ML20133C726
| ML20133C726 | |
| Person / Time | |
|---|---|
| Issue date: | 12/23/1996 |
| From: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Pomeroy P NRC ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW) |
| References | |
| REF-WM-3 FACA, NACNUCLE, NUDOCS 9701080070 | |
| Download: ML20133C726 (3) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20556-0001
- ,o December 23, 1996 i
Dr. Paul W. Pomeroy, Chairman Advisory Committee on Nuclear Waste U.S. Nuclear Regulatory Commission Washington, DC 20555
SUBJECT:
SCREENING METHODOLOGY FOR ASSESSING PRIOR LAND BURIALS OF RADI0 ACTIVE WASTE AUTHORIZED UNDER FORMER 10 CFR 20.304 AND 20.302
Dear Dr. Pomeroy:
l I am responding to the letter of November 20, 1996, from you to Chairman Jackson concerning staff plans relevant to decommissioning of sites in which i
radioactive waste had been buried as authorized under former 10 CFR 20.304 and j
l 20.302.
On October 25, 1996, the staff issued a draft Branch Technical l
Position (BTP) to provide a screening methodology that the staff finds acceptable for determining the need for further characterization and/or l
remediation of prior low-level radioactive waste disposals conducted under the t
provisions of former 10 CFR 20.304 and 20.302.
Such disposals, at facilities licensed under 10 CFR Parts 30, 40. and 70, that have been unused for licensed 0)erations for a period of 24 months, are subject to the requirements of the "rinal Rule on Timeliness in Decommissioning Nuclear Facilities." Licensees who have unused outdoor areas containing elevated levels of licensed j
l radioactive materials are required to notify the U.S. Nuclear Regulatory Commission that they are in possession of these areas and must begin following J
a schedule for decommissioning these areas.
The staff briefed the ACNW on the l
BTP on October 22. 1996.
A copy of the BTP is attached for reference.
In response to the ACNW's comments and recommendations, the staff agrees that I
independent audits and reviews are necessary to verify that risks are reasonably assessed.
It will conduct an independent assessment of each licensee submittal.
It expects that sites for which the ACNW expressed concern (e.g., sites containing uranium and sites with little or no records) will have to be addressed on a case-by-case basis outside of the screening methodology.
In addition, it agrees that the risks and contributors to risk l
must be clearly understood in site decommissioning evaluations.
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,k P. W. Pomeroy As the staff completes its evaluation of public comments and prepares the final technical position it looks forward to further discussions with the ACNW.
Sincerely.
LL James M. Tay or Executive Director for Operations
Attachment:
Branch Technical Position cc:
Chairman Jackson Commissioner Rogers Commissioner Dicus Commissioner Diaz Commissioner McGaffigan SECY
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P. W. Pomeroy As the staff completes its evaluation of public comments and prepares the final technical position, it looks forward to further discussions with the ACNW.
Sincerely.
Originalsignodby:
JamesLIMhosn James M. Taylor Executive Director for Operations
Attachment:
Branch Technical Position j
cc: Chairman Jackson Commissioner Rogers Commissioner Dicus Commissioner Diaz Commissioner McGaffigan i
SECY TICKET: GT960884 DISTRIBUTION:
Central 2 File LLDP r/f DWM r/f NMSS r/f PUBLIC l
BJDavis DWM t/f CPoland JMTaylor HLThompson EDO r/f l
FMiraglia/NRR DMorrison/RES EJordan, AE0D KCyr, OGC ACNW File PTressler. EDO NMSS Dir. Off. r/f SECY OCA OPA Path & Fig gme: A:\\ACNW-BTP.LTR cpfenooreofoscensen ig, 1996 0FC LLDP TEditor OGC [
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P. W. Pomeroy I As the staff completes its evaluation of public comments arid prepares the l
final technical position, it looks forward to further discussions with the i
ACNW.
1 Sincerely.
James M. Taylor l
Executive Director for Operations
Attachment:
Copy of Branch Technical Position cc: Commissioner Rogers Commissioner Dicus Commissioner Diaz Commissioner McGaffigan l
SECY TICKET: GT960884 DISTRIBUTION: Central File LLDP r/f DWM r/f NMSS r/f PUBLIC
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BJDavis DWM t/f CPoland JMTaylor HLThompson E00r l
FMiraglia/NRR DMorrison/RES EJordan. AEOD KCyr. OGC ACNW File
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DATE 12/ /96 12/ /96 12/ /96 12/- /96 OFFICIAL RECORD COPY pg ACNW: YES X
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DRAFT BRANCH TECHNICAL POSITION i
i SCREENING METHODOLOGY FOR ASSESSING PRIOR LAND BURIALS OF RADIOACTIVE WASTE i
AUTHORIZED UNDER FORMER 10 CFR 20.304.
