ML20261H551
| ML20261H551 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 08/12/2020 |
| From: | John Hickman Division of Decommissioning, Uranium Recovery and Waste Programs |
| To: | Barley W Pacific Gas & Electric Co |
| Hickman J | |
| References | |
| Download: ML20261H551 (1) | |
Text
From: Hickman, John To: Barley, William Cc: Lopez, Brandy
Subject:
Last question on Caisson FSSR Date: Wednesday, August 12, 2020 4:50:00 PM
- Bill, We have one last clarification on the Caisson FSSR.
In response to RAI 2 for the Caisson, you had the following notes:
Note 1 - Production of Cs-137 is greater than Nb-94 to start. The ratio of half-lives is provided below:
30 years for Cs-137 divided by 2.1 E+4 years for Nb-94 equals 1.4 E-3 (combined with production difference, less than a significant number for the sum of fractions calculation).
Note 2 - Production of Pu-239 is much greater than that of Np-237 because of direct neutron capture by U-238 vs. multiple decays and capture to produce Np-237. The ratio of half-lives is provided below: 2.4 E+4 years for Pu-239 divided by 2.14 E+6 years for Np-237 = 1E-2 (combined with difference in production, less than a significant number in the sum of fractions calculation).
Could you clarify what is meant by Production is greater to start and less than a significant number in the notes. Additionally, it appears that you are claiming there is a surrogate relationship between the stated radionuclides. If so, what is the impact to the surrogate radionuclide DCGL value per MARSSIM methods? Please clarify that the surrogate relationship will remain consistent given the difference in environmental transport mechanisms for the specified radionuclides (e.g., Np-237 is extremely mobile environmentally).
It appears to us that the one nuclide (or two in this case) is being used as a surrogate for the unreported nuclide(s) based on known production ratios and similar characteristics for environmental transport, and doing so has no impact on the applicable DCGL due to the difference in production rates and specific activity of the radionuclides. If you can provide the math to demonstrate this per MARSSIMs surrogate measurement process and demonstrate that the change to the surrogate radionuclides DCGL value is negligible (e.g.,
a delta less than 0.05 pCi/g would be appropriate for Cs-137s DCGL of 7.9 pCi/g), then we can find the logic adequate.
As you have not yet responded to the RAIs on the Trailer City FSSR, you could add this response to that one. Please try to make your response clear enough for a member of the public to understand.
Let me know if you have any questions on this.
- Thanks, John