; WIPP 
Recertification Background Document in Docket No. EPA-HQ-OAR-2014-
0609). These conditions are discussed in Section V.C of this document.

B. 2006 Recertification Decision

    The first recertification process, which occurred in 2004-2006, 
included an EPA review of all changes made at the WIPP facility since 
the original 1998 certification decision. The Agency received the DOE's 
first compliance recertification application on March 26, 2004. The EPA 
issued the completeness determination \6\ for the 2004 Compliance 
Recertification Application by letter to the DOE on September 29, 2005 
(see 70 FR 61107-61111, October 20, 2005). On March 29, 2006, the EPA 
officially recertified the WIPP facility for the first time (71 FR 
18010-18021, April 10, 2006).
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    \6\ A ``completeness determination'' is an administrative step 
by the Agency to notify the DOE and the public that the Agency has 
enough information to conduct a final technical review of the DOE's 
application. It does not reflect any conclusion regarding the WIPP's 
continued compliance with the radioactive waste disposal regulations 
at 40 CFR part 191 and the compliance criteria at 40 CFR part 194. 
The completeness determination represents the start of the six-month 
period specified in the WIPP LWA for issuance of the recertification 
decision.
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C. 2010 Recertification Decision

    Following receipt of the DOE's second compliance recertification 
application on March 24, 2009, the EPA requested additional information 
from the DOE and the DOE responded with the requested supplemental 
information. All pertinent 2009 Compliance Recertification Application 
correspondence was placed in the docket (Docket ID No. OAR-2009-0330 on 
www.regulations.gov) and linked to on the WIPP Web site (https://www.epa.gov/radiation/certification-and-recertification-wipp#tab2). On 
June 29, 2010, the EPA sent a letter to the DOE announcing that the 
DOE's recertification application was complete (75 FR 41421-41424, July 
16, 2010). The EPA's second recertification of the WIPP compliance was 
published on November 18, 2010 (75 FR 70584).

IV. With which regulations must the WIPP comply?

A. Compliance With Radioactive Waste Disposal Regulations & the WIPP 
Compliance Criteria

    The WIPP must comply with the EPA's radioactive waste disposal 
regulations, located at subparts B and C of 40 CFR part 191. These 
regulations limit the amount of radioactive material which may escape 
from a disposal facility, and protect individuals and ground water 
resources from dangerous levels of radioactive contamination. In 
addition, the compliance recertification application and other 
information submitted by the DOE must meet the requirements of the WIPP 
Compliance Criteria at 40 CFR part 194. The WIPP Compliance Criteria 
implement and interpret the general disposal regulations specifically 
for the WIPP, and clarify the basis on which the EPA makes the 
certification decision.

B. Compliance With Other Environmental Laws and Regulations

    In addition to the EPA's radioactive waste disposal regulations, 
the WIPP must also comply with a number of other federal laws and 
regulations pertaining to public health and safety or the environment, 
including, for example, the Solid Waste Disposal Act (also known as the 
Resource Conservation and Recovery Act (RCRA)) (42 U.S.C. 6901 et seq.) 
and the EPA's environmental standards for the management and storage of 
radioactive waste (subpart A of 40 CFR part 191). Various regulatory 
agencies are responsible for overseeing the enforcement of these 
federal laws and regulations. For example, enforcement of some parts of 
the hazardous waste management regulations has been delegated to the 
State of New Mexico. The State is authorized by the EPA to carry out 
the State's RCRA programs in lieu of the equivalent federal programs, 
and New Mexico's Environment Department (NMED) reviews the DOE's permit 
applications for treatment, storage, and disposal facilities for 
hazardous waste, under Subtitle C of RCRA. NMED's RCRA authority, such 
as issuing a hazardous waste operating permit for the WIPP, is not 
affected by the EPA's recertification decision. The DOE is responsible 
for biennially reporting to the EPA and the State of New Mexico on the 
WIPP's compliance with all applicable federal laws pertaining to public 
health and safety (WIPP LWA Sec.  9).\7\ This action does not address 
the WIPP's compliance with environmental or public health and safety 
laws and regulations other than the EPA's radioactive waste disposal 
regulations (40 CFR part 191) and the WIPP Compliance Criteria (40 CFR 
part 194).
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    \7\ Compliance with these laws and regulations is addressed in 
the site's Biennial Environmental Compliance Report (BECR).
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V. Continuing Compliance With the WIPP Compliance Criteria

    The EPA monitors and ensures continuing compliance with the EPA 
regulations through a variety of activities, including the following: 
review and evaluation of the DOE's annual change reports, monitoring of

[[Page 33109]]

the conditions of compliance, addressing planned change requests, 
inspections of the WIPP site and inspections of waste characterization 
operations. Because of the 2014 incident, the EPA also reviewed health 
and monitoring data to ensure the radiological releases remained below 
the limits of subpart A of 40 CFR part 191 and the Clean Air Act 
National Emissions Standards for Hazardous Air Pollutants at 40 CFR 
part 61, subpart H.
    The DOE must timely report any planned or unplanned changes in 
activities or conditions pertaining to the disposal system that differ 
significantly from the most recent compliance application and, at least 
annually, report any other changes in disposal system conditions or 
activities (40 CFR 194.4(b)(3), (4)). The Department must also report 
any releases of radioactive material from the disposal system (40 CFR 
194.4(b)(3)(iii)). In addition, the EPA may request additional 
information from the DOE at any time (Sec.  194.4(b)(2)). These 
requirements assist the EPA with monitoring the performance of the 
disposal system and evaluating whether the certification should be 
modified, suspended or revoked.

A. Annual Change Reports

    In addition to reporting significant changes to the WIPP disposal 
system, the DOE is required to report at least annually other changes 
to the conditions or activities concerning the WIPP disposal system (40 
CFR 194.4(b)(4)). The DOE submitted the first annual change report in 
November 1998.
    The DOE's annual change reports reflect the progress of quality 
assurance and waste characterization inspections, minor changes to the 
DOE documents, information on monitoring activities and any additional 
EPA approvals for changes in activities. All correspondence and 
approvals regarding the annual change reports can be found in hard copy 
in the Air Docket A-98-49, Categories II-B2 and II-B3.

B. Monitoring the Conditions of Compliance

    1. Panel Closure Rulemaking. Waste panel closure systems are 
required by the State of New Mexico during the WIPP's operational 
phase. Since they are a feature of the disposal system design, the EPA 
requires panel closures to be included in the long-term modeling of the 
repository. The panel closures impact long-term disposal system 
performance because they can impede brine and gas flow between waste 
panels. As originally promulgated, the WIPP Certification Condition 1 
required the DOE to implement the Option D panel closure system at the 
WIPP, using Salado mass concrete.\8\ By final action published October 
8, 2014, the EPA modified Condition 1 to remove the specific reference 
to Option D and generally require that the DOE close filled waste 
panels as specifically approved by the EPA (40 CFR part 194, Appendix 
A, as amended; 79 FR 60750-60756). With the same action, the EPA 
approved a design which primarily consists of 100 feet of run-of-mine 
salt. The DOE submitted a performance assessment \9\ to support its 
request to change the panel closure system design. The DOE asserted 
that the performance assessment demonstrated that a panel closure 
design using run-of-mine salt would be compliant with the EPA's 
disposal regulations (40 CFR part 191). The modification to the WIPP 
Certification Condition 1 also removed the requirement for the Agency 
to make future panel closure design changes by formal rulemaking.
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    \8\ ``Salado'' mass concrete refers to concrete made using 
Salado brines instead of fresh water.
    \9\ Performance assessment is an important tool used in various 
contexts or evaluations relating to the WIPP and such assessments 
are mentioned in different circumstances throughout this notice, 
especially in Section VI.E. In general, performance assessment 
means: ``an analysis that: (1) Identifies the processes and events 
that might affect the disposal system; (2) examines the effects of 
those processes and events on the performance of the disposal 
system; and (3) estimates the cumulative release of radionuclides, 
considering the associated uncertainties, caused by all significant 
processes and events'' (40 CFR 191.12). Performance assessment, for 
example, is required to show compliance with containment 
requirements (40 CFR 191.13).
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    2. Quality Assurance. Certification Condition 2 requires each TRU 
generator site to establish and execute a quality assurance program for 
waste characterization activities. Section 194.22 establishes quality 
assurance requirements for the WIPP. The DOE must adhere to a quality 
assurance program that implements the requirements of ASME NQA-1-1989 
edition, ASME NQA-2a-1990 addenda, part 2.7, to ASME NQA-2-1989 
edition, and ASME NQA-3-1989 edition (excluding Section 2.1 (b) and 
(c), and Section 17.1).The EPA determined that the 2014 Compliance 
Recertification Application provides adequate information to verify the 
establishment and implementation of each of the applicable elements of 
the ASME NQA-1-1989.The EPA has also verified the continued proper 
implementation of the Nuclear Quality Assurance Program through 
periodic audits conducted in accordance with Sec.  194.22(e).
    The EPA's determination of compliance with 40 CFR 194.22 can be 
found in Table 1 of the 2014 Compliance Recertification Application 
CARD 22. Between March 2008 and April 2012, the EPA conducted several 
quality assurance audits and found the site-specific quality assurance 
programs to be adequate. The EPA conducted quality assurance audits at 
several waste generator sites and entities supporting the WIPP 
Performance Assessment activities at Los Alamos and Sandia 
Laboratories. The EPA also audited the quality assurance program of the 
Carlsbad Field Office.
    3. Waste Characterization. Certification Condition 3 requires TRU 
waste generator sites to have waste characterization systems approved 
by the EPA. The Agency has conducted numerous audits and inspections at 
waste generator sites in order to implement Condition 3 and the 
relevant provisions of 40 CFR part 194, including Sec.  194.8. The EPA 
inspected site-specific TRU waste characterization programs implemented 
to (a) characterize physical and radiological components in individual 
waste containers and (b) demonstrate compliance with the WIPP waste 
disposal requirements at 40 CFR 194.24.
    To support the 2014 Compliance Recertification Application, the DOE 
reported the EPA's waste characterization inspections and approvals 
between January 2007 and December 2012 (see Table 1 in CARD 8). The EPA 
evaluated previously approved site-specific waste characterization 
program for continued compliance in accordance with 40 CFR 194.24, as 
well as changes to the systems of controls approved as part of the 
baseline (initial) approvals, and concluded them to be technically 
adequate. The TRU waste sites approved by the EPA to ship contact-
handled TRU waste to the WIPP facility in accordance with the 
requirements of Sec.  194.8 since the 2009 Compliance Recertification 
Application are as follows: Advanced Mixed Waste Treatment Project, 
Hanford's Richland Laboratory, Idaho National Laboratory, Los Alamos 
National Laboratory, Oak Ridge National Laboratory and Savannah River 
Site. Since the 2009 Compliance Recertification Application, the TRU 
waste sites approved by the EPA to ship remote-handled TRU waste to the 
WIPP facility in accordance with the requirements of Sec.  194.8 are 
Argonne National Laboratory, Bettis Atomic Power Laboratory, General 
Electric Vallecitos Nuclear Center, Idaho National Laboratory, Oak 
Ridge National Laboratory and Savannah River Site. Since the 2009 
Compliance

[[Page 33110]]

