[Federal Register Volume 61, Number 214 (Monday, November 4, 1996)]
[Notices]
[Pages 56716-56724]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28223]


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NUCLEAR REGULATORY COMMISSION

Notice of Issuance of Branch Technical Position on Screening 
Methodology for Assessing Prior Land Burials of Radioactive Waste 
Authorized Under Former 10 CFR 20.304 and 20.302 for Interim Use and 
Comment

SUMMARY: This notice is to advise the public of the U.S. Nuclear 
Regulatory Commission's issuance of a Branch Technical Position (BTP) 
which provides a screening methodology that the staff finds acceptable 
to determine the need for further characterization and/or remediation 
of prior low-level radioactive waste disposal conducted under the 
provisions of former 10 CFR 20.304 and 20.302.
    Burial of certain quantities of radioactive waste in soil, by 
licensees, without prior NRC approval, was authorized on January 29, 
1959 (22 FR 548). This authorization was codified in former 10 CFR 
20.304. On January 28, 1981, the NRC concluded that it was 
inappropriate to continue generic authorizations of burials pursuant to 
10 CFR 20.304 without regard to factors such as location of burial, 
concentrations of radioactive material, form of packaging, and 
notification of NRC. Therefore, NRC rescinded 10 CFR

[[Page 56717]]

20.304 (45 FR 71761). As of January 28, 1981, licensees wishing to 
perform on-site disposal of the type previously authorized under 10 CFR 
20.304 were required to obtain prior NRC approval in accordance with 10 
CFR 20.302.
    Disposals made pursuant to former 10 CFR 20.304 and 20.302 at 
facilities licensed under 10 CFR Parts 30, 40, and 70, and that have 
been unused for NRC licensed operations for a period of 24 months, are 
subject to the requirements of the ``Final Rule on Timeliness in 
Decommissioning Nuclear Facilities'' (59 FR 36026, effective August 15, 
1994) (hereinafter called the ``Timeliness Rule''). Licensees who have 
unused outside areas (e.g., burial areas) containing elevated levels of 
licensed radioactive materials, are required to notify NRC, that they 
are in possession of these areas and must begin following a schedule 
for decommissioning these areas. For timing provisions related to 
decommissioning, see 10 CFR 30.36(d), 40.42(d), 70.38(d), and 72.54(d).
    On August 19, 1996, NRC published Information Notice 96-47 
``Recordkeeping, Decommissioning Notifications for Disposal of 
Radioactive Waste by Land Burial Authorized under Former 10 CFR 20.304, 
20.302, and Current 20.2002.'' This notice re-emphasized NRC's position 
that former burials are covered under the Timeliness Rule, outlined the 
decommissioning schedule required by the rule, and stated that NRC 
would develop a screening methodology for assessing former burials. 
This screening methodology is being issued as a draft BTP and is 
attached to this notice.
    Because of the deadlines associated with the Timeliness Rule, this 
BTP is being issued for public use and comment for 90 days. At the end 
of the 90 day period, the comments received will be evaluated to 
determine if the BTP should be revised. Since there is a possibility 
that the comments could result in a substantial change to the BTP, NRC 
will not make any decisions regarding the assessment of prior burials 
until after the comments can be evaluated.
    All comments should be addressed to Heather Astwood, Mail Stop T-
7F-27, U.S. Nuclear Regulatory Commission, Washington, DC 20555. A copy 
of the BTP is also located in the NRC's Public Document Room, 2120 L 
Street NW., Washington, DC 20555. A copy is also on the NRC homepage 
which can be accessed at www.nrc.com.

FOR FURTHER INFORMATION CONTACT: Heather Astwood, Division of Waste 
Management, Office of Nuclear Material Safety and Safeguards, U.S. 
Nuclear Regulatory Commission, Mail Stop T-7F-27, Washington, DC 20555, 
telephone (301) 415-5819.

    Dated at Rockville, MD this 25th day of October 1996.

    For the U.S. Nuclear Regulatory Commission.
Michael F. Weber,
Chief, Low-Level Waste and Decommissioning Projects Branch, Division of 
Waste Management, Office of Nuclear Material Safety and Safeguards.

Draft--Branch Technical Position

Screening Methodology for Assessing Prior Land Burials of Radioactive 
Waste Authorized Under Former 10 CFR 20.304 and 20.302

October 1996

Low-Level Waste and Decommissioning Projects Branch, Division of Waste 
Management, Office of Nuclear Material Safety and Safeguards

Table of Contents

1.0  Purpose
2.0  Introduction
3.0  Discussion
4.0  Regulatory Position
    4.1  Scope
    4.2  Screening Methodology
    4.2.1  General Approach
    4.2.2  Step 1--Records Review
    4.2.3  Step 2--Ingestion
    4.2.4  Step 3--Exhumation Concentration
    4.2.5  Results
    4.3  Dose Screening Level and Basis
Appendix A  Analysis of Other Pathways
Appendix B  Metric Conversion Table
Appendix C  Sample Calculations

Draft--Screening Methodology for Assessing Prior Land Burials of 
Radioactive Waste Authorized Under Former 10 CFR 20.304 and 20.302

1.0  Purpose

    This Branch Technical Position (BTP) provides a screening 
methodology that the staff finds acceptable to determine the need for 
further characterization and/or remediation of prior low-level 
radioactive waste disposals conducted under the provisions of former 10 
CFR 20.304 and 20.302. This BTP is intended to be a final evaluation 
for former burials. Decisions made based on this BTP are not expected 
to change because of the issuance of future rules or standards.