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and 20.302
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October 1996
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Low-Level Waste and Decommissioning Projects Branch i
Division of Waste Management Office of Nuclear Material Safety and Safeguards 2
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1.0 PURPOSE 1
2.0 INTRODUCTION
3.0 DISCUSSION 2
6 4.0 REGULATORY POSITION.
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4 4.1 Scope...
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4.2 Screening Methodology 5
4.2.1 General Approach 5
4.2.2 Step 1 - Records Review 6
4.2.3 Step 2 - Ingestion 7
4.2.4 Step 3 - Exhumation Concentration 8
4.2.5 Results 9
4.3 Dose Screening Level and Basis APPENDIX A ANALYSib OF OTHER PATHWA'.'S APPENDIX B METRIC CONVERSION TABLE APPENDIX C SAMPLE CALCULATIONS i
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DRAFT SCREENING METHODOLOGY FOR ASSESSING PRIOR LAND BURIALS OF RADIOACTIVE WASTE AUTHORIZED UNDER FORMER 10 CFR 20.304 AND 20.302 1.0 PURPOSE j
This Branch Technical Position (BTP) provides a screening methodology that the staff finds j
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 cf radioactive waste in soil, by licensees, without prior NRC approval, was authorized on January 29,1959 (22 8 548). This authorization was codified in former 10 CFR 20.304. On January 28,1981, NRC concluded that it was j
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 @ 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 N9C 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 f acilities 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 FB 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).
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The evaluations required before the Commission terminates a license or releases a former I
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."
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On August 19,1996, NRC published Information Notice 96-47 "Recordkeeping, i
l Decommissioning 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 l
develop a screening methodology for assessing former burials.
3.0 DISCUSSION l
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 i
unrestricted use, based on their potential impact on the health and safety of the public.
The acceptability of 1 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 cetermine 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 smallinventories. 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 f acility which contains larger quantities of contamination would be required to
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complete a site and f acility characterization program and a detailed dose assessment that accounts for doses from all sources. Because such a siterf acility 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 severalissues 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 j
for decommissioning Meny universities and hospitals disposed of small quantities of wastes associated with research and medical applications. The cost to c.iaracterize 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 eveluate 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 buriats 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 Draf t Regulatory
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4 Guide on Release Criteria for Decommissioning: NRC Staff's Draf t for Comment" The j.
NRC will defer decisions on releasing former burials based on this methodology until this draf t is finalized.
2 4.0 REGULATORY POSITION
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I-4.1 Scone 3
The methodology of this BTP applies to prior burials of radioactive material that were l
buried under 10 CFR 20.304 and 20.302. This methodology is not intended to be applied j
j 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 i
Termination: Documentation Additions," was issued on July 26,1993 (58 F_R 39628), and j
requires a single documer.t listing: (1) all areas outside restricted areas where current and i
previous wastes have been buried, (as documented under 10 CFR 20.2108); and 12) other i
information necessary to ensure that decommissioning is carried out in accordance with
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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 i
for release in accordance with recordkeeping and decommissioning requirements. In i
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 evalmting these burials is con ained in NUREG 1101, "Gnsite Disposal of Radioactive Waste." As i
stater:I previously, this screening is intended to be used for sites in which the former burial l
is expected to be the only source of residual contamination at the time of decommissioning. Thir creening 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 j
screening. If the NRC's review indicates the site passes the screening, no further 4
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 l
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.
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l NUREGs can be ordered by calling (202) 512-1800.
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4.2 Screeninn Methodoloov l
4.2.1 General Approach I
l This methodology consists of three steps. The first step invcives collecting information on the materials which were buried at the site. The other two involve conservative dose a
j assessments using this histoncal 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 arr. easy to perform. If a site passes Step 2, there is no need to collect additional information required 4
i 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
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3, this site requires more detailed analysis to determine whether it poses an unacceptable risk to the public.
I 4.2.2 Step 1 Records Review The first step for the licensee should be a review of the bunal records. These records should indicate the activity and types of isotopes that were disposed of at the site and the j
time penod for those disposals. All available and relevant records should be used to
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develop a complete inventory for the burial area. The total activity of each isotope in the 3
entire burial site should be determined and converted into microcuries ( Cih This total l
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 i
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 reasonablc 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 f ailure 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
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6 basis in consultation with NRC staf f. NRC draf t " 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 I
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 l
Following the general screening model approach described in NCRPM Report No.123, this l
step assumes thet the total activity for each isotope is leached into the minimum quantity l
of water needed to meet an family of four's average use in one year (91 m'). Therefore,
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the activity of each isotope (after decay) should be divided by 9.1E7 milliliters (ml) to l
obtain a concentration (C) for each isotope as follows:
C pC4ml _ tot Iinventory (pct) g3) 9.167 m/
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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 l
contained in this table are estimated to produce a dose of approximately 50 mremlyr l
assuming an individual consumes 2 liters / day. Because Appendix B lists concentrations in I
Ci/ml for isotopes which result in a dose of 50 mrem, this concentration / dose ratio can be 1
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:
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D miemlyr = (C pCHmh@ miem/M g2y (B Ci/m0 1
where: C = the concentration of a burial site isotope in groundwater Ci/ml; l
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 allisotopes in the burial site. After the doses are estimated for each isotope, the doses should be totaled, if the total dose is less than the l
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 i
the analyses of Step 3 should be performed, i
i 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 l
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7 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 f ails the screening and must be evaluated on a case by case basis.
