Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 53775 | 4 December 2018 17:12:00 | On 12/4/2018 at 1340 (PST), Columbia entered a planned evolution to replace the seismic monitoring system. Use of the Modified Mercalli Intensity Scale has been implemented as a compensatory measure per station procedures. The expected duration of the replacement activity will exceed 72 hours, therefore, this is being reported as a major loss of emergency assessment capability in accordance with regulation 10 CFR 50.72(b)(3)(xiii). Compensatory measures will remain in place until the seismic system replacement has been completed. The NRC Resident Inspector has been notified. |
| ENS 52443 | 19 December 2016 07:39:00 | On December 18, 2016 at 2320 (PST), a leak was discovered on the High Pressure Core Spray (HPCS) system minimum flow line. The leak is located at a bolted flange downstream of the manual isolation valve HPCS-V-53. The location of the leak is not isolable from the suppression pool. This provides a direct path from inside the Primary Containment to the Reactor Building. High Pressure Core Spray system is a single train Emergency Core Cooling System (ECCS) system, therefore inoperability is reportable per 10 CFR 50.72(b)(3)(v)(D). Based on the location of the leak, Primary Containment integrity is compromised. Primary Containment was declared inoperable and is reportable per 10 CFR 50.72(b)(3)(ii)(A). The cause of the leak is under investigation. Actions are underway to cool down and enter MODE 4. The licensee has notified the NRC Resident Inspector.
Engineering evaluations indicate that there was neither a High Pressure Core Spray (HPCS) system inoperability nor a condition that resulted in a significantly degraded principal safety barrier (Primary Containment). Therefore, this event does not meet the reporting criteria in 10 CFR 50.72(b)(3)(v)(D) and 10 CFR 50.72(b)(3)(ii)(A), and Event Notification# 52443 is being retracted. Bases for the retraction are: (1) Extent or accumulation of water flooding the HPCS room would not have prevented the system from fulfilling any of its designated safety functions, if the system had received a starting signal due to an emergency; and (2) the consequences of the HPCS Minimum Flow Line leak into the Reactor Building were within the dose limits and did not have a significant effect on Primary Containment integrity; therefore, the Primary Containment was degraded but operable. The licensee has notified the NRC Resident Inspector. Notified R4DO (Groom). |
| ENS 51201 | 6 July 2015 20:41:00 | A recent review of Fire Protection and Post Fire Safe Shutdown (PFSS) Programs at Columbia Generating Station (CGS) identified a potential unanalyzed condition with Multiple Spurious Operation (MSO) Scenario 2x. Review of the circuit design for High Pressure Core Spray (HPCS) HPCS-V-10, HPCS-V-11 and HPCS-V-15 identified that fire-induced circuit failure (hot shorts) on the OPEN function control circuits for each valve would create the flow path to potentially drain inventory from the suppression pool (SP). The normal operation of HPCS-P-3 (keep-fill pump) would allow additional inventory from the SP to be transferred to the CSTs (Condensate Storage Tank). If a fourth hot short is postulated, HPCS-P-1 would transfer inventory from the SP to the CST at a much faster rate. HPCS-V-11 was deactivated on 6/12/2015 due to a maintenance repair issue and will be left in the fully closed position. This plant alignment resolves current concern for MSO scenario 2x as fire-induced circuit damage cannot cause spurious opening of HPCS-V-11. However, with an incomplete analysis for MSO scenario 2x, compliance with PFSS MSO requirements would have been challenged from the completion of the MSO project (October 2012) up to June 2015. CGS is reporting this event as an unanalyzed condition in conformance with 10 CFR 50.72(b)(3)(ii)(B). Further analyses are being implemented to confirm the condition and to develop appropriate remedial actions. The licensee will notify the NRC Resident Inspector. |