2.0  Introduction

    Burial of certain quantities of radioactive waste in soil, by 
licensees, without prior NRC approval, was authorized on January 29, 
1959 (22 FR 548). This authorization was codified in former 10 CFR 
20.304. On January 28, 1981, NRC concluded that it was inappropriate to 
continue generic authorizations of burials pursuant to 10 CFR 20.304 
without regard to factors such as location of burial, concentrations of 
radioactive material, form of packaging, and notification of the 
Nuclear Regulatory Commission. Therefore, NRC rescinded 10 CFR 20.304 
(45 FR 71761). As of January 28, 1981, licensees wishing to perform on-
site disposals of the type previously authorized under 10 CFR 20.304 
were required to obtain prior NRC approval in accordance with 10 CFR 
20.302.
    On May 21, 1991, 10 CFR Part 20 was revised (56 FR 23360) and 10 
CFR 20.302 was replaced by 20.2002. According to 10 CFR 20.1008(b), 
licensees were required to comply with the new 10 CFR 20.2002 
exclusively on January 1, 1994. The requirements of 10 CFR 20.2002 are 
similar to the original requirements in former 10 CFR 20.302, with the 
addition of requirements for submitting analyses and procedures for 
maintaining doses within established dose limits and as low as 
reasonably achievable (ALARA).
    Disposals made pursuant to former 10 CFR 20.304 and 20.302 at 
facilities licensed under 10 CFR Parts 30, 40, and 70, and that have 
been unused for NRC licensed operations for a period of 24 months, are 
subject to the requirements of the ``Final Rule on Timeliness in 
Decommissioning Nuclear Facilities'' (59 FR 36026, effective August 15, 
1994) (hereinafter called the ``Timeliness Rule''). Licensees who have 
unused outside areas (e.g., burial areas) containing elevated levels of 
licensed radioactive materials, are required to notify NRC, that they 
are in possession of these areas and must begin following a schedule 
for decommissioning these areas. For timing provisions related to 
decommissioning, see 10 CFR 30.36(d), 40.42(d), 70.38(d), and 72.54(d).
    The evaluations required before the Commission terminates a license 
or releases a former burial area from a license related to disposed 
material were discussed in the supplemental information to the final 
rule on the ``General Requirements for Decommissioning Nuclear 
Facilities'' (53 FR 24021), published June 27, 1988. In the statement 
of considerations for the final rule, NRC stated that it ``. . . will 
take a hard look at the extent to which the site has been previously 
used to dispose of low-level radioactive waste by land burial and 
decide what remedial measures, including removal of such soil off-site, 
are appropriate before the site can be released for unrestricted use 
and the license terminated.''
    On August 19, 1996, NRC published Information Notice 96-47 
``Recordkeeping, Decommissioning

[[Page 56718]]

Notifications for Disposals of Radioactive Waste by Land Burial 
Authorized under Former 10 CFR 20.304, 20.302, and Current 20.2002.'' 
This notice re-emphasized NRC's position that former burials are 
covered under the Timeliness Rule, outlined the decommissioning 
schedule required by the rule, and stated that NRC would develop a 
screening methodology for assessing former burials.

