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Etats-Unis : Beaver Valley : Problème sur deux pénétrations supérieures de cuves




5 octobre 2015


C’est pendant l’arrêt du réacteur n° 2 pour rechargement qu’ont été découverts les problèmes sur les pénétrations de cuve. Les défauts mis à jour par ultrasons montrent que les prescriptions de limite de pression pour le système de refroidissement ne pouvaient pas répondre aux exigences de "l’American Society of Mechanical Ingeneers". Les dégradations ne sont pas traversantes car il n’y a pas eu de trace de fuite détectée, mais ce problème est susceptible de remettre en cause l’intégrité du circuit primaire. Les réparations sont en cours de planification.

Type : PWR - Puissance : 2 900 MWth - Première divergence : 08/1987

Available in english only.


Event Number : 51453

Facility : BEAVER VALLