05000397/LER-2004-001
| Columbia Generating Station | |
| Event date: | 1-23-2004 |
|---|---|
| Report date: | 3-23-2004 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 3972004001R00 - NRC Website | |
DESCRIPTION OF EVENT
At 1315 on January 23, 2004, with the plant in Mode 1 at approximately 100 percent rated thermal power, it was determined that a condition prohibited by the Columbia Generating Station Technical Specifications (TS) existed from 1500 on October 27 through 2100 on October 29, 2003 and from 1305 on November 10 through 1052 on November 11, 2003 when testing was conducted to measure control room in-leakage. The test employed ANSI N510-1989 component test methodology and was not a routine surveillance. _During.preparationfor and restoration from this test,_ the_ approved_ test.
allowed common ducts for both Control Room Emergency Filtration (CREF) subsystems to be breached by removing duct access panels. The access panels were removed to allow installation and removal of test equipment. During the time that the access panels were removed, an airflow path was created that would have challenged the ability of both CREF subsystems to pressurize the control room to the pressure required by the TS. Since the extent of the system challenge could not be determined, both CREF subsystems were conservatively determined to have been inoperable when the access panels were removed.
With two CREF subsystems inoperable TS 3.7.3, Required Action D.1, directs immediate entry into TS Limiting Condition for Operation (LCO) 3.0.3. TS LCO 3.0.3 requires actions to be initiated within one hour to place the plant in applicable modes. It was not recognized at the time the tests were performed that both CREF subsystems were inoperable because removal of access panels was allowed by the plant barrier impairments procedure. This procedure allowed the access panels to be removed provided the breach was continuously attended and could be restored quickly. During performance of the test, the subsystem being tested was tagged out of service and the applicable TS Action Statement was entered for that subsystem.
ASSESSMENT OF SAFETY CONSEQUENCES
The CREF System is designed to provide a radiologically controlled environment to ensure the habitability of the control room for the safety of control room operators under all plant conditions.
Because there was no demand to pressurize4he.main control.room.with filtered air, there were no actual- safety consequences associated with both CREF subsystems being rendered inoperable. Since the duct breach was continuously attended and could have been restored quickly if the CREF system was called upon, there is a reasonable expectation that the CREF system would have been able to perform its safety function. It is expected that the system would have been restored within a short time period to keep dose to Control Room personnel within regulatory limits.
This event is considered reportable in accordance with 10 CFR 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 10 CFR 50.73(a)(2)(vii).
IMMEDIATE CORRECTIVE ACTIONS
This event was discovered during a review of test documents after the test was completed. At the time of discovery, the testing was complete and the CREF system was in a normal standby configuration.
FACILITY NAME (1) Columbia Generating Station DOCKET (2) '4 05000397 LER NUMBER (6)
NUMBER
A Stop Work Order was generated to ensure that breaches of plant systems and barriers were performed in accordance with regulatory requirements and guidance. Procedures and model work order instructions related to Control Room HVAC were reviewed to identify those activities that, if implemented as written, could challenge CREF system operability or result in conditions prohibited by TS.
CAUSE OF THE EVENT
The cause of this event is attributed toinadequate and incorrect guidance in.the Columbia Generating Station barrier impairment process and procedures. The cause of the inadequate guidance in the procedure was a lack of understanding of regulatory guidance associated with barrier impairments.
ACTIONS TO PREVENT RECURRENCE
The Barrier Impairment procedure will be modified to clarify equipment operability requirements, to further reinforce the need for a thorough risk assessment of hazard barrier breaches, and to ensure other types of hazard barrier breaches do not result in violating TS requirements.
Other procedures were reviewed for similar vulnerabilities. Several procedures were identified that referenced the Barrier Impairment procedure and/or had similar wording. These procedures have been corrected, are temporarily deactivated, or a Stop Work Order has been issued until adequate corrections have been implemented.
PREVIOUS SIMILAR EVENTS
50.73(a)(2)(v)(D) and 10 CFR 10 CFR 50.73(a)(2)(vii) existed. On November 4, 2003, with the plant in Mode 1, it was determined that a condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident had existed on November 1, 2003. This condition occurred when the normal and both remote outside air intakes for the CREF system were manually isolated for a period of approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> during testing to measure control.room in-leakage. In this configuration,_ the CREF system cannot perform its design safety._ function to pressUrize the main control room with filtered air as described in Columbia's accident analysis. The cause of this event is attributed to inadequate preparation and review of the test procedure used to measure control room in-leakage.
An Energy Northwest team investigating the root cause for the event described in LER 203-012-00 discovered the event described in this LER.
26158 R1