[Federal Register Volume 82, Number 117 (Tuesday, June 20, 2017)]
[Proposed Rules]
[Pages 28017-28020]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-12792]


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NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

[NRC-2008-0602, NRC-2002-0020]
RIN 3150-AH43


Decoupling an Assumed Loss of Offsite Power From a Loss-of-
Coolant Accident

AGENCY: Nuclear Regulatory Commission.

ACTION: Discontinuation of rulemaking activity and denial of petition 
for rulemaking.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is discontinuing 
the rulemaking activity, ``Decoupling an Assumed Loss of Offsite Power 
from a Loss-of-Coolant Accident'' (the LOOP/LOCA rulemaking), and 
denying the associated petition for rulemaking (PRM), PRM-50-77. The 
purpose of this action is to inform members of the public of the 
discontinuation of the rulemaking activity and the denial of the PRM, 
and to provide a brief discussion of the NRC's decision regarding the 
rulemaking activity and PRM. The rulemaking activity will no longer be 
reported in the NRC's portion of the Unified Agenda of Regulatory and 
Deregulatory Actions (the Unified Agenda).

DATES:  Effective June 20, 2017, the rulemaking activity discussed in 
this document is discontinued and PRM-50-77 is denied.

ADDRESSES: Please refer to Docket IDs NRC-2008-0602 (rulemaking 
activity) and NRC-2002-0020 (PRM) when contacting the NRC about the 
availability of information regarding this document. You may obtain 
publicly-available information related to this document using any of 
the following methods:
     Federal Rulemaking Web site: Go to http://www.regulations.gov and search for Docket IDs NRC-2008-0602 (rulemaking 
activity) and NRC-2002-0020 (PRM). Address questions about NRC dockets 
to Carol Gallagher; telephone: 301-415-3463; email: 
[email protected]. For technical questions, contact the 
individual listed in the FOR FURTHER INFORMATION CONTACT section of 
this document.
     NRC's Agencywide Documents Access and Management System 
(ADAMS): You may obtain publicly-available documents online in the 
ADAMS Public Documents collection at http://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``ADAMS Public Documents'' and 
then select ``Begin Web-based ADAMS Search.'' For problems with ADAMS, 
please contact the NRC's Public Document Room (PDR) reference staff at 
1-800-397-4209, 301-415-4737, or by email to [email protected]. The 
ADAMS accession number for each document referenced in this document 
(if that document is available in ADAMS) is provided the first time 
that a document is referenced.
     NRC's PDR: You may examine and purchase copies of public 
documents at the NRC's PDR, Room O1-F21, One White Flint North, 11555 
Rockville Pike, Rockville, Maryland 20852.

FOR FURTHER INFORMATION CONTACT: Robert Beall, Office of Nuclear 
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001; telephone: 301-415-3874; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. Background

[[Page 28018]]

II. Process for Discontinuing Rulemaking Activities
III. Decoupling an Assumed Loss of Offsite Power From a Loss-of-
Coolant Accident
IV. Petition for Rulemaking (PRM-50-77)
V. Conclusion

