05000397/LER-2015-001
| Columbia Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| LER closed by | |
| IR 05000397/2015000 (7 August 2015) IR 05000397/2015002 (7 August 2015) | |
| 3972015001R00 - NRC Website | |
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Columbia Generating Station
2. DOCKET
05000 397 2 OF 3
Plant Conditions
At the time of the event reactor power was 100% from December 3, 2014, to December 19, 2014, except from December 13, 2014, 23:05 until December 14, 2014, 00:20 when it was 97% for Main Steam Bypass Testing. There were no structures, systems, or components that were inoperable at the start of the event which contributed to the event.
Event Description
On March 2, 2015, it was identified that Columbia Generating Station's (Columbia) barrier impairment procedure which allowed for floor plugs over the Emergency Core Cooling System (ECCS) and Reactor Core Isolation Cooling (RCIC) [BN] System pump [P] rooms to be removed with a one hour flood tour to maintain operability of the system was non- conservative and Columbia had been non-compliant with Technical Specifications (TS).
On December 3, 2014, a floor plug for the Residual Heat Removal (RHR) [BO] System B on the Reactor Building (RB) [NG] 471' elevation was removed per the barrier impairment process. A one hour flood tour was initiated for this barrier impairment, and a berm was erected; however, the one hour flood tour was non-conservative and the berm did not meet procedural requirements for flood height nor was it a continuous berm. On December 18, 2014, the NRC Resident questioned the adequacy of the installed berm and its non-compliance with the barrier impairment procedure. On December 19, 2014, a berm was erected which met procedural requirements to protect against flooding in the RHR System B pump room below.
Cause
The cause of the non-compliance with TS occurred because the flood tour was allowed by the barrier impairment procedure as a compensatory measure to support operability based on engineering judgement without a thorough technical evaluation. The inadequate compensatory measure was allowed because specific guidance for the evaluation of compensatory measures for barrier impairments was not available.
Extent of Condition Extent of condition was examined for all of the ECCS and RCIC Systems during the past three years when floor plugs were removed. Floor plugs were removed from above 5 of the 6 ECCS and RCIC System pump rooms 7 times during the modes of applicability, Modes 1, 2, and 3. Below is a list of the dates of times when a floor plug was removed and additional conditions prohibited by TS were found to exist.
1. March 5, 2012 – RHR A – 14 days inoperability time – TS 3.5.1, 3.6.1.5, and 3.6.2.3 completion times were exceeded 2. May 2, 2013 – RHR B – 9 days inoperability time – TS 3.5.1, 3.6.1.5, and 3.6.2.3 completion times were exceeded.
3. December 3, 2014 – RHR B – 16 days inoperability time – TS 3.5.1, 3.6.1.5, and 3.6.2.3 completion times were exceeded 4. December 17, 2014 – RHR A, RHR B, and Low Pressure Core Spray (LPCS) [BM] – 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and 42 minutes of inoperability time – TS 3.5.1 completion times were exceeded and LCO 3.0.3 was not entered 26158A R3 NRC FORM 366A (01-2014) Immediate Corrective Action When it was discovered on December 18, 2014, that the installed berm was inadequate, actions were taken to erect a berm which is compliant with the barrier impairment procedure. This was completed on December 19, 2014. An operations standing order was put in place to ensure that floor plugs would not be removed without either declaring the affected system inoperable or erecting a berm which can maintain operability.
Operating Experience & Previous Occurrences A previous occurrence has been found to have a similar cause. A NRC violation from 2013 was found against the same barrier impairment procedure for failure to translate flooding design and calculation into procedures. An extent of condition was performed which reviewed the barrier impairment procedure for compensatory measures which were based on calculations or quantitative analysis. Floor plug removal was identified as having no quantitative analysis, however based upon engineering judgement an hourly flood tour which had been in place since 2002 was determined to be adequate.
Further Corrective Actions A revision to the barrier impairment procedure has been completed which removes the option for an hourly flood tour to maintain operability of the ECCS and RCIC systems when floor plugs are removed.
Planned corrective actions include further enhancement to the barrier impairment procedure and creation of a procedure for proper berm installation.
Assessment of Safety Consequences
There were no actual safety consequences of the event. There was no equipment damage, injuries or dose exposure to station personnel. There was no change in plant status or operating condition and there was no actual risk to the public at any time. The floor plugs are designed to protect the ECCS and RCIC systems during a medium energy line crack (MELC). During each instance where floor plugs were removed, although systems were not declared inoperable, no actual MELC occurred.
There was a potential safety consequence if a MELC were to have occurred while the floor plugs were removed. Flooding procedures direct operators to physically render the ECCS and RCIC pumps inoperable upon flooding in the respective pump room; therefore, the pump with the floor plugs removed would not have been available to perform its safety function.
During the period of time when floor plugs were removed there was a period of inoperability of other ECCS systems which resulted in a loss of safety function. This was due to inoperability of three ECCS Systems, RHR A, RHR B, and LPCS.
On December 17, 2014, with RHR B floor plugs removed and RHR A, and LPCS systems declared inoperable, the RHR A and LPCS systems were maintained available to provide cooling to the reactor since they were operating in suppression pool cooling mode and suppression pool mixing mode, respectively, during this time period. The High Pressure Core Spray (HPCS) [BG] system was also operable and available to support ECCS injection/spray. The normal method of heat removal from the reactor, the condenser, was also available for heat removal. At no period of time, with the provision of operating the pumps, was there more than one pump, RHR B, incapable of providing cooling to the reactor.
Energy Industry Identification System Information Energy Industry Identification System Information codes from IEEE Standards 805-1984 and 803-1983 are represented in brackets as [X] and [XX] throughout the body of the narrative.