3.0  Discussion

    During decommissioning, NRC will evaluate disposals authorized 
under former 10 CFR 20.304 and 20.302, to determine whether they are 
acceptable for release for unrestricted use, based on their potential 
impact on the health and safety of the public. The acceptability of a 
disposal will depend on the potential for significant exposure to 
members of the public who may, at some time in the future, develop and 
use the disposal site for a private residence, farm, business, or other 
purpose.
    This methodology is intended to be used by the licensee as a 
screening tool to determine which burial sites, in general, are 
acceptable for release for unrestricted use, recognizing that 
exceptions may be identified by NRC and/or the licensee. This screening 
tool will be based on the total activity disposed of in the burial 
ground and the potential for that activity to produce a significant 
dose to a member of the public. Although this methodology estimates 
doses, they are very conservative estimates. Actual doses produced by a 
site would be a fraction of the doses estimated using this screening.
    For those sites which pass this screening, in general, the staff 
will require no further characterization or remediation effort. Those 
sites that do not pass the screening would require more detailed 
analysis. This may consist of site characterization and dose 
assessments by the licensee and NRC. Remediation may also be necessary. 
This is not to say that sites that do not pass the screening will be 
required to remediate. This process is intended to screen out simple 
sites with small inventories. More detailed evaluations can then be 
performed for the more complex sites, or sites with unique 
circumstances (i.e., no records, or burial located under a building). 
It is recognized that spot concentrations in the waste may exceed NRC's 
radiological criteria for decommissioning (57 FR 13389, ``Action Plan 
to Ensure Timely Cleanup of Site Decommissioning Management Plan 
Sites''), but the overall risk to the public is limited by the total 
inventory, site characteristics, or other factors. It is also 
recognized that these burials may not be the only residual activity 
contained at a site. This screening is intended to evaluate the risks 
posed by an on-site burial independent of any other evaluations of dose 
contributions from other areas of the site. A facility which contains 
larger quantities of contamination would be required to complete a site 
and facility characterization program and a detailed dose assessment 
that accounts for doses from all sources. Because such a site/facility 
could conceivably have residual contamination levels that result in 
doses that are just below the unrestricted release criterion, it is not 
justified to exclude a former burial site or sites. Therefore, this 
screening cannot be used for sites that have surface soil or building 
contamination outside of what is contained in the burial site and sites 
where members of the public would be exposed concurrently to both the 
burial and other residual radioactivity. It is restricted for use at 
those sites where a former burial is expected to be the only source of 
residual contamination at time of decommissioning.
    The Timeliness Rule, published August 15, 1994, outlines a schedule 
for licensees to follow in performing decommissioning activities and 
requires licensees to notify NRC of plans to meet this schedule. It 
also requires licensees to decommission portions of their site, 
including ``unused outdoor areas,'' which have not been used for a 
period of 24 months. These outdoor areas include former 10 CFR 20.304 
and 20.302 disposals, and are, therefore, subject to the Timeliness 
Rule.
    There are several issues associated with the assessment of prior 
burials. Many licensees considered these burials to be permanent 
disposals at the time of placement. Licensees did not budget the time 
nor monetary resources to evaluate these sites at the time of 
decommissioning. There is also a concern about the cost benefit of 
evaluating these sites for decommissioning. Many universities and 
hospitals disposed of small quantities of wastes associated with 
research and medical applications. The cost to characterize and 
remediate small burials of byproduct materials may outweigh the hazards 
avoided. However, some burials may pose greater risks to the public, 
such as those containing significant quantities of source and special 
nuclear material wastes. At these sites, characterization and/or 
remediation may be needed and costs of remediation will be considered 
for sites that are below 100 mrem/yr and have an adequate ALARA 
analysis. In addition, there are concerns about the quantity and 
quality of available disposal records. At the time of decommissioning, 
complete records of 10 CFR 20.304 and 20.302 disposals are necessary 
for NRC to evaluate the acceptability of the disposals. Former 10 CFR 
20.401(c)(3) stated that records of disposals made pursuant to 10 CFR 
20.302 and 20.304 should be maintained until NRC authorizes their 
disposition. However, for many of the older sites, these records are 
scarce or unavailable. The sites that have no burial records, may be 
required to evaluate and/or characterize the burials. Then, if NRC 
determines that the site does not pose a risk to the public, the site 
could be released for unrestricted use. If, however, it is determined 
that the site could pose a significant risk, the licensee may be 
required to remediate the burial. This analysis is based on the 
radiological risks associated with the burial. If the burial areas 
require characterization and/or remediation, other applicable local, 
state, or federal radiological and non-radiological regulations should 
be considered.
    To help alleviate some of these concerns, the staff developed this 
screening methodology to determine which former burials require 
additional characterization and assessment and which burials are 
acceptable for unrestricted use. To perform this screening, the 
licensee will need a copy of Part 20, Appendix B, and NUREG-1500 
``Working Draft Regulatory Guide on Release Criteria for 
Decommissioning: NRC Staff's Draft for Comment.'' 1 The NRC will 
defer decisions on releasing former burials based on this methodology 
until this draft is finalized.
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    \1\ NUREGs can be ordered by calling (202) 512-1800.
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4.0  Regulatory Position

4.1  Scope

    The methodology of this BTP applies to prior burials of radioactive 
material that were buried under 10 CFR 20.304 and 20.302. This 
methodology is not intended to be applied to burial sites that are 
currently in use or to evaluate former or proposed burials under 10 CFR 
20.2002. The final rule on ``Decommissioning Recordkeeping and License 
Termination: Documentation Additions,'' was issued on July 26, 1993 (58 
FR 39628), and requires a single document listing: (1) All areas 
outside restricted areas where current and previous wastes have been 
buried, (as documented under 10 CFR 20.2108); and (2) other information 
necessary to ensure that decommissioning is carried

[[Page 56719]]

out in accordance with the NRC's regulations. Therefore, for disposals 
made pursuant to 10 CFR 20.2002, waste disposal records should be 
sufficiently accurate and complete to demonstrate acceptability for 
release in accordance with recordkeeping and decommissioning 
requirements. In addition, recent approvals of 10 CFR 20.2002 disposal 
requests have been based on the assumption that the site would be 
released for unrestricted use. Guidance for evaluating these burials is 
contained in NUREG-1101, ``Onsite Disposal of Radioactive Waste.'' As 
stated previously, this screening is intended to be used for sites in 
which the former burial is expected to be the only source of residual 
contamination at the time of decommissioning. This screening is based 
only on the radiological risks associated with the burial. If the 
burial areas require characterization and/or remediation, or contain 
hazardous and/or mixed wastes, other applicable local, state, or 
Federal radiological and non-radiological regulations should be 
considered.
    This screening is intended to be used by both the licensee and NRC 
to determine the ultimate disposition of the burial ground. Licensees 
will perform the screening calculations, NRC staff will review the 
calculations and make a final determination if the site passes the 
screening. If the NRC's review indicates the site passes the screening, 
no further evaluation or characterization of the site will generally be 
required. The site can be removed from the license, if that is the wish 
of the licensee, and the site will not need to be revisited during 
license termination. Those sites that do not pass this screening will 
require more detailed analysis to assess potential radiological risks. 
The amount of analysis required beyond this screening depends on the 
complexity of the site, the amount of available site characterization 
information and site characteristics, and will be determined on a case-
by-case basis.