I. Background

    In both SECY-01-0133, ``Status Report on Study of Risk-Informed 
Changes to the Technical Requirements of 10 CFR part 50 (Option 3) and 
Recommendations on Risk-Informed Changes to 10 CFR 50.46 (ECCS 
Acceptance Criteria),'' dated July 23, 2001 (ADAMS Accession No. 
ML011800492), and SECY-02-0057, ``Update to SECY-01-0133, 'Fourth 
Status Report on Study of Risk-Informed Changes to the Technical 
Requirements of 10 CFR part 50 (Option 3) and Recommendations on Risk-
Informed Changes to 10 CFR 50.46 (ECCS Acceptance Criteria)' '' (ADAMS 
Accession No. ML020660607), the NRC staff recommended developing a 
possible risk-informed alternative to reliability requirements in Sec.  
50.46 of title 10 of the Code of Federal Regulations (10 CFR) and 
General Design Criterion (GDC) 35, ``Emergency Core Cooling,'' of 
appendix A, ``General Design Criteria for Nuclear Power Plants,'' to 10 
CFR part 50, ``Domestic Licensing of Production and Utilization 
Facilities.'' On March 31, 2003, in the staff requirements memorandum 
(SRM) for SECY-02-0057, the Commission directed the NRC staff to 
proceed with a rulemaking to risk-inform the emergency core cooling 
system (ECCS) functional reliability requirements in GDC 35 (ADAMS 
Accession No. ML030910476). This proposed rulemaking would provide 
licensees an option to relax the current analysis requirements for 
considering a loss of offsite power (LOOP) to occur coincident with a 
large-break loss-of-coolant accident (LOCA) (the LOOP/LOCA rulemaking). 
The SRM also stated that the NRC staff should include relevant issues 
and uncertainties that can impact plant risk (e.g., delayed LOOP and 
``double sequencing'' \1\ of safety functions).
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    \1\ Double sequencing is defined as a situation where 
electrically powered safety and accident mitigation equipment 
automatically start, shut down, and restart in rapid succession when 
called on to operate. Delayed LOOP and double sequencing were 
evaluated and dispositioned in GSI-171, ``ESF Failure from LOOP 
Subsequent to LOCA,'' for the current regulations (https://www.nrc.gov/sr0933/Section%203.%20New%20Generic%20Issues/171r1.html#). GSI-171 does not need to be reevaluated if the LOOP/
LOCA rulemaking is discontinued.
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    In parallel with the LOOP/LOCA rulemaking, the NRC pursued a 
separate rulemaking for a risk-informed definition of large-break LOCA 
ECCS analysis requirements (the 50.46a ECCS rulemaking). The proposed 
regulations in the 50.46a ECCS rulemaking would have allowed both 
pressurized water reactors (PWRs) and boiling water reactors (BWRs) to 
decouple a LOOP from a LOCA for certain break sizes.

II. Process for Discontinuing Rulemaking Activities

    When the NRC staff identifies a rulemaking activity that can be 
discontinued, the staff requests approval from the Commission to 
discontinue it in a Commission paper. The Commission provides its 
decision in an SRM. If the Commission approves discontinuing a 
rulemaking activity, the NRC staff informs the public of the 
Commission's decision.
    A rulemaking activity may be discontinued at any stage in the 
rulemaking process. For a rulemaking activity that has received public 
comments, the NRC considers those comments before discontinuing the 
rulemaking activity; however, the NRC staff will not provide individual 
comment responses.
    After Commission approval to discontinue the rulemaking activity, 
the NRC staff updates the next edition of the Unified Agenda to 
indicate that the rulemaking is discontinued. The rulemaking activity 
will appear in the completed section of that edition of the Unified 
Agenda but will not appear in future editions.
    A rulemaking activity proposed for discontinuation may have been 
initiated in response to accepting one or more PRMs, or may include 
issues from one or more PRMs that were accepted and added to the 
ongoing related rulemaking activity. Therefore, discontinuation of the 
rulemaking activity also requires the NRC to take action to resolve the 
associated PRM(s) and to inform the petitioner(s) and the public of the 
NRC's action. The NRC's action to discontinue a rulemaking would 
normally result in NRC denial of the associated PRM for the same 
reasons.