4.2.4 Step 3 - Exhumation Concentration j
in this step, it is assumed that the total inventory of the site is evenly distributed throughout the bt. rial 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 materialin the trenches. This will produce a trench concentration ( Ci/ gram of waste) for j
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' site contained 6 burial trenches with each one having a volume of 10 m, u1e totalinventory would be assumed to be l
3 evenly distributed over the volume of the trenches (60 m'), not the volume of the site
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I (100 m ). ' For sites where the volume of the trenches cannot be reasonably determined, 3
licensees should consult with NRC staff for et se 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 i
September 1981 (NUREG-0782), contains information concerning the dilution of waste j
caused by exhumation of a building foundation. Appendix G of NUREG-0782 contains the inadvertent intruder scenario and states that the waste noncentration should be reduced by a f actor 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 picoctuies per gram !pCi/g) for comparison with NUREG-1500 values. NUREG-1500, ^.ppendix A, Table A-1, " Total Dose" column f
contains the total dose calculated using a residential scenario, with def ault assump..ons, 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.
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O mretrtyr C pCig pC4g 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 allisotopes in the burial site. Af ter the doses are estirnated 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
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8 is generally necessary for the site: however, extenuating circumstances may wctrant further review. If the estimated dose is greater than 100 mremlyr screening level, the site f ails 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 l
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 l
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 l
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 j
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 t; 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 cnteria for license termination.
There may be instances where the licensee's calculatiorc indicate the site passes the screening, but NRC :etermines the site requires more evaluation to consider additirinal 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 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 draf t " Branch Technical Fosition 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 mremlyr and ALARA,
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9 considering corrective actions. The staff will consider the magnitude of the projected dose.
and existing radiological criteria for decommissioning, in conjunction with 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 dvailable to determine totalinventory, 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 Screenino 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 staf f 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 Nc,.123, dated January 22, 1996, Step 2 of this methodology assumes the total inventory in the buria' ground is leached into the minimum qt antity of water needed to meet the average water use of a family of four for 1 year (91 m ). The dose is than calculated assuming an individual 3
3 3
member of the family drank 2 liters / day of the 91 m for 1 year. The use of 91 m is also the screening def ault value used in NUREG/CR 5512, " Residual Radioactive Contamination From Decommissioning," (Table 6.22).
NRC staff analysis in NUREG 1500, Table A-1 contains estiinated annual total effective dose equivalent f actors. 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 i
likely be in the range of a few millirem per year if the dose using this methodology is less than 100. wem/yr.
I
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,y* p s ', p,
l 10 Step 3 of this methodology assumes that a f armer 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 totalinventory originally placed in the burial remains: (2) that an intruder inadvertently digs into the waste and brings the entire inventory to the surf ace; 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 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 sita, 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 (NUREG/CR 5512, Table 6.23). Therefore, to 2
2 contain the house and garden, the contaminated area has to be largt than 2500 m.
Many of the on site disposals that have been reviewed by NRC in the past have had areas less than 2500 m. These sites are generally too small to contain a house and a garden, 2
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 l
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.
l The following example of a Cs 134 burial is used to illustrate the level of conservatism in these scenarios. Assuming a burial contains 270 pCi of Cs 134, the resulting dose for 2
the ingestion scenario in Step 2 equals approximately 160 mrem /yr. If this same inventory j
i is evenly distributed in a trench which is 5m x 2m x 1m, the exhumation conceritration is calculated to be 4.2 pCilg 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 l
Sm 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 l
bottom of the burial). Therefore, although the scenarios in this methodology can predict l
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 j
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.
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3 APPENDIX A 3
ANALYSIS OF OTHER PATHWAYS i
j 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, j
Appendix A, Table A-1. For all of these, however, the direct exposure pathway is even 3
i 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 externa! hazard (e.g., Co 60), the dose produced, based on i
ingestion, is higher than one produced using an external scenario, as in NUREG 1500.
j Based on calculations performed using Step 3 of this BTP and the RESRAD, version 5.1, i
i 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 i
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 whi>:h contained a total i
activity of 270 Ci of Co 60. Co 60 was chosen because NUREG-1500 indicates it i
produces the largest external dose per pCilg. It was assumed that the entire inventory of
}
tha burial was contained in a relatively small trench, with an area of 10 m' and depth of 1 2
meter This area was used to be consistent with the contaminated zone area used in the l
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 j
is used in Step 2, a screening dose of 48 mremlyr is estimated. Step 3 o' the screening
)
estimates a dose of approximately 40 mrem /yr, and a RESRAD analysis predicts l
18 mrem /yr. A RESRAP analysis using more site specific parameters (i.e., cover thickness, Opth to groundwater) would likely reduce this dose even further.
