ML20154D001
| ML20154D001 | |
| Person / Time | |
|---|---|
| Issue date: | 02/27/1986 |
| From: | Clark A NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Hannum W ENERGY, DEPT. OF, IDAHO OPERATIONS OFFICE |
| References | |
| REF-PROJ-M-32 NUDOCS 8603050444 | |
| Download: ML20154D001 (6) | |
Text
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'NMSS~R/F PDR & LPDRs FCAF R/F Project M-32 FEB 2 71986 ATClark I
LCRouse RBoyle, WM JRoth, Reg. I IE Region I Dr. William Hannum, Director NDavison West Valley Project Office FBrown (LA File)
Department of Energy. Idaho Operations RBrowning P.O. Box 191 MBell West Valley, New York 14171 LHigginbotham
Dear Dr. Hannum:
We have received, and are currently reviewing, the Department of Energy's document, " Environmental Assessment for Disposal of Project Low-Level Waste,"
(WVDP_045).
I am enclosing our initial comments in response to your letter, dated February 6, 1986. You may expect additional comments within a month after we have completed our review.
If the Department decides to use the tumulus concept for the disposal of project low-level radioactive waste, we should be kept fully informed as design i
of the tumulus proceeds.
In that regard it would be helpful to incorporate in
)
the design monitoring provisions which would enable 1) a continual assessment of confinement performance over the early years, 2) allow for predictions of long-term performance, and 3) not interfere with performance.
We appreciate the uppu.'tunities you have provided for discussion of your planning for the disposal of project low-level waste and I believe additional discussion related to botn tumulus and trench design would be useful.
Sincerely, Olt1G1x^L SIGNED By; A. Thomas Clark, Jr.
Advanced Fuel and Spent Fuel Licensing Branch Division of Fuel Cycle and Material Safety
Enclosure:
4 As stated i
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______f_p(,______4_b___:_'hs w _______________________________________
NAME:ATClark:kd:LCRouse :REBr ing BATE bhf[7fbb bhk/b6 Obk/86 0FFICIAL RECORD COPY i
G603050444 B60227 PDR PROJ M-32 PDR
b, NRC COMMENTS ON THE DEPARTMENT OF ENERGY ENVIRONMENTAL ASSESSMENT FOR DISPOSAL OF PROJECT LOW-LEVEL WASTE 1.
Other viable engineered alternatives for on-site disposal should have been considered in the EA.
Examples are concrete bunkers, the Westinghouse SURPAK system, and deep trenches.
2.
The affects of the proposed disposal units (trenches and tumulus) on the existing disposal areas (NRC licensed site and New York state site) have not been addressed. Due to the close proximity of the proposed disposal units to the existing disposal areas and the potential role that the proposed disposal units will play in the overall stabilization of the West Valley site, it is suggested that the Department analyze these affects and the exact location of the tumulus should not be designated until completion of the analysis.
3.
It appears that additional erosion protection is needed to adequately stabilize the site. While it is feasible that site integrity could be maintained under normal rc nfall conditions, occurrences of large, intense storms could cause a significant amount of erosion to occur in the nearby gullies and on the trench and tumulus covers.
During such events, waste isolation and site integrity may not be maintained.
Therefore, it is suggested that designs should be developed to mitigate the erosion problems that would be produced by intense storm events.
1 4.
Your reference er. titled, " Subsurface Characterization Report - Low-Level Waste Disposal Area," West Valley Nuclear Services Comoany (WVNSC), is a good start tcward understanding the physical characteristics of the site as it affects waste confinement.
This effort should be continued until a validated mcdel of these site characteristics can be adequately supported.
For example, ground-water flow in the unsaturated zone remains to be sufficiently supported since less than one complete year of data has been collected. At least two complete and continuous years of data and analysis for both the saturated and unsaturated zones is necessary, l
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1 5.
A direct comparison of the two principal alternatives being conside' red for the disposal of Class B/C waste is difficult because of the lack of performance experience information for the tumulus and of sufficient analysis of trench performance as based on ground-water measurements.
Your final decision should consider and balance both normal and abnormal conditions for both alternatives insofar as you can judge the most likely modes of failure for either alternative.
In that regard we believe that you may not have given sufficient credit to the performance of trench capping when compared relative to the tumulus.
6.
Recent information (see Quarterly Progress Report for " Properties of Radioactive Waste and Waste Containers," FIN-A3027, 1985) reported by Brookhaven National Laboratory indicates that during dry periods of leaching, when intermittent leaching occurs, leach specimens may experience movement of material from the enriched subsurface zone of the specimens towards the depleted surface with subsequent release of this material during the next period of contact with water.
This appears to cause an increased release of radionuclides depending on the length of the i
dry period (the longer the dry period, the greater the release of radionuclides). WVDP should consider this phenomenon when assessing the leaching of waste material from the tumulus.
7.
Caution should be exercised when utilizing the FEMWATER computer code to determine ground-water velocities because it utilizes a non-standard technique to calculate ground-water fluxes.
Subsequently, interpretation of ground-water conditions generated by the model simulations should be verified.
8.
The numerous input values and assumptions that are required by PRESTO should be justified in terms of how they were estimated or calculated. As an example, the Kd values used do not appear to be conservative and the method by which they were determined is not presented. Also, the chemical effects of the geologic materials, ground water, and waste on the site performance, have not been adequately considered.
Biotic effects have not a
been thoroughly addressed in terms of microorganism behavior that could affect trench chemistry (e.g., bacterial sulfate reduction changing redox conditions).
t 9.
The proposed disposal method for Class A waste could result in a subsidence problem similar to that already observed at the Maxey Flats and West Valley sites.
Since most of the waste will exist as compressible trash, " miscellaneous dry solids," and failed equipment disposed in 55 gallon drums and steel boxes, these drums and boxes could fail within a few years and create voids within the trenches.
Experience from other disposal facilities has shown that trench voids can result in depressions several feet in diameter being created in the trench caps.
Such voids and depressions will increase water infiltration into the trenches and disrupt any drainage system built into the trench caps. Given the impermeable nature of the site soils, the infiltrating water will collect in the trenches. Also it is conceivable that subsidence will also be observed in the Class B/C tumulus. Although this subsidence may not result in the development of fully saturated conditions, there may be contaminated leachate generated.
10.
In the final design of the tumulus (if selected) attention should be given to local surface-water drainage and vegetative cover to minimize erosion.
- 11. Consideration should be given to designing deeper trenches to utilize to the extent possible the full thickness of the Lavery Till. We believe that resaturation times could be significantly increased, as well as increased ground-water pathways and consequent travel times.
- 12. The tumulus should be analyzed to determine its performance characteristics in the event of clogging of the toe drain.
13.
For the tumulus there are some engineering and/or hydraulic features for which early testing and analysis is necessary to demonstrate its performance over its intended confinement period. These features are tabulated below.
FEATURE PERFORMANCE _ VERIFICATION ASPECT Geotextile Durability, long-term filtering fabric capability, potential for biological and chemical fouling Clay and pore water Deterioration of barriers caused by chemistry leaching and chemical redeposition Hydraulic Determination of moisture retention properties curves for the geotechnical materials used for the various tumulus barriers.
- 14. Differential settlement has a real potential for compromising the' '
integrity of the confinement systems in both the tumulus and the trenches.
This should be adequately analyzed in subsequent design work.
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