4.2  Screening Methodology

4.2.1  General Approach

    This methodology consists of three steps. The first step involves 
collecting information on the materials which were buried at the site. 
The other two involve conservative dose assessments using this 
historical information to determine the possible consequences from 
human exposure to the buried material. The Step 2 calculations are 
performed first because they require a minimal amount of information 
about the site, and are easy to perform. If a site passes Step 2, there 
is no need to collect additional information required to perform Step 3 
calculations because Step 2 is more conservative. If the site does not 
pass Step 2, then Step 3 calculations should be performed. If a site 
fails both Steps 2 and 3, this site requires more detailed analysis to 
determine whether it poses an unacceptable risk to the public.

4.2.2  Step 1--Records Review

    The first step for the licensee should be a review of the burial 
records. These records should indicate the activity and types of 
isotopes that were disposed of at the site and the time period for 
those disposals. All available and relevant records should be used to 
develop a complete inventory for the burial area. The total activity of 
each isotope in the entire burial site should be determined and 
converted into microcuries (Ci). This total inventory should 
be adjusted to account for radioactive decay which has occurred since 
the time of burial.
    It may be difficult to find records for some of the older burials. 
Many of these sites may have had several changes in management or 
location of record storage, and the records may have been misplaced or 
lost. If no records are available, this methodology can be performed 
using the original possession limits contained in the license for the 
site for the actual or reasonable estimate of time in which the trench 
was in operation and estimating the throughput resulting from the 
licensed activity during that time. This approach would most likely 
overestimate the quantities in the burial site because the activity 
disposed of in a burial is typically only a fraction of the activity 
allowed to be possessed under the license based on NRC staff 
experience. This will only be allowed for estimating the total 
inventory for use in Step 2. If there are no records, the trench size 
could not be determined, and, therefore, Step 3 could not be 
implemented. If using the original possession limits results in not 
passing this screening criteria, the licensee should consult with NRC 
for case-by-case guidance for evaluating the site. The maximum quantity 
that was allowed to be buried in the trenches under rescinded 10 CFR 
20.304, Appendix C cannot be used as an estimate for the quantity of 
isotopes in the trenches because NRC has identified instances in 
decommissioning burial sites where disposal limits were exceeded. 
Without some evidence (i.e., disposal records) that these guidelines 
were followed, the licensee and NRC can have little confidence in the 
trench inventory.
    If no records are available and the use of license limits result in 
a failure at Step 2, the licensee can take some intrusive samples of 
the burial ground to determine the general type and concentration of 
isotopes at the site and then perform this screening. The level of 
characterization necessary (i.e., number of samples) will be determined 
on a case-by-case basis in consultation with NRC staff. NRC draft 
``Branch Technical Position on Site Characterization for 
Decommissioning Sites,'' dated November 1994, contains a description of 
the type of site characterization information that could be required. 
After Step 1 is complete and the total activity for each isotope in the 
burial site is estimated, the licensee should continue with Step 2.

4.2.3  Step 2--Groundwater Pathway

    Following the general screening model approach described in NCRPM 
Report No. 123, this step assumes that the total activity for each 
isotope is leached into the minimum quantity of water needed to meet a 
family of four's average use in one-year (91 m\3\). Therefore, the 
activity of each isotope (after decay) should be divided by 9.1E7 
milliliters (ml) to obtain a concentration (C) for each isotope as 
follows:
[GRAPHIC] [TIFF OMITTED] TN04NO96.011

    The concentration of each isotope can be compared to the effluent 
release criteria contained in Part 20, Appendix B, Table 2, Column 2 
for water. The concentrations contained in this table are estimated to 
produce a dose of approximately 50 mrem/yr assuming an individual 
consumes 2 liters/day. Because Appendix B lists concentrations in 
Ci/ml for isotopes which result in a dose of 50 mrem, this 
concentration/dose ratio can be used to estimate the dose produced from 
a different concentration of that isotope. The potential dose from the 
estimated concentration for the isotopes in the burial can be estimated 
as follows:
[GRAPHIC] [TIFF OMITTED] TN04NO96.012

where:

C=the concentration of a burial site isotope in groundwater 
Ci/ml;
B=the Appendix B, Table 2, Col. 2 concentration for the same isotope; 
and
D=the dose from exposure to this isotope.

    This calculation should be performed for all isotopes in the burial 
site. After the doses are estimated for each isotope,

[[Page 56720]]

the doses should be totaled. If the total dose is less than the 100 
mrem/yr screening level, the site passes Step 2 and, in general, the 
site will require no additional evaluations. If the dose is greater 
than the 100 mrem/yr screening level, then the analyses of Step 3 
should be performed.

    Note: Step 3 CANNOT be used for isotopes with atomic numbers of 
88 or higher. Step 3 uses draft NUREG-1500, which is currently 
undergoing revisions for these isotopes. If a site contains these 
isotopes, licensees should consult with NRC staff for case-by-case 
guidance for evaluating these sites. If a site passes Step 2, then 
it passes the screening. If a site contains isotopes with atomic 
weight greater than 88, and it fails Step 2, then the site fails the 
screening and must be evaluated on a case-by-case basis.

