ML20137F294
| ML20137F294 | |
| Person / Time | |
|---|---|
| Issue date: | 03/26/1997 |
| From: | Joseph Holonich NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Sena R ENERGY, DEPT. OF |
| References | |
| REF-WM-67 NUDOCS 9704010050 | |
| Download: ML20137F294 (2) | |
Text
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g NUCLEAR REGULATORY COMMISSION o-wAsn Norow, o.c. 2osss.ooot March 26, 1997 Mr. Richard Sena, Acting Director Environmental Restoration Division Uranium Mill Tailings Remedial Action Project U.S. Department of Energy 2155 Louisiana NE, Suite 4000 Albuquerque, NM 87110
SUBJECT:
TAILINGS IMPOUNDMENT SETTLEMENT AT AMBROSIA LAKE
Dear Mr. Sena:
The U.S. Nuclear Regulatory Commission technical staff is reviewing the final Ambrosia Lake Completion Report (CR), including page changes / additions to the draft CR transmitted to us by letter dated November 22, 1996.
The U.S. Department of Energy (DOE) has not adequately addressed the open geotechnical issue noted in the NRC's review of the draft Ambrosia Lake Completion Report.
Open Issue No.1 (NRC - July,1996) requested that DOE present the tabulated tailings embankment displacement data of Volume 5 graphically.
DOE responded by providing graphs of the settlement monitored at eight locations on the cell. The 750-day time period covered by the graphs began April 27, 1993. Although the graphs show that the rate of settlement has lessened at each monitoring point, the extent of settlement indicated remains a concern.
Furthermore, post-750-day settlement readings were absent.
Phone conversations on March 6, March 12 and March 20, 1997, were held to discuss the issue with DOE and its contractors.
Subsequently, DOE sent various modified time-settlement curves, each of which included a single settlement reading from December of 1996. However, the trend indicated by the 1996 readings and questionable final survey data still imply that long-term differential settlement is a concern.
Since the apparent rate of settlement shown graphically may jeopardize the predicted long-term cell performance, additional assurance that cover cracking and erosion channel formation will not occur is warranted.
Confirmation that: 1) the indicated settlement behavior will not adversely affect the radon barrier, and 2) that preferential erosion channels will not form should be provided, taking into account the inaccuracy of the December 1996 survey data, j
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R.' Sena 2
I This open issue needs to be resolved in the final Completion Report in order for the NRC to concur in the remedial action at the Ambrosia Lake site.
If you have any questions concerning this letter, please contact the NRC Project Manager, Ken Hooks, at 301-415-7777.
Sincerely, (Original signed by)
Joseph J. Holonich, Chief Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards cc:
L. Woodworth, DOE Alb S. Hamp, DOE Alb E. Artiglia, TAC Alb l
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