ML20126H029
| ML20126H029 | |
| Person / Time | |
|---|---|
| Issue date: | 12/17/1992 |
| From: | Surmeier J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Chernoff A ENERGY, DEPT. OF |
| References | |
| REF-WM-61 NUDOCS 9301050042 | |
| Download: ML20126H029 (4) | |
Text
__
Albert R. Chernoff, Project Manager 3 Uranium Mill Toilings Remedial Action
- Project Office U.S. Department of Energy DEC 171993 Albuquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115
Dear Mr. Chernoff:
The U.S. Nuclear Regulatory Commission staff has completed its review of the final Remedial Action Plan (RAP) and associated documents for the Gunnison, Colorado, uranium mill tailings site. Our review indicates that there are two issues from our review of the preliminary final RAP that remain to be resolved, as well as several additional issues that have arisen from the new information in the final RAP.
The additional issues include concerns on Th-230 cleanup and verification.
NRC staff is aware that DOE is preparing a generic policy paper on thorium,-as H
a result of our ongoing issues at other sites.
Th-230 cleanup )olicy and j
procedures will be established for this and other sites, througi NRC's review and concurrence of that document.
DOE should place appropriate priority on completing the thorium policy paper, since it will be instrumental in resolving the open issues concerning thorium for Gunnison and other sites.
All of the open issues are delineated in the enclosure. We also note in the enclosure that most of our comments presented in Section 7 of our draft Technical Evaluation Report (TER) were not addressed. All issues must be -
satisfactorily addressed before we can complete our final TER and concur in the RAP.
If you have any questions regarding the enclosure, please contact me at 301-504-3439, or the NRC Project Manager, Elaine Brummett at 301-504-2533.
Sincerely, DRtGNAt. SIGNED BY John J. Surmeier, Chief Uranium Recovery Branch Division of Low-level Waste Management-and Decommissioning Office of Nuclear Material Safety and Safeguards-
Enclosure:
As stated cc:
S. Hamp, DOE, AL Distribution:
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l 1
NRC ISSVES ON THE GUNNISON FINAL REMEDIAL ACTION PLAN Draft Technical Evaluation Report Issues Remainina to be Resolved (original numbering) 9.
The radon barrier borrow material specifications and the RAIP should le revised to include an Atterberg limits test requirement on the amended material, and the frequency of testing should be specified.
Atterberg limits testing during construction should be performed on bentonite-amended radon barrier soil because the plasticity index of the soil will affect radon diffusion and cover cracking.
The Nuclear Regulatory Commission staf f has recommended testing at least once a day for cover material placement in excess of 150 cubic yards (Staff Technical Position on Testing and Inspection Plans, 1989), but the Department of Energy (DOE) has not agreed to perform such testing during construction at Gunnison.
In response to draft Technical Evaluation Report (TER) Issue 9, DOE indicated that tests for plasticity index during placement are not necessary, if the bentonite-amended soils are adequately characterized and appropriate design assumptions are made.
NRC staff does not believe that this approach provides adequate safeguards.
23.
Although NRC staff has approved the DOE generic procedure for bulk averaging of radionuclides in cobbly soil, discussion of a site-specific procedure still needs to be included in the Remedial Action Plan (RAP).
The site-specific aspects should include any modifications to the generic procedure, and discussion of the options chosen, i.e., whether tests pits or running average will be used for the statistical mass partition function, and whether grid-specific or statistical methods will be used for site verification.
Additional Issun 1.
At the bottom of page 91 of the Remedial Action Selection Report (RAS), DOE states that the bulk soil cleanup standard for Th-230 is 35 pCi/g for 15-cm thiek layers averaged over 100 sq. meters, and that this will ensure that the bulk Ra-226 levels will conform to standards for 1000 years.
This latter statement is only true if the residual Ra-226 in each grid is less than 7 pCi/g.
The Th-230 cleanup criteria should be revised to reflect this. DOE should consider determining the Th-230 cleanup level for each grid af ter the remaining Ra-226 level is known, or basing the Th-230 cleanup standard on the maximum Ra-226 that can remain.
In the latter case, the Th-230 cleanup standard would be 16.8 pCi/g, based on the maximum Ra-??S that can
- remain, i.e., 16.7 pCi/g (15 + background of 1.7).
Enclosure 1
1 l
2.
The last sentence on page 91 of the RAS is misleading.
It refers to I
supplemental standards being applied to bulk Th-230 in cobbly soil in excess of 35 pC1/g, similar to the standards applied for the Th-230 below the water table at the Riverton and above the water table at the Durango designated sites.
The 35 pCi/g level is not a generically applicable standard for cleanup of Th-230 (see Comment 1).
In fact, supplemental standards for elevated levels of Th-230 at the Durango site set variable cleanup criteria, based on the 1000-year projected Ra-226 concentration.
The upper limit was set at 42 pCi/g Th-230 with no current residual Ra-226 (above background).
Therefore, the sentence in the RAP should be replaced with a commitment to provide a site-specific rationale, if and when DOE proposes to apply supplemental standards for Th-230 that would exceed the EPA standards (projected 1000-year Ra-226 concentration).
3.
At the top of page 93 of the RAS, DOE indicates that four percent of the verification grids will be assessed for Th-230 and uranium. This is a change from the preliminary final RAP, in which DOE stated that ten percent of the grids were to be analyzed for Th-230.
Based on ongoing Th-230 issues at other sites, NRC staff considers four percent to be inappropriate for the necessary level of confidence for sites known to have elevated Th-230 concentrations deeper than the radium contamination.
NRC staff is aware that DOE is preparing a generic policy paper on thorium. Th-230 cleanup policy and procedures will be established for this and other sites, through NRC's review / concurrence of that document.
4.
Calculation 640-02-02 refers to procedures for determining depth of frost protection in the DOE Technical Approach Document. The procedures for this determination are based on a 200-year, rather than a 1000-year, period.
The EPA standards require that control of residual radioactive materials be effective for up to 1000 years, to the extent reasonably achievable, and, in any case, for at least 200 years.
DOE should provide a frost protection design that meets the 1000-year criterion, or include justification that a design meeting a more stringent criterion than they have considered in the present analysis is impracticable.
5.
Note 13 on the revised excavation plan (drawing GUN-PS-10-0212) states that the wetland areas shall not be disturbed.
In contrast, the Information for Reviewers indicates that the wetland areas will be excavated.
Information should be provided to clearly show what areas are officially designated wetlands. Justification for not excavating contamination from any areas that are not official wetlands also should be provided.
6.
In Specification 02228, Section 3.2.B.2, DOE indicates that a minimum of five percent bentonite by weight will be added to the radon barrier material. However, in Calculation 640-05-03, page B-3, DOE states that "To realize the minimum of five percent, the actual percent bentonite added will be substantially higher." To account for this fact, DOE should revise the Specification to require addition of a minimum of six percent bentonite (an increase of one percent would be normal engineering practice to ensure the design five percent is met).
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I NRC COMMENTS ON THE GUNNISON FINAL REMEDIAL ACTION PLAN 4 ?
Most of the comments on the preliminary final RAP, that NRC staff presented in Section 7.0 of the draf t TER, have not been addressed.
These mainly concern errors or omissions in the RAS, RAP attachments, RAIP, and several calculations, in the RAS, the last paragraph on page 16 indicates that the closest fault is within 1.7 km of the site.
This is probably a typographical error since page 50 of Attachment 2 states that the fault is 2.7 km (1.7 miles) from the site.
W 3