ENS 46603
ENS Event | |
|---|---|
14:00 Feb 8, 2011 | |
| Title | Unanalyzed Event Could Initiate High Pressure Core Spray and Overfill the Reactor Pressure Vessel |
| Event Description | 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. While it is not expected that a failure of the MSSRV discharge line will occur, a confirmatory analysis will be performed. Compensatory measures for Multiple Spurious Operations have been determined to be adequate until the analysis is complete. The licensee added additional fire zone surveillance to operator plant walk downs and will investigate to determine further corrective actions. The license has notified the NRC Senior Resident Inspector. |
| 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
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (97 %) |
| After | Power Operation (97 %) |
WEEKMONTHYEARENS 531102017-12-09T19:48:0009 December 2017 19:48:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Manual Reactor Scram Due to Loss of Division 1 Ac Power to Numerous Components ENS 526012017-03-09T09:19:0009 March 2017 09:19:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Relay Failure ENS 523772016-11-17T23:00:00017 November 2016 23:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Incorrect Method Used for Calculation of Control Room Habitability ENS 516692016-01-20T19:11:00020 January 2016 19:11:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Primary-Secondary Containment Pressure Differential Exceeded Due to Ccp Exhaust Fan Trip ENS 493732013-09-20T14:17:00020 September 2013 14:17:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Safe Shutdown Analysis Reveals Noncompliance for a Fire Outside Diesel Room ENS 475102011-12-08T11:00:0008 December 2011 11:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Non Fused Dc Bus Ammeters Could Short and Cause a Fire ENS 466032011-02-08T14:00:0008 February 2011 14:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Event Could Initiate High Pressure Core Spray and Overfill the Reactor Pressure Vessel ENS 451222009-06-10T14:20:00010 June 2009 14:20:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Unknown Cable with Combustible Coating Found in Division I / Division II Cable Tray 2017-03-09T09:19:00 | |