ML20235V594
| ML20235V594 | |
| Person / Time | |
|---|---|
| Issue date: | 08/29/1983 |
| From: | Higginbotham L NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Nussbaumer D NRC OFFICE OF STATE PROGRAMS (OSP) |
| Shared Package | |
| ML20235U845 | List:
|
| References | |
| FOIA-87-235 NUDOCS 8707230238 | |
| Download: ML20235V594 (8) | |
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Distribution:
NMSS r/f 201.6/SN/83/08/26 M WMLL r/f SNeuder s
AUG 2 91983 PHLohaus i
O REBrowning J0 Bunting MEMORANDUM FOR: Don A. Nussbaumer, Assistant Director Office of State Programs FROM:
Leo B. Higginbotham, Chief Low-Level Waste Licensing Branch
SUBJECT:
DECOMMISSIONING PLAN FOR MAXEY FLATS We have reviewed the draft of the Decommissioning Plan for the Maxey Flats Disposal Site, Task 2:
Identification of Alternatives. Our comments are enclosed. Dr. Stan Neuder is the Branch Technical contact 1
for this project. Please contact him at 427 4607 should any questions arise, ons:inal signed by Im 13. lliggiubotham Leo B. Higginbotham, Chief Low-Level Waste Licensing Branch
Enclosure:
As stated i
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SPECIFIC COMMENTS ON MAXEY FLATS PLAN 1.
Page 2, 2nd paragraph: Commissioner Taimi identified five tasks l
(July 19, 1983 letter). This paragraph identifies 7 tasks.
1 2.
Page 3, top line: What criteria were established to determine the appropriateness and applicability of the alternatives? These criteria should be listed or referenced early in the document.
3.
Page 7, throughout:
Name of rock unit should be Nancy M_ ember.
4.
Page 10, last line: Meaning of "(4)" in that line?
5.
Page 10-11, Site History discussion: Waste disposal operations were much less orderly than that implied in this section. The trenches were haphazardly dug. The boundaries and outlines of several trenches are not known. Some trench floors looked like "rollercoasters" and " zig-zagged."
Trenches were placed close together so that the intervening wall would sluff off, exposing waste in the next trench.
6.
Page 11 and Page 25, 3rd paragraphs: These paragraphs do not agree as to the depth of the trench cover (more than three feet compared with less than 45 cm of soil).
7.
Page 12, Bathtub Effect discussion: This effect is not present in all trenches.
8.
Page 13, center paragraph: Should it be stated as follows: "This situation occurred where a sandstone lens was exposed in the side of the trench. Water which had accumulated moved into the trench..."?
9.
Page 13, center paragraph: The assumption underlying this section is that since significant migration has not been detected, it is not occurring. This need not be the case in view of the difficulty in monitoring the site.
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- 10. Page 14,1st paragraph: We agree that given the present system "it is difficult to implement a (water) monitoring program which will give adequate assurance that if any significant migration should occur,, it is observed." We believe that there are other alternatives.
For example, i
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AUG 2 91983 201.6/SN/83/08/26/ ENCL /1 (a) Plants seek water. With impermeable strata which are fractured, trees could serve as a very inexpensive monitoring system.
(b) The VSGS has several wells located along the hillside slopes which may prove to be reliable indicator sites for contaminant migration.
(c) An array of porous cups may prove to be an inexpensive but reliable monitoring system. Of course, if the Positive Trench Drainage alternative was adopted, a reliable iTater monitoring program would be feasible.
- 11. Page 15, Table 2-2: This table could be moved into the appendix.
- 12. Page 23, 1st paragraph: With regard to sealing the site with PCV sheeting, it should be noted that with the plastic in place, the trench did not drain. Once pumped and drained, the trench stayed " dry."
Or.e would conclude that the ground water flow is extremely slow.
- 13. Page 24. Hydrological Evaluations discussion: This discussion needs to have references cited. Also, reference any work on " attempts to fit the site to hydrological models..."
- 14. Page 25, top three lines: References needed here on " Studies by NRC, EPA and other investigators have concluded that there is no significant public health problem..."
- 15. Page 25-6, Environmental Monitoring: References needed here, too.
- 16. Page 26, Missing Paragraph:
It seems that there should be a paragraph added at bottom of p. 26 entitled " Engineering Evaluation and Designs," in order to conform with list on page 14.
