05000397/LER-2016-002

LER-2016-002, 1 OF 3

Columbia Generating Station
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
Initial Reporting
ENS 52276	10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
3972016002R00 - NRC Website

LER 16-002-01 for Columbia Generating Station Regarding Valve Closure Results in Momentary Increase in Secondary Containment Pressure

ML17270A195
Person / Time
Site:	Columbia
Issue date:	09/27/2017
From:	Javorik A L Energy Northwest
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
G02-17-165 LER 16-002-01
Download: ML17270A195 (4)

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource©nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000- NUMBER NO.

, _002 00 Columbia Generating Station 397 2016 -

Plant Conditions

At the time of the event, the plant was operating in Mode 1 at 100% power.

Event Description

On October 3, 2016 at 1008 PDT, Operations personnel received an annunciator alarm for high Secondary Containment [NH] differential pressure when the Reactor Building [NG] exhaust inboard isolation valve [V] (REA-V-1) failed shut. For a time period of approximately four minutes, Secondary Containment differential pressure increased above -0.25 inches of vacuum water gauge (inwg), resulting in Technical Specification (TS) 3.6.4.1 not being met.

This event is reportable as an event that could have prevented fulfillment of safety functions needed to control the release of radiation, and mitigate the consequences of an accident per 10 CFR 50.73(a)(2)(v)(C) and 10 CFR 50.73(a)(2)(v)(D).

This condition was reported under 10 CFR 50.72(b)(3)(v)(C) via Event Notification #52276 for an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material.

Immediate Corrective Actions

Per plant procedure, Operations personnel manually started Standby Gas Treatment [BH] (SGT) System A and Secondary Containment was restored to less than -0.25 inwg at 1012 PDT.

Assessment of Safety Consequences

This event resulted in an unplanned entry into TS 3.6.4.1.A, in which Secondary Containment pressure was greater than -0.25 inwg for approximately four minutes. The peak pressure during this event was +4.17 inwg. While the actual pressure was beyond the range allowed by Technical Specifications, the purpose of maintaining a slight vacuum is to assist in drawdown of secondary containment to support accident response of the safety related SGT system. Existing engineering analysis demonstrates that for this event, the drawdown credited in Columbia's accident analysis could have been attained using either of the two available trains of the SGT system, thus there were no potential safety consequences. There was no actual safety consequence associated with this event since SGT did in fact restore Secondary Containment, and there was no loss of safety function or potential for radiological release.

Cause of Event

The investigation into the apparent cause of the unexpected closure of the Reactor Building exhaust valve, and resultant loss of Secondary Containment, is currently under way and the results of the investigation will be provided in a supplement to this LER.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000- Columbia Generating Station 397 Similar Events A loss of the ability to maintain Secondary Containment pressure greater than required by Technical Specifications has occurred at Columbia Generating Station (Columbia) one time in the past two years, which was the result of a power supply failure. Prior to this two year time period, Columbia has experienced losses of Secondary Containment due to weather-related conditions, as well as human performance errors. Columbia has implemented corrective actions for these previous events.

Further Corrective Actions Additional corrective actions will be provided in a supplement to this LER following completion of the cause evaluation.

Energy Industry Identification System (EIIS) Information codes from IEEE Standards 805-1984 and 803-1983 are represented in brackets as [X)(] and POOq throughout the body of the narrative.