The following was reported by
Westinghouse Electric Company via email:
As part of a review to revalidate the design of passive safety controls, on October 16, 2019 an engineering calculation was completed which demonstrates that one of two independent and redundant passive overflow devices used in the Solvent Extraction (SOLX) process was undersized for its credited safety function. This passive overflow device is an Item Relied On For Safety (IROFS), designated as SOLX -115. The IROFS prevents the potential backflow of uranium bearing solution from the SOLX process into the commercially-provided, chemical supply drums. These drums are non-favorable geometry (NFG) containers used to add chemicals to the batch process. Upon review of the calculation, the process engineer reported the issue at 3:05 p.m. [EDT] to the Environmental Health and Safety (EH&S) department.
The design of the second, redundant passive overflow IROFS in this accident sequence (SOLX-117) has been validated and is available and reliable to perform its safety function. Under the new calculation, with no credit for SOLX-115, the overall likelihood index (OLI) for this scenario increased from -6 to -3. Therefore, the 10CFR70.61 performance requirements (OLI < -4) are not satisfied.
The process was shut down, and the NFG chemical drums were isolated from the process until appropriate controls are established. This event has been entered into the facility's Corrective Action Program (CAP).
The licensee notified the NRC Region II office (McCurry).