05000454/FIN-2009008-01
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Finding | |
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| Title | Potential Failure of all the Emergency Diesel Generators (EDG) for Both Units 1 and 2 during a Loss of Offsite Power Event |
| Description | The inspectors identified an unresolved item regarding the EDG Jacket Water (JW) thermostatic 5043 control valves (5043 valves). As part of the review of the root cause evaluation for the partial loss of instrument air for both units that occurred August 18, 2007, the inspectors reviewed piping and instrumentation diagrams (P&IDs) to identify equipment that would fail to operate after a loss of instrument air. The inspectors identified that a loss of offsite power would cause a loss of instrument air and would cause the EDG JW thermostatic control valve 5043 valve on each EDG to fail open. The EDG Jacket Water Cooling System is a closed system and is cooled by the Essential Service Water System (SX) through the JW heat exchanger (HX). The system keeps engine warm to promote rapid starts in standby and removes heat from engine during EDG operation. After a design basis accident, the EDGs might be operated in unloaded condition for short periods of time during swapping of loads or starting and stopping of EDGs. As a result the system would not be able to control the amount of JW going to the JW HX with a loss of instrument air. The Updated Final Safety Analysis Report stated that the SX system temperature was designed to range from 40 to 100 degrees Fahrenheit. The inspectors were concerned that during low SX temperature periods (e.g. winter months), these failed open valves might allow excessive cooling to the JW system of EDG and adversely affect the operability of the EDGs and the ability to perform the required safety functions. The licensee initiated IR 958882 to document this NRC concern and perform a thorough evaluation to demonstrate that the EDGs will adequately perform the required safety functions. In addition, Section 6 of the licensees 10 CFR 50.59 Safety Evaluation 6G-98-0275 for a previously replaced 5053 valve controller stated that Failure of the original or replacement controller may affect the quick start of the diesel as the engine is not pre-warmed. The licensee stated that the evaluation required by the IR would demonstrate that the statement in the Safety Evaluation was not applicable. Pending the licensees submittal of the evaluation and calculation to the NRC for review to resolve this issue, this item will be tracked as an unresolved item (URI 05000454/2009008-01; URI 05000455/2009008-01) |
| Site: | Byron  |
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| Report | IR 05000454/2009008 Section 4OA2 |
| Date counted | Sep 30, 2009 (2009Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | C Thompson J Robbins E Coffman R Skokowskib Bartlettb Palagi C Thompson J Cassidy J Robbins N Adorno R Jickling R Ng R Skokowski |
| INPO aspect | |
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Finding - Byron - IR 05000454/2009008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2009Q3
Self-Identified List (Byron)
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