5 mai 2010
Les pompes de recirculation n’ont pas démarré après l’arrêt d’urgence. Ce défaut a engendré un problème de niveau d’eau qui lui-même a engendré un problème de pressions dans le réacteur. Le cœur étant critique, ces évènements ont activé le système de protection du réacteur ainsi que d’isolement du circuit primaire.
Type : BWR Mark1 - Puissance : 2 923 MWTh - Première divergence : 10 1976 -
Available in english only
Event Number : 45902 Facility : BRUNSWICK Region : 2 State : NC Unit : [1] RX Type : [1] GE-
Event Date : 05/05/2010 Event Time : 11:44 [EDT]
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Initial PWR : 100 % Current PWR : 0 %
Event Text
AUTOMATIC REACTOR SCRAM DUE TO REACTOR FEED PUMP TRIP
"On May 5, 2010, at 1144 hours Eastern Daylight Time (EDT), an automatic reactor scram occurred on Unit 1 following a trip of the 1B Reactor Feed Pump (RFP). Following the 1B RFP trip, the reactor recirculation pumps did not run back as expected. The resulting water level shrink caused level in the Reactor Pressure Vessel (RPV) to drop to Low Level 1, causing the activation of the Reactor Protection System (RPS) and the Primary Containment Isolation System (PCIS). All control rods properly inserted.
"PCIS Group 2 (i.e., Drywell Equipment and Floor Drain, Residual Heat Removal (RHR) Discharge to Radwaste, and RHR Process Sample), Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems), and Group 8 (i.e., RHR Shutdown Cooling) isolation signals were received on Low Level 1. Actuations of the Primary Containment Isolation Valves (PCIVs) were completed and the affected equipment responded as designed.
"Due to the expected RPV level reduction following a reactor scram, water level in the RPV momentarily reached Low Level 2. This initiated the High Pressure Coolant Injection (HPCI) System, the Reactor Core Isolation Cooling (RCIC) System, and a partial Group 3 PCIS (i.e., RWCU) isolation. The HPCI and RCIC systems did not inject. The 1-G31-F001 isolated (i.e., inboard isolation) but 1-G31-F004 (i.e., outboard isolation) did not automatically isolate. Based on a preliminary assessment, this response appears to be in accordance with plant design. Further assessments of plant response are on-going to validate plant response.
"The licensee has notified the NRC Resident Inspector."
The scram was uncomplicated. No SRVs lifted. Decay heat removal is via the ’A’ feed water pump via the turbine bypass valves to the condenser. The electrical line-up of Unit 1 is normal. Brunswick Unit 2 was not affected.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2010/20100506en.html