ENS 45937
ENS Event | |
|---|---|
21:40 May 19, 2010 | |
| Title | Both Trains of Residual Heat Removal (Rhr) Inoperable |
| Event Description | On 5/19/2010 at 1209 CDT, Unit 2 entered Mode 4 from Mode 5 and started realigning RHR from a shutdown cooling to an Emergency Core Cooling System (ECCS) lineup. During this transition, the suction check valves for the RHR pump are tested for safety function closed per the In-service testing program . The valves are closed to provide train separation for the RHR trains and to prevent diversion of flow from suction sources.
On 5/19/2010 at 1228 CDT, both Unit 2 trains of RHR were declared inoperable due to the failure of the pump suction line check valve for each RHR pump (2RH-3-1 and 2RH-3-2) to meet In-Service Testing (IST) acceptance criteria. Technical Specification 3.5.2 Condition A was entered for inoperability of the one required ECCS train (RHR) in Mode 4 with Reactor Coolant System (RCS) cold leg temperatures above safety injection pump disable temperature. On 5/19/2010 at 1640 CDT, both RHR pit sump covers were opened to facilitate multiple entries into each sump while performing a revised test procedure to verify the operability of check valves 2RH-3-1 and 2RH-3-2. The pit sump covers are required to be closed in [Modes 1 through 4] for each operable RHR train. Since both trains of RHR were inoperable both covers were opened. On 5/19/2010 at 1947 CDT the pit sump cover was closed for one train of RHR. On 5/19/2010 at 2005 CDT the revised test procedure was approved and completed satisfactorily. The train of RHR with the pit sump cover closed was declared operable and Technical Specification 3.5.3 Condition A was exited. Both suction check valves passed the closed safety function and a loss of safety function did not occur as originally thought on 5/19/2010 at 1228 CDT. On 5/19/2010 from 1640 CDT to 1947 CDT both trains of RHR were inoperable due to both pit sump covers open on both RHR trains. The inoperability of both trains of RHR represents a condition that prevented the fulfillment of the safety function of structure or systems that are needed to remove residual heat and mitigate the consequences of an accident. The licensee has notified the NRC Resident Inspector.
The purpose of this report is to retract the ENS report made on May 20, 2010 at 0124 hours0.00144 days <br />0.0344 hours <br />2.050265e-4 weeks <br />4.7182e-5 months <br /> [ET] (ENS #45937) under 10 CFR 50.72(b)(3)(v)(D), a condition that could have prevented fulfillment of a safety function. The pump suction line check valve for each Unit 2 RHR pump failed to meet acceptance criteria per the in-service testing program. A revised test was performed which demonstrated that the check valves could perform their safety function. The RHR pit covers were removed to facilitate this test. After test completion, it was identified that both trains of RHR were inoperable due to both pit covers being open. However, subsequent review has determined that the condition where pit covers were open did not impair the ability of the RHR system to meet its safety function. Also, there was not a loss of safety function due to the check valve testing issue. Thus, there was no safety system function failure of the RHR system. The licensee has notified the NRC Resident Inspector." Notified R3DO (Dickson) |
| Where | |
|---|---|
Prairie Island  Minnesota (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:+3.73 h0.155 days <br />0.0222 weeks <br />0.00511 months <br />) | |
| Opened: | Darell Lapcinski 01:24 May 20, 2010 |
| NRC Officer: | Charles Teal |
| Last Updated: | Jul 16, 2010 |
| 45937 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Hot Shutdown (0 %) |