ML20133N178
| ML20133N178 | |
| Person / Time | |
|---|---|
| Issue date: | 07/25/1985 |
| From: | Smykowski S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Gillen D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-58 NUDOCS 8510280432 | |
| Download: ML20133N178 (1) | |
Text
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" MEG'r/f Mreeves JUL 2 51985 SSmykowski MNataraja SS/7/25/85 BJagannath NOTE T0: Daniel M. Gillen Low-level Waste and Uranium Recovery Projects Branch, WM
- N.hb f C FROM: Steve Smykowski Engineering Branch, WM
SUBJECT:
REVIEW 0F THE RAD 0N BARRIER DESIGN FOR THE SHIPROCK UMTRAP SITE This note is in response to Technical Assistance Request #85041. We have reviewed
. the most current radon barrier design calculations performed by the RAC (Calc.
No. 04-07-RO-14-Embankment Radium Content and Calc. No. 04_07-R0-15-Thickness Design). These calculations were given to Banad Jagannath when he visited the TAC's offices in Albuquerque last May.
Based on a review of these calculations, we find the values of the diffusion coefficient, D, for the cover material to be nonconservative. Samples obtained from six test pits at the borrow site were experimentally tested to determine values for D. The arithmetic mean of these values is 0.031 (standard deviation 0.007) for the top foot of cover soil and a value of 0.026 (standard deviation 0.009) for the remainder of the cover thickness. These average values were used in their calculations. We do not feel average values are conservative estimates and therefore do not provide reasor.able assurance that the cover design will attenuate radon to the acceptable EPA standards.
When these average values of D are replaced by more conservative values (D = 0.040 and 0.039), the covered tailings ' lux increases from 20 pCi/m2s to 32 pCi/ma s. An additional 2 feet of cover material would be required to reduce the flux to the EPA standards. This would result in a significant modification i in the design.
Additionally, the RAC has submitted calculations for two design variations that differ from the design proposed in the RAP. The designs differ due to different placement plans for the relocated tailings. The DOE should indicate to the staff which design has been accepted and document this design in the RAP.
So we can form a position, please contact me when you return from travel regarding the nonconservative values of the diffusion coefficients before the addendum to the Technical Evaluation Memorandum is prepared.
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