III. Decoupling an Assumed Loss of Offsite Power From a Loss-of-Coolant 
Accident

    The Boiling Water Reactor Owners Group (BWROG) submitted for NRC 
review a licensing topical report NEDO-33148, ``Separation of Loss of 
Offsite Power from Large Break LOCA,'' dated April 27, 2004 (ADAMS 
Accession No. ML041210900). The BWROG stated that the licensing topical 
report would support plant-specific exemption requests to implement 
plant changes that are currently not possible with the existing 
regulatory requirements to consider a LOOP coincident with a large 
break LOCA. The NRC intended to derive some of the technical support 
for the proposed LOOP/LOCA rulemaking from NEDO-33148. The proposed 
rulemaking would allow BWR licensees to make specific design changes 
that otherwise could not be made without exemptions from the current 10 
CFR 50.46 requirements.
    The BWROG initially chose to pursue an approach that relied on a 
generic probabilistic risk assessment (PRA) and other published reports 
for justification of several important assumptions made in NEDO-33148 
(e.g., large-break LOCA probability, consequential/delayed LOOP, and 
double sequencing of electrical loads). The BWROG proposed to address 
these issues in Revision 2 of NEDO-33148, which was submitted on August 
25, 2006 (ADAMS Accession No. ML062480321). Revision 2 presented the 
risk analyses as risk assessment methodologies rather than a generic 
risk assessment. In a letter to the BWROG dated March 24, 2008 (ADAMS 
Accession No. ML080230696), the NRC detailed the conditions and 
limitations that were required for approval of NEDO-33148, Revision 2. 
Some of the outstanding technical issues included LOOP/LOCA frequency 
determinations, seismic contributions to break frequency, the 
maintenance of defense-in-depth, and the treatment of delayed LOOP and 
double sequencing issues. The NRC staff determined that these issues 
needed to be adequately addressed in order to complete a regulatory 
basis that could support a proposed LOOP/LOCA rulemaking.
    On June 12, 2008, the BWROG formally withdrew its licensing topical 
report, NEDO-33148, from further NRC review and discontinued its 
supporting effort. The BWROG's withdrawal letter (ADAMS Accession No. 
ML081680048) stated that further development of NEDO-33148 ``is no 
longer cost effective and, if ultimately approved in the form presently 
desired by NRC staff, adoption by licensees would most likely be 
prohibitively expensive.'' The withdrawal of NEDO-33148 and the 
discontinued effort by the BWROG demonstrated a potential loss of 
industry interest in this initiative.
    In SECY-09-0140, ``Rulemaking Related to Decoupling an Assumed Loss 
of Offsite Power From a Loss-of-Coolant Accident, 10 CFR part 50, 
Appendix A, General Design Criterion 35 (RIN 3150-AH43),'' dated 
September 28, 2009 (ADAMS Accession No. ML092151078), the NRC staff 
proposed three options for the Commission to consider as a path

[[Page 28019]]

forward on the LOOP/LOCA rulemaking: (1) Discontinue the LOOP/LOCA 
rulemaking, (2) proceed with the LOOP/LOCA rulemaking without the BWROG 
topical report, or (3) continue to defer the LOOP/LOCA rulemaking until 
implementation of the 50.46a ECCS rulemaking. The Commission approved 
the third option, to defer the LOOP/LOCA rulemaking, in the SRM for 
SECY-09-0140, dated July 2, 2010 (ADAMS Accession No. ML101830056).
    In SECY-16-0009, ``Recommendations Resulting from the Integrated 
Prioritization and Re-Baselining of Agency Activities,'' dated January 
31, 2016 (ADAMS Accession No. ML16028A189), the NRC staff recommended 
that the 50.46a ECCS rulemaking be discontinued. In the SRM for SECY-
16-0009, dated April 13, 2016 (ADAMS Accession No. ML16104A158), the 
Commission approved discontinuing the 50.46a ECCS rulemaking. A Federal 
Register notice, published on October 6, 2016 (81 FR 69446), informed 
the public of the NRC's decision to discontinue the 50.46a ECCS 
rulemaking.
    In support of the potential risk-informed alternative to 
reliability requirements in 10 CFR 50.46 and GDC 35, the NRC performed 
substantial work in a number of technical areas, including estimating 
LOCA frequencies and the conditional probability of a LOOP, given a 
LOCA (see memorandum from A. Thadani to S. Collins, ``Transmittal of 
Technical Work to Support Possible Rulemaking on a Risk-Informed 
Alternative to 10 CFR 50.46/GDC 35,'' dated July 31, 2002 (ADAMS 
Accession No. ML022120661)). As part of this work, the NRC identified a 
number of areas of uncertainty associated with estimating the 
conditional probability of a LOOP, given occurrence of a LOCA, 
including very limited data on major ECCS actuations and LOOPs after 
such actuations, incomplete knowledge about all of the factors that can 
impact the probability of consequential LOOP because of electrical 
transient factors,\2\ and the impact on offsite system voltage due to 
deregulation of the electric utility industry. To complete a fully 
developed regulatory basis for the LOOP/LOCA rulemaking, the NRC staff 
would need to ensure that these areas of uncertainty are adequately 
addressed as part of the rulemaking activity.
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    \2\ As used here, transient factors include the electrical 
disturbance triggered by starting electrically powered safety and 
accident mitigation equipment as a result of the LOCA and the 
conditions of the offsite transmission system grid.
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    On June 28, 2016, and October 26, 2016, the NRC held public 
meetings (ADAMS Accession Nos. ML16203A003 and ML16319A153, 
respectively) to receive external stakeholder feedback on the need for 
a LOOP/LOCA rulemaking. The NRC presented information on what would be 
required by the NRC and the industry to continue the proposed 
rulemaking activity. The NRC's position was similar to the March 24, 
2008, letter to the BWROG detailing the information that would be 
needed to complete review of licensing topical report NEDO-33148. 
Representatives from the Nuclear Energy Institute and the PWR and BWR 
Owners Groups also presented their perspectives on continuing the 
proposed LOOP/LOCA rulemaking effort. The industry re-stated its view 
from the 2008 withdrawal of the licensing topical report that the 
estimated implementation costs would be prohibitively expensive for the 
benefit received. In addition, industry representatives recommended 
that the NRC staff devote its resources to other risk-informed 
licensing activities that have significantly higher industry interest, 
such as applications to implement 10 CFR 50.69, ``Risk-informed 
categorization and treatment of structures, systems and components for 
nuclear power reactors,'' and risk-informed technical specifications.
    The NRC is discontinuing the LOOP/LOCA rulemaking activity. The 
current regulations provide adequate protection of public health and 
safety. This rulemaking would have provided licensees an option to 
relax the current analysis requirements for considering a LOOP to occur 
coincident with a LOCA. Based on the feedback from the industry, it is 
unlikely that any licensee would seek licensing basis changes that 
would rely on the proposed rulemaking. The issues that caused the 
industry to withdraw the BWROG topical report in 2008 are still 
applicable today and the industry has greater interest in the progress 
of other risk-informed initiatives. Therefore, pursuit of this effort 
would likely have minimal practical impact on safety. Based upon (1) 
the assessment that there is no current adequate protection issue with 
respect to compliance with the current ECCS rule, (2) the lack of 
significant safety benefits from the rulemaking, (3) the industry's 
representation that it would be unlikely for any licensee to 
voluntarily use the LOOP/LOCA rule because the estimated implementation 
costs would be prohibitively expensive for the benefit received, and 
(4) the industry's stated interest in pursuing other risk-informed 
licensing activities, the NRC is discontinuing the LOOP/LOCA 
rulemaking.

