05000261/FIN-2011002-07
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Finding | |
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Title | None |
Description | TS 3.4.9, Pressurizer, required Pressurizer heaters operable with a capacity of greater than or equal to 125 kW and capable of being powered from an emergency power supply. Contrary to this in December of 2008 the pressurizer heaters were inoperable for approximately 95 hours0.0011 days <br />0.0264 hours <br />1.570767e-4 weeks <br />3.61475e-5 months <br /> which exceeds the allowed outage time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The cause of the event occurred in the fall of 1979 in response to NUREG- 0578, TMI-2 Lessons Learned Task Force Status Report and Short-term Recommendations. The licensee revised procedure EI-15, Control Room Inaccessibility based on the assumption the pressurizer heater emergency power supply scheme was redundant. The cause of the violation was the licensee did not recognize the low pressurizer level heater cutoff relay was powered from the A train and would preclude energizing the required pressurizer heaters from the B train if the A train was inoperable. Immediate corrective actions included revising the implementing procedure to lift a control lead to allow the B EDG to power the required pressurizer heaters if needed during an event with the A EDG inoperable. The licensee entered the issue into the corrective action program as NCR 413865. The finding was evaluated in accordance with IMC 0609.04, Significance Determination Process. A regional Senior Reactor Analyst evaluated the performance deficiency using the Phase 3 protocol of the Significance Determination Process. Based upon the results of that evaluation, the performance deficiency was characterized as of very low safety significance (Green). The major assumptions of the evaluation included a one year exposure time, that the performance deficiency was only associated with a Loss of Offsite Power initiator and, that the lack of Pressurizer heaters eventually led to a loss of sub-cooled margin, which removed the steam generators as a viable heat sink and resulted in a feed and bleed safety injection condition. The postulated dominant accident sequence was a switchyard induced Loss of Offsite Power with Emergency Diesel Generator A out of service for test and maintenance. Neither offsite power nor Emergency Diesel Generator A was returned to service within one hour. Within that one hour operators were unable to preclude a feed and bleed safety injection. Consequently, the opened safety relief valve initiated a Small Break Loss of Coolant Accident. Operators then failed to place High Pressure Recirculation into service properly in response to the Small Break Loss of Coolant Accident. Therefore, the core was not cooled and core damage ensued |
Site: | Robinson ![]() |
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Report | IR 05000261/2011002 Section 4OA7 |
Date counted | Mar 31, 2011 (2011Q1) |
Type: | NCV: Green |
cornerstone | Mitigating Systems |
Identified by: | Licensee-identified |
Inspection Procedure: | |
Inspectors (proximate) | J Hickey R Musser E Lea C Scott W Deschaine M Riches |
INPO aspect | |
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Finding - Robinson - IR 05000261/2011002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Robinson) @ 2011Q1
Self-Identified List (Robinson)
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