Recertification Application, no waste characterization occurred at 
Bettis Atomic Power Laboratory, General Electric Vallecitos Nuclear 
Center, Hanford's Richland Laboratory and Oak Ridge National 
Laboratory.
    During the period covered by the 2014 Compliance Recertification 
Application, all site-specific waste characterization systems of 
controls at active TRU waste generator sites had necessary baseline 
approvals. Over the years, when warranted, the EPA approved 
modification to waste characterization program components. Notices 
announcing the EPA inspections or audits are routinely published in the 
Federal Register and also announced on the Agency's WIPP Web site 
(https://www.epa.gov/radiation/epas-role-waste-isolation-pilot-plant-wipp) and WIPP-NEWS email listserv.\10\
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    \10\ For more information on the WIPP-NEWS email listserv, see 
Section VIII.B below.
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    Records of the EPA's quality assurance correspondences and waste 
characterization approvals can be found in Air Docket A-98-49, 
Categories II-A1 and II-A4, respectively, as well as online in Docket 
ID No. EPA-HQ-OAR-2001-0012 on www.regulations.gov.
    4. Passive Institutional Controls. Certification Condition 4 
requires the DOE to submit a schedule and plan for implementing passive 
institutional controls, including markers and other measures indicating 
the presence of the repository. The standards under the WIPP 
Certification Condition 4 do not require the submission of any reports 
until the final compliance recertification application prior to closure 
of the WIPP. The EPA has not received any submissions from the DOE 
during the period addressed by the 2014 Compliance Recertification 
Application and has not taken any actions relating to Condition 4. The 
EPA anticipates that it will evaluate the DOE's compliance with 
Condition 4 of the certification when the DOE submits a revised 
schedule and additional documentation regarding the implementation of 
passive institutional controls. Once received, the information will be 
placed in the EPA's public dockets, and the Agency will evaluate the 
adequacy of the documentation. After receiving Condition 4 submissions 
from the DOE, and during the operational period when waste is being 
emplaced in the WIPP (and before the site has been sealed and 
decommissioned), the EPA will verify that specific actions identified 
by the DOE in the compliance certification application, and 
supplementary information (and in any additional documentation 
submitted in accordance with Condition 4) are being taken to test and 
implement passive institutional controls.

C. Inspections

    The WIPP Compliance Criteria provide the EPA the authority to 
conduct inspections of activities at the WIPP and at off-site 
facilities which provide information relevant to compliance 
applications (40 CFR 194.21). The Agency has conducted periodic 
inspections to verify the adequacy of information relevant to 
certification applications. The EPA has conducted annual inspections at 
the WIPP site to review and ensure that the monitoring program meets 
the requirements of Sec.  194.42. The EPA has also inspected the 
emplacement and tracking of waste in the repository. The Agency's 
inspection reports can be found in Air Docket A-98-49, Categories II-A1 
and II-A4, as well as online at www.regulations.gov, Docket ID No. EPA-
HQ-OAR-2001-0012.

VI. What is the EPA's 2017 Recertification Decision?

    The EPA determines, in accordance with WIPP LWA Sec.  8(f)(2), that 
the WIPP facility is in compliance with the final disposal regulations, 
subparts B and C of 40 CFR part 191. Compliance recertification ensures 
that accurate and up-to-date information is considered in the 
determination that WIPP remains in compliance with these radioactive 
waste disposal regulations. The EPA makes this recertification and 
determination of continued compliance following the ``Criteria for the 
Certification and Recertification of the WIPP's Compliance with the 40 
CFR part 191 Disposal Regulations'' (WIPP Compliance Criteria, 40 CFR 
part 194), including the WIPP certification conditions (40 CFR part 
194, Appendix A).

A. Performance Assessment and the EPA's Standards

    The disposal regulations at 40 CFR part 191 include requirements 
for containment of radionuclides. The containment requirements at 40 
CFR 191.13 specify that releases of radionuclides to the accessible 
environment \11\ must be unlikely to exceed specific limits for 10,000 
years after disposal. The DOE assesses the likelihood that the WIPP 
will meet these release limits through a process known as performance 
assessment.
---------------------------------------------------------------------------

    \11\ The accessible environment is defined in 40 CFR 191.12 as 
(1) The atmosphere: (2) land surfaces; (3) surface waters; (4) 
oceans; and (5) all of the lithosphere that is beyond the controlled 
area.
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    The disposal regulations provide that there must be a reasonable 
expectation that cumulative releases of radionuclides from the WIPP and 
into the environment over 10,000 years will not exceed specified 
quantities of these radionuclides (40 CFR 191.13 and Appendix A). A 
reasonable expectation standard is used because of the long time period 
involved and the nature of the events and processes at radioactive 
waste disposal facilities leads to uncertainties about future 
performance. The DOE's probabilistic performance assessments assess the 
likelihood of environmental radionuclide release so that future 
uncertainties are accounted for in the calculations through the use of 
alternative scenarios and variations in values of uncertain parameters 
via probability distributions.
    The containment requirements in 40 CFR 191.13 are expressed in 
terms of ``normalized releases.'' At the WIPP, the specific release 
limits are based on the estimated amount of waste in the repository at 
the time of closure, and the projected releases are ``normalized'' 
against these limits (Sec.  194.31). Normalized releases are expressed 
as ``EPA units''. The EPA units are calculated by dividing all the 
combined projected releases by the total combined radioactivity of all 
the waste in the repository.
    The DOE must demonstrate, in each 5-year compliance recertification 
application, that the total average of combined releases are below two 
compliance criteria at a higher probability of occurrence and a lower 
probability of occurrence. These compliance points are as follows:
    1. For a probability of 0.1 (a 1 in 10 chance) in 10,000 years, 
releases to the accessible environment will not exceed 1 EPA unit, and
    2. For a probability of 0.001 (a 1 in 1,000 chance) in 10,000 
years, releases to the accessible environment will not exceed 10 EPA 
units.
    DOE evaluates four release mechanisms in the WIPP performance 
assessment modeling:
    Cuttings and cavings. This consists of material that gets brought 
to the surface when a borehole intersects waste in a WIPP waste panel. 
The cuttings are the material intersected by the borehole itself and 
the cavings material is waste that fails around the borehole, collapses 
into it and is brought to the surface.
    Spallings. This is solid material that fails and gets brought to 
the surface under high pressure conditions in the

[[Page 33111]]

repository. This only occurs when the pressure is above 8 megapascal 
\12\ (MPa).
---------------------------------------------------------------------------

    \12\ ``Pascal'' is a unit of pressure, defined as 1 kg/m-sec\2\.
---------------------------------------------------------------------------

    Direct Brine Releases. This is a release of dissolved actinides in 
brine when there is sufficient brine and high pressure in the 
repository (i.e., above 8 MPa) and brine saturations are above residual 
saturation (i.e., brine is not ``trapped'' between pore spaces) as a 
borehole intersects a waste panel. The contaminated fluid is brought to 
the surface over a period of hours to days.
    Releases to the Culebra. This occurs when contaminated brine from 
repository is introduced via a borehole to the Culebra Dolomite and 
then moves to the edge of the accessible environment (i.e., the 
boundary established by the WIPP LWA).
    The DOE estimates the potential releases from these release 
mechanisms, i.e., the cumulative releases, for comparison with the 
specified limits provided in 40 CFR part 191, Appendix A. The DOE is to 
provide in the application overall mean calculated releases and the 
upper 95th confidence limit of that mean.

B. Summary of the EPA's Review

    After reviewing the DOE's documentation and additional studies that 
the DOE conducted at EPA's request, the aspects of the performance 
assessment of most interest to EPA are those that affect the direct 
brine release mechanism, by which actinides \13\ dissolved in brine are 
transported to the surface during a drilling intrusion. Direct brine 
release is the overall dominant release mechanism at the low 
probability compliance point, and is influenced primarily by the 
availability of liquid (i.e., brine) in the repository, the 
availability of radionuclides to dissolve in that liquid (i.e., 
inventory and solubility) and the pressure in the repository (providing 
a motivating force for dissolved radionuclides to move out of the 
repository).
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    \13\ Actinide means any of the series of fifteen metallic 
elements from actinium (atomic number 89) to lawrencium (atomic 
number 103) in the periodic table. They are all radioactive, the 
heavier members being extremely unstable and not of natural 
occurrence.
---------------------------------------------------------------------------

    The key issues involving these aspects of the repository are: (1) 
The actinide solubility, which is addressed through changes to the 
geochemical database, colloid contribution updates and the 
determination of the actinide solubility uncertainty; (2) the 
probability of hitting a brine pocket under the repository; (3) the 
steel corrosion rate and steel's interactions with hydrogen sulfide and 
magnesium oxide (affecting the gas pressure); and (4) the overall 
modeling of direct brine releases that involve the interactions of 
items 1-3 plus the conditions of the repository (e.g., panel and drift 
permeability and porosity) that can influence the pressure 
characteristics of the waste areas. These issues are discussed in more 
detail in Section VI.D, along with other issues that are noteworthy but 
have more limited impact on performance assessment results.
    The following information describes the EPA's compliance evaluation 
related to the disposal regulations and Compliance Criteria.

C. What information did the Agency use to make the decision?

    In general, compliance applications must include information 
relevant to demonstrating compliance with each of the individual 
sections of 40 CFR part 194 to determine if the WIPP will comply with 
the Agency's radioactive waste disposal regulations at 40 CFR part 191, 
subparts B and C. The EPA begins the compliance recertification 
evaluation once the EPA receives a complete compliance recertification 
application (40 CFR 194.11).
    To make this decision, the EPA evaluated basic information about 
the WIPP site and disposal system design, as well as information which 
addressed the various compliance criteria. As required by 40 CFR 
194.15(a), the DOE's 2014 Compliance Recertification Application 
updated the previous submission in 2009.
    On March 26, 2014, the DOE submitted the compliance recertification 
application. The EPA began to identify areas of the application where 
additional information was needed. On October 10, 2014, the EPA gave 
public notice of the compliance recertification application and opened 
the official public comment period (79 FR 61268). On January 13, 2017, 
the EPA sent a letter to the DOE stating that the DOE's recertification 
application was complete. On March 10, 2017, the EPA issued a Federal 
Register notice announcing the completeness determination and stating 
that the public comment period would close one month later, on April 
10, 2017 (82 FR 13282). The compliance recertification application 
completeness-related correspondence can be found in Docket ID No. EPA-
HQ-OAR-2014-0609 on www.regulations.gov.
    The EPA relied on materials prepared by the Agency or submitted by 
the DOE in response to the EPA requests. For example, the EPA requested 
that the DOE conduct specific, additional modeling calculations for the 
performance assessment, known as sensitivity studies. The purpose of 
these studies was to evaluate the impact on performance assessment 
results of changing specific parameter values. The studies aided the 
EPA in determining how significant the differences in some parameter 
values were to a demonstration of compliance. The four sensitivity 
studies and the EPA's evaluation of them are discussed in more detail 
in Section VI.E.
    To determine whether the WIPP facility continues to be in 
compliance with the final disposal regulations, the EPA engaged in a 
technical review of the compliance recertification application against 
the WIPP Compliance Criteria. The Agency focused the review on areas of 
change identified by the DOE since the 2010 recertification decision.
    The Agency produced many documents during the technical review and 
evaluation of the compliance recertification application. The EPA's 
Compliance Application Review Documents (CARDs) correspond in number to 
the sections of 40 CFR part 194 to which the documents primarily 
relate. Each CARD enumerates all changes made by the DOE relating to a 
particular section of the rule or certification criterion, and 
describes the EPA's process and conclusions. The EPA also prepared 
technical support documents (TSDs) to address specific topics in 
greater detail. Both the CARDs and the TSDs for this recertification 
decision can be found in Docket ID No. EPA-HQ-OAR-2014-0609 on 
www.regulations.gov. Together, the CARDs and TSDs thoroughly document 
the EPA's review of the DOE's compliance recertification application 
and the technical rationale for the Agency's decisions.
    In summary, the EPA's recertification decision is based on the 
entire record available to the Agency, which is located in the public 
docket dedicated to this recertification (Docket ID No. EPA-HQ-OAR-
2014-0609 on www.regulations.gov). The record consists of the 2014 
Compliance Recertification Application, supplementary information 
submitted by the DOE in response to the EPA requests for additional 
information, technical reports generated by the EPA, the EPA audit and 
inspection reports, and comments submitted on the DOE's application and 
the EPA's completeness review during the public comment period. All 
pertinent 2014 Compliance Recertification Application correspondence 
was placed in the docket and linked to via the EPA's WIPP Web site 
(https://www.epa.gov/

[[Page 33112]]

radiation/certification-and-recertification-wipp).