4.2.4  Step 3--Exhumation Concentration

    In this step, it is assumed that the total inventory of the site is 
evenly distributed throughout the burial trenches. Most burial sites 
consist of several burial trenches located at the same site. The 
activity of each isotope should be divided by the total grams of 
material in the trenches. This will produce a trench concentration 
(Ci/gram of waste) for each isotope. This calculation should 
only consider the specific burial area containing the waste and 
contaminated soils. It should not include the soil cap, if one is 
present, or the 6 feet of clean soil which was required to be placed 
between burials conducted under the provisions of 10 CFR 20.304. For 
example, if a 100 m\3\ site contained 6 burial trenches with each one 
having a volume of 10 m\3\, the total inventory would be assumed to be 
evenly distributed over the volume of the trenches (60 m\3\), not the 
volume of the site (100 m\3\). For sites where the volume of the 
trenches cannot be reasonably determined, licensees should consult with 
NRC staff for case-by-case guidance for evaluating these sites.
    This step of the methodology assumes that a member of the public 
builds a house directly on the burial site. The Draft Environmental 
Impact Statement developed for 10 CFR Part 61, ``Licensing Requirements 
for Land Disposal of Radioactive Waste,'' dated September 1981 (NUREG-
0782), contains information concerning the dilution of waste caused by 
exhumation of a building foundation. Appendix G of NUREG-0782 contains 
the inadvertent intruder scenario and states that the waste 
concentration should be reduced by a factor of 4 to account for 
dilution during excavation (the contaminated material would be mixed 
with the clean cover material as well as the clean soil surrounding the 
burial). This concentration should be converted into picocuries per 
gram (pCi/g) for comparison with NUREG-1500 values. NUREG-1500, 
Appendix A, Table A-1, ``Total Dose'' column contains the total dose 
calculated using a residential scenario, with default assumptions, and 
is based on 1 Pci/g of an isotope. To calculate a screening dose for 
the burial site, the above calculated exhumed concentration can be 
multiplied by the Appendix A values.
[GRAPHIC] [TIFF OMITTED] TN04NO96.013

where

C=the concentration of a single isotope in the burial ground;
A=the NUREG-1500 Appendix A, Table A-1 dose for the same isotope; and
D=the dose from exposure to this isotope.

    This calculation should be performed for all isotopes in the burial 
site. After the doses are estimated for each isotope, the doses should 
be totaled. If the total estimated dose is less than the 100 mrem/yr 
screening level, the site passes the screening and no further analysis 
is generally necessary for the site; however, extenuating circumstances 
may warrant further review. If the estimated dose is greater than 100 
mrem/yr screening level, the site fails this screening analysis and the 
licensee will be required to perform additional site-specific analyses 
(Section 4.3.5). Example calculations are provided in Appendix C.

4.2.5  Results

    If the site passes one of the steps above, the site would generally 
not require any further characterization or remediation. The licensee 
should submit the results of this screening, including a description of 
the site, as known, and copies of the calculations performed for this 
screening. This should be submitted to NRC, along with a statement 
concerning the licensee's intention to take no further actions at the 
site. In accordance with recordkeeping requirements, the licensee will 
be required to maintain these records until the NRC authorizes their 
disposal. Assuming that the licensee submitted the notification and 
analysis in a timely manner (as described in IN 96-47), NRC would then 
issue a letter stating that the licensee has complied with the 
Timeliness Rule and that the former burial is suitable for unrestricted 
release. It will then be determined by NRC and the licensee when the 
burial site would be released. This BTP is intended to be a final 
evaluation for former burials. Decisions made based on this BTP are not 
expected to change because of the issuance of future rules such as 
NRC's radiological criteria for license termination.
    There may be instances where the licensee's calculations indicate 
the site passes the screening, but NRC determines the site requires 
more evaluation to consider additional hazards that may be associated 
with the waste. This would include sites which contain both radioactive 
and hazardous wastes. This methodology may determine the site is 
suitable for release based on the radioactive materials alone. However, 
the presence of hazardous chemical wastes may warrant additional 
evaluation to ensure protection of the public and the environment. This 
could also include sites where it is known the burial will be excavated 
in the future (i.e., the burial is in the path for a future road), 
sites with very limited burial records, and sites where there is other 
residual contamination outside of the burial area.
    If the site fails Step 3 above, the licensee will be required to 
perform more specific characterization of the site. The details of the 
characterization process and the level of detail required will be 
determined on a case-by-case basis. NRC draft ``Branch Technical 
Position on Site Characterization for Decommissioning Sites,'' dated 
November 1994, contains a description of the type of site 
characterization information that could be required. In some cases, if 
the characterization information indicates that total activity in the 
burial site is less than the activity originally used in the screening 
method, this more realistic total activity can be used in the screening 
methodology. If the site then passes the screening using this new 
activity, the site would not require further evaluation. If the site 
fails again, then the licensee will have to work with NRC staff to 
develop a plan for additional actions to be taken at the site. 
Evaluations beyond this methodology may require site characterization 
information and a dose assessment. More detailed assessment of the 
environmental transport and potential doses should be conducted in 
accordance with Policy and Guidance Directive PG-8-08, ``Scenarios for 
Assessing Potential Doses Associated with Residual Radioactivity.'' In 
such cases, sites will be acceptable for unrestricted release, if 
projected doses are a small fraction of 100 mrem/yr and ALARA, 
considering corrective actions. The staff will consider the magnitude 
of the projected dose, and existing radiological criteria for 
decommissioning, in conjunction with

[[Page 56721]]

the objectives of keeping residual contamination levels ALARA, to 
determine if the waste may pose a significant risk to the public and 
the burial requires remediation.
    It should be noted that the results of this screening are most 
affected by the quantity and quality of the records available to 
determine total inventory, and the assumptions used in determining the 
trench concentration. Slight variations in the trench size could be the 
difference between a site failing or passing the methodology.

