05000286/LER-2003-004
| Indian Point Unit 3 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(E) 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2862003004R00 - NRC Website | |
Note: The Energy Industry Identification System Codes are identified within the brackets ().
DESCRIPTION OP EVENT
The 31 Battery (BTRY) was declared inoperable on August 5, 2003, at 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br /> due to low voltage on one battery cell. Unit 3 was placed in Technical Specification (TS) action statements 3.8.4.E (inoperable battery) and 3.8.2.E (two Emergency Diesel Generators (EDG) {DG} inoperable). The battery was repaired and declared operable at 1738 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.61309e-4 months <br />, prior to required entry into Mode 3. The entry into the TS action statements was made at 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br /> following the Shift Manager's (SM) recognition that an error had been made in not declaring the battery inoperable at about 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on August 4, 2003. The battery cell low voltage had been identified during a surveillance test and the test results were discussed with the SM at about 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />. The initial test failure and the subsequent entry into TS actions were identified in plant Condition Reports CR-IP3-2003-4514 and CR-IP3- 2003-4536.
This event was evaluated in a root cause analysis report. At about 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br /> on August 4, 2003, cell 26 in 31 Battery failed surveillance test 3-PT-Q01A on low cell voltage. The Supervisor for the test informed the SM and discussed reasons why he believed that the battery remained operable. The SM made an error at this time. The SM did not directly consult the TS or follow verbatim the direction in 3PT-QO1A to take the required Technical Specification 3.8.6 action. Although the operability issue was failure of a battery cell, the evaluation by Engineering looked at how many cells were required for 31 Battery to meet its required design function. This was the response that had been requested. Consequently, the engineering review did not consider the requirement in TS 3.8.6 for each connected cell. As a result, the test Supervisor reported a conclusion that the battery was operable to the SM who accepted this conclusion.
On August 5, the NRC Resident and engineering representatives discussed the operability and looked at TS 3.8.6 ‘Battery Cell Parameters." Later, the NRC Resident and SM discussed operability in the context of TS 3.8.6. At that time, the SM recognized the error made in not declaring the battery inoperable on August 4. The SM declared 31 Battery inoperable as of 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br /> on August 5 and entered TS action statement 3.8.4.B.1. The SM also entered TS action statement 3.8.1.E for two EDG inoperable. The 31 EDG had been taken out of service for maintenance at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> and the 33 EDG required the 31 Battery for field flashing so it was also considered inoperable. A protective tag out was issued at 1517 hours0.0176 days <br />0.421 hours <br />0.00251 weeks <br />5.772185e-4 months <br /> and the battery was disconnected by opening the battery connections to the bus and to the battery charger. At 1738 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.61309e-4 months <br /> 31 Battery was declared operable following replacement and testing of cell 26.
There were no other surveillance tests requiring an operability determination at the time so the event was limited to the 31 Battery.
NRC FORM 31343A (I
- 2031) CAUSE- OF EVENT The root cause was work practices - document use practices- documents not followed correctly. The sM did not directly consult the TS and did not follow verbatim the direction in 3PT-QO1A to take the required TS action.
A contributing cause was work practices - error detection practices - peer checking not applied to ensure correct determination with adequate basis. The SM overly relied on engineering review results and did not seek peer review from an SRO or STA.
Another contributing cause was verbal communications - pertinent information was not transmitted. Although the operability issue was failure of a battery cell, the System Engineer was asked how many cells were required for 31 Battery to meet its required design function, so the engineering review did not consider TS 3.8.6
CORRECTIVE ACTIONS
The following corrective actions have been or will be performed under the corrective action program to address the cause and prevent recurrence:
1. Testing is being scheduled to evaluate whether the 31 Battery was functional with degraded cell 26 in service.
2. The Operations Manager communicated the expectation that operability determinations will be performed by a SRO or STA and approved by the SM to achieve the advantages of peer review.
