ENS 48002
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ENS Event | |
|---|---|
08:29 Jun 7, 2012 | |
| Title | Both Trains of Low Temperature Overpressure System Inoperable |
| Event Description | On June 7, 2012, at 0129 PDT, both trains of the low temperature overpressure (LTOP) system were rendered inoperable when the vital 120 VAC panel PY-13 was de-energized due to a human performance error. DCPP Unit 1 was in Mode 5, reactor coolant system loops not filled. Technicians were troubleshooting an existing de-energized vital 120 VAC panel PY-14 that had resulted from the supply breaker tripping open. The technician incorrectly opened the supply breaker to panel PY-13 instead of PY-14. With PY-14 de-energized, one train of LTOP was inoperable due to loss of signal from Reactor Coolant System (RCS) wide range pressure transmitter PT-405A. With PY-13 de-energized, the second train of LTOP was rendered inoperable due to loss of signal from RCS wide range pressure transmitter PT-403A. Operations immediately recognized the error and had the technician reclose the PY-13 supply breaker, thereby re-energizing panel PY-13, returning one train of LTOP back to its operable condition.
Plant personnel notified the NRC Resident Inspector. |
| Where | |
|---|---|
| Diablo Canyon California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| LER: | 05000275/LER-2012-003 Regarding Low Temperature Overpressure Protection System Inoperable Due to Human Performance Error |
| Time - Person (Reporting Time:+3.45 h0.144 days <br />0.0205 weeks <br />0.00473 months <br />) | |
| Opened: | Michael Quitter 11:56 Jun 7, 2012 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Jun 7, 2012 |
| 48002 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
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