4.3  Dose Screening Level and Basis

    This methodology uses the public dose limit of 100 mrem/yr in Part 
20 as a screening level for determining if a site poses a significant 
risk to the public. Although this is higher than the dose levels 
previously imposed for on-site burials (i.e., a few mrem/yr), the staff 
believes this is appropriate for screening these sites because of the 
high degree of conservatism built into the methodology and limitations 
of existing information.
    Following the general screening model approach described in the 
National Council on Radiation Protection and Measurements (NCRPM) 
Report No. 123, dated January 22, 1996, Step 2 of this methodology 
assumes the total inventory in the burial ground is leached into the 
minimum quantity of water needed to meet the average water use of a 
family of four for 1 year (91 m\3\). The dose is then calculated 
assuming an individual member of the family drank 2 liters/day of the 
91 m\3\ for 1 year. The use of 91 m\3\ is also the screening default 
value used in NUREG/CR-5512, ``Residual Radioactive Contamination From 
Decommissioning'' (Table 6.22).
    NRC staff analysis in NUREG-1500, Table A-1 contains estimated 
annual total effective dose equivalent factors. These dose factors 
indicate that there are cases, in which the inhalation of an isotope in 
a residential scenario would produce a larger dose than the ingestion 
of an equal amount of activity. It also indicates that the direct 
exposure pathway for some isotopes may be more limiting than either the 
ingestion or inhalation pathway. However, Appendix A, of this BTP, 
contains an analysis which demonstrates that the ingestion scenario, as 
used in this methodology, is so restrictive that inhalation and direct 
exposure calculations are not necessary.
    The staff considers the assumptions used in this ingestion scenario 
to overestimate likely doses to potential members of the public, such 
as: (1) There has been no migration from the burial so that the total 
inventory originally placed in the burial remains; (2) the entire 
inventory leaches into the groundwater in a one-year period; (3) 
someone moves onto the site, and places a well near the burial ground 
that would capture all of the contaminated water; (4) there is no 
sorption of the radionuclide during transport and only limited dilution 
and dispersion; (5) a single individual drinks only well water from the 
site for that year. As shown in the example given later in this 
section, more likely doses to a hypothetical individual would be a 
small fraction of the doses estimated in this methodology and would 
likely be in the range of a few millirem per year if the dose using 
this methodology is less than 100 mrem/yr.
    Step 3 of this methodology assumes that a farmer lives on top of 
the burial ground at some point in the future. This scenario also 
contains several conservative assumptions such as: (1) There has been 
no migration from the burial so that the total inventory originally 
placed in the burial remains; (2) that an intruder inadvertently digs 
into the waste and brings the entire inventory to the surface; and (3) 
the intruder fails to recognize the waste. These are assumptions used 
in developing the exhumed concentrations. There are also several 
conservative assumptions contained in the dose conversion factors 
developed for soils in NUREG-1500, which are used in this step to 
estimate screening doses.
    NUREG-1500 uses a family farm scenario, in which an individual 
lives on the site, drinks water from an on-site well, and ingests 25 
percent of his/her food from a garden, on-site. The resident's house 
and garden are assumed to be in the contaminated area, and the garden 
alone is assumed to be 2500 m\2\ (NUREG/CR-5512, Table 6.23). 
Therefore, to contain the house and garden, the contaminated area has 
to be larger than 2500 m\2\. Many of the on-site disposals that have 
been reviewed by NRC in the past have had areas less than 2500 m\2\. 
These sites are generally too small to contain a house and a garden, 
and, since they are smaller than those used in NUREG-1500, would likely 
produce a smaller dose than predicted using NUREG-1500 values. 
Therefore, based on the conservative assumptions used in both 
estimating the soil concentration, and estimating the doses, the actual 
doses produced from a site are expected to be a small fraction of the 
screening doses predicted using this methodology.
    The following example of a Cs-134 burial is used to illustrate the 
level of conservatism in these scenarios. Assuming a burial contains 
270 Ci 2 of Cs-134, the resulting dose for the ingestion 
scenario in Step 2 equals approximately 160 mrem/yr. If this same 
inventory is evenly distributed in a trench which is 5m x 2m x 1m, the 
exhumation concentration is calculated to be 4.2 pCi/g Cs-134 based on 
Step 3. Using NUREG-1500, this results in a dose of approximately 13 
mrem/yr. As an independent check, a RESRAD analysis was also performed 
using a concentration of 4.2 pCi/g Cs-134 and a contaminated zone area 
of 5m x 2m, but no other site specific information. This analysis 
produced a dose of 7 mrem/yr (assuming no soil cover and that the 
groundwater was within 2 meters of the bottom of the burial). 
Therefore, although the scenarios in this methodology can predict 
elevated doses, they are only for screening purposes and do not 
necessarily reflect actual doses which could be produced from the site. 
The projected doses calculated using a more rigorous approach are a 
small fraction of 100 mrem/yr screening level.
---------------------------------------------------------------------------