D. Content of the Compliance Recertification Application (Sec. Sec.  
194.14 and 194.15)

    The DOE's WIPP compliance applications must include, at a minimum, 
basic information about the WIPP site and disposal system design, 
including information about the following topics: the geology, 
hydrology, hydrogeology and geochemistry of the WIPP disposal system 
and the WIPP vicinity; the WIPP materials of construction; standards 
applied to design and construction; background radiation in air, soil 
and water; and past and current climatological and meteorological 
conditions (40 CFR 194.14). Section 194.15 states that the DOE's 
recertification applications shall update this information to provide 
sufficient information for the EPA to determine whether or not the WIPP 
facility continues to be in compliance with the disposal regulations.
    1. Changes to the Disposal System Identified by the DOE. In Section 
15 of the 2014 Compliance Recertification Application, the DOE 
identified changes to the disposal system between the 2009 Compliance 
Recertification Application and 2014 Compliance Recertification 
Application and changes to technical information relevant to Sec. Sec.  
194.14 and 194.15. Noteworthy changes identified by the DOE in the 2014 
Compliance Recertification Application include the following: an update 
to the parameters defining drilling rate and plugging pattern, 
revisions to the calculations of the probability of encountering a 
pressurized brine reservoir, replacing the Option D panel closure 
design with run-of-mine salt, modeling open areas in the repository, 
revision of the steel corrosion rate, revision of the effective shear 
strength of waste, revisions of the repository water balance including 
variable brine volumes for radionuclides to dissolve and revisions of 
the colloid parameters.
    Before determining that the compliance recertification application 
was complete, the EPA raised numerous technical questions with the DOE, 
as described below. For each topic, a brief summary is provided of how 
the DOE addressed the issue in the 2014 application, followed by the 
EPA's perspective on the change, including any follow-up analyses 
requested. The DOE also updated the waste inventory. This topic is 
discussed in Section VI.F.1.
    Since the initial Compliance Certification performance assessment, 
the DOE's calculated releases in performance assessments have increased 
with every performance assessment until the 2014 Compliance 
Recertification Application performance assessment. The changes the DOE 
made to the performance assessment in the current application reduce 
the calculated releases. For example, the calculated release of 
radionuclides at the low probability compliance point (a likelihood of 
less than a one in 1,000 chance), was assessed by the DOE in the 2009 
Compliance Recertification Application as 0.72 EPA Units, but in the 
2014 Compliance Recertification Application, the similar calculated 
release initially was assessed as 0.261 EPA Units.
    Changes that reduce the calculated releases involve the shear 
strength of the waste, revised steel corrosion rate, incorporating 
water balance as part of the chemical model implementation as it 
relates to steel corrosion and interactions with the magnesium oxide 
engineered barrier, correcting errors associated with brine volume mass 
balance and calculation of actinide solubility and the change to how 
the DOE calculates the probability of hitting a brine pocket under the 
repository. In general, the result of the DOE's methodology changes is 
to reduce calculated releases by about a factor of two between the 2009 
and 2014 Compliance Recertification Applications at both the 0.1 and 
0.001 probability compliance points.
    The EPA has identified issues with some of these changes, but even 
with changes the EPA asked the DOE to investigate, projected releases 
stay well under the numerical release limits. For example, at the 0.001 
probability compliance point where the EPA normalized release limit is 
10 EPA units, the changes the EPA requested resulted in increased 
releases from 0.261 EPA units in the DOE's 2014 performance assessment 
to 0.299 EPA units in sensitivity study SEN3 and 0.541 EPA units in 
sensitivity study SEN4. The sensitivity studies are discussed in depth 
in Section VI.E.
    a. Update to the Drilling Rate and Borehole Plugging Patterns. As 
with previous recertification applications, the DOE updated the 
Delaware basin drilling rates based on the methodology previously 
approved. For the 2014 Compliance Recertification Application, the 
drilling rate increased to 0.00673 boreholes per km\2\ per year 
(equivalent to 67.3 boreholes/km\2\ over the 10,000-year regulatory 
period) compared to that used in the 2009 performance assessment 
baseline calculation, which was .00598 boreholes per km\2\ per year (or 
59.8 boreholes/km\2\ over 10,000 years). The Agency accepted the DOE's 
drilling rate increase.
    The DOE also updated information on the type of plugs installed in 
exploratory, disposal and resource extraction boreholes. There are 
three types of borehole plugs used in the Delaware basin. There are 
boreholes that are continuously plugged through the entire salt 
section, and the DOE reports a slight increase in the use of this 
design. There are boreholes plugged with a two-plug configuration (at 
the Salado/Rustler and the Bell Canyon/Castile Formation interfaces). 
This two-plug design also slightly increased from that used in the 2009 
application. There is also a three-plug configuration (i.e., borehole 
plugs at the Rustler/Salado, Salado/Castile and Castile/Bell Canyon 
interfaces); the DOE reports a slight decrease in this configuration. 
The Agency accepted the DOE's update to the change in the plugging 
patterns.
    b. Replacement of Option D Panel Closure System with the Run-of-
Mine Salt Panel Closure Design. Part of the design for the WIPP 
includes the use of a closure system to separate the waste rooms in a 
panel from active areas in the mine, which can affect long-term brine 
and gas flows within the repository. As part of the design, the panel 
closure system that is installed needs to be represented in the 
modeling of long-term performance.
    On September 28, 2011, the DOE provided a change request to the EPA 
(Docket EPA-HQ-OAR-2013-0684) to modify the panel closure system design 
specified in Appendix A of 40 CFR part 194 from that of a concrete 
monolith plug, noted as Option D, to a 100-foot long barrier consisting 
of run-of-mine salt (EPA 2013; 2014). The panel closure system 
performance assessment release calculations were well within the 
numerical limits established in 40 CFR 191.13. The EPA approved the 
DOE's use of the proposed run-of-mine salt closure design (79 FR 60750, 
Oct. 8, 2014) (Docket EPA-HQ-OAR-2013-0684-0004 on 
www.regulations.gov).
    The DOE incorporated the run-of-mine salt design for panel closures 
into the 2014 Compliance Recertification Application. To evaluate this 
change, the Agency reviewed a broad set of information related to the 
evolution of salt repository properties, including run-of-mine salt and 
adjacent disturbed rock zone in the WIPP repository setting (Salt 
Characteristics TSD \14\). From this

[[Page 33113]]

review, the Agency's interpretation of the data is that healing of the 
run-of-mine salt in the panel closures, the surrounding disturbed rock 
zone and open areas should occur within about the first 200 years of 
post-closure instead of the relatively asymptotic closure for the 200-
10,000 years used by the DOE. The DOE's use of the longer period of 
time assumes permeability and porosity for the salt will be low within 
200 years, but not at the very low end state properties of intact 
halite.
---------------------------------------------------------------------------

    \14\ ``Technical Support Document for Section 194.23: Technical 
Review of Salt Aggregate, Disturbed Rock Zone, and Open Drift 
Healing Characteristics'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    To identify the potential effect of the difference in the 
repository properties between what the EPA has identified may be 
applicable and what the DOE modeled, the Agency requested that the DOE 
analyze the repository performance using parameter values for the run-
of-mine salt panel closure system and adjacent disturbed rock zone that 
simulate complete healing. The DOE did this in the sensitivity study 
SEN3 discussed in Section VI.E. The calculated releases increased for 
direct brine releases and spallings releases in SEN3, but overall 
releases remained well within the numerical limits of 40 CFR 191.13 and 
the EPA concludes that there is a reasonable expectation that the 
repository remains in compliance with the numerical limits at 40 CFR 
191.13, and 40 CFR part 191, Appendix A.
    If the DOE determines, in light of the announced decision to 
abandon the area previously designated for panel 9, that worker safety 
considerations preclude installing panel closures in affected areas of 
the repository, the DOE's treatment of panel closures in performance 
assessment may be more appropriately addressed in the context of 
modeling open areas representative of no panel closures. The Agency 
will review future panel closure modeling in the context of future 
facility design changes.
    c. Modeling of Open Areas in the Repository. In the 2014 Compliance 
Recertification Application, the DOE increased the modeled volume of 
the open rooms and drifts by approximately forty percent to accommodate 
future planned experiments. These new areas are located north of the 
waste area drifts and are to be separated from the waste area by two 
sets of run-of-mine salt panel closures. For the 2014 Compliance 
Recertification Application performance assessment, the DOE modeled 
these areas as open for the entire 10,000-year regulatory period even 
though it is expected that the creep closure process will close the 
open areas within a few hundred years (Overview TSD \15\). The Agency 
evaluated the impact of the DOE's assumption to model these areas as 
open (relatively large porosity and high permeability) by requesting 
the DOE perform sensitivity study SEN2, where the non-waste rooms and 
open drifts are assumed to have creep closed during the entire 10,000-
year regulatory period.
---------------------------------------------------------------------------

    \15\ ``Overview of Changes Between PABC-2009 and CRA-2014 WIPP 
Performance Assessments'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    The results from the SEN2 studies indicate modeling creep closure 
and healing of the operations and experimental areas (i.e., non-waste 
areas) of the repository was shown to have little effect on the 
prediction of total releases from the repository although, relative to 
the 2014 Compliance Recertification Application performance assessment, 
a slight increase in spallings releases does occur if these areas are 
assumed to creep closed. This is a result of higher pressures occurring 
in panels. See Section VI.E for discussion of the SEN2 study.
    If, in the future, there are repository design changes that result 
in more non-waste drifts mined or left open in the facility, the issue 
of open areas will need to be re-evaluated in the context of those 
design changes, as releases could be expected to increase in that 
circumstance. The DOE's plan to abandon panel 9 would leave large areas 
of open space in the repository in the panel 9 drifts and possibly no 
panel closures for multiple panels. Performance assessment modeling 
should address these expected future repository conditions. The EPA 
believes that an independent technical review of issues related to salt 
behavior and modeling of open areas would be of benefit to the DOE as 
it further develops its plans.
    d. The DOE's Revised Estimate of the Probability of Encountering 
Pressurized Brine. Highly pressurized zones of brine (i.e., pressurized 
brine reservoirs) occur in the Castile Formation below the Salado 
Formation, which is the formation that hosts the WIPP. If a future 
driller encounters a Castile pressurized brine reservoir and brine 
enters the waste panels, it can dissolve radionuclides that then could 
be transported up a borehole to the surface. In the modeling of the 
repository, the probability of a future borehole intersecting a waste 
panel and a Castile brine reservoir below the repository is denoted by 
the parameter name PBRINE. Because the probability of hitting a brine 
pocket is uncertain, it is represented by a probability distribution, 
and the actual value of the PBRINE parameter for an individual model 
run is sampled from the PBRINE probability distribution.
    In the 2014 Compliance Recertification Application, the DOE changed 
the basis it used to develop the probability distribution for parameter 
PBRINE. The DOE's revision to the estimated probability of a future 
driller encountering pressurized brine relies heavily on voluntarily 
reported drilling logs \16\ combined with an updated probability 
distribution. The DOE eliminated from consideration site-specific data 
collected through geophysical detection methods, which had previously 
been incorporated into the PBRINE parameter.
---------------------------------------------------------------------------

