ENS 46603: Difference between revisions
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| event date = 02/08/2011 08:00 CST | | event date = 02/08/2011 08:00 CST | ||
| last update date = 02/08/2011 | | last update date = 02/08/2011 | ||
| title = Unanalyzed Event Could Initiate High Pressure Core Spray | | title = Unanalyzed Event Could Initiate High Pressure Core Spray and Overfill the Reactor Pressure Vessel | ||
| event text = During the performance of a Fire Protection self assessment, it was discovered that a calculation for the safe shutdown analysis has an assumed action for an operator to locally depress the internal breaker trip plunger to trip the High Pressure Core Spray (HPCS) pump in response to a fire in the main control room. However, due to personnel safety concerns related to potential arc flashing events associated with this action, the remote shutdown procedure was revised to locally close the HPCS injection valve (1E22FOO4) in lieu of depressing the internal breaker trip plunger. | | event text = During the performance of a Fire Protection self assessment, it was discovered that a calculation for the safe shutdown analysis has an assumed action for an operator to locally depress the internal breaker trip plunger to trip the High Pressure Core Spray (HPCS) pump in response to a fire in the main control room. However, due to personnel safety concerns related to potential arc flashing events associated with this action, the remote shutdown procedure was revised to locally close the HPCS injection valve (1E22FOO4) in lieu of depressing the internal breaker trip plunger. | ||
During engineering's review of this procedure and supporting calculation, it was determined that the HPCS system could be initiated due to concurrent fire induced hot short cable damage to the two automatic initiation logic instrument cables routed in the same raceway in the area. In this event, even if the HPCS breaker could be tripped or the HPCS injection valve could be closed locally, HPCS would continue to fill the reactor pressure vessel (RPV) and flood the main steam lines. Once pressure reaches the setpoint for the Main Steam Safety Relief Valves (MSSRVs), they would lift and discharge mixed-phase water through the discharge line to the suppression pool. This conservatively postulated scenario would place the MSSRVs and their associated tailpipes in an unanalyzed condition for the stresses expected during the two-phase flow event. | During engineering's review of this procedure and supporting calculation, it was determined that the HPCS system could be initiated due to concurrent fire induced hot short cable damage to the two automatic initiation logic instrument cables routed in the same raceway in the area. In this event, even if the HPCS breaker could be tripped or the HPCS injection valve could be closed locally, HPCS would continue to fill the reactor pressure vessel (RPV) and flood the main steam lines. Once pressure reaches the setpoint for the Main Steam Safety Relief Valves (MSSRVs), they would lift and discharge mixed-phase water through the discharge line to the suppression pool. This conservatively postulated scenario would place the MSSRVs and their associated tailpipes in an unanalyzed condition for the stresses expected during the two-phase flow event. | ||
Latest revision as of 22:07, 1 March 2018
| Where | |
|---|---|
Clinton  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| LER: | 05000461/LER-2011-001 |
| Time - Person (Reporting Time:+1.1 h0.0458 days <br />0.00655 weeks <br />0.00151 months <br />) | |
| Opened: | Dan Hunt 15:06 Feb 8, 2011 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Feb 8, 2011 |
| 46603 - NRC Website
| |