    \2\ NRC's standard metrification policy is to place metric units 
first, followed by non-metric units in parentheses. However, the 
supporting tables for this BTP (i.e., 10 CFR Part 20, Appendix B) 
are presented in non-metric units, therefore, for comparison 
purposes non-metric units are used in this BTP. A conversion table 
is contained in Appendix B.
---------------------------------------------------------------------------

Appendix A--Analysis of Other Pathways

    There are only a limited number of isotopes for which the 
inhalation pathway is more limiting than the ingestion pathway for the 
residential scenario in NUREG-1500, Appendix A, Table A-1. For all of 
these, however, the direct exposure pathway is even more limiting than 
either the inhalation or ingestion pathways. The staff created the 
ingestion pathway scenario used in this methodology to be so 
restrictive, that even for isotopes which are primarily an external 
hazard (e.g., Co-60), the dose produced, based on ingestion, is higher 
than one produced using an external scenario, as in NUREG-1500.
    Based on calculations performed using Step 3 of this BTP and the 
RESRAD, version 5.1, the dose modeling code, Step 2 of this methodology 
produces a higher screening dose, and, therefore, is more restrictive 
than the other two methods. Since both Step 3 and RESRAD consider all 
pathways, including direct exposure, in the dose calculations, if Step 
2 doses are high then the other pathways do not need to be considered 
independently. To demonstrate this, it was assumed that there was a 
burial trench which

[[Page 56722]]

contained a total activity of 270 Ci of Co-60. Co-60 was 
chosen because NUREG-1500 indicates it produces the largest external 
dose per pCi/g. It was assumed that the entire inventory of the burial 
was contained in a relatively small trench, with an area of 10 m2 
and depth of 1 meter. This area was used to be consistent with the 
contaminated zone area used in the Step 3 screening of this BTP. It was 
assumed that the groundwater was within 1 meter of the bottom of the 
burial, and that there was no cover on the material. If the total 
activity is used in Step 2, a screening dose of 48 mrem/yr is 
estimated. Step 3 of the screening estimates a dose of approximately 40 
mrem/yr, and a RESRAD analysis predicts 18 mrem/yr. A RESRAD analysis 
using more site specific parameters (i.e., cover thickness, depth to 
groundwater) would likely reduce this dose even further.

Appendix B--Metric Conversion Table

----------------------------------------------------------------------------------------------------------------
              Quantity                            From                        To metric             Multiply by 
----------------------------------------------------------------------------------------------------------------
Activity............................  Ci (curie)..................  MBq (becquerel).............        37,000.0
Dose equivalent.....................  rem.........................  Sv (sievert)................            0.01
Length..............................  ft (feet)...................  m (meter)...................          0.3048
Volume..............................  ft3.........................  m3..........................      0.02831685
Volume..............................  gal (gallon)................  L (liter)...................        3.785412
----------------------------------------------------------------------------------------------------------------

Appendix C--Sample Calculations

1.0  Example Site No.1

    This site contains 1-3 animal carcasses that were tagged with 41 
millicuries (mCi) Cs-134, 10.5 Mci Fe-55, 60 Mci Zn-65, 2.7 Mci Co-60 
and 25 Mci I-125. These animals were placed in a 5m x 2m x 1m burial 
pit in 1980.

1.1  Step 1--Records Review

    No burial records were available to determine how many of the 
tagged animals were placed in the pits. There were records on the 
number of animals tagged, and the maximum activity that was used to tag 
these animals. Therefore, the maximum activity of each isotope was used 
to estimate the total inventory. The burial has been in place for 15 
years, which is sufficient time for Zn-65 and I-125 to decay to 
insignificant activities. Therefore, they can be excluded from 
consideration. The calculated activities for the remaining isotopes are 
adjusted for decay.

------------------------------------------------------------------------
                          Isotope                            Ci
------------------------------------------------------------------------
Cs-134.....................................................         270 
Fe-55......................................................         233 
Co-60......................................................         376 
------------------------------------------------------------------------

1.2  Step 2--Groundwater Pathway

    The total inventory for each isotope was divided by 9.1E7 ml (91 
m3) of groundwater. This represents the concentration in Ci/ml 
of that isotope which could be ingested by a person in 1 year.

------------------------------------------------------------------------
              Isotope               Ci   Ci/ml(water) 
------------------------------------------------------------------------
Cs-134............................         270   2.9E-6.                
Fe-55.............................         233   2.5E-6.                
Co-60.............................         376   4.1E-6.                
------------------------------------------------------------------------

    This concentration was then compared to Part 20, Appendix B, Column 
2, limits. These limits represent concentrations in effluent releases 
which could cause doses of approximately 50 mrem/yr assuming ingestion 
of 2 liters per day. The Appendix B ratio of concentration to dose was 
used to determine roughly the dose that could be produced from the 
waste concentrations in groundwater. For example,
[GRAPHIC] [TIFF OMITTED] TN04NO96.014

161 mrem/yr from Cs-134

    This calculation was preformed for the remaining two isotopes and 
the results are included in the following table.

                                                   Appendix B                                                   
----------------------------------------------------------------------------------------------------------------
                                                                                          Ci/          
                           Isotope                             Ci  Ci/  ml/50  mrem/   mrem/yr
                                                                                 ml            yr               
----------------------------------------------------------------------------------------------------------------
Cs-134.......................................................       270         2.9E-6           9E-7        161
Fe-55........................................................       233         2.5E-6           1E-4       1.25
Co-60........................................................       376         4.1E-6           3E-6         68
----------------------------------------------------------------------------------------------------------------

    The doses were summed and the result was a dose of over 230 mrem/
yr. This dose exceeds the 100 mrem/yr screening level, and, therefore, 
this site fails Step 2 of the screening methodology. Since this burial 
did not contain any isotopes greater than atomic number 88, Step 3 was 
performed.

