ML20058P572

Forwards Comments on Pacific Northwest Labs Draft Rept, Application of Infiltration Methodology to Hypothetical LLW Disposal Facility

ML20058P572
Person / Time
Issue date:	10/12/1993
From:	Bell M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Silberberg M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
References
REF-WM-1 NUDOCS 9310250081
Download: ML20058P572 (2)

Text

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i' OCT 121993 i

HEMORANDUM FOR:

Melvin Silberberg, Chief Waste Management Branch Division of Regulatory Applications Office of Nuclear Regulatory Research f

FROM:

Michael J. Bell, Chief Low-Level Waste Management Branch Division of Low-level Waste Management and Decommissioning Office of Nuclear Material Safety l

and Safeguards

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SUBJECT:

REVIEW 0F PACIFIC NORTHWEST LABORATORIES' DRAFT REPORT ENTITLED " APPLICATION OF AN INFILTRATION METHODOLOGY TO A s

HYPOTHETICAL LOW-LEVEL WASTE DISPOSAL FACILITY" AL Enclosed are comments on the subject report as requested by your October 1, 1993, memorandum. Overall,~ the~ report appears to be well written and the analyses quite good. The information provided in the report will be useful in supporting the approach that we are recommending in the draft Branch Technical Position on Performance Assessment for Low-level Waste Disposal Facilities.

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We look forward to discussing the contents of this report with the author, Dr. Meyer, on October 20, 1993.

If you have any questions regarding the enclosed comments, please contact Mark Thaggard on 504-2568.

(Original Signed by

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Michael J. Bell, Chief Low-Level Waste Management Branch Division of Low-Level Waste Management and Decommissioning Office of Nuclear Material Safety and Safeguards t

Enclosure:

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s -m COMMENTS ON:

APPLICATION OF AN INFILTRATION EVALUATION METHODOLOGY 1

TO A HYPOTHETICAL LOW-LEVEL WASTE DISPOSAL FACILi1Y i

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1. Since the Blackville and Wagener weather stations are more than 20 miles apart, some type of correlation analysis should be performed to demonstrate the applicability of using the Wagener data.

2. The report does a good job of pointing out some of the difficulties and i

problems with using daily rainfall data forTthTs type of analysis; however, stating that such data is of limited value is too broad of a conclusion.

Daily data can be used for this type of analysis if certain assumptions i

are made concerning how it is distributed over a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. The author, in his December 14, 1992, report, show clearly how such assumptions can be made.

Results in the December 14~~ T992, report, where the author i

distributed daily rainfall over a limited number of hours, are very similar to the results reported in this repoit nsing hourly data.

3. A different scale should be used on Figure 10. The author's point is almost lost due to the small scale.

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4. In his comparison between the UNSAT-H and HELP models, the author should provide more information on the parameters selected for the HELP model.

I Nichols (1991) showed the HELP model to be conservative, in terms of estimating drainage, in comparison to the UNSAT-H model; this is the opposite of what is being shown by the author's analysis.

The author's reported evapotranspiration value from the HELP analysis appears questionably high.

In our analyses with the HELP model, in which our results agree quite closely with those reported by the author for the UNSAT-H analysis (i.e., using daily data), we found the HELP model to be very sensitive to the evaporative depth used.

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Reference:

Nichols, W. E., " Comparative Simulations of a Two-Layer Landfill i

Barrier Using the HELP Version 2.0 and UNSAT-H Version 2.0.

Computer Codes," PNL--7583, Pacific Northwest Laboratory, Richland, Washington, January 1991.

i Enclosure s

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