ENS 40161
ENS Event | |
|---|---|
04:30 Sep 16, 2003 | |
| Title | Reactor Coolant System Pressure Increase Caused a Valid Signal |
| Event Description | At 1150 hours0.0133 days <br />0.319 hours <br />0.0019 weeks <br />4.37575e-4 months <br /> on 9/15/03 during Reactor Coolant System (RCS) pressure increase to approximately 700 psig, the Core Flood (CF) Tank 1 outlet motor-operated valve (CF1B) opened when the breaker for the valve was closed. Because RCS pressure was not high enough to actuate the pressure switch setpoint of 770 psig to open this valve, it was believed this was an invalid signal, and therefore the valve opening was not reportable under the criteria of 10 CFR50.72
After further review, at 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> on 9/16/03 it was determined the sensed pressure was within the setpoint range of the switch, making this a valid signal to open the valve. The CF Tank pressure at the time (approximately 600 psig) was less than the RCS pressure of approximately 700 psig, therefore no discharge into the RCS occurred, and this event is not reportable per 10 CFR50.72(b)(2)(iv). The CF System is a passive system, but is used in conjunction with other Emergency Core Cooling Systems to mitigate significant events. Therefore, this event involving the opening of the CF Tank discharge valve CF1B is being conservatively reported in accordance with 10 CFR50.72(b(3)(2)(iv)(A) as a valid actuation of a train of the Emergency Core Cooling System. Upon opening of this valve, CF Tank 1 level and pressure were observed lowering with a corresponding rise in the Reactor Coolant Drain Tank, most likely due to leakage past a check valve. CF1B was closed according to procedures and the source breaker for the valve opened. The NRC Resident Inspector was notified by the licensee.
The actuation of the interlock for the Core Flood Tank 1 Outlet Isolation Valve did not constitute an actuation of the Core Flood System. The valve opened automatically as designed to ensure the Core Flood System was capable of performing its safety prior to being manually opened by the Operators. As part of the Emergency Core Cooling Systems, the primary function of the Core Flood System is to deliver cooling water to the reactor core in the event of a Loss of Cooling Accident per the Updated Safety Analysis Report. However, plant conditions (namely, Reactor Coolant System pressure lowering below Core Flood Tank pressure) did not exist that would have required the Core Flood System to perform its safety function. Therefore, the automatic opening of this valve does not constitute the actuation of the Emergency Core Cooling System, so this event is not reportable per 10CFR50.72(b)(3)(iv)(A). Therefore, NRC Event Number 40161 is retracted." R3DO (Anne Marie Stone) & NRR EO (Herb Berkow) notified. The NRC Resident Inspector will be informed of this retraction by the licensee. |
| Where | |
|---|---|
Davis Besse  Ohio (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+3.77 h0.157 days <br />0.0224 weeks <br />0.00516 months <br />) | |
| Opened: | Lewis 08:16 Sep 16, 2003 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Nov 11, 2003 |
| 40161 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Hot Shutdown (0 %) |
WEEKMONTHYEARENS 522322016-09-10T07:43:00010 September 2016 07:43:00
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