    \16\ Kirchner, T., T. Zeitler, and R. Kirkes. 2012. Evaluating 
the Data in Order to Derive a Value for GLOBAL:PBRINE. Memorandum to 
Sean Dunagan dated December 11, 2012. ERMS 558724. Carlsbad, NM: 
Sandia National Laboratories.; EPA Completeness Comment 1-23-6; 
Docket EPA-HQ-OAR-2014-0609-0004.
---------------------------------------------------------------------------

    The EPA has several concerns regarding the DOE's update to the 
PBRINE parameter,\17\ including the DOE's elimination of the site 
geophysical data leading to estimates of the potential for brine 
encounters based only on the voluntary data reported by the driller, 
and that more recent site data supports the potential for more brine 
under the repository than the DOE or the EPA had previously considered. 
For a more in-depth discussion of these issues, see the PBRINE TSD.\18\ 
The EPA's concerns were significant enough that the EPA developed a 
modified methodology for determining the probability distribution for 
parameter PBRINE in the WIPP performance assessment calculations.
---------------------------------------------------------------------------

    \17\ See Completeness Question 1-23-6, Probability of 
Encountering a Castile Brine Pocket and subsequent clarifying 
questions, as well as the PBRINE TSD, for more detail in Docket ID 
No. EPA-HQ-OAR-2014-0609.
    \18\ ``Probability of Encountering Castile Brine Beneath the 
WIPP Waste Panels Using the TDEM Block Method.''
---------------------------------------------------------------------------

    The Agency's revision to the PBRINE parameter was incorporated into 
Sensitivity Study SEN4. The study results indicate the modified PBRINE 
probability distribution contributed to an increase in estimated direct 
brine releases and increased the total releases at the 0.001 low 
probability compliance point to roughly double those in the 2014 
Compliance Recertification Application performance assessment.\19\ 
Because the Agency is unable to accept the DOE approach used to define 
the PBRINE parameter, the EPA views the updated probability 
distribution used in

[[Page 33114]]

the SEN4 study as the baseline for PBRINE in future performance 
assessments. The EPA will evaluate alternative approaches proposed by 
the DOE. See Section VI.E for more discussion of the SEN4 study.
---------------------------------------------------------------------------

    \19\ DOE 2014 Appendix PA, Sections PA-9.3 and PA-9.5 Kirchner 
2013 and the EPA, 2017 Technical Support Document.
---------------------------------------------------------------------------

    e. Revised Corrosion Rate of Steel. The WIPP corrosion rate model 
includes anoxic corrosion (i.e., corrosion in the absence of oxygen) of 
iron in the waste containers. This corrosion is caused by hydrogen 
sulfide gas produced from the microbial degradation of cellulosic, 
plastics and rubber materials from the contaminated rubber gloves and 
KimwipesTM included in the waste.
    The EPA reviewed the 2014 Compliance Recertification Application 
model and had concerns with the way the model addressed expected 
repository carbon dioxide concentrations in the experimental derivation 
of corrosion rates. The EPA also found that the model did not 
incorporate hydrogen sulfide induced steel passivation,\20\ which could 
result in an overestimation of corrosion in the longer-term. Once steel 
is passivated, hydrogen sulfide consumption will decrease significantly 
as corrosion will be limited by the ability for the gas to diffuse 
through the iron sulfide coating the outer surface of the container.
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    \20\ Passivation refers to the creation of an outer coating 
layer on the steel canisters due to the interaction of iron and 
sulfide.
---------------------------------------------------------------------------

    In addition, other components of this model, which the DOE 
considered to be minor, may have more impact. Calculations of the 
potential lead inventories at the WIPP only include current waste 
containers without accounting for the maximum potential of future 
containers.
    To address the EPA's concerns about corrosion, part of the DOE's 
SEN4 sensitivity study involved turning off the hydrogen sulfide 
corrosion parameter to simulate steel passivation. These changes 
resulted in a slight increase in gas pressures as well as a decrease in 
the saturation of the waste area because both hydrogen gas and water 
were eliminated from the end products. Results from this study 
indicated that projected releases would remain within the limits of 40 
CFR 191.13. Therefore, the EPA accepts the corrosion approach 
incorporated in the 2014 Compliance Recertification Application. See 
Section VI.E for more discussion of the SEN4 study.
    To ensure that future performance assessments adequately address 
the mechanisms that affect gas generation in the repository, it would 
be appropriate for the DOE to update the corrosion model to better 
address steel passivation and account for radiolysis and address lead 
corrosion to be consistent with the expected inventory of the 
repository.
    f. Revised Effective Shear Strength of the WIPP Waste. The 
parameter TAUFAIL represents waste shear strength and is used in 
calculating potential releases of waste materials from the WIPP 
repository when a drilling operator drills a borehole through the 
waste. The drilling mud will apply a hydrodynamic shear stress to the 
punctured waste and cause it to erode and be transported up the 
borehole to the surface. The sheared waste transmitted to the surface 
is called ``cavings''. A higher shear strength means the material is 
less likely to break into pieces and be transported up a borehole. The 
parameter TAUFAIL has an uncertain value which is sampled from a range 
of experimental values for individual model runs. In the 2014 
Compliance Recertification Application, the DOE updated the mean and 
lower bound for the TAUFAIL parameter value distribution based on a 
suite of laboratory flume tests specifically designed to represent the 
range of values for the WIPP waste.
    In the 2009 Compliance Recertification Application the lower bound 
value was 0.05 Pa, while for the 2014 Compliance Recertification 
Application the lower bound of the distribution was increased to 2.22 
Pa (the mean value from the laboratory flume tests). The upper bound of 
the distribution, 77 Pa, remained the same. The EPA believes the DOE's 
overall approach of using experimental data to revise the TAUFAIL 
parameter is reasonable; however, the EPA had concerns with the DOE's 
lower ``bounding'' range value derived from the experiments. The Agency 
was concerned that three of the five low shear-strength tests had 
highly scattered results. The DOE attributed the scatter to pre-test 
sample damage and/or a high degree of variability in sample 
preparation, rather than testing an equivalent suite of samples. As a 
result, the mean of the low shear strength test results may not be 
truly representative of low shear strength samples.
    In the SEN4 study, the EPA requested the DOE include the lowest 
shear-strength flume test results (1.6 Pa) as the bounding value, 
rather than the average (2.22 Pa). The SEN4 results indicate modifying 
the lower range to include the lowest value as the bounding value 
insignificantly impacted releases. This is due to the fact that the 
change from 2.22 Pa to 1.6 Pa (i.e., from the mean of experimental 
values to the lowest experimental value) is much less than would be the 
change from the 0.05 Pa used in previous performance assessments to 
either the 1.6 Pa or the 2.22 Pa values. Based on these results, the 
EPA accepts the DOE's range of values used in the 2014 Compliance 
Recertification Application, though for future performance assessments 
the EPA believes it is more appropriate for the DOE to use the lower-
bound result instead of the mean. See Section VI.E for more discussion 
of the SEN4 study. See also the TAUFAIL TSD.\21\
---------------------------------------------------------------------------

    \21\ ``Technical Support Document for Section 194.23: EPA Review 
of Proposed Modification to the Waste Shear Strength Parameter 
TAUFAIL'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    g. Revised Repository Water Balance. Repository water balance is 
the culmination of multiple chemical reactions that produce or consume 
water and affect actinide concentrations in the brine. These reactions 
include microbial degradation of the cellulosic, plastic and rubber 
materials, the anoxic corrosion of iron in the steel waste canisters, 
and reactions of the magnesium oxide (MgO) used to control carbon 
dioxide (CO2) buildup in the repository. Magnesium oxide, in 
particular, reacts with brine and results in hydromagnesite 
(Mg5(CO3)4(OH)24H2
O), which consumes water in the process.
    Previous compliance recertification applications only included 
anoxic corrosion in water balance calculations. The 2014 Compliance 
Recertification Application includes an assessment of the microbial 
degradation of the cellulosic, plastic and rubber material, the anoxic 
corrosion of iron in the steel waste canisters and reactions of the 
engineered barrier. The DOE did not change the rates for microbial 
cellulosic, plastic and rubber material degradation and water 
production from the 2009 Compliance Recertification Application. As 
discussed previously, the DOE revised steel corrosion rates. The DOE 
developed magnesium reaction rates for the compliance recertification 
application based on previous studies (Chemistry TSD \22\).
---------------------------------------------------------------------------

    \22\ ``Technical Support Document for Section 194.24: Evaluation 
of the Compliance Recertification Actinide Source Term, Gas 
Generation, Backfill Efficacy, Water Balance and Culebra Dolomite 
Distribution Coefficient Values'' in Docket ID No. EPA-HQ-OAR-2014-
0609.
---------------------------------------------------------------------------

    Although changes to each of these parameters is minor, the 
reactions will have a cumulative effect. Based on previous exchanges 
with the DOE (see comment 2-C-5 in Docket ID No. EPA-HQ-OAR-2014-0609) 
as well as the SEN4 sensitivity study, the water balance updates do not 
appear to significantly affect the WIPP performance. However, the EPA

