Good Day, I know this has come up a couple of times before, but I could not find the information I was looking for in the Archives.
Our most recent (and first) ISFSI dry cask transfer campaign was in 2008. We use the NUHOMS -61BT Dry Storage Cask and HSM. During that campaign we determined that our neutron dose should be based on a low energy neutron spectrum (predominantly around 40 to 50 keV). We determined this, in part, by comparing a set of TLD, CR-39 TED, and Bubble Dosimeters monitoring the dose from the first transfer cask over a 24-hr period. The TED and bubbler results were significantly lower than the TLD results which was interpreted to mean the energy of the spectra was less than the at or below the energy cutoff for the TED (150 keV) or bubbler (200 keV). We therefore used, from advice from our TLD vendor, their Thermal neutron correction factor (NCF) for determining the neutron dose for personnel. This NCF provided neutron results for the campaign that were outside what had been expected and what was seen at most other plants. For BWRs that have done ISFSI DSC moves (or plan to), What type of neutron spectrum are you seeing from your transfer casks? If you are using a REM-500 as the basis for determining an ISFSI NCF (using it as the standard), are you compensating in any way for the 70 keV drop-off? Did you do a more thorough study of the neutron spectra with a Bonner sphere set or a bubbler spectrometer? Your input is appreciated. Scott Huneycutt Xcel Energy | Responsible By Nature Senior Health Physicist Monticello Nuclear Generating Plant 2807 West County Road 75, Monticello, MN 55362 P: 763.295.1380 F: 763.295.1225 E: [email protected]<mailto:[email protected]> ________________________________________________ XCELENERGY.COM<http://www.xcelenergy.com/> Please consider the environment before printing this email