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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 it (feet) m (meter) 0.304 8 3
0.028 316 85 volume ft' m
volume gal (gallon)
L (hter) 3.785 412 l
- / * '".[..,
APPENDIX C SAMPLE CALCULATIONS
~
1.0 EXAMPLE SITE No.1 This site contains 13 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 1-125. 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 1125 to decay to insignificant activities.
Therefore, they can be excluded from consideration. The calculated activities for the remaining isotopes are adjusted for decay.
Isotope gCj Cs 134 270 Fe 55 233 Co 60 37G 1.2 Step 2 Groundwater Pathway The total inventory for each isotope was divided by 9.1 E7 ml (91 m ) of groundwater.
3 This represents the concentration in Ci/mi of that isotope which could be ingested by a person in 1 year.
Isotone gCi uCi/ml(water)
Cs-134 270 2.9E 6 Fe 55 233 2.5E 6 Co 60 376 4.1 E 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 mremlyr 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, D mrem /yr =
(2.9E 6 uCi/mi Cs 134)(50 mrem /vrl (9E-7 Ci/ml Cs 134) 161 mrem /yr from Cs-134 C-1
g d ' '" k$.
This calculation was preformed for the remaining two isntopes and the results are included in the following table.
Appendix 8 Isotope gG.i pCi ml pCi ml.50 mremiyr m re m_yr Cs 134 270 2.9E.6 9E 7 161 Fe 55 233 2.5E.6 IE-4 1.25 Co 60 376 4.1 E 6 3E-6 68 The doses were sumnied and the result was a dose of over 230 mrem /yr. This dose exceeds the 10C mrem /yr screening level, and, therefore, this s.'e 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/cm' to determine an average concentration (activity per cml. Th s 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.
Trench Concentration =
(270 nCi Cs-134H1 E6 oCiwCd (1.6E7 g)
Trench Concentration 17 pCi< gram
=
Exhumation Concentration 17 oCi/a
=
4 Exhumatior r acentration = 4.2 pCi g p_Cj oCi/aram C
Isotone 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 pCilg Cs-134 l
1 D = 12.8 mrem /yr from Cs-134 q
C2
pf"b.
This calculation was performed for the remaining two isotopes, and the results are summarized in the following table.
NUREG 1500 Isotope p_Qi DCUoram mrem vr pCi a mrem /vr Cs-134 2.7E8 4.2 3.06 12.8 Fe55 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 uran;um 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 frorn consideration, and the calculations will be performed with the quantities cited above.
Isotope gCi U 234 SE5 U 238 2.5E6 2.2 STEP 2 - TOTAL ACTIVITY INGESTED FROM GROUNDWATER 3
The total inventory for each isotope was divided by 9.1E7 ml (91 m ) of groundwater.
This represents the concentration in Ci/ml of that isotope that could be ingested by a person in 1 year.
Isotooe ufCi uCi/mi U 234 SES 0.005 U-238 2.5E6 0.027 C-3
- 's. 'cd, This concentration was then compared to Part 20. Appendix B, Column 2, limits. These limits represent concentrations in ef fluent 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, D mrem yr (0.005 vCi mi U 234)(50 mrem vr)
(3E 7 Ci ml U 234) 8E5 mremlyr from U 234 This calculation was performed for the remaining two isotopes, and the results are included in the following table.
Isotope yCj vCi/ml App 8 uCi/mi mrem /vr U-234 SE5 0.005 3E-7 8E5 U 238 2.5E6 0.027 3E-7 4.5E6 The doses are well over the 100 mrem.yr screening level, and, therefore, this site f ails Step 2 of the screening methodology.
2.3 STEP 3 - EXriUMATION CONCENTRATION This site contains isotopes that have atomic numbers greater than 88, and, therefore, cannot be used in Step ' Since this site f ailed Step 2 and cannot be used in Step 3, this site f ails this screening methodology.
C4
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RESPONSES TO NRC STAl'F CO.\\l.\\lENTS ON Tile IIRANCil TECilNICAI POSITION 4
FOR SCREENING.\\lETilODOLOGIES FOR PRIOR 1,AND llCRIALS These responses were compiled from comments that were received on the previous sersion ot the 13TP but were either not included in this draft IITP or had an associated question which fell outside the scope of the 13TP Comments which were incorporated in the llTP are not included in this summary.