[[Page 33115]]

recommends that the DOE re-evaluate the water balance issue for future 
performance assessments to address questions associated with 
interactions involving magnesium oxide (e.g., hydration rates in the 
water balance calculations), and as previously discussed in Section 
VI.D.1.e, the associated steel corrosion model and passivation 
processes.
    h. Variable Brine Volume. Brine volume plays an important role in 
calculating actinide and organic ligand concentrations. In previous 
performance assessments, the DOE calculated concentrations of these 
species using the minimum brine volume needed for a direct brine 
release, regardless of how much brine is projected to be released. This 
failed to account for dilution and thus resulted in an overestimation 
of organic ligand concentrations as well as actinide releases. To 
correct for this in the 2014 Compliance Recertification Application, 
the DOE adjusted actinide and organic ligand concentration calculations 
to incorporate multiple brine volumes. The DOE continues to calculate 
actinides and organic ligand concentrations at the minimum brine volume 
required for a release. However, the DOE now also calculates 
concentrations by dissolving these species at volumes 2, 3, 4 and 5 
times the minimum volume to simulate larger volume releases. Thus, 
concentrations at 5 times the volume will be lower than those 
calculated at the minimum volume because more brine will be present to 
dilute these aqueous species. The EPA finds that this approach 
realistically addresses the issue of variable brine volumes involved in 
a direct brine release and accepts this model for the compliance 
recertification application.
    i. Revised Colloid Parameters. Colloids are particles larger than 
molecules that can be suspended in the WIPP brine. Because colloids 
migrate more rapidly through the subsurface than actinides dissolved in 
solution, colloids are an important contribution to actinide mobility 
during a direct brine release. Intrinsic colloids are actinide 
macromolecules that eventually increase in size. Microorganisms are 
considered large colloids capable of mobilizing actinides because of 
actinide sorption to their charged cell walls or because of actinide 
bio-uptake.
    In the original Compliance Certification Application, the colloid 
parameters were based on experimentally derived values examining 
actinide macromolecules or actinides sorbed onto biomass (e.g., 
Completeness Comment 3-C-9 in EPA-HQ-OAR-2014-0609-0010). Since then, 
the DOE has performed multiple new investigations to update the 
intrinsic and microbial colloid parameters. These investigations 
prompted the DOE to reduce the contribution of colloids in the 2014 
performance assessment.
    Because of issues with experimental data used to develop the 2014 
colloid contributions to actinide solubility, the 2014 performance 
assessment calculations using those experimental results may 
underestimate colloidal concentrations, and therefore, actinide 
solubility. However, the EPA finds that the use of an updated 
uncertainty distribution for actinide solubility in the SEN4 
sensitivity study provides adequate information to determine that an 
increase in colloid concentrations would not cause releases to exceed 
the disposal standards. The EPA recommends that additional review of 
the experimental results would benefit the DOE's treatment of colloid 
formation mechanisms in future performance assessments. The EPA's 
review of this topic is provided in the Chemistry TSD. See Section VI.E 
of this document for discussion of the SEN4 study.
    j. New Actinide Solubility Code (EQ3/6). Prior to the 2014 
Compliance Recertification Application, the DOE used the Fracture 
Matrix Transport (FMT) geochemical modeling code for actinide 
solubility calculations. The DOE has since moved actinide solubility 
calculations to the EQ3/6 code using the database DATA0.FM1, which 
contains the values needed to calculate chemical speciation of the 
ions, actinides and minerals present in the WIPP. The move to EQ3/6 is 
logical as the program is widespread and has been used in other the DOE 
projects. EQ3/6 can provide more robust calculations than FMT, 
particularly in dynamic reaction-path calculations. The EPA accepts the 
move to the EQ3/6 code. For additional discussion on this topic see the 
EQ3/6 TSD.\23\
---------------------------------------------------------------------------

    \23\ ``EQ3/6 Computer Code Evaluation'' in Docket ID No. EPA-HQ-
OAR-2014-0609.
---------------------------------------------------------------------------

    2. Other Key Issues Identified by the EPA During Review. The EPA 
identified three key topics where the Agency believes new information 
can be incorporated into future compliance recertification 
applications. These topics relate to the chemical conditions within the 
repository and are of fundamental importance in determining the 
potential for releases of radionuclides from the disposal system. These 
topics are discussed in more detail in the Chemistry TSD.
    a. Chemical Database. Actinide solubility, or the ability for 
actinide solids to dissolve in brine, is important in calculating 
releases. In performance assessment calculations, these radionuclides 
include americium, curium, neptunium, plutonium, thorium, and uranium. 
Americium(III) solubility is used to predict plutonium(III) and 
curium(III) concentrations while thorium(IV) is used to predict 
plutonium(IV), neptunium(IV) and uranium(IV).
    The EPA's review identified that the DOE's update of the chemical 
assumptions used in the actinide solubility database (DATA0.FM1) did 
not reflect all data available prior to the DOE's data cut-off date of 
December 31, 2012.The EPA raised several issues (in Docket ID No. EPA-
HQ-OAR-2014-0609-0010) about americium and thorium solubility and 
speciation and in response, the DOE modified the database to produce 
DATA0.FM2. However, the EPA identified flaws in the modified database 
that need to be corrected before it can be considered to be of 
sufficient quality for use in recertification. The EPA concluded that, 
even with identified data gaps, the original DATA0.FM1 database was of 
higher quality and provided sufficient information to support a 
determination of continued compliance. The DOE's updates of the 
chemical database for future performance assessments should more 
comprehensively incorporate recent data.
    b. Revised Radionuclide Uncertainty Distribution. The DOE also 
examined the uncertainty distribution used to model the +III and +IV 
actinide concentrations in the performance assessment by comparing 
modeled solubility calculations to experimental data from multiple 
reports and peer-reviewed studies. These studies include solubility 
measurements from americium, thorium and their analogues using a 
specific set of criteria (Chemistry TSD; 2014 Compliance 
Recertification Application, Appendix SOTERM-2014 Section 5.1.3). 
During the performance assessment solubility calculations, this 
uncertainty distribution is sampled and used in calculating dissolved 
actinides in a release.
    After reviewing the actinide solubility uncertainty distribution 
for the 2014 Compliance Recertification Application, the EPA identified 
relevant studies that were not considered in developing this 
distribution, as well as identifying studies that should have been 
excluded from consideration, based on the DOE's evaluation criteria. 
Using relevant studies would result in a revised actinide solubility 
uncertainty distribution with overall higher +III

[[Page 33116]]

actinide solubility. The DOE included a revised solubility uncertainty 
distribution based on the EPA's input in the sensitivity study SEN4. 
The higher actinide solubility used in the SEN4 study contributed to 
higher releases compared to the 2014 performance assessment, although 
releases in the SEN4 study still remain below the regulatory limits. 
See Section VI.E for more discussion of the SEN4 study.
    The EPA recommends that updating the actinide solubility 
uncertainty distribution should be part of the update to the 
geochemical database. This would include incorporating new solubility 
data for thorium and americium under the WIPP repository conditions, 
and re-evaluating how studies are included in or excluded from the 
DOE's analyses.
    c. Plutonium Oxidation State. Oxidation states refer to an actinide 
ion's charge. Actinides with a higher charge likely exist in 
environments with greater oxygen content while actinides with lower 
charges likely exist where there is less oxygen. Although plutonium has 
multiple oxidation states including +VI, +V, +IV, and +III, the WIPP 
model assumes plutonium oxidation state is dominated by the +III or +IV 
charge in the aqueous phase due to the rapid removal of oxygen in the 
repository. Identifying the dominant oxidation state is particularly 
important as plutonium(III) is much more soluble than plutonium(IV). To 
address this uncertainty, the plutonium oxidation state model does not 
calculate oxidation state but instead considers plutonium(III) in 50% 
of the realizations and plutonium(IV) in the other 50%. Since the 2009 
Compliance Recertification Application, experiments have verified that 
the iron metal corrosion of the WIPP waste containers largely mediate 
the conditions conducive to plutonium(IV) and plutonium(III) oxidation 
states. While experiments have confirmed the WIPP conditions post-
closure, the debate has shifted towards whether plutonium(IV) or 
plutonium(III) is dominant in the WIPP conditions, or whether they will 
be present in equal proportions. More recent experimental information 
leads the EPA to believe that, under the WIPP conditions, aqueous 
plutonium(III) will be the dominant state of plutonium and will exist 
in equilibrium with the different solid plutonium phases present. In 
addition, organic ligands, iron and microbial processes will also 
increase the likelihood that plutonium(III) will dominate in solutions.
    While the sensitivity studies did not directly test the presumption 
that +III and +IV species would be equally present, the SEN4 study 
indirectly examined this proposition by including a modified solubility 
uncertainty distribution that was more heavily weighted toward higher 
+III solubility (see Section VI.E.2.d). Both the compliance 
recertification application and the SEN4 study indicate plutonium 
release levels will be below the compliance points. Combined with the 
related analysis of the actinide solubility uncertainty distributions, 
the Agency can accept the DOE's assumption that the plutonium(III) and 
plutonium(IV) oxidation states will each occur 50% of the time in 
performance assessment calculations for the current recertification. 
However, because of the available data that the EPA has identified 
supporting the presence of plutonium(III) over plutonium(IV), the EPA 
believes this issue is of sufficient significance to benefit from 
independent technical review of the available data and the assumption 
that both plutonium oxidation states will occur equally under the WIPP 
conditions. The EPA's review of the plutonium oxidation state issue is 
addressed more thoroughly in the Chemistry TSD.

E. Performance Assessment: Modeling and Containment Requirements 
(Sec. Sec.  194.14, 194.15, 194.23, 194.31 through 194.34)

    1. Overview. Section VI.A provided a basic description of the 
requirements in 40 CFR 191.13 and the performance assessment process 
required to show compliance with those standards. This section provides 
additional information on performance assessment and how it is 
evaluated by the EPA in the compliance recertification application. As 
described earlier, the DOE must use the performance assessment to 
demonstrate compliance with the containment requirements in 40 CFR 
191.13. The containment requirements are expressed in terms of 
``normalized releases.'' The DOE assembles the results of the 
performance assessment into complementary cumulative distribution 
functions, which indicate the probability of exceeding various levels 
of normalized releases (Sec.  194.34).
    For both of the DOE's 2004 and 2009 Compliance Recertification 
Applications, the EPA requested that the DOE modify those respective 
performance assessments to (1) address completeness and technical 
issues raised during the EPA review process and with these 
modifications, and (2) assure the disposal regulations were met.
    These additional sets of calculations have been termed by the DOE 
to be performance assessment ``baseline calculations'' and the EPA has 
considered these calculations as updated ``baselines'' for each 
respective compliance recertification application. The EPA then used 
these baseline calculations for the comparison performance assessment 
in each of the DOE's subsequent five-year compliance recertification 
applications.
    In this recertification review process, the Agency proceeded 
differently than in the past. During the completeness review, the EPA 
identified issues with parameters or approaches used by the DOE in the 
calculations. These have been discussed in Section VI.D. The Agency 
requested that the DOE conduct additional calculations so the EPA could 
better understand how alternative parameter values would affect 
repository performance. These calculations, or sensitivity studies as 
they have been referred to, are summarized below and are the subject of 
a TSD.\24\ With the completion of these sensitivity studies, the Agency 
has decided not to request another set of performance assessment 
baseline calculations as was done for previous recertifications. The 
Agency believes that the sensitivity studies, coupled with the DOE's 
documentation, provide a reasonable expectation that the WIPP complies 
with the radioactive waste disposal regulations at 40 CFR part 191 and 
the compliance criteria at 40 CFR part 194. Further, with the February 
2014 incidents and the DOE's resulting need to change the facility 
design,\25\ the Agency felt it was not necessary or appropriate at this 
time to conduct additional calculations using a facility design that 
will be changed in the near future.
---------------------------------------------------------------------------

    \24\ ``Review of EPA Sensitivity Studies of the DOE CRA-2014 
WIPP Compliance Recertification Performance Assessment'' in Docket 
ID No. EPA-HQ-OAR-2014-0609.
    \25\ The DOE has stated that it intends to abandon plans to use 
the area previously designated as waste panel 9 for waste 
emplacement because of worker safety issues (``Installation of 
Ventilation Barriers and Prohibiting Personnel Access to Equivalent 
Panel 9 Areas,'' Letter from Todd Shrader, DOE, to Alan Perrin, EPA 
dated April 18, 2017, Docket ID No. EPA-HQ-OAR-2014-0609). The DOE 
also plans to develop a new ventilation shaft to increase airflow in 
the mine, which is limited after the February 2014 incidents.
---------------------------------------------------------------------------

    The Agency requested that the DOE conduct four sensitivity studies 
(labeled as SEN1, SEN2, SEN3 and SEN4) to address technical concerns 
raised during the EPA's 2014 Compliance Recertification Application 
review. The EPA has compared these sensitivity results to the DOE's 
2014 performance assessment calculations. The purpose of these 
sensitivity studies is to provide an understanding of how repository

