15 septembre 2014
Deux gaines ont été découvertes endommagées sur 20 à 25 cm. L’assemblage a été placé dans un compartiment précis de la piscine de combustible et il n’y aurait eu aucune augmentation anormale de l’activité radiologique lors de son transfert. Cet assemblage était en fin de vie car il avait été utilisé durant trois cycles. Une inspection vidéo du 15 septembre a montré que les ressorts supérieurs d’appui des pastilles de combustible avaient été délogés. Une analyse visuelle de la cuve indique la présence de débris qui pourraient être des fragments de pastille de combustible sur le fond de la cuve. Des enquêtes complémentaires sont en cours. La déclaration de ce problème est exigée suite à la découverte d’une dégradation importante de l’une des barrières de sécurité.
Type : PWR - Puissance : 2 940 MWth - Première divergence : 06/1980
Available in english only.
Event Number : 50457
Facility : NORTH ANNA - State : VA Unit : [2] W-3-LPNRC
Event Date : 09/15/2014 Event Time : 09:00 [EDT]
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(A) - DEGRADED CONDITION Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode 2 N N 0 Refueling 0 Refueling
Event Text
FAILED FUEL ASSEMBLY IDENTIFIED DURING CORE OFF-LOAD
"With North Anna Unit 2 in Mode 6 during a scheduled refueling outage, discharged assembly 4Z9 was identified as a failed fuel assembly by In-Mast Sipping. The fuel assembly was located in core location B11. Initial inspection of the fuel assembly identified two (2) visibly split fuel pins of eight (8) to ten (10) inches long with visible damage to the top of the pins. The internals of the affected pins are visible and the springs from the top of each pellet stack are touching the top nozzle. The fuel assembly has been placed into its designated location in the Spent Fuel Pool. No abnormal increase was noted on any radiation monitor either after or during fuel assembly movement. This fuel assembly had been used during three (3) previous operating cycles and is not scheduled for reuse.
"On September 15, 2014, at 0900 [EDT], subsequent video inspection of the fuel assembly identified that the top springs of the two (2) fuel pins were dislodged. Video inspection of the reactor vessel identified debris that has the potential to be fragments of fuel pellets resting on the core plate. Additional investigations are in progress.
"Due to the fact that the failure exceeded expected conditions, this event is being reported per 10 CFR 50.72(b)(3)(ii)(A), as any event or condition that results in the condition of the nuclear plant, including its principle safety barriers, being seriously degraded."
The licensee has notified the NRC Resident Inspector and will notify local county authorities.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140916en.html#en50457