RASCAL is a software code used to estimate projected dose as a result of a radioactive release. AREVA reported that the software underestimates the dose in its calculation of a
uranium release using the enrichment option. This underestimate is reported to be on the order of a factor of 0 to 8.6 times when the enrichment is in a range of 0 to 5 percent.
AREVA is recalculating the doses in their Radiation Hazards Analysis. Specifically, the licensee indicated that it will apply a factor to correct for the "enrichment" option of the code if a real or potential emergency release needs to be assessed.
Other facilities that use RASCAL are not known.
- * * UPDATE FROM NRC TO R. ALEXANDER AT 1036 EST ON 12/17/07 * * *
On Friday, December 14, 2007, the Areva fuel manufacturing facility of Richland, Washington, notified NRC regarding an error in the RASCAL computer code. The reported issue involves a code option that would be used primarily by fuel cycle facilities. Specifically, the issue involves use of an option in the code that allows users to select a uranium enrichment percentage instead of entering the activity of each uranium nuclide separately (U-234, U-235, and U-238).
This error is not present for uranium hexafluoride releases. Doses from the release of enriched uranium hexafluoride are calculated correctly.
The NRC is currently evaluating the RASCAL computer code issue reported by Areva. Until the computer code is updated, fuel cycle facilities should not use the uranium enrichment percentage option for releases other than uranium hexafluoride. As an alternative, users should enter the activity of each uranium nuclide separately (U-234, U-235, and U-238) in order to insure correct dose projections from the code.
All registered RASCAL code users and the RASCAL Users Group have been notified by email regarding this issue. Any RASCAL user seeking additional information on this issue can contact the NRC via email at sam2@nrc.gov.
Notified R1DO (Trapp), R2DO (Seymour), R3DO (Duncan), R4DO (Farnholtz), and
NRR (Kuo and Hodge).