[[Page 33117]]

compliance would be affected when modifying specific inputs in the 2014 
performance assessment calculations. A brief explanation of those 
selected parameters is provided below.
    The ability of salt openings and aggregates to quickly compress, 
consolidate and ``heal'' within a few hundred years, mostly due to the 
creep-closure process, is one of the unique properties of bedded salt 
geologic units that make them potentially suitable to use as nuclear 
waste repositories. The DOE's 2014 performance assessment parameter 
values assigned to the non-waste rooms, the panel closure system and 
the adjacent disturbed rock zone did not reflect the creep-closure and 
rapid healing of these areas that the EPA expects to occur. That is, 
the DOE did not use permeability, porosity, residual gas and brine 
saturations and capillary pressures reflective of in-situ (i.e., 
undisturbed) conditions.
    Three of the EPA requested sensitivity studies, SEN1, SEN2 and 
SEN3, focused on modifying parameters to test how assuming complete 
creep-closure and healing of these areas would impact long-term 
performance through modifying values related to the permeability, 
porosity and two-phase flow parameter values for the run-of-mine salt 
panel closure system, the disturbed rock zone and non-waste areas for 
the 10,000-year modeled period. The fourth sensitivity study, SEN4, 
investigated the cumulative effects and impact on repository 
performance by making changes to five important parameter values as 
well as using an updated numerical code.
    As with the 2014 performance assessment, all of the sensitivity 
studies had three replicate calculation sets and included the same 
future scenarios. The four scenarios are briefly described below:
    (1) The undisturbed scenario--where the repository is not impacted 
by human activities,
    (2) The E1 Scenario--where one or more boreholes penetrate a 
Castile brine reservoir and also intersect a repository waste panel,
    (3) The E2 Scenario--where one or more boreholes intersect a 
repository waste panel but not a brine reservoir, and
    (4) The E1/E2 Scenario--where there are multiple penetrations of 
waste panels by boreholes of either the E1 or E2 type, at many possible 
combinations of intrusion times and locations for either E1 or E2 
drilling type of event.
2. Sensitivity Studies
    a. The SEN1 Study. The intention of the SEN1 study was to determine 
the impact on repository performance by modeling the stepped (i.e., 
gradual) reduction in porosity, permeability, residual gas and brine 
saturation, and capillary pressures that reflect creep-closure and 
healing of the open rooms and disturbed rock zone during the first 200 
years after repository closure. The DOE was then to model these areas, 
from 200 years to 10,000 years, as fully healed.
    This study had to be terminated because the numerical flow code 
used in these calculations produced non-physical and unrealistic 
results when these parameters were modified in time-intervals to 
reflect healing. The Agency accepted termination of this study, in 
part, because modeling changes in these values for the first 200 years, 
a relatively short time compared to the 10,000-year regulatory time 
period, would not be as important to long-term repository performance. 
The Agency considered that the SEN2 and SEN3 studies described below 
adequately addressed the issues targeted by the SEN1 study because the 
latter two studies both modeled the open and disturbed areas as fully 
healed for the entire 10,000-year regulatory time period, essentially 
bounding the conditions specified for the SEN1 study.
    b. The SEN2 Study. This study tested the impacts on repository 
performance by modeling the non-waste areas and open drifts as 
completely creep-closed during the entire 10,000-year regulatory 
period. In this study, parameter values for all the non-waste areas 
(i.e., the operations and experimental room open drifts) and adjacent 
disturbed rock zones were modified. The permeability and porosity were 
reduced to that of intact halite. The residual brine and gas 
saturations were also increased to better reflect healed conditions and 
capillary pressures (the pressure needed for fluid to flow between 
pores) were increased.
    Compared to the 2014 Compliance Recertification Application 
performance assessment, the SEN2 study waste room pressures generally 
increased and brine saturations decreased. The most affected primary 
release mechanism saw an increase in solid waste moving up a borehole 
(spallings) because this release mechanism increases when waste panel 
pressure increase. All other release mechanisms remained essentially 
unchanged from the 2014 performance assessment calculations. Total 
spallings releases remained small compared with cuttings, cavings and 
direct brine releases. Spallings releases therefore did not materially 
contribute to total repository releases in either SEN2 or the 2014 
Compliance Recertification Application.
    c. The SEN3 Study. For the SEN3 study, the DOE assumed that the 
panel closure system, the adjacent disturbed rock zone and the non-
waste areas and open drifts are healed for the 10,000-year regulatory 
period. The DOE reduced porosity and permeability in the repository, 
increasing initial residual brine and gas saturations, and invoking 
two-phase flow parameters for intact halite. Using these modifications 
effectively isolated the individual waste panels and the non-waste 
areas from one another for the entire modeled period due to limited 
brine and gas flows between areas of the repository.
    The modifications made in the SEN3 study caused increases in waste-
panel pressures and decreases in waste panel saturations. The dominant 
releases were from spallings, which are only dependent on a waste panel 
pressure high enough to force solids to the surface, and direct brine 
releases, which are dependent on having sufficient brine in the waste 
panels coupled with high enough pressure to force brine to the surface. 
The release mechanism that increased the most was for spallings, and 
the increase was seen at both the low and high probability compliance 
points. The impact on direct brine release was primarily at low 
probabilities because this release depends on both high waste panel 
pressure and high saturation conditions, the combination of which were 
less likely to occur in this study.
    Factoring in all combined releases, the total mean and low-
probability (0.001 probability) releases increased by approximately 15% 
from the initial 2014 Compliance Recertification Application results, 
although the upper bound of the 95% confidence interval was essentially 
the same as in the 2014 Compliance Recertification Application (0.384 
EPA Units in the 2014 Compliance Recertification Application and 0.387 
EPA Units in SEN3). Total releases did not exceed the EPA's WIPP 
release limits.
    The parameter values used in the SEN3 study created a ``tight'' 
repository (panel closure system, disturbed rock zone and non-waste 
rooms) in which brine and gas flow is limited. The study results 
indicate that such conditions may produce calculated releases higher 
than the more open and brine- and gas-conducive set of conditions 
presented by the DOE in the 2014 Compliance Recertification 
Application.
d. The SEN4 Study
    i. Overview. The fourth sensitivity study was intended to 
understand the cumulative effects on repository performance by making 
changes to

[[Page 33118]]

several parameters that the Agency questioned in the completeness 
review. This study also incorporated a DOE-corrected version of the 
DRSPALL code, which calculates waste that is released up a borehole to 
the surface. This study does not address all of the EPA's completeness 
questions, but provides significant insights as to the degree in which 
some parameter values of interest to the EPA impact releases. Note, the 
parameter changes in SEN2 and SEN3 representing creep closure were not 
made in the SEN4 study, so the results reflect the 2014 Compliance 
Recertification Application creep closure assumptions. The 
modifications requested for this study are provided below:
     Use the EPA's updated distribution for the probability of 
intersecting a waste panel and a Castile brine reservoir, denoted as 
the PBRINE parameter and discussed in Section VI.D.1.d previously.
     Use the revised data set for the plutonium oxidation state 
uncertainty distribution discussed in Section VI.D.2.c.
     Modify the lower limit for the parameter that predicts 
waste strength, denoted as the parameter TAUFAIL discussed in Section 
VI.D.1.f.
     Use the updated version of the computer code DRSPALL that 
models waste carried up a borehole. After the 2014 performance 
assessment calculations had been completed and submitted to the EPA, 
the DOE discovered an error in the computer code, DRSPALL. The DOE 
corrected this error and reported it to the EPA. For the SEN4 study, 
the EPA requested that the DOE use the corrected version.
     Eliminate the hydrogen sulfide reaction with iron as 
discussion in Section VI.D.1.e.
     Use the correct modeled length for north panel closure. 
The WIPP repository design includes two sets of panel closures emplaced 
at the north end of the repository. For the 2014 performance assessment 
calculations, the DOE modeled the ``effective'' length of only one 
panel closure rather than two. The EPA requested that the DOE increase 
the effective length of the modeled north waste panel to be consistent 
with the facility design.
    ii. Cumulative effects of the changes evaluated by release pathway.
    aa. Direct Brine Releases. Direct brine releases are a function of 
actinide solubility, repository pressure and brine saturation. Of these 
changes, the most significant are the revised solubility uncertainty 
distributions that increase the concentration of the more soluble 
plutonium(III) in repository brine, the increased likelihood of a 
higher probability of hitting a brine pocket and the iron sulfidation 
reaction stoichiometric coefficient changes. The combined effects of 
these changes increased direct brine calculated releases and total mean 
low probability (0.001) repository releases to about twice those of the 
2014 Compliance Recertification Application performance assessment 
(0.541 EPA Units for SEN4 versus 0.261 EPA Units for 2014 performance 
assessment).
    bb. Spallings Releases. Spallings releases are affected in SEN4 by 
a combination of corrections using the updated version of the DRSPALL 
code as well as increases in repository pressure. Repository pressure 
was generally increased in SEN4 as a result of the updated distribution 
of the PBRINE parameter, the increased length of the northernmost panel 
closure and the updated iron sulfidation reaction stoichiometric 
coefficients. The combined effect of these changes was to increase 
spallings releases by about half an order of magnitude. However, 
spallings releases remained low compared to direct brine releases and 
the effect of this increase in spallings on total mean releases was 
minimal.
    cc. Cuttings and Cavings Releases. Cavings releases were affected 
by the Agency's requested reduction of the lower bound of the 
distribution for the TAUFAIL parameter. The small reduction in the 
lower bound did not have a meaningful effect on total mean releases.
    dd. Releases from the Culebra. Releases from lateral flow through 
the Culebra Dolomite are a function of actinide solubility, repository 
pressure, and brine saturation. These are affected by the revised 
solubility uncertainty distributions, the increased likelihood of 
sampling higher values for the PBRINE parameter, the increased length 
of the northernmost panel closure and removal of the iron sulfidation 
reactions. The combined effect of these changes on Culebra releases was 
too small to have a meaningful effect on total mean repository 
releases.
    ee. Insights from the SEN4 Study. In the SEN4 study, the most 
significant effects on repository performance were an increase in 
direct brine releases and, by extension, an increase in total low 
probability repository releases. The Agency concludes that these 
increases were primarily the result of updating the solubility 
uncertainty distributions, updating the distribution of PBRINE and 
incorporating hydrogen sulfide steel passivation. The remaining 
changes, updating the TAUFAIL lower bound, using the corrections in the 
code DRSPALL and correcting the panel closure length, provided 
important updates and corrections to the performance calculation but 
had only a negligible effect on total mean releases. As in the previous 
sensitivity studies, the total mean releases, the upper 95% confidence 
limit on those means and all individual vectors in the three replicates 
remained below regulatory limits in SEN4.
    3. How the Four Sensitivity Studies Affect the WIPP's Compliance. 
The results indicate that modifications to the selected parameters 
reported in these evaluations increased calculated releases. However, 
the total mean releases, the upper 95% confidence limit on those means, 
and all individual vectors in the three replicates remained below the 
EPA's WIPP release limits.
    These sensitivity studies were intended to address a subset of the 
EPA technical issues. These studies do not address all the technical 
issues identified in the EPA's 2014 Compliance Recertification 
Application review. The major issues identified in the EPA's review 
primarily influence the direct brine releases and how the performance 
assessment addresses those releases. The EPA recommends that, 
especially with respect to calculating direct brine releases, the DOE 
re-evaluate the implementation of features, events and processes, along 
with model assumptions, to ensure their appropriate integration in the 
2019 Compliance Recertification Application. The EPA has identified two 
areas in particular (modeling of open areas and plutonium oxidation 
states) that the Agency believes would greatly benefit from independent 
technical review for consideration in the DOE's 2019 Compliance 
Recertification Application.

