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Nuclear Event – Full Reactor Scram (Hot Shutdown): Columbia Generating Station, Washington State

2016/12/20

The Columbia Generation Station, Washington’s only commercial reactor, sits inside the Department of Energy’s Hanford Nuclear Reservation, a former nuclear weapons production site.

North America – USA | State of Washington, Hanford Nuclear Reservation, Columbia Generation Station
Location: 46°38’51.0″N 119°35’55.0″W
Present Operational Age: ~32 years
Event: AUTOMATIC SCRAM – HOT SHUTDOWN/ACCIDENT MITIGATION

Nuclear Event in USA on Sunday, 18 December, 2016 at 23:20 [PST].

UNISOLABLE LEAK ON HIGH PRESSURE CORE SPRAY

“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.

Source: NRC  Event Number: 52443

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Nuclear Event in USA on Sunday, 18 December, 2016 at 11:24 [PST].

AUTOMATIC SCRAM DUE TO LOAD REJECT FROM SUBSTATION

“On December 18, 2016 at time 1124 PST the plant experienced a full reactor scram. Preliminary investigations indicate that the scram was caused by a load reject from the Bonneville Power Administration (BPA) Ashe substation. Further investigations continue. The following conditions have occurred:

“Turbine Governor valve closure
Reactor high pressure trip
+13 inches reactor water level activations
E-TR-B (backup transformer) supplying E-SM-7/SM-8 (vital power electrical busses)
Complete loss of Reactor Closed Cooling (RCC)
E-TR-S (Startup transformer) supplying SM-1/2/3 (non-vital power electrical busses)
E-DG-1/2/3 (emergency diesel generators) auto start
Low Pressure Core Spray (LPCS) and Residual Heat Removal (RHR) A/B/C initiation signals
Main Steam Isolation Valves (MSIV) are closed

“Reactor Core Isolation Cooling (RCIC) RCIC and High Pressure Core Spray (HPCS) were manually activated and utilized to inject and maintain reactor water level. Pressure control is with Safety Relief Valves (SRV) in, manual. Level control is with RCIC and Control Rod Drive (CRD). RCIC has experienced an over speed trip that was reset so that level control could be maintained by RCIC.

“This event is being reported under the following:
10 CFR 50.72(b)(2)(iv)(A) which requires a 4 hour notification for Emergency Core Cooling System (ECCS) discharge into the reactor coolant system.
10 CFR 50.72(b)(2)(iv)(B) which requires a 4 hour notification for any event or condition that results in actuation of the Reactor Protection System (RPS) when the reactor is critical.
10 CFR 50.72(b)(3)(iv)(A) which requires an 8 hours notification for actuation of ECCS systems.

“All control rods fully inserted.

“The NRC Resident Inspector has been informed.”

The licensee indicated that no increase in radiation levels were detected.

Source: NRC  Event Number: 52442

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