ENS 47857
ENS Event | |
|---|---|
09:15 Apr 21, 2012 | |
| Title | Main Steam Isolation Valves Fail to Shut |
| Event Description | At approximately 0515 EDT on April 21, 2012, the Harris Nuclear Plant [HNP] was in the process of a normal plant shutdown for a refueling outage. HNP was at 0% power in Mode 4. During OST-1046, MSIV Operability Test, 'B' and 'C' Main Steam Isolation Valves (MSIV), failed to close from the main control board.
At 0648 EDT an April 21, 2012 'B' MSIV shut immediately after the instrument air supply was isolated. At 0938 EDT an April 21, 2012 'C' MSIV shut after the instrument air supply was isolated. The cause of the equipment failure is not yet known but is currently being investigated. This report is being made in accordance with 10 CFR 50.72 (b)(3)(v)(C), inability to isolate and mitigate a radioactive release, and 10 CFR 50.72 (b)(3)(v)(D), a condition which could have prevented the fulfillment of a safety function to mitigate the consequences of an accident. The plant continues to remain shutdown at 0% power. Other equipment functioned as expected including the turbine isolation valves. The licensee notified the NRC Resident Inspector.
Investigation into the condition revealed the instrument air supply to the MSIVs was isolated at 0530 EDT and 'B' MSIV indicated [drifted] shut at 0607 EDT. The plant is currently in Mode 6, Refueling, and the investigation is ongoing. The licensee notified the NRC Resident Inspector. Notified R2DO (Musser). |
| Where | |
|---|---|
Harris  North Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.5 h0.146 days <br />0.0208 weeks <br />0.00479 months <br />) | |
| Opened: | Al Bostic 12:45 Apr 21, 2012 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Apr 24, 2012 |
| 47857 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Hot Shutdown (0 %) |