ML20035B149

Submits Results of Review of Draft Protocol for Th-230 Cleanup/Verification at Umtrap Sites,Transmitted Via DOE .Basic Principles of Proposed Protocol Compromise Reasonable Approach.Detailed Comments Encl

ML20035B149
Person / Time
Issue date:	03/23/1993
From:	Surmeier J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Chernoff A ENERGY, DEPT. OF
References
REF-WM-39 NUDOCS 9303310237
Download: ML20035B149 (4)

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Mr. Albert R. Chernoff, Project Manager '

j Uranium Mill ~ Tailings Remedial Action S

Project Office U.S. Department of Energy

~i Albuquerque Operations Office P.O. Box 5400'.

MAR 2 3 '1993 l

Albuquerque, New Mexico 87115

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Dear Mr. Chernoff:

f We have reviewed the Generic Protocol for Th-230 C1'eanup/ Verification at i

Uranium Mill Tailings Remedial Action (UMTRA) Project Sites transmitted by the l

Department of. Energy's letter dated February 26, 1993. The staff considers j

the basic principles of the proposed protocol to comprise a reasonable approach. However, the narrative form of the protocol does not present'a-l clear, step-by-step approach for establishing thorium cleanup requirements.

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The present narrative form could lead to uncertainties 'in the future 1

applications of the protocol. The document should be reformatted to include'~a j

step-by-step / decision tree procedure.

In addition, there are a number of statements in the protocol that require.

l further justification. For example, a depth of 8 feet is set as'the point where the basis of the standard will change from the projected Ra-226 concentration in 1000 years to the estimated radon progeny concentration-in'a i

hypothetical residence. The basis for this selection of 8 feet should be

.i discussed.

Our detailed comments are enclosed. We would be available to meet with your staff for additional discussion of the comments to facilitate their resolution.

If you have any questions regarding our review, please contact me l

at FTS 8-301-504-3439, or the Nuclear Regulatory Commission Project Manager, Elaine Brummett at FTS 8-301-504-2533.

l Sincerely,

$134ED F John J. Surmeier, Chief-Uranium Recovery Branch Division of Low-Level. Waste Management

_t and Decommissioning Office of Nuclear Material Safety and Safeguards 1

Enclosure:

As stated

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NRC COMMENTS ON THE GENERIC PROTOCOL FOR Th-230 CLEANUP / VERIFICATION AT UMTRA PROJECT SITES GENERAL l

t 1.

The present narrative form could lead to uncertainties in the future applications of the protocol. The document should be reformatted to include step-by-step procedures, as well as the basis for decisions that may need to be made. The procedures should always start with the most conservative assumptions, and then, if appropriate, work to less-

.i conservative assumptions giving reasons why the more conservative are

.l unreasonable.

2.

The protocol should clearly separate the procedures for~ establishing l

Th-230 supplemental standards from the procedures for verification of cleanup.

l 3.

The Department of Energy (DOE) should indicate that this protocol will-be used at any site undergoing cleanup and verification after March 1993.

INTRODUCTION 4.

The lead pt: agraph or the introduction should include discussion of. the supplemental standard regulation that requires cleanup criteria for radionuclides other.than Ra-226.

5.

While 42.7 pCi/g of Th-230 will decay to 15 pCi/g Ra-226 in 1000 years,_

65% of the current Ra-226 will also be present in 1000 years. The1 equation takes this_into account, but the wording in this section should make this point.

l GENERIC PROTOCOL 6.

The first part of the first sentence incorrectly states that the~ rate of-ingrowth of Ra-226 from Th-230 is determined by the rate of decay ofl i

current Ra-226, and overall, this first-paragraph is confusing.

j Therefore, the following wording is suggested:.

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In general, the supplemental standard for Th-230 cleanup will be such ~

l that the soil Ra-226 concentration in 1000 years'will not exceed the l

Environmental Protection Agency standards. Because the 1000-year Ra-226 i

level is dependent upon the residual Ra-226 (not yet decayed), plus the Ra-226 resulting from the decay of Th-230, the Th-230 cleanup level for a -

grid will be based on the verification level of Ra-226 for that grid.

Therefore,-if 1 pC1/g (net) Ra-226 remained in a subsurface grid, the l

Th-230 could not exceed 41 pCi/g (net).

If the verification Ra-226' level-l was 14 pCi/g (net), then the Th-230 could not exceed = 15.5 pCi/g (net).

When original Th-230 concentrations are equal to, or less-than, Ra-226 concentrations'in the sa' me 15 cm layer sample, no additional: cleanup ~ of Th-230 is necessary since the supplemental standard will be; met' through j

the normal cleanup of Ra-226.

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Enclosure L

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l 7.

00E should provide justification for choosing a depth of 8 feet as the point at which the basis of the supplemental standard will change from Ra-226 concentration (from'Th-230 decay plus residual Ra-226) in soil, to radon progeny concentration in a residence.

8.

The step-by-step procedure (see Comment 1) should make it' clear how partial basements will be accounted for since a condition of " shallow groundwater" should consider any probable foundation level, not just sl ab-on-grade.

I PROTOCOL FOR CONTAMINATION AT DEPTH 9.

The fIrst sentence implies that 42.7 pCi/g is a Th-230 cleanup standard, i

DOE should indicate that this concentration only applies if the Ra-226 level in that grid is background.

10. This section discusses assuming 8 feet less fill in " areas where basements are feasible." Additional explanation should be provided on i

the factors, such as groundwater levels and standard construction practice in the area, that determine the feasibility of basements.

11. The procedure should explain how the groundwater level is determined (for example, annual average or lowest level in 5 years).

12. The DOE cover letter indicates that, in the absence of site-specific parameters, generic default parameters would be used in RAECOM analyses i

associated with the Th-230 protocol.

Instead, this section should indicate that when site-specific data is not available, DOE will use reasonably conservative parameters that consider the expected site conditions.

PROTOCOL FOR CONTAMINATION IN THE SATURATED ZONE

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13. This section should include justification (or a reference) for the statement that the diffusion coefficient decreases dramatically as soils approach full saturation.

14. The last sentence in this section states that excavations will halt at the level of the saturated zone. The protocol should require an ALARA analysis that compares the dose projection for the worst-case exposure scenario to the estimated remediation cost. The analysis should consider the estimated long-term (200-year) water table level.

In general, DOE should consider excavation one-foot-deep into the saturated zone if pumping the water or other controls are reasonable.

VERIFICATION SAMPLING

15. This section could indicate that the Processing Site Characterization Report, or similar data, will be reviewed to identify areas of elevated Th-230 where the Th-230/Ra-226 ratio exceeds a specified and justified number.

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16. DOE states that ore storage areas will not be sampled. DOE should i

provide justification to support the position that Th-230 does not leach below such areas.

17. This section of the protocol must discuss what will be done when any of the verification grids exceed the Th-230 criteria. This should include:

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Plans for determination of the extent of the elevated Th-230 area. -

We suggest that the protocol include analysis of Th-230 in grids j

adjacent to the grid with the elevated Th-230. This is possible even after the area has been backfilled because the remaining soil sample from each grid is saved until the site is certified.

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Plans for activities, such as additional cleanup or a health effect I

analysis, if DOE is not considering further remediation.

i 18.

Since some sites may have Th-230 concentrations determined by the on-site lab, DOE should provide full details (quality assurance plan, etc.) in a

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separate document for NRC review as soon as such information is available.

CONCLUSION

19. This section should be revised as appropriate to reflect changes made to the protocol in response to Comments 1-17.

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