- 17. Page 40, Deep Compaction discussion: Although the benefits of dynamic compaction are discussed quite thoroughly (, the possible disadvantages are not mentioned. These include: a) the destruction of protective packages - this would be of particular concern with liquid wastes or the highly mobile, large inventory of tritium - especially if the Positive Trench Drainage system was adopted, (b) the rendering of nearly all radioactive materials available for transport, and (c) a possible short-term rise in the water table leading to additional leaching.
- 18. Page 40, Piles discussion: Again, the authors do not mention possible disadvantages such as the likely destruction of protective waste packaging and the possible fracturing of bedrock beneath the trenches.
Fracturing may provide new drainage pathways for leachate and therefore J
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I 3 2 9 1993 201.6/SN/83/08/26/ ENCL /1 l l
be incompatible with a positive trench drainage system.
i.e., drainage l
flows into the fracture rather than into the trench drain. What about direct radiation hazard to workers if piles are removed?
- 19. Page 42 top paragraph: The reduction of drainage from the trench I
2 (by grouting) fs also a positive characteristic of any other method of
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waste stabilization.
- 20. Page 41-4E Grouting discussion:
It seems that the authors emphasize
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the negative aspects of this tuode of stabilization as opposed to, say, the emphasis on the positive aspects of Deep Compaction (page 40) or of Positive Trench Drainage (page 49-50).
- 21. Pace 42, Explosivcs discussion:
Conments made with respect to Piles (comment 18) apply to this paragraph as well.
- 22. Page 44, 2nd paragraph:
It need not be necessarily true that a raised structura over the site be impractical because of substantial maintenance. Consider, for example, pressure treated lumber and corrugated steel roofing which could provide a low-cost, virtually maintenance-free system for at least 50 year.s.
- 23. Page 44, 3rd paragraph:
" Intensive" perpetual care and maintenance may not be necessary to correct site deficiencies as they appear.
This would depend on the final site configuration / stabilization.. Sea our General Comment No. 5 regarding a stabilization alternative not addressed by the authors.
If a similar system was adopted, maintenance ney then be minimal.
- 24. Page 45, 3rd paragraph: One reviewer questioned the assertion regarding the Tifficulty" in assessing the effectiveness of particular i
trench covers in preventing the bathtub effect.
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- 25. Pace 45, last paragraph 1 Complicated trench cap designs may prove unrelTa6Te. Moreover, a trench cap itself is not effective without trench stability. That is, trench structural stability is most important in avoiding the bathtub effect.
- 26. Page 46, Plastic Sheeting: Sheating is a disadvantage in that it
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requires constant maintenance. Also, reference / explain " Burial of 1
membranes with soil general'ly enhances their performance."
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201.6/SN/83/n8/26/ ENCL /1 27.
Page 46,1st paragraph: While it may be true that "a multi-loyer trench cover can be effective in achieving all of these objectives" (for I
controlling infiltration) it would not accommodate the collapse of large I
voids. Some means of structural stability must be provided. The University of Arizona is investigating this question. See Volume 2, paper by Nowatasky and McCray (page 186).
28.
Page 47, 2nd Paragraph:
Regarding the use of bentonite or smectite group of clay minerals, work at Los Alamos (see Hakonson) pointed out problems in using the bentonite. Kentucky has local sources of some very plastic clayey shales which should do a good job. The Estill shale I
member of the Crab Orchard Formatior. is one source.
- 29. Page 47, 3rd paragraph:
Elaborate on " multiple layers alternative with gravel."
- 30. Page 48, Coarse Gravel Layer: This heading should not be under'Uned.
31.
Page 49-50, Positive Trench Drainage discussion:
It is obvious to the reviewers that this is one of the options favored by the authors since there are niany posit 1ve statements but no drawbacks listed.
Possible problems with this option which must be addressed include: (a)
Providing a pathway for non-sorbing radionuclides transport to the environment, especially tritium, in view of the high inventory in the trenches, (b) Trenches may drain into the fractures beneath the trenches rather than be captured by this kind of drainage system, and (c) The low permeability (1-10 f t/yr) may not result in significant drainage capability.
32.
Page 50,1st paragraph: What happens to any radioactive materials and non-sorbed effluents? Also, drainage effluent should be collected and analyzed prior to release.
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- 33. Page 51, last four lines:
Regarding the appropriateness of j
constructing a ground water flow barrier to prevent the movement of any off-site groundwater into the waste disposal area, there are several lines of evidence that there was little ground water flow at Maxey Flats.
Interviews with older workers pointed out that trenches were bone dry when first excavated.
