ENS 40983
ENS Event | |
|---|---|
14:17 Aug 24, 2004 | |
| Title | High Pressure Core Spray (Hpcs) Declared Inoperable |
| Event Description | At 1128 hours0.0131 days <br />0.313 hours <br />0.00187 weeks <br />4.29204e-4 months <br /> on 8/23/04, the Division 3 Essential Switchgear Heat Removal System (VX) was removed from service and declared inoperable for performance of system flow verification and balance. The test includes an as found flow check on the Division 3 Essential Switchgear Heat Removal System Condensing Unit, rendering the Division 3 VX safety-related chiller 1VX06CC INOPERABLE. The non-safety VX subsystem remained OPERABLE during the test.
At 0917 hours0.0106 days <br />0.255 hours <br />0.00152 weeks <br />3.489185e-4 months <br /> on 8/24/04, the non-safety Division 3 VX Heat Removal Supply Fan 1VX04CC, tripped due to the breaker for the safety-related fan being removed for replacement. The Main Control Room received alarm 5042-6A, Auto Trip Pump/Fan. Since both the safety and non-safety subsystems of VX were unavailable Operators declared the High Pressure Core Spray (HPCS) System inoperable per Technical Specification 3.7.2, Action A.1. At 1153 hours0.0133 days <br />0.32 hours <br />0.00191 weeks <br />4.387165e-4 months <br />, the breaker replacement was complete, 1VX04CC was restored to service, and the HPCS System was declared OPERABLE. The VX System maintains safety-related switchgear, battery and inverter room, and cable spread areas within the design temperature limits of the equipment. The VX system is support system for the HPCS System. With both subsystems of the VX System out of service, the HPCS System may not have been capable of performing its safety function to provide Emergency Core Cooling, aid in depressurization and maintain reactor vessel water level following a loss of coolant accident. An engineering evaluation is currently in progress to determine if the HPCS System would have been capable of performing its safety function with both safety and non-safety subsystems of VX out of service. This issue is being reported in accordance with 10CFR50.72(b)(3)(v)(D), as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function needed to mitigate the consequences of an accident. The NRC Resident Inspector was notified of this event by the licensee.
Upon further review of this event, additional analysis has been performed which bounds the design bases heatup of the associated rooms cooled by the Division III Essential Switchgear Heat Removal System (VX). This analysis concludes that the areas cooled by the Division 3 VX subsystem would not have exceeded design temperatures while the cooling was secured, prior to cooling recovery, and that the supported systems remained operable. Based upon this additional analysis, it can be reasonably concluded that the safety function of High Pressure Core Spray, as a single train safety system, was fulfilled. Therefore this event is not reportable and Event #40983 is being retracted. The NRC Resident Inspector was notified of this retraction by the licensee. R3DO (Clayton) has been notified. |
| Where | |
|---|---|
Clinton  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.32 h0.138 days <br />0.0198 weeks <br />0.00455 months <br />) | |
| Opened: | Steven Meng 17:36 Aug 24, 2004 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Oct 8, 2004 |
| 40983 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (95 %) |
| After | Power Operation (95 %) |