ENS 43042
ENS Event | |
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00:08 Dec 11, 2006 | |
Title | |
Event Description | On December 10, 2006, at 1608 PST, operators manually tripped the reactor while it was subcritical. This is an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> notification per 10 CFR 50.72(b)(3)(iv)(A) for actuation of the reactor protection system while subcritical. On December 10, 2006, with Unit 2 operating in Mode 1 at 100% power, operators initiated an unplanned reactor shutdown due to indications of increasing stator temperature on reactor coolant pump 2-2. In accordance with plant procedures, when the reactor coolant pump stator temperature reached 300 degrees Fahrenheit, operators manually tripped the reactor and tripped the coolant pump 2-2. The reactor was subcritical at the time of the reactor trip but all rods had not been fully inserted.
All control rods fully inserted in response to the reactor trip and all systems functioned as required. The auxiliary feedwater system was already in service as part of the shutdown. The grid is stable and with the exception of RCP 2-2, all major equipment including the 3 emergency diesel generators remain operable. Unit 2 electrical loads are being supplied by the normal startup power. The other 3 RCPs are maintaining forced circulation of the reactor coolant system. Investigations into the high RCP stator temperature are ongoing, the unit will remain in Mode 3 pending the results of these investigations. An estimated restart date is not known at this time. The NRC Resident Inspector has been informed and was onsite at the time of the trip. Unit 1 is unaffected and remains in Mode 1. The licensee stated that a press release related to this event is likely.
Licensee believes the cause of the high RCP stator temperature was due to a failed RTD.
Unit 2 was in Mode 3 (Hot Standby) at 0 percent power at the time of the manual trip. At the time of the Initial notification, all procedural requirements for declaring Mode 3 had not been met, but upon further review, PG&E has verified K effective was less than 0.99. The licensee notified the NRC Resident Inspector. Notified R4DO (Proulx). The original report was modified by this change. The 'RX Crit' field was changed from 'Y' to 'N'. The 'Init Power' field was changed from '5' to '0'. The 'Curr Power' field was changed from 'Startup' to 'Hot Standby'. |
Where | |
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Diablo Canyon California (NRC Region 4) | |
Reporting | |
10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
LER: | 05000323/LER-2006-003 |
Time - Person (Reporting Time:+0.38 h0.0158 days <br />0.00226 weeks <br />5.20524e-4 months <br />) | |
Opened: | Steve Hackleman 00:31 Dec 11, 2006 |
NRC Officer: | Bill Huffman |
Last Updated: | Dec 14, 2006 |
43042 - NRC Website
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Unit 2 | |
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Reactor critical | Not Critical |
Scram | Yes, Manual Scram |
Before | Hot Standby (0 %) |
After | Hot Standby (0 %) |
WEEKMONTHYEARENS 567692023-10-01T03:14:0001 October 2023 03:14:00
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Valid Bus Undervoltage Signal 2023-10-01T03:14:00 | |