ENS 43391
ENS Event | |
|---|---|
18:17 May 27, 2007 | |
| Title | Manual Reactor Trip in Mode 3 During Control Rod Testing |
| Event Description | On May 27, 2007, at 11:17 PDT, with Diablo Canyon Power Plant (DCPP) Unit 1 in Mode 3 (Hot Standby) during day 28 of refueling outage 14, operators manually actuated the reactor protection system. All rods fully inserted.
Operators were performing Surveillance Test Procedure (STP) R-1 C 'Digital Rod Position Indictor Functional Test'. While control bank C was being re-inserted, at 42 steps withdrawn, rod N-13 indicated position changed to 24 steps withdrawn. In response to this 18 step deviation, and in accordance with STP R-1C, operators opened the reactor trip breakers. At the time of the event, the reactor coolant system remained at normal operating temperature and pressure, and all other shutdown and control rod banks remained fully inserted. This event is being reported as an 8-hour non-emergency event in accordance with 10 CFR 50.72(b)(3)(iv)(A) for a valid actuation of the reactor protection system. Unit-1 is maintaining temperature with atmospheric steam dumps and aux feed water. Electrical power is from 500 KV backfeed (normal electrical shutdown lineup). Control rod N-13 was being tested along with seven other control rods. The licensee notified the NRC Resident Inspector.
(STP) R-1C 'Digital Position Indicator Functional Test' was re-performed on control bank C to obtain additional information. At 1706 hours0.0197 days <br />0.474 hours <br />0.00282 weeks <br />6.49133e-4 months <br />, while control bank C was being re-inserted, at 138 steps withdrawn, rod N-13 indication dropped to 126 steps withdrawn. Rod motion was stopped to gather data. All other shutdown and control banks remained fully inserted. At 1725 hours0.02 days <br />0.479 hours <br />0.00285 weeks <br />6.563625e-4 months <br />, operators manually actuated a reactor trip to fully insert all control bank C rods. All rods fully inserted. (STP) R-1C 'Digital Rod Position Indicator Functional Test' was re-performed on control bank C for further evaluation. At 1838 hours0.0213 days <br />0.511 hours <br />0.00304 weeks <br />6.99359e-4 months <br />, while control bank C was being re-inserted, at 168 steps withdrawn, rod N-13 indication dropped to 150 steps withdrawn. Rod motion was stopped to gather data. All other shutdown and control banks remained fully inserted. At 1840 hours0.0213 days <br />0.511 hours <br />0.00304 weeks <br />7.0012e-4 months <br />, operators manually actuated a reactor trip to fully insert all control bank C rods. All rods fully inserted. At the time of the event, the reactor coolant system remained at normal operating temperature and pressure, and all other shutdown and control rod banks remained fully inserted." R4DO (C. Johnson) notified. The licensee will notify the NRC Resident Inspector.
On May 27, 2007, in response to the initial occurrence of Rod N-13 slipping at 11:17 PDT, PG&E contacted the vendor and researched operating experience to develop a troubleshooting plan. Management approved a plan based on the vendor recommendations, which consisted of exercising all rods successfully five cycles. It was acknowledged that additional slipping events could occur requiring mitigation by opening the reactor trip breakers. Upon implementation of this plan, two similar events occurred and are described in the update above [provided on 05/27 at 2301 EDT]. Following these events, Rod N-13 was successfully cycled five times without any deviation. Reactor startup was then allowed to proceed and there have been no further rod position deviation events. The licensee notified the NRC Resident Inspector. Notified R4DO (C. Cain) |
| Where | |
|---|---|
Diablo Canyon  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000275/LER-2007-002 |
| Time - Person (Reporting Time:+-0.15 h-0.00625 days <br />-8.928571e-4 weeks <br />-2.0547e-4 months <br />) | |
| Opened: | Matt Coward 18:08 May 27, 2007 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | May 31, 2007 |
| 43391 - NRC Website
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Unit 1 | |
|---|---|
| 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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