Now, it’s an issue with functionality of emergency diesel generators to maintain ventilation.
SRS Occurrence Report, November 8, 2018 – linked here
“On October 31, 2018, during a review of the functional performance requirements for the S-4404 project to upgrade the H-Canyon Canyon Exhaust (CAEX) System, it was identified that the protection of the Safety Class (SC) single failure criteria per DOE 6430.1A was not properly implemented in the H-Canyon safety basis documents from 2001 (WSRC-RP-95-635) to the present (S-DSA-H-00001). The S-4404 project installed two independent SC diesel generators (DGs) that have the capability to support two SC CAEX fans per DG. The safety basis documents did not assume loss of one of the SC DGs during a seismic event when developing the functional performance and minimum Limiting Condition for Operation requirements for the CAEX system as required per DOE Standard 3009-94. Potentially Inadequate Safety Analysis (PISA) PI-2018-0011 requires that U-JCO-H-00003 shall remain implemented until PISA PI-2018-0011 has been resolved to place and maintain the facility in a safe condition. ”
Defense Nuclear Facilities Safety Board (DNFSB) weekly report, November 2, 2018 – linked here
“Enterprise Assessment personnel recently identified that the H-Canyon Exhaust Ventilation System did not meet the required single failure criteria for safety class components. The ventilation system includes two safety class diesel generator trains that each support two safety class exhaust fan, which are credited to function during and after a design basis earthquake (DBE).”