4 GENERAL COSIAIENT j
There were several comments regarding the 100 mrem /yr screening limit. There was concern that this limit was inappropriate and not consistent with other NRC guidance ti.e. a few mrem /yr,15 mrem /yr). Several commenters stated that this screening is in direct conflict with the screening level chosen for NUREG 5512, and that licensees will screen a portion of their site to 100 mremlyr and screen the remainder of the site to 15 mrem'yr.
There was a concern that a bacial site would be evaluated with out consideration for the rest 3
j of the site and that there would be public concern resulting from the perception of NRC raisine the screenine level (from 15 to 100 to allow sites to pass.
i f
Response
The scenarios used in the screening calculations overestimate the doses for a site and the actual doses produced would be a fraction of the 100 mrem /yr. Therefore, although the i
screening level is higher than that used in the past (afew mrem) the difference in the screening level is a result of the conservative screening scenario, not in the actual doses l
producedfrom the site. The staffis confident that the methodology would screen out sites which could actually prod:.:e a dose of ICO mrem /yr to the public. In addition, this screening methodology will only be usedfor sites where the burial is the only source of residual contamination. There will be no other contributions to the public dose from sources on the site other that produced from the burial ground.
The use of this limit could cause a public perception issue and result in questions about why this level is used here but lower levels (i e.15 mremlyr) are used at other sites. There are many different types of sites and many different uses for screening tools. One screening tool.
and/or one screening level, may not be appropriate for all sites. NRC has developed several e
different screening techniques, all of which were developedfor use in specific circumstances.
One of these tools is intended to be used during the decommissioning process to evaluate the potential doses from residual activity for an entire site (soils, and buildings) and has a screening level of 15 mremlyr but requires more site-specific information. This on-site burial methodology has been developedfor smaller sites which do not have site specific information
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available. Because there is little site in/iirmation, the u reenure tool must he conwnatise
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enough to be applicable to a majority ot the uret ihmeter. the wreening lesel nunt he hiqh
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1' enough to allow some sites, which do not pose a rid to the public to be wreened out..tlore i
site specific information would be required to reduce the screening level to 15 mremiyr. 1his may not be cost effectiveJitr these smaller sites.
1 I'
- l. TINS CO.\\l.\\lENTS Comment:
[The use of 100 mrem /yr..l... may also be in violation of Part 51, which appears to require an environmental assessment for such actions that may result in a dose exceeding a few mrem.
Response
There is no such threshold in Part 51. Part 51 would be applied to the specilic licensine action that wouldJiillow the use of the methodoiney, not to the methodology itsell Comment:
The connection between an individual's water consumption of 41 m' in a year and 2 liters / day is not clear. It is not immediate.ly clear that consumption does not mean drinking.
and this should be pointed out e.xplicitly. In any case, the 2 liters / day figure is not needeu because the method is based on the concentration in the 91 m', regardless of how much water the person drinks, it should be deleted to avoid confusion.
Response
The ingestion dose is calculated using 10 CFR 20 Appendix B Table 2 Cohann 2 e))Inent release criteria for water. The dose associated with these release limits was developed based on ingestion of 2 liter /dayfor an adult individual. Although the methodology does not require the licensee to calculate a concentration or a dose using 2 liter / day, it is used in the dose calculation indirectly and the reference was left in the BTP.
i i
l Comment:
The concentrations in Appendix B give doses of 50 mrem /yr to adults, but the tables include an allowance for exposure of other than workers (e.g. members of the general population, that include children) and the tables are actually calculated on the basis of 100 mrem /yr to these members of the public. Doses to children from ingestion at the concentrations in Appendix B result in doses that may be higher than 50 mremlyr. For example, the doses from ingestion of tritium or "C by a 1-year-old are about 1.5 times the doses to adu!ts.
Other isotopes show greater differences (See ICRP Publications 56. 67, and 69). We therefore suggest that the concentrations in Appendix B be regarded as delivering a dose of 100 mrem /yr to a member of the general public. We suggest changing the 50 mremlyr in the numerator to 100 mremlyr.
.pvu, 1
One limitation to this approach is that it is based primarily on ecmparisons to 10 Cl R Part 2
i 20 numbers for adult consumption. It there is reason to espect that the sne may be released i
for use, for example as a school, applicable considerations and adjustments to the calculations should be pursued.
Response
i Appendit B limit.s were developed to be applicable to the average member of the public. It is adnouledged that dilli> rent age groups are afi'cted in Jilli> rent ways by esposure to radionuclides. However, this was taken into account in the development of 10 CFR 20 i
Appendix B.
Therep>re the screening level was left at 100 mremiyr.
