ENS 48002

v t e 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.

ENS 48002 +/-
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
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v • d • e

v t e Emergency Notification System
Diablo Canyon with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
WEEKMONTHYEAR2019-11-30T19:00:00 [Table view]
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