F. Additional Requirements

    This section summarizes the EPA's review as it relates to specific 
sections of the WIPP Compliance Criteria in 40 CFR part 194 that do not 
directly involve performance assessment.
    Information on continuing compliance activities related to waste 
characterization (40 CFR 194.8 and 194.24), inspections (Sec.  194.21) 
and quality assurance (Sec.  194.22) may be found in Section V of this 
document.
    The DOE did not conduct any activities during the period covered by 
the 2014 Compliance Recertification Application related to future state 
assumptions (Sec.  194.25), expert judgment (Sec.  194.26) or assurance 
requirements (Sec.  194.41-46). See the corresponding CARDs for more 
discussion. Information on passive institutional controls, which is an 
element of the assurance

[[Page 33119]]

requirements, may also be found in Section V.B.4.
    1. Waste Characterization (Waste Inventory) (Sec.  194.24). Section 
194.24 generally requires the DOE to identify, quantify and track the 
important chemical, radiological and physical components of the waste 
destined for disposal at the WIPP. The DOE collects data from generator 
sites and compiles the waste inventory on an annual basis. The DOE's 
2012 Annual Transuranic Waste Inventory Report (ATWIR 2012), which was 
used for the 2014 Compliance Recertification Application, reflects the 
disposal intentions of the waste generator sites as of December 31, 
2010. The DOE classified the wastes as emplaced, stored or projected 
(to-be-generated). The DOE used data from the WIPP database to identify 
the characteristics of the waste that has been emplaced at the WIPP. 
The projected wastes were categorized similarly to existing waste 
(e.g., heterogeneous debris, filter material, soil).
    The EPA reviewed the compliance recertification application and 
supplemental information to determine whether these documents provided 
a sufficiently complete estimate and description of the chemical, 
radiological and physical composition of the emplaced, stored and 
projected wastes proposed for disposal in the WIPP. The Agency also 
reviewed the DOE's description of the approximate quantities of waste 
components (for both existing and projected wastes). The EPA found that 
the radionuclides, cellulosic, plastic and rubber materials, organic 
ligands, oxyanions and cements in the waste are being appropriately 
tracked and characterized. In the 2014 Compliance Recertification 
Application, there is an update on the inventory of curium and 
neptunium, which remain in concentrations well below their solubility 
limits even after accounting for decay. The EPA accepts this updated 
inventory, which is relatively similar to the one used in the 2009 
Compliance Recertification Application. See the Baseline Inventory TSD 
\26\ for more information.
---------------------------------------------------------------------------

    \26\ ``Technical Support Document for Section 194.24: Review of 
the Baseline Inventory Used in the Compliance Recertification 
Application (CRA-2014)'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    2. Peer Review (Sec.  194.27). Section 194.27 of the WIPP 
Compliance Criteria requires the DOE to conduct peer review 
evaluations, when warranted, of conceptual models, waste 
characterization analyses, and a comparative study of engineered 
barriers. The required peer reviews must be performed in accordance 
with the Nuclear Regulatory Commission's NUREG-1297, ``Peer Review for 
High-Level Nuclear Waste Repositories,'' which establishes guidelines 
for the conduct of a peer review exercise. The DOE has conducted one 
peer review since the 2009 Compliance Recertification Application to 
establish radiological properties for two waste streams, titled the 
``Savannah River Site Historical Radiochemistry Data Peer Review,'' 
demonstrating its compliance with the requirements of Sec.  194.27.
    Based on a review and evaluation of the 2014 Compliance 
Recertification Application and supplemental information provided by 
the DOE (Docket ID No. EPA-HQ-OAR-2014-0609-0330), the EPA determines 
that the DOE continues to comply with the requirements of 40 CFR 
194.27.

G. Individual and Groundwater Protection Requirements (Sec. Sec.  
194.51 Through 194.55)

    Sections 194.51 through 194.55 of the WIPP Compliance Criteria 
implement the individual protection requirements of 40 CFR 191.15 and 
the groundwater protection requirements of subpart C of 40 CFR part 
191. Assessment of the likelihood that the WIPP will meet the 
individual dose limits and radionuclide concentration limits for ground 
water is conducted through a process known as compliance assessment. 
Compliance assessment uses methods similar to those of performance 
assessment (for the containment requirements in 40 CFR 191.13 and 
Appendix A) but is required to address only undisturbed performance of 
the disposal system. That is, compliance assessment does not include 
human intrusion scenarios (i.e., drilling or mining for resources). 
Compliance assessment can be considered a ``subset'' of performance 
assessment, since it considers only natural (undisturbed) conditions 
and past or near-future human activities (such as existing boreholes), 
but does not include the long-term future human activities that are 
addressed in the performance assessment.
    In the 2014 Compliance Recertification Application, the DOE re-
evaluated each of the individual and groundwater requirements. The DOE 
updated the data for ground water quantity determination to define an 
underground source of drinking water for purposes of calculating 
groundwater concentrations and doses. In the 2014 Compliance 
Recertification Application, the DOE used 2011 (U.S. Bureau of Census 
2013) census data to update the number of persons per household.\27\ 
The DOE continued to use the 2009 compliance recertification 
application data for the average household water consumption values. 
The water consumption data show that the average per capita consumption 
is 273 gallons per day.\28\ The DOE concludes that the sub-criterion of 
5 gallons per minute rate of production from a well continues to 
accurately define an underground source of drinking water \29\ and any 
change in this sub-criterion is not warranted as a result of applying 
more current water-consumption data to the calculation.
---------------------------------------------------------------------------

    \27\ 2014 Compliance Recertification Application Appendix IGP-
2014, Table IGP-3
    \28\ 2014 Compliance Recertification Application Appendix IGP-
2014, Table IGP-3
    \29\ 2014 Compliance Recertification Application Appendix IGP-
2014, Section IGP-3.1.1)
---------------------------------------------------------------------------

    The updates made by the DOE in the 2014 Compliance Recertification 
Application did not significantly impact the conclusions regarding the 
groundwater standard in the Compliance Certification Application. The 
DOE did not change the criteria for making underground source of 
drinking water determinations, and for the 2014 Compliance 
Recertification Application evaluation, the maximum potential dose 
remains below the Compliance Certification Application value calculated 
and continued compliance with the individual protection standard is 
maintained. The DOE states that the conservative bounding analysis used 
for the 1998 certification decision compliance assessment is still 
applicable for 2014 Compliance Recertification Application.\30\
---------------------------------------------------------------------------

    \30\ 2014 Compliance Recertification Application Appendix IGP-
2014, Section IGP-4.0
---------------------------------------------------------------------------

    The EPA finds the DOE in continued compliance with 40 CFR 194.51-
194.55 requirements.

VII. How has the public been involved in the EPA's WIPP recertification 
activities?

A. Public Information

    The EPA interacts with the public through various means. The EPA's 
main mechanism for distributing information is the EPA Web site and 
email messages via the WIPP-NEWS listserv. The EPA will also 
occasionally have meetings, in person or via teleconferences or 
webinars.
    Throughout the recertification process, the Agency posted pertinent 
new information and updates on the EPA WIPP Web site (https://www.epa.gov/radiation/epas-role-waste-isolation-pilot-plant-wipp). All 
pertinent recertification documents

[[Page 33120]]

(including the DOE-submitted recertification materials, correspondence, 
Federal Register notices, outreach materials, hearing transcripts as 
well as TSDs) are available for review or download (in Adobe PDF 
format) via the electronic docket dedicated to the 2014-2017 
recertification process (http://www.regulations.gov, Docket ID No. EPA-
HQ-OAR-2014-0609).
    Since October 2014, the EPA has sent out numerous announcements 
regarding the recertification schedule and availability of any WIPP-
related documents on the EPA WIPP Web site and the dockets, as well as 
details for the Agency's June 2015 stakeholder meetings in New Mexico 
and January 2017 stakeholder webinar (via Adobe Connect).

B. Stakeholder Meetings

    As discussed in the WIPP LWA, the recertification process is not a 
rulemaking and public hearings are not required. However, the EPA held 
a series of stakeholder meetings in June 2015 (Carlsbad and 
Albuquerque, NM) as well as a stakeholder webinar in January 2017 (via 
Adobe Connect software, with public hosting locations in Carlsbad and 
Albuquerque, NM) to provide information and updates about the 
recertification process. In an effort to make these meetings as 
informative as possible to all attending parties, the EPA listened to 
stakeholder input and concerns and tailored the meetings around the 
public as much as possible. The first meeting was held on June 16, 
2015, in Carlsbad, New Mexico and consisted of one three-hour afternoon 
session. The second public meeting was held on June 17, 2015, in 
Albuquerque, New Mexico, with afternoon and evening sessions.
    The main purpose of these meetings was to discuss the EPA's 
recertification process and timeline, as well as the DOE's application 
and important changes at the WIPP since the last recertification in 
2010. The meetings featured brief presentations on the aforementioned 
topics, as well as a facilitated discussion. In response to stakeholder 
suggestions, the DOE staff members were also on hand to provide 
information and answer any stakeholder questions. Staff from the New 
Mexico Environment Department (NMED) were present as observers. Public 
participants were encouraged to provide comments to the EPA for 
consideration during review of the DOE's 2014 Compliance 
Recertification Application.
    The EPA also held a stakeholder webinar using the Adobe Connect 
software on January 12, 2017. The Agency hosted the webinar from 
Washington, DC, with physical hosting locations set up in both Carlsbad 
and Albuquerque, NM, to accommodate members of the public as well as 
the DOE and NMED staff. The main purpose of this webinar was to inform 
the public of the current recertification schedule and provide updated 
technical information related to stakeholder questions and comments 
received at the June 2015 meetings.
    All of the issues raised at these meetings have been addressed by 
the EPA in Section VII.C of this document or in the CARDs under the 
relevant section and are available in the public docket 
(www.regulations.gov, Docket ID No. EPA-HQ-OAR-2014-0609).