Comment:
j Application of Step 3 is not clear. The source of the B values in the equation should be clearly stated, namely Table B-2 of NUREG 1500. We suggest that the appropriate sections of Table B-2 he made part of this BTP. if the table is not too long.
4
}
Response
l'he application of Step 3 and the reli>rences to NUREG-1500 have been clarified ahhoueh the ~B values" have been changed to 'A values" and now reli>rences fishle A-l. A copy of
}
Appendix B has not been included because ofit's length.
i i
Comment:
Another thing you may wisn to consider is that in screening situations such r.; this, each j
higher level of screenin, represents an elaboration of the previous level, using more detailed l
site specific data to make a more realistic estimate. Your proposed method deviates from l
this practice in that it goes to a different scenario at the second level. We believe this may be hard to justify, since the second method is no more site-specific than the first.
Response
Thefirst calculational step involves a resident drinking groundwaterfrom the site. The i
second step of this screening requires the licensee to calculate a screening dose using i
NUREG 1500. This NUREG uses a residential scenario, assuming an individual lives on the site, eats food grown on-site and drinks waterfrom a well on-site.
Therefore, the second step is a no > refined screening scenario than thefirst step. The second step is more site j
j specific than thefirst step because it requires the use of the actual trench dimensions and the i
j actual volume of soil and waste in the trench.
1 i
i Comment:
1 l
The document repeatedly claims that the screening methodology is conservative. We suggest that such statements be limited to a separate discussion addressing the conservative nature of 1
J 3
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1.:
4 1
)
the approach. A brief explanation supporting such claims should be provided in support ot the need for future claritication.
1 i
Response
In response to this conunent, some of the conservative language was modified, however, the
)
general approach was not changed. Iliere were several other conunents wlich stated that 4
there was not entmgh emphasis and explanation of the conservatism in this method. The l
modtjications to the language attempted to satisfy both concerns.
i j
REGION III i
Comment:
l On page 6. there is a note that Step 3 cannot be used for isotopes with atomic number of 88 or higher due to the current revisions to NUREG-1500. I suggest we state that for sites with j
I atomic number of 88 or higher that can not pass Step 2 that they may want to request a time i
extension until NUREG-1500 has been revised so they can try to pass Step 3. I don't think j
it appropriate for someone to spend 10's or 100's of thousands of dollars remediating a site needlessly because we are revising one of documents. if it is powible they may not have to.
j j
Response
l The staff did not place this statement in the BTP because of the uncertainty associated wah the revision to NUREG-1500. the iruent of the timeliness rule is for licensees to address these sites sooner, rather than later. If a licensee has a site which contains isotopes with SS or higher and it does not pass Step 2. then it must work with NRC on a case-by-case to evaluate the potential Jose ey some other manner than this screening. If a site does not pa.u l
the screening, it will not at.tomatically be required to be remediated. The licensee and NRC l
will work with more site specific information to evaluate the potential risks posed by the
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burial.
1 Comment:
We suggest that the screening model include an estimate of the average annual dose over a j
generation (i.e., assume that the inventory takes approximately 30 years to fully enter the i
aquifer). The results of this calculation would still represent very conservative estimates of possible ingestion exposure, but will be less likely to result in misinterpretation of the results.
?
Response
Reducing the estimated screening dose for the ingestion pathway would no longer make the ingestion pathway the most limiting pathway. Several calculations were performed to demonstrate that the ingestion pathway in the most limiting pathway based on Step 2 scenario. If this dose is reduced by a factor of 30 the ingestion scenario will not be the most limiting and in some instances will produce a dose smaller than that produced in Step 3. For i
4
..g, r%
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4 e\\ ample. ist the HTP it was shomn that unne 270 pG of Cv134 produced a u reenine d<ne of Inl mrem yr in Step 2.13 mrem ;r m Step 3. and 7 mrem \\ r urine RESR.lly.1hhoueh thn is a nmqh calculation, if the Step 2 weertion June is redm ed hv a factor of 30. the done would be approximately 5 mremor. Tlus results in Sten 2 screening doses hemg lower than Step 3 screenine and the inhalation and etternal pathuar r sould have to be evaluatedfor each site.
REGION IV CO.\\l.\\lENTS Comment:
An addendum could be added to the methodology which would treat the burial site's inventory of C-14 and 11-3 separately, and would compare these concentrations to the 0.05 micro curie / gram release criteria specified in 10 CFR 20.2005 for disposal of liquid semtillation medium and/or animal tissue. On N1 arch 11.1981. the NRC regulations were amended to exempt specific types of biomedical waste containing II-3 and C 14 The i
precedent we believe. for authorizing the 0.05 microcurie' gram concentrations of 11-3 and C-14 discarded without regard to its radioactise compenent has been established. We awume that very careful evaluations were made by the NRC when authorizing the remosal of control
]
over this type of disposal. We would urge that this. or a similar type of evaluation be made in support of the above suggested increased concentrations
Response
The staff reali:es that if a site contains the matimum quantity of C-1J allowed to be disposed ofin one year, the site will not pass step 2 of the screening. Ilowever, depending on the j
concentration of C-14 in the trench soils the site may pass Step 3. The concentration in 10 CFR 20.2005 was developed based on incineration of materials containing these isotopes and can not be applied t0 burials in a generic method.
