ML20236E049
| ML20236E049 | |
| Person / Time | |
|---|---|
| Issue date: | 03/20/1989 |
| From: | Starmer R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Thomas Nicholson NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20236E052 | List: |
| References | |
| CON-FIN-B-2934, REF-WM-3 NUDOCS 8903230424 | |
| Download: ML20236E049 (3) | |
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gR 10 GB9 MEMORANDUM FOR: Thomas J. Nicholson l Waste Management Branch Division of Engineering, RES FROM: R. John Starmer, Section Leader Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS
SUBJECT:
COMMENTS ON PNL LETTER REPORT NO. 1:
7 SIGNIFICANT FACTORS AFFECTING INFILTRATION 1
In response to your request dated February 28, 1989, my staff and I have reviewed PNL's Letter Report No I for FIN 82934 entitled "Significant Factors l Affecting Infiltration." As you are aware, we are keenly interested in this '
project because it promises to develop an infiltration evaluation methodology, l which NRC needs to assess the performance of low-level waste disposal ;
facilities. Infiltration estimates are essential for assessing the release and j transport of radionuclides from disposal facilities. Based on our review, we 6
, suggest that the report be revised to improve its utility to NRC reviewers in l assessing infiltration through earthen covers. This memorandum summarizes our !
generalcommentsandtransmitsspecificcomments(seeEnclosure). '
Based on our review, the report should be revised to communicate with a l technical audience that is already familiar with general aspects of infiltration. As presently written, the report is too general to be of l use to NRC staff, who requires expert insight about infiltration to perform reviews of proposed disposal facility designs. The report's general scope also obscures PNL's strategy in developing the Infiltration Evaluation Methodology (IEM) by describing a wide range of factors that affect infiltration without assessing how they affect infiltration or ranking their relative significance. The report should be revised to describe how each factor influences infiltration and to assess the significance of each factor in terms of potential water flux into waste disposal units. We anticipate that such an expanded analysis will demonstrate that several of the factors are not significant and, therefore, can be eliminated from further consideration in developing the IEM. The significance evaluation will also aid PNL in refining and articulating its strategy for IEM development.
As presently written, the report is very uneven in scope and depth of coverage
, of the various factors that could affect infiltration into earthen covers.
l For example, the report describes interception of precipitation by vegetation ll h 2 h y 890320 g1M PDC ltlMI' b
!Y
427.5.2/82934/MFW/89/03
.in detail (cf. pg. 6) and devotes minimal attention to the other factors that have greater influence on infiltration _(e.g., precipitation and material characteristics). In contrast, the report effect of root zene depth on infiltration (provides useful pg. 10). These descriptions descriptions of the should be expanded in any revisions of the report to provide NRC reviewers with useful information on the factors that significantly affect infiltration into carthen materials in support of reviews of license applications and remedial action plans.
3 In addition, the report's discussion about design factors appears to be based l .on the premise that man-made materials, for example concrete and flexible membrane liners, cannot be relied upon to minimize infiltration over hundreds i of years. Although this approach may be appropriate given limited experience with the performance of these materials, the report does not present or reference a justification for the premise. We anticipate that future low-level waste disposal facilities will employ man-made materials-in covers to help demonstrate that infiltration has been minimized in accordance with NRC requirements in 10 CFR part 61.51. The report would be of more use to NRC reviewers if it presented the basis for the PNL staff position so that they could use a similar approach, and appropriate information and analyses, to judge the drawbacks and limitations of man-made materials on a case-by-case basis. PNL's IEM should be flexible enough to consider the performance of man-made as well as natural materials used to limit infiltration ;
l into waste disposal units. J 1
Finally, PNL's description of the regulatory basis for minimizing infiltration at low-level waste disposal sites should be revised to emphasize the q i performance objective in 10 CFR Part 61.41. This objective requires license j applicants to demonstrate that doses to offsite individuals are as low l as reasonable achievable and be less than specific dose limits. The technical l requirements in Subpart D of 10 CFR Part 61 are intended to help meet the J performance objectives in Subpart C. Systems analysis of a disposal facility and site may demonst' ate that relatively high infiltration rates are acceptable as long as the perfoiniance objectives are met. Consequently, the design l requirement that infiltration be minimized and the site suitability requirement '
that the site be "modelable" should be viewed in the context of compliance ;
with the performance objectives. The report should be revised to emphasize i the relationship between the technical requirements and performance objectives I in 10 CFR Part ~61 in evaluating infiltration and the adequacy of disposal unit Covers.
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4 427.5.2/B2934/MFW/89/03
_3-The enclosed mark-up provides more specific comments on the report. This review was performed by Michael Weber, Lynn Deering,- and myself. If you have any questions, please contact Mr. Weber at telephone extensicn 20565.
R. John Starmer, Section Leader Technical Branch Division of Low-Level Waste Management-and Decommissioning, NMSS
Enclosure:
Mark-up of Letter Report No.1 DISTRIBUTION:
L:CENTRAllFILES: NMSS Subject File 427.5.2 (FIN B2934)
.NMSS r/f LLTB r/f DBangart JGreeves JSurmeier PLohaus MBell RJStarmer MTokar MWeber LDeering ACNW: Yes No ,_ (SL's initials)
PDR/NUDOCS: Yes No
~-
(SL's initials)
SUBJECT ABSTRACT: COMMENTS ON TASK 1 INFILTRATION REPORT FOR RES FIN B2934 it 1 0FC :LLTD :LLTD :LLTB : : : :
s.... : ... _/_MA/ ______:_____ a_}___: ___ g_ g :____________:____________.._______ __:___. ______
RAME :MWeber :LDee ng :RJStarmer : : : :
c..._: ......_____:... ____....: ___________:____._______:___.. ______: ... _______:...._. ___.
@ ATE:03/[/89 :03//f/89 :03/2.*/89 : : : :
0FFICIAL RECORD COPY
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