ML20199A994
| ML20199A994 | |
| Person / Time | |
|---|---|
| Issue date: | 05/19/1986 |
| From: | Justus P NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Knapp M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-39 NUDOCS 8606160294 | |
| Download: ML20199A994 (6) | |
Text
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!Ws/f (W-39) DJBrooks MAY 191986 WGT r/f TJohnson WM-39/86286 Wss r/f Albrahim 1
REBrowning MYoung MBell JOBunting PsJustus MEMORANDUM FOR: Malcolm R. Knapp, Acting Chief PDR WMLU JValdes & r/f JSTrapp FROM: Philip S. Justus, Acting Chief DGillen WMGT KCJackson MFliegel
SUBJECT:
REVIEW 0F THE DOE DOCUMENT TITLED " ALTERNATE SITE SELECTION PROCESS FOR UMTRA PROJECT SITES" In response to TAR 86286, we have completed our review of the subject document.
Based on this review, we conclude that whereas the document provides a general description of an alternate site selection process, it does not present an adequate procedure for selecting technically sound alternate disposal sites.
The reasons for this conclusion are documented in the attached comments along with specific recommendations on suggested corrective changes.
This review was coordinated by Jose Valde's (geology) with input from Michael Young (groundwater hydrology), David Brooks (geochemistry), Terry Johnson (surface water hydrology), and Abou-Dakr Ibrahim (seismology). If you have any questions regarding our review, please contact Mr. Valde,s.
Phili S. Justus Acting Branch Chief, WMGT
Enclosure:
As stated 8606160294 e60519 PDR WASTE WM Record File WM Project N Docket No.
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GENERAL COMMENT
S A) The present document is not rigorous or detailed enough to meet its stated purpose of providing procedures for selecting technically sound alternate disposal sites. _In this regard, the following general deficiencies in the document have been identified:
- 1) Though it is stated that different factors will be " considered," no .
description of the methodology that will be employed to consider these factors is presented. In its'present form, the document is merely an
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outline of the process by which alternate sites will be chosen and does not include a description of the procedures that will be used. The revised document should either include or provide references to such procedures.
- 2) Exclusionary criteria are presented without providing any basis or justification for their selection. The revised document should clarify the rationale used for selecting the specific guidelines presented.
B) The staff considers that the site selection process should lead to at least the following conclusions:
- 1) the alternate site (s) selected are among the best that can reasonably be found and; (2) the alternate site (s) are better/ worse than, or as good as, the existing site.
NRC suggests that reaching these conclusions become a part of the UMTRAP alternate site selection process.
SPECIFIC COMMENTS Figure 1.1, Page 2 It is stated in section 2.1 (pg. 3) that "it should be recognized that the ASSP
[ Alternate Site Selection Process] (see Figure 1.1) is one of iteration. That is, [if no suitable sites are found] the evaluation process [will] be
L WM-39/JV/5/6/86/ ALT repeated." Co'ntrary to this statement, however, 81gure 1.1 portrays the screening process as a unidirectiorfal sequence of steps with no loops for iterations. Figure 1.1 in the revised document should reflect that iterations can occur in the screening process. (Also see comment on Section 2.3, pg. 6).
Section 2.2, Page 3 A) It is stated that Table 2.1 provides "the basic list of regional screening guidelines" but that these ". . . will be modified as site conditions dictate."
The NRC staff considers that to, change the rating guidelines arbitrarily from site to site would defeat the purpose of attempting to establish a systematic
- and uniform alternate site selection process. The guidelines selected should be sufficiently generic to apply uniformly to all sites under consideration.
The staff recommends that DOE revise this section to address the concerns noted.
B) It is stated that guidelines for Phase II preliminary screening of search regions "will be identified . . . from existing information and [ areas excluded based on these guidelines] will be plotted on the topographic maps." However, the document does not describe the process that will be used to locate pertinent " existing information." The revised document should describe the methodology that will be used by DOE to ensure that all relevant information has been obtained.
Table 2.1, Pages 4-5 A) The bases for selection of the guidelines (including numerical values) cited are not stated and the definitions provided tend to be equivocal. For example, in addition to being deficient in its interpretability, the definition of
" slopes and escarpment" includes specific numerical values that are cited without stating the reasons why these values are considered significant. As another example, the definition of " erosive soils" is ambiguous as it does not include a justified range of soil erodibility factor values that would be considered unacceptable for a candidate area. DOE should provide the rationale used for selecting specific criteria and clarify the meaning of the definitions i presented.
B) The recharge and isolation of sole source aquifers is identified as one of the guidelines for rejecting or accepting areas within a region for possible alternative disposal sites. The definition of the screening guideline for
" aquifers" is given as: " areas directly overlying, or recharge areas for, l
sole-source aquifers or aquifers containing potable water; unless . . . those l
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W.1-39/JV/5/6/86/ ALT aquifers are hy'drologically isolated . . . by low permeability geologic formations." However,' in many areas within a region there may not be
' sufficient information available to reach a conclusion on confinement or i
potability. The document does not indicate how areas will be classified if
( sufficient information is not available, i.e., will the area be included for
.further detailed investigation during site selection or will it be eliminated as unsuitable? DOE should indicate how they will deal with the situation of-inadequate data with regard to the aquifer system.
4 C) According to the definition of the screening guideline for " aquifers", areas that are located above " potable" groundwater supplies will be excluded. ,
However, the meaning of " potable" water is ambiguous as the concentration of j
constituents that determine potability can vary from state to state. The staff recommends that DOE explicitly define how the term is being used in the document.
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! D) No guidelines for chemical attenuation or availability of suitable rock for j riprap are included in the table. Given the primary importance of these
! parameters, the staff recommends including and adequately defining criteria for the same in the list of regional screening guidelines.