Comment:
Review of waste streams in some former 10 CFR 20.304 burials suggests the existence of unspecified materials in unspecified waste forms. In using the screening methodology, if the amount indicated is a small fraction of the total amount could this portion of the waste stream be disregarded in the screening methodology? If the existence of an unspecified waste type or form is indicated in a records review. should all such cases be sent to NNISS in a technical assistance request (TAR)? Should disposal involving any quantity of mixed waste, as defined by the EPA. be forwarded to NNISS under a TAR? If so, before sending TARS to NNISS, must the licensee conduct sampling?
Response
Burials with unique circumstances may need to be evaluated on a case-by-case basis. This could include sites containing mixed waste or other unknown waste streams. These evaluations should be coordinated with NMSS through I'ARs. in accordance with existing 5
.,.n. v w,.
procedures.
J Comment:
Language contained in 10 CFR 20.304(b) includes as covered, all licensed and other radioactive material, llased on this, one could assume that waste streams containing radioactive accelerator produced material, uranium, special nuclear material. or NORM will be included in the screening methodology. Should these radioactive materials be included in the assessments?
Response
All radioactive materials placed in the burial under 10 CFR 20.304 or 20.302 shmad be considered during the screening.
Comment Section 4.3.2 Step 1 - Records Review. specifies that the licensee should carefully review the activity and types of isotopes disposed of at the site for the specified time 10 CFR 20.302/20.304 disposal activities occurred. All available and relevant records should be used 4
to develop a complete inventory for the burial area. It is further recommended that the total activity of each isotope in the entire burial site should be determined and converted into microcuries (pCi). We suggest that any isotope, which has decayed 10 half-lives since the time of emplacement, need not be included in the screening methodology. This will greatly simplify the screening methodology and calculations.
Response
The staff agrees with your recommendation that this would simphh the calculation.
However, if the initial inventory is large enough, there would still be some activity remaining after 10 half-lives. To ensure all activities are addressed, this method was not added to the BTP. However, radioactive decay is accountedfor in this methodology and example. If sufficient decar hat x.rred, the calculations will be greatly simphfied.
Comment:
LLWM has determined that the maximum quantity allowed to be buried in the trenches under the rescinded 20.304 cannot be used as an estimate for the quantity of isotopes in the trenches. We concur with LLWM's assessmcat that there may be instances in decommissioning where disposal limits were exceeded unintentionally. We understand that without some evidence (i.e., disposal records) that burial guidelines were followed, that the licensee and NRC can have little confidence in the trench inventory. However, if a docket file search does not produce inspection evidence that the licensee exceeded the allowable burial limits of radioactive material under 10 CFR 20.304, it is our opinion that we can put a degree of trust in their records. We believe that NRC and licensees can review the docket files and determine the maximum quantities of material disposed of during this interval and 6
4
i
' -w h v
.^
l make appropriate calculations and assumptions to decide whether the screening methodolog) will pass or fail the site. We also contend that alternatise esposure scenarios may be accepted as appropriate when submitted by a licensee and based on the site specific factors that affect the likelihood and extent of potential future exposure to residual radioactivity. We must have some degree of trust in our records and those of the licensee, or the NRC could i
be overwhelmed with sites requiring remediation. Further, decisions on remediation should l
also consider risks associated with other non-radioactive hazardous materials which may be buried such as toxic chemicals and hiohazards.
Response
The regulations in 10 CFR 20.304 did not re<pdre the licensee to nonly NRC that a burial was planned or performed, therefore there were no requirernents for NRC to inspect the j
disposal of waste as it was placed in the trenches. The docketfile is unlikely to contain j
inspection reports concerning the burials, at least not reports with su)]icient detail that could l
be used to estiinate trench inventory. The staff does agree that the licensee and NRC staff f
could determine the inventory in the trenches by reviewing records provided by the licensee.
1 The statement in the BTP (cited above) referred to a site which did not have any disposal records and simply wanted to use the inatinnon quantity allowed to be disposed in Appendit C. If there were no records it would be dt))icultfor either the licensee or NRC to determine which isotopes were disposed ofin the trenches, and if Appendix C limits were not eaceeded.
j If the licensee wishes to use other means tojusufy the total inventory, or to use other j
eaposure scenarios. it can do so on a case by-case basis with its NRC contact. However.
this situation is outside the scope of this screening method and the 100 mremlyr screening criteria can only be used with the eaposure scenarios developedfor this screening.