Recent installation of lysimeters at the northwest corner of the site bears this out.
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l IO 201.6/SN/83/08/26/ ENCL /1 34. Page 54, top two lines: What animals burrow at Maxey Flats? Is this of substantial magnitude to be of concern? Note that coarse gravel and cobbles for a bio-intrusion barrier will be hard to fino locally and that the most common local cobbles (limestone) would not be desirable.
- 35. Page 56, missing items (2): Should one also include in the list functionality, ease of implementation, cc.ct-effectiveness, etc.?
- 36. Page 58, Table 6-1: Missing from this table of alternatives is the Positive Trench Drainage technique. Also, what about other kinds of raised covers (under " Infiltration Barriers") such as corrugated aluminum? How were these screening characteristics judged? Why, for example, is feasibility of a concrete cap judged to be " poor"? With what
" Standards" are the alternatives judged to be in " compliance"? (Third column in Table).
- 37. Page 60, Alternative 2-B: Has a tile covering cver the site been considered as an alternative? This method was discussed at the August 3, 1983 DOE Headquarters Workshop. This has the disadvantage however of requiring continuing maintenance.
- 38. Page 60, Alternative 2-B: What does the coarse cover layer refer to? Is it for wicking or erosion retardation? If it is not the wick system it should be listed as an option.
- 39. Page 61, Alternate 3-A:
" " Retard the migration of radionuclides" should be
"...of some radionuclides" since some radionuclides, uch as H-3, will not be slowed.
- 40. Page 62:
Is this page missing or blank?
- 41. Appendix, Page 146: Additional references on vitrification include:
(a) Oma, K.H., et. al.
In-situ vitrification: Applicational analysis for Stabilization of Transuranic Waste; PNL 4442, PNL, Richland, Washington, Sept. 1982. This document discusses application of the t
technique at Maxey Flats.
(b) Brouns, R.A. and C.L. Timberman.
In-situ Thermoelectric Stabilization of Radioactive Waste.
Proceedings of the Symposium on Waste Management, 1982,
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AUG 2 91983
GENERAL COMMENT
S 1.
Volumes 1 and 2 of task 2 are comprehensive documents which were generally well received. Several reviewers commented on an apparent subjective presentation of some of the individual decommissioning alternatives.
For example, the " Positive Trench Drainage "(p. 49) and
" Deep Compaction" (p.40) options were elaborately described in a very positive fashion with little, if any, negative characteristics mentioned.
See, also, our Specific Comments section on the disadvantages of the Positive Trench Drainage and Deep Compaction options. Unbalanced descriptions could lead tc poorly supported decisions on selecting decommissioning alternatives.
2.
With respect to the Positive Trench Drainage option, the authors are presenting (almost recommending) an untried and unproven sys, tem which does not meet most of the authors' selection criteria for viable options (e.g., page 56: Applicability, Maturity, Complexity, Safety, QA).
Moreover, this system seems to present a potentially long-term (indefinite?) maintenance requirement with a high frequency of repair, allows direct pathways to the environment, provides little if any i
assurance of capturing and transmitting all radioactive contaminants and may violate the general criterion that releases from the site be minimized.
3.
More thought needs to be given to developing monitoring alternatives - especially if the Trench Drainage option is not exercised.
4 With respect to Chapter 6, Selection of Alternatives (p.57-61), A much more meaningful list of alternatives would be a combination of measures and alternatives.
(See, for example, our Specific Coments section, item 25 on trench cap-trench stability combined options.)
Individual alternatives in themselves are almost meaningless. See also, for example, pages 337, 3rd paragraph and p. 272, both in Volume 2.
5.
One combination of alternatives apparently not considered in Chapter 6 is the following: Remove about a 20-foot soil layer of farmland found north of the site (State property). Cover the disposal facility with I
20-30 feet of the soil layer. Contour to promote. runoff. Use plant I
management techniques to optimize evapotransportation and reduce water i
infiltration to zero levels (trees with 6 ft. rooting - see Volume 2, Pg.
21, Table 2.).
Maintenance would be very low, and inexpensive,
201.6/SN/83/08/26/ ENCL /2 subsidence would no longer be a critical problem in that it could be accommodated / managed, and the waste would then be at sufficient depths to mitigate against intrusion without having to excavate the waste.
6.
Appendix needs some editing. Some of the references are incomplete (e.g., p. 330, p. 352), some of the figures are not in correct order, etc. The addition of an author index in volume 2 would be extremely helpful to the reader.
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