ENS 53135
ENS Event | |
|---|---|
01:50 Oct 26, 2017 | |
| Title | Invalid Actuation of Cooling Water System |
| Event Description | At 2050 [CDT] on October 25, 2017, during the Unit 2 refueling outage, with no fuel in the Reactor Vessel, control room operators found that Unit 1 Train B Containment Fan Coil Units (FCUs) had swapped from chilled water to cooling water (CL). Construction Electricians were installing a new relay 2Sl-22X when the plunger on adjacent relay 2Sl-23X was bumped, which caused the swap of the Unit 1 Containment Fan Coil Units (CFCUs) from chilled water to cooling water. Relay 2SI-23X is a slave relay that starts 22 Turbine Driven Auxiliary Feed Water Pump, illuminates blue lights on various control switches, closes MV-32159 Loop A/B CLG WTR HDR XOVR MV B, closes chilled water Isolation Valves to Unit 1 Train B, and closes chilled water Isolation Valves to Unit 2 Train B.
This actuation was as expected. CL is a shared system and, upon a Safety Injection (SI) signal on either unit, the CL header splits into two trains and, as a result, the CL supply is isolated to the chillers that supply chilled water to both units' CFCUs. By design, CL is the safety related source of cooling to the CFCUs. 22 Turbine Driven Auxiliary Feed Water Pump did not start as the unit was in 'No Mode' with the control switch for the pump in manual. MV-32159 did automatically close per design. Unit 2 Chilled Water was already isolated due to work in progress with the unit in 'No Mode.' There was no impact on public health and safety. This event is being reported as a 60-day telephone notification in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an invalid actuation of a containment heat removal system (the FCUs were running, but were swapped to their safeguards source due to an invalid actuation of a relay). The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
| Prairie Island Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1376.32 h57.347 days <br />8.192 weeks <br />1.885 months <br />) | |
| Opened: | Alex Thornburg 11:09 Dec 22, 2017 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Dec 22, 2017 |
| 53135 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 531352017-10-26T01:50:00026 October 2017 01:50:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Cooling Water System ENS 531342017-10-23T13:56:00023 October 2017 13:56:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Emergency Diesel Generator ENS 507022014-10-26T08:40:00026 October 2014 08:40:00 Other Unspec Reqmnt, 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification of Invalid Actuation of Residual Heat Removal Pump ENS 438342007-10-15T20:02:00015 October 2007 20:02:00 10 CFR 50.73(a)(1), Submit an LER Inadvertent Start of Emergency Diesel Generator D2 2017-10-26T01:50:00 | |