C. Public Comments on Recertification

    The EPA posted the recertification application on the Web site 
immediately following receipt. The EPA formally announced receipt of 
the recertification application in the Federal Register on October 10, 
2014. The notice also officially opened the public comment period on 
the recertification application.
    For recertification, the EPA sought public comments and input 
related to changes in the DOE's application that may have a potential 
impact on the WIPP's ability to remain in compliance with the EPA's 
disposal regulations.
    The comment period for the recertification application closed on 
April 10, 2017, approximately two years and six months after it 
initially opened. This closing date was 30 days after the EPA's 
announcement in the Federal Register that the recertification 
application was complete.
    The EPA received 17 sets of written public comments during the 
public comment period. The EPA considered significant comments from the 
written submissions and the stakeholder meetings in the evaluation of 
continuing compliance. The EPA addresses these comments in CARDs that 
are relevant to each topic. In addition, a listing of all comments 
received and responses to each is included in Appendix 15-C of CARD 15. 
Two specific comments are addressed here.
    Comment: One comment addressed shipment of waste from Argonne 
National Lab. Citing the EPA's inspection reports, the commenter stated 
that he believed that the DOE had shipped and emplaced at the WIPP 
waste from the Lab that contained spent nuclear fuel and high level 
waste. He correctly stated that the WIPP LWA bans the transport to and 
disposal at the WIPP of high level radioactive waste and spent nuclear 
fuel. He wanted to know (a) how the EPA failed to uncover that the 
Argonne Lab was to ship spent nuclear fuel to the WIPP and approved 
this disposal, (b) how the EPA assures that this waste will not be sent 
to the WIPP, (c) how much of this waste has been sent to the WIPP, and 
the identity of all waste of these types, (d) what authority allowed 
the shipment and disposal of these prohibited wastes, and (e) how the 
EPA did not bar the DOE's shipment and disposal of these wastes.
    In a related comment, on February 3, 2017, the DOE, responded to 
this commenter and stated that the Argonne Lab waste is derived from 
atomic energy defense activities and did not contain any spent nuclear 
fuel (see EPA-HQ-OAR-2014-0609-0042). The DOE acknowledged that the 
WIPP LWA prohibits the disposal at WIPP of spent nuclear fuel and also 
acknowledged that some of the waste from the Argonne Lab was debris 
from specimens taken from fuel pins that were originally irradiated in 
commercial nuclear reactors. However, the DOE commented that the 
statutory definition of spent nuclear fuel does not speak directly to 
the issue of whether debris from specimens of commercial fuel rods is 
spent nuclear fuel. The DOE explained that, here, the debris--although 
including material that originated from fuel pins that had been 
irradiated in nuclear reactors--resulted from research and development 
activities at Argonne. The DOE stated that to try to segregate debris 
originating from irradiated fuel pins from other waste would be 
technically infeasible and cost prohibitive and would increase worker 
exposure. The DOE asserted that resolution of whether the material 
should be considered spent nuclear fuel was within its discretion and 
that it was its longstanding practice to classify such debris as waste 
and not spent nuclear fuel. In response to the DOE's February 3, 2017 
comment, the original commenter resubmitted his original comment.
    EPA Response: Under the WIPP LWA, the focus of the EPA's present 
recertification determination is whether the WIPP continues to comply 
with the final disposal regulations. Although--as the commenter notes 
and the DOE acknowledges--the WIPP LWA bans disposal at the WIPP of 
spent nuclear fuel, the disposal regulations, themselves, currently do 
not expressly address disposal of spent nuclear fuel. The WIPP LWA 
incorporates the definition of spent nuclear fuel found in the Nuclear 
Waste Policy Act of 1982: ``fuel that has been withdrawn from a nuclear 
reactor following irradiation, the constituent elements of which have 
not been separated by reprocessing.'' 42 U.S.C. 10101(23) (as 
incorporated by

[[Page 33121]]

WIPP LWA Sec. 2(15)). There seems to be no dispute that waste from the 
Argonne Lab includes some quantity of material that is not presently in 
the intact physical form of fuel withdrawn from a reactor following 
irradiation,\31\ but is fragments of or particulates from fuel pins 
withdrawn from a reactor following irradiation. The DOE states that the 
fragments or particulates resulted from research and development 
activities on test specimens from fuel pins withdrawn from a reactor 
following irradiation and claims that treatment of such material as 
other than spent nuclear fuel is consistent with the intent of the WIPP 
LWA. The DOE also asserts that attempting to segregate the fuel pin 
fragments and particulates from other debris shipped to the WIPP is 
infeasible and cost prohibitive and would increase worker exposure.
---------------------------------------------------------------------------

    \31\ There also seems to be no doubt that, as to the material in 
question, the ``constituent elements'' have not been ``separated by 
reprocessing.''
---------------------------------------------------------------------------

    Reasonable contentions may be made that fragments and particulates 
resulting from research and development activities on specimens from 
fuel withdrawn from a nuclear reactor following irradiation (``pieces 
of pieces'' of fuel pins) do not meet the statutory definition of spent 
nuclear fuel. The practical considerations of feasibility, cost, and 
worker safety associated with attempting to segregate such particulates 
from other waste shipped to the WIPP bear consideration. It is not 
essential, however, to the EPA's present recertification decision to 
attempt to definitively resolve this issue, because the current 
disposal regulations do not expressly address disposal of spent nuclear 
fuel.
    On an on-going basis, aside from the periodic recertification of 
the WIPP, the EPA communicates with the DOE concerning the 
characterization of WIPP waste. The DOE provides the EPA with 
documentation relating to WIPP waste streams, including but not limited 
to, waste from the Argonne National Laboratory, and including 
documentation for both contact handled and remote handled TRU waste 
streams. The relevant information is confirmed by analyzing individual 
waste containers using the EPA approved processes, procedures and 
equipment. These steps allow the DOE to demonstrate that waste 
containers for WIPP disposal meet the EPA's WIPP waste limits for 
physical and radiological contents of the waste. So, concerning the 
waste shipped from Argonne National Laboratory, the EPA evaluated the 
waste characteristic information prepared for remote handled waste. The 
DOE provided historical information to document that waste generated 
from laboratory experiments at Argonne was defense related, and through 
radiological assay concluded that the waste in question met the 
definition of TRU waste and was appropriate for disposal at the WIPP. 
Following this determination, Argonne provided this waste for 
characterization. Radiological and physical characterization confirmed 
that the TRU waste in question (a) is remote handled waste; (b) 
exhibits the characteristics of debris waste; and (c) meets the 
regulatory limits of the EPA's WIPP waste acceptance requirements at 40 
CFR 194.24.
    The EPA thoroughly inspects and approves the waste characterization 
processes in place at all waste characterization sites including 
Argonne National Laboratory. As part of the waste characterization 
inspections and approvals, the EPA is responsible for evaluating the 
adequacy of characterization methods used to identify and measure 
radiological and physical contents of the TRU waste that affect the 
long term containment and isolation of waste at the WIPP and for 
ensuring that the WIPP-bound waste meets the disposal requirements 
under 40 CFR 194.24.
    Comment: Another commenter disagreed with the DOE's proposed 
revision of the PBRINE parameter. The commenter noted that the DOE's 
2014 approach resulted in a lower probability of intersecting a brine 
pocket than was used in the original certification and previous 
recertifications, and finds this to be ``invalid.'' The commenter 
recommends using a fixed value of 60% probability, based on historical 
well testing and geophysical data. The commenter also disputes a number 
of the DOE's underlying assumptions for revising the approach, 
including the DOE's view of the geophysical data as unreliable and what 
the commenter sees as the DOE's misinterpretation of more recent 
drilling data.
    EPA Response: The EPA agrees with the commenter that the DOE's 
revised approach raises concerns. In particular, the EPA does not agree 
with the DOE's conclusions regarding the geophysical data. However, 
after reviewing the data again, the EPA disagrees with the commenter 
that a fixed probability of 60% is necessary. The EPA notes that 60% 
was the high end of the probability distribution used in performance 
assessments prior to 2014, with a mean probability of 30.5%, as 
recognized by the commenter. The updated approach developed by the EPA 
uses the geophysical data, but also incorporates newer drilling 
information into the probability distribution. The EPA believes this 
approach is sound and is acceptable for use in future performance 
assessments. The EPA will evaluate future proposals by the DOE to 
update the method for determining PBRINE. The EPA's review is discussed 
further in Section VI.D.1.d of this document and in the PBRINE TSD.

VIII. Where can I get more information about the EPA's WIPP-related 
activities?

A. Supporting Documents for Recertification

    The CARDs discuss DOE's compliance with each of the individual 
requirements of the WIPP Compliance Criteria. The CARDs also list the 
EPA TSDs and any other references used by the EPA in rendering the 
decision on compliance. All TSDs and references are available in the 
Agency's dockets, via www.regulations.gov (Docket ID No. EPA-HQ-OAR-
2014-0609), with the exception of generally available references and 
those documents already maintained by the DOE or its contractors in 
locations accessible to the public. For more detailed information on 
the technical issues considered in the EPA's recertification decision, 
see the TSDs.

B. The WIPP Web site & WIPP-NEWS Email Listserv

    For more general information and updates on the EPA's WIPP 
activities, please visit the WIPP internet homepage at <https://www.epa.gov/radiation/epas-role-waste-isolation-pilot-plant-wipp>. All 
pertinent recertification-related documents (including the DOE-
submitted recertification materials, letters, Federal Register notices, 
outreach materials, etc.) are available for review or download in Adobe 
PDF format. The Agency's WIPP-NEWS email listserv, which automatically 
sends messages to subscribers with up-to-date WIPP announcements and 
information, is also available online. Any individuals wishing to 
subscribe to the listserv can join by visiting <https://lists.epa.gov/read/all_forums/subscribe?name=wipp-news> and providing all requested 
information to register.

C. Dockets

    In accordance with 40 CFR 194.67, the EPA maintains public dockets 
via www.regulations.gov (Docket ID No. EPA-HQ-OAR-2014-0609) that 
contain all the information used to support the Agency's decision on 
recertification. The Agency maintains the formal hard

[[Page 33122]]

copy/paper docket in Washington, DC, as well as informational dockets 
in three locations in the State of New Mexico (Carlsbad, Albuquerque, 
and Santa Fe). The docket consists of all relevant, significant 
information received to date from outside parties and all significant 
information considered by the EPA in reaching a recertification 
decision regarding whether the WIPP facility continues to comply with 
the disposal regulations.

IX. What is the EPA's role in future WIPP activities?

    The EPA's regulatory role at the WIPP does not end with this 
recertification decision. The Agency's future WIPP activities include 
additional recertifications every five years (the next being scheduled 
to be submitted by the DOE in March 2019), review of the DOE reports on 
conditions and activities at the WIPP, assessment of waste 
characterization and quality assurance programs at waste generator 
sites, announced and unannounced inspections of the WIPP and other 
facilities and, if necessary, modification, revocation or suspension of 
the certification.
    As a result of the February 2014 incidents at the WIPP, the DOE 
will be making changes to the repository design. The DOE has indicated 
that it no longer plans to use panel 9 for waste operations due to the 
worker safety hazards in that location, so an alternative panel will be 
needed. This decision may also have implications for panel closures in 
the panels accessed through the panel 9 drifts (i.e., panels 3-6). In 
addition, the DOE is planning a new ventilation shaft that will allow 
for increased airflow through the underground operations area. The EPA 
will be keeping abreast of the DOE's requested changes and will make 
that information available as it is received.
    As described in Section VI of this notice, the EPA's review of the 
2014 Compliance Recertification Application identified where the DOE's 
technical basis for the modeling has limitations with assumptions used 
or with the basis for some parameter values. The EPA concerns with 
these limitations were generally addressed by the results of the SEN 
studies. While this approach of using a series of sensitivity studies 
to examine identified limitations was sufficient in the context of this 
compliance recertification application, it was to some extent driven by 
the known upcoming physical changes in the repository. The EPA would 
prefer to be able to evaluate a complete revised performance assessment 
in future compliance recertification application reviews. The EPA 
recommends that the performance assessment technical basis be evaluated 
for improvement in these areas: (1) Calculations of actinide 
solubility, (2) modeling the chemical conditions in the repository, and 
(3) modeling direct brine releases.
    Although not required by the Administrative Procedure Act (APA), 
the WIPP LWA or the WIPP Compliance Criteria, the EPA intends to 
continue docketing all inspection or audit reports and annual reports 
and other significant documents on conditions and activities at the 
WIPP, as well as formal communications between the two agencies.
    The EPA plans to conduct future recertification processes using an 
administrative process generally similar to that described in today's 
action.

    Dated: July 10, 2017.
Sarah Dunham,
Acting Assistant Administrator, Office of Air and Radiation.
[FR Doc. 2017-15182 Filed 7-18-17; 8:45 am]
BILLING CODE 6560-50-P