IV. Petition for Rulemaking (PRM-50-77)

    On May 2, 2002, the NRC received a PRM from Bob Christie, 
Performance Technology (ADAMS Accession No. ML082530041), related to 
the topics in the proposed LOOP/LOCA rulemaking. The PRM requested that 
the NRC amend its regulations in appendix A to 10 CFR part 50 to 
eliminate the requirement to assume a LOOP coincident with postulated 
accidents. The NRC docketed the petition and assigned it Docket No. 
PRM-50-77. The NRC published a notice of receipt and request for 
comment on the PRM on June 13, 2002 (67 FR 40622), and received one 
comment supporting the PRM from the Strategic Teaming and Resource 
Sharing organization (ADAMS Accession No. ML022490192). The petition 
was resolved by a decision to consider its issues within the LOOP/LOCA 
rulemaking, but the petition remained open because of the ongoing 
developments related to this rulemaking. However, in late 2007, the NRC 
Executive Director for Operations approved changes to the PRM process 
to enhance the efficiency and effectiveness of dispositioning a PRM. As 
a result of those enhancements, the NRC closed this petition on April 
13, 2009 (74 FR 16802), with a commitment to follow through with the 
original resolution to consider it within the LOOP/LOCA rulemaking.
    Because of the agency's decision to discontinue the LOOP/LOCA 
rulemaking, the associated petition, PRM-50-77, is denied for the 
reasons discussed above. As provided at Sec.  2.803(i)(2), the NRC has 
decided not to complete the rulemaking action and is documenting this 
denial of the PRM in the docket for the closed PRM.

V. Conclusion

    The NRC is no longer pursuing the LOOP/LOCA rulemaking and is 
denying PRM-50-77 for the reasons discussed in this document. In the 
next edition of the Unified Agenda, the NRC will update the entry for 
the rulemaking activity and reference this document to indicate that 
the rulemaking is no longer being pursued. The rulemaking activity will 
appear in the completed actions section of that edition of the Unified 
Agenda but will not appear in future editions. If the NRC decides to 
pursue a similar or related rulemaking activity in the future, it will 
inform the public through a new rulemaking entry in the Unified Agenda.

    Dated at Rockville, Maryland, this 14th day of June 2017.


[[Page 28020]]


    For the Nuclear Regulatory Commission.
Annette L. Vietti-Cook,
Secretary of the Commission.
[FR Doc. 2017-12792 Filed 6-19-17; 8:45 am]
 BILLING CODE 7590-01-P