3. This internal operating experience (OE) has been added to the 2003 third session of the Engineering Support Program continuing training.
4. The Operations Department Training Coordinator will present the OE to the Operations Training Review Group for inclusion as an illustration or case study in SRO Initial License and License Requalification Training on TS usage and/or operability determination by 11/21/03.
EVENT ANALYSIS
The event is reportable under 10 CFR 50.73(a)(2)(i)(E), any operation or condition that was prohibited by plant Technical Specifications. Although not recognized at the time, the 31 Battery was inoperable about 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on August 4, 2003 when the test was performed and reviewed by the SM. The battery remained inoperable until 1738 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.61309e-4 months <br /> on August 5. The TS 3.8.4.C.1 requirement was exceeded by 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> and 38 minutes. The late recognition of the inoperable battery also resulted in TS 3.8.1.F being exceeded by 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and 38 minutes (1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> until 1738 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.61309e-4 months <br />) unless failure analysis shows the cell could have provided field flashing for the 33 EDG. The event is also reportable under 10 CFR 50.73(a)(2)(v)(1)), any event or condition that could have prevented the fulfillment of a safety function necessary to mitigate the consequences of an accident. The 31 EDO was declared inoperable at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on August 5, 2003 while Battery 31 was inoperable. Battery 31 provides field flashing and is required for 33 EDG to be operable. Therefore, a loss of the onsite AC power system {EK} EDG function occurred for up to 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and 38 minutes. If failure analysis shows the 31 Battery could have provided flashing for the 33 EDG, the loos of safety function may be reduced to one hour and 22 minutes.
PAST SIMILAR EVENTS
A review of Licensee Event Reports reporting operation outside TS or safety system functional failures over the last two years identified the following:
- LER 2002-001 reported an inoperable Service Water pipe caused by a leak that was reportable when the allowed outage time was exceeded. Enforcement discretion allowed the outage time to be exceeded.
- LER 2002-002 reported an inoperable Isolation Valve Seal Water System due to a mispositioned valve. This condition was outside TS and a safety system functional failure. The cause of the mispositioning of the valve was human error, the failure to perform all system restoration steps during performance of a surveillance test.
EVENT SAFETY SIGNIFICANCE
These conditions had no significant effect on the health and safety of the public.
The 31 Battery is part of DC electrical power (E.]} subsystem 31, which supplies normal and emergency DC electrical power for 33 EDG, and control and switching for 480 volt Bus {BU} 5A loads. The subsystem also supplies one of the four 120 V AC vital instrument (EB) buses via 31 Static Inverter (INVT). The 31 Static Inverter, in turn, powers:
■ one of the four Reactor Protection System (RPS) {JO instrumentation channels.
■ one of the two trains of ESFAS instrumentation logic.
one of the four Engineered Safety Features Actuation System (ESFAS) {,TE} instrumentation channels.
■ one of the two trains of RPS instrumentation actuation logic.
There were no actual safety consequences for this event because the plant systems were not required due to any events while the battery was inoperable.
The safety significance was also evaluated based on risk and determined to be non- risk significant. The most conservative case is considering the 31 Battery out of service for 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> (1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on August 4 to 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on August 5) with the 31 EDG concurrently out of service for 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> (0400 to 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on August 5). The increase in core damage probability for this condition is 3.91E-7, which is not risk significant. Engineering judgment indicates that the 31 Battery would have remained operable, except for the one hour and 22 minutes when it was isolated for repairs, long enough to flash the field of the 33 EDG so that two EDG would have been functional and possibly for the two hour duty cycle. The testing of Cell 26 that is currently being scheduled will establish the extent of battery operability and could change the core damage probability. The increase in core damage probability for the 31 Battery out of service for 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> and the two EDG out of service for one hour and 22 minutes is 1.04E-7. The increase in core damage probability for the 31 Battery and the two EDG out of service for one hour and 22 minutes (i.e., within the TS allowed outage time) is 3.78E-8.