- Section 2.3, Page 6 The need for Phase III of the screening process is not apparent. As presently structured, Phase III involves selecting three candidate areas based on reexamination of the literature and application of extremely subjective criteria (Table 2.2) very similar to those employed for Phase II area-screening. The staff considers that a more efficient approach would be to eliminate Phase III and divide Phase IV into two steps
Step 1. This step would involve the preparation of " factor maps" for the study areas not eliminated during Phase II. The data for the maps would i De obtained from the available literature and rated in accordance to the criteria in Table 2.3. The result of this exercise would be maps of the study areas displaying composite rankings that could be easily contoured to produce " suitability maps." Based on such maps, a minimum of three sites within the most suitable areas would be selected for further investigation and unsuitable areas eliminated from further consideration.
j Step 2. This step would consist of rating the three or more sites selected in step 1 by applying the criteria in Table 2.3 to the i; site-specific field data obtained for each. The procedures applied to collect the appropriate field data should be presented or adequately l referenced in the document. 1 DOE should consider revising the document to reflect these recommendations. l 3
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Table 2.3, Pages 8-15 ,
A) Many of the criteria specified for rating the different factors in the table are not specific or quantitative enough to allow reproducible results to be reached by independent site-raters. For example, in rating chemical attenuation (factor #13), the significance of " low," " moderate," and "high" clay content is subjective and would be subject to different interpretations by
- different individuals. This problem would be solved by specifying numerical i ranges of clay content for each rating category based on reasonable and adequate justifications. As another example, in rating conflict with mineral resources, the interpretation of." serious," " moderate," and " minor" conflicts.
is very ambiguous. Application of the principles of a resource / reserve i
classification scheme similar to that outlined by the U.S. Geological Survey and the Bureau of Mines (U.S. Geological Survey Circular 831, 1980)
- - would minimize the ambiguities noted. The staff recommends that DOE revise the table to address the concerns noted.
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- 8) A particularly desirable characteristic for any site is its proximity to a source of good quality-rock for riprap. The staff recommends including and j adequately defining this criterion in Table 2.3.
I C) Though the presence and quality of groundwater is included as a
" hydrological" rating factor, the use of the resource is not considered.
, Presumably, sites that overlie " potable" groundwater would have been excluded l in Phase II. However, there are several uses of non potable drinking water that may affect the safety of the public and the environment. For' example, water that is not adequate for drinking by humans may be fine for livestock
- watering or irrigation. Contamination of water used for these and other purposes will eventually impact the public health. The staff recommends, therefore, that DOE introduce a factor into Table 2.3 that deals with the situation of non potable groundwater use.
4 D) Factor #10 in the site ranking matrix deals with the relative permeability of soil and/or rock formations. Although permeability is an important characteristic that affects the ability of the porous medium to transmit fluid,
! the staff takes issue with the use of the term " relative permeability." As
' defined in the Dictionary of Geological Terms (American Geological Institute, 1976), the term is commonly used in reference to: "The permeability to one fluid phase when two or more fluid phases are present in the porous medium."
Thus, as used in the table, the term can be misleading given that it is unlikely that fluid phases will be considered in characterization. The staff t
j therefore suggests that DOE use the term " hydraulic conductivity" in describing j
characterization of rock properties rather than fluid properties.
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_.. 3, 5-a E) Though -it is stated (section 2.
based in part on the geotechnical r,4, p.
anking 6)' that the matrix'used by criteria presented are the Colorado Geological Survey (CGS), many modifications hate been made to the latter without technical justification. For example, in evaluating surficial materials thickness as a factor, the CGS rating matrix gives the highest ("best") ranking to sites that are underlaid by clay or silty clay _ or by 0 to 2 ft, of other types of surficial material; sites underlaid by more than 20 feet of non-clayey deposits are given the lowest ranking for this particular factor. By contrast, in evaluating surfietal materials thickness as a factor (factor #2), the DOE rating matrix would assign the highest ranking to sites having 20 or more feet of any' type of surficial sedinents. As another example, the CGS rating matr.ix rates the land slope factor'(factor #1) as highest for sites with slopes of 2%
to 5%, thus striving for a compromise between the requirements for slope stability and minimizatidn of on-site ponding. The DOE rating matrix, on the other hand,:would. rate the land slope factor as highest for sites with slopes of 2.5% to'0%. The' bases for selection or modification of specific criteria should be presented _in the revised document.
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F) The ranges of distances to be rated iii evaluating the hazards to a site from the " nearest]' seismic risk capable fault",(factor #4) should depend on the magnitude of'the earthquakes anticipated. The fixed distance ranges specified in the table may not be adequate in all cases. For example, an earthquake of magnitude 6.5 or greater may pose significant hazLrds to a site 20 km away.
The staff recommends modifying this rating ~parameteF'to be dependent of earthquake magnitude and shortening the term " seismic gisk capable fault" to
" capable' fault." -
G) In rating the "present erosion / depositional environa'nt" e (factor #6) the highest ranking is given to sites with: "No erosion or undergoing deposition."
This criterion appears to have been adopted from the rating matrix used by the Colorado Geological Survey. It should be emphasized, however, that the rating matrix used by the Colorado Survey nasLdesigned to select sites for below grade disposal (i.e., burial) of tailings. By contrast, the DOE's rating matrix is intended to select locations for above ground, disposal of tailings piles.
Given the importance of maintaining drainage, ditches around such piles free of sediments and debris, it is questionable whether sites located in depositional settings should be given a high ranking._,The staff recommends revising this ranking factor to reflect the concern nbted. .
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