Comment:
[The BTP]... referenced NRC draft Branch Technical Position on Site Characterization for Decommissioning Sites dated July 1992, containing a description of the type of site characterization information that could be required. Consideration should be given to attaching this document as an appendh for reference.
Response
This document has been superseded by a draft dated November 1994. Both the July 1992 and the November 1994 are considered too lengthy to attach as an appendix.
7 l
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[
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l EDO Principal Correspondence Control
' FROM:
DUE: 12/17/96 EDO CONTROL: G960884 4
DOC DT: 11/20/96 FINAL REPLY:
Paul W.
Pomeroy
, ACNW TO:
Chairman Jackson l
FOR SIGNATURE OF :
- CRN CRC NO:
Exeuctive Director DESC:
ROUTING:
SCREENING METHODOLOGY FOR ASSESSING PRIOR LAND Taylor BURIALS OF RADIOACTIVE WASTE AUTHORIZED UNDER Milhoan FORMER 10 CFR 20.304 AND 20.302 Thompson Blaha Miraglia, NRR Morrison, RES DATE: 11/22/96 Jordan, AEOD Cyr, OGC ASSIGNED TO:
CONTACT:
SPECIAL INSTRUCTIONS OR REMARKS:
~
ACTON:
AEY--@
Prepare response to ACNW for EDO signature.
m DV/M Put Commissi mers and SECY on cc (shown on t
original) for reply.
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UNITED STATES NUCLEAR REGULATORY COMMISSION n
U U
ADVISORY COMMITTEE ON NUCLEAR WASTE k
WASHINGTON, D.C. 20066 s,...../
November 20, 1996 1
The Honorable Shirley Ann Jackson i
Chairman l
U.S. Nuclear Regulatory Commission Washington, D.C.
20555-0001 j
Dear Chairman Jackson:
i
SUBJECT:
SCREENING METHODOLOGY FOR ASSESSING PRIOR LAND BURIALS OF RADIOACTIVE WASTE AUTHORIZED UNDER FORMER 10 CFR 20.304 1
AND 20.302 During its 87th meeting, October 22-23,
- 1996, the Advisory Committee on Nuclear Waste (ACNW) reviewed staf f plans relevant to 8
the decommissioning of sites in which radioactive waste had been buried as authorized under former 10 CFR 20.304 and 20.302.
In addition to receiving information on the history and background leading to the development of the screening criteria to be promulgated in a branch technical position (BTP), the ACNW was briefed on related agency rules and information notices.
The BTP, j
which was not available for ACNW review during its 87th meeting, will be finalized when more directly related field experience is obtained and public and licensee comments are evaluated.
These screening criteria are directed at potentially hundreds of
- onsite, non-reactor burial locations that will require an f
evaluation or screening process to determine if further remediation is required.
The NRC staff has prepared a simple, conservative e
three-step method to evaluate the risk from these burial sites:
1.
review burial records, 1
2.
estimate the dose from ingestion of the total inventory in groundwater (a conservative approach), or 3.
estimate the dose to a resident farmer from all pathways.
If the estimated dose from Step 2 or step 3 is less than 100 mrem /yr, no further site work is required, and the site can be released for unrestricted use.
The ACNW agrees with the NRC staff approach.
The ACNW offers the following comments and recommendations:
1.
The NRC staff does have a responsibility to assure itself through independent audits and reviews that the risks are
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reasonably assessed.
These reviews are especially important
- where, for example, the burials may include greater than anticipated inventories of uranium; disposed wastes that contain isotopes, such as chlorine-36, which at the time of disposal were not perceived to be a significant problem; the location and distribution of wastes are imprecisely recorded (or, in some instances, unrecorded).
2.
In those situations requiring review and approval of the NRC staff prior to final site decommissioning, the staff must be certain that the risks and contributors to the risks are understood, and should not rely only on an assessment of how the input parameters were either measured or calculated.
3.
We concur with the staff's position that licensees not be allowed to use Step 3 of the BTP screening process for isotopes with atomic numbers of 88 or higher due to the lack of confidence in the dose equivalent factors in the current version of NUREG-1500,
" Working Draft Regulatory Guide on Release Criteria for Decommissioning: NRC Staff's Draft for Comment," August 1994.
The ACNW recognizes the benefit in providing a simple, relatively straightforward approach to resolving the problems extant from these past burials.
We note that this issue might provide the Commission with an opportunity to advance $ts risk-informed, performance-based decision-making process.
The ACNW anticipates further discussions on this specific issue with the NRC staff as the staff completes its evaluation of public/ comments and gains applicable field experience.
Further, the ACp intends to explore the compatibility of various screening criteria and methodology currently used by the NRC in the decommissioning process.
Sincerely m
Paul W.
Pom Chairman
Reference:
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.
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