1.3  Step 3--Exhumation Concentration

    In this step, the total inventory was averaged over the volume of 
the burial ground, which is 5 m x 2 m and 1 meter deep or equivalent to 
1.6E7 grams of waste and soil assuming a soil density of 1.6 g/cm3 to 
determine an average concentration (activity per cm3). This 
concentration is then converted into pCi/g for comparison with NUREG-
1500 values in Table A-1 and divided by 4 to represent expected 
dilution from cover material and clean soil on the sides during 
exhumation.

[[Page 56723]]

[GRAPHIC] [TIFF OMITTED] TN04NO96.015


Trench Concentration = 17 pCi/gram
[GRAPHIC] [TIFF OMITTED] TN04NO96.016

Exhumation Concentration = 4.2 pCi/g

------------------------------------------------------------------------
               Isotope                          pCi             pCi/gram
------------------------------------------------------------------------
Cs-134..............................  2.7E8..................        4.2
Fe-55...............................  2.3E8..................        3.5
Co-60...............................  3.8E8..................        5.7
------------------------------------------------------------------------

    These concentrations were then compared to NUREG-1500 values in 
Table A-1, Column 9, for the total dose in mrem/yr, as follows:

D mrem/yr = (4.2 pCi/g Cs-134)(3.06 mrem/yr), where NUREG-1500 
relates 3.06 mrem/yr to 1 pCi/g Cs-134
D = 12.8 mrem/yr from Cs-134

    This calculation was performed for the remaining two isotopes, and 
the results are summarized in the following table.

                                                   NUREG-1500                                                   
----------------------------------------------------------------------------------------------------------------
                                                                                        mrem/yr/pCi/            
                             Isotope                                 pCi      pCi/gram        g         mrem/yr 
----------------------------------------------------------------------------------------------------------------
Cs-134..........................................................      2.7E8        4.2     3.06           12.8  
Fe-55...........................................................      2.3E8        3.5     1.65E-3         0.006
Co-60...........................................................      3.8E8        5.7     5.06           28.78 
----------------------------------------------------------------------------------------------------------------

    Based on the above calculations, the total dose is approximately 40 
mrem/yr and is less than 100 mrem/yr. Therefore, this site passes 
screening Step 3 and does not require any further characterization nor 
remediation.

2.0  Example Site No. 2

    This site contains process waste from the manufacture of uranium 
fuel. The burial contains approximately 3 curies of uranium in several 
trenches. The material was placed in trenches throughout the 1960s.

2.1  Step 1--Records Review

    Burial records were available and reviewed to determine that 
approximately 3 curies of uranium were disposed of in trenches. For 
this example, it was assumed that there was 0.5 curies of U-234 and 2.5 
curies U-238. Approximately 27 years have passed since the time of the 
last burial, which is insufficient time for either uranium to have 
decayed. Therefore, they cannot be excluded from consideration, and the 
calculations will be performed with the quantities cited above.

------------------------------------------------------------------------
                          Isotope                            Ci
------------------------------------------------------------------------
U-234......................................................         5E5 
U-238......................................................       2.5E6 
------------------------------------------------------------------------

2.2  Step 2--Total Activity Ingested From Groundwater

    The total inventory for each isotope was divided by 9.1E7 ml (91 
m3) of groundwater. This represents the concentration in Ci/ml 
of that isotope that could be ingested by a person in 1 year.

------------------------------------------------------------------------
                                                            Ci/
                   Isotope                     Ci       ml     
------------------------------------------------------------------------
U-234........................................         5E5        0.005  
U-238........................................       2.5E6        0.027  
------------------------------------------------------------------------

    This concentration was then compared to Part 20, Appendix B, Column 
2, limits. These limits represent concentrations in effluent releases 
that could cause doses of approximately 50 mrem/yr. The Appendix B 
ratio of concentration to dose was used to determine, roughly, the dose 
that could be produced from the waste concentrations in groundwater. 
For example,
[GRAPHIC] [TIFF OMITTED] TN04NO96.017

8E5 mrem/yr from U-234

    This calculation was performed for the remaining two isotopes, and 
the results are included in the following table.

----------------------------------------------------------------------------------------------------------------
                                                                                          App B Ci  Ci/     m>Ci/ml     mrem/yr
                                                                                 ml                             
----------------------------------------------------------------------------------------------------------------
U-234........................................................        5E5         0.005          3E-7         8E5
U-238........................................................      2.5E6         0.027          3E-7       4.5E6
----------------------------------------------------------------------------------------------------------------


[[Page 56724]]

    The doses are well over the 100 mrem/yr screening level, and, 
therefore, this site fails Step 2 of the screening methodology.

2.3  Step 3--Exhumation Concentration

    This site contains isotopes that have atomic numbers greater than 
88, and, therefore, cannot be used in Step 3. Since this site failed 
Step 2 and cannot be used in Step 3, this site fails this screening 
methodology.

[FR Doc. 96-28223 Filed 11-01-96; 8:45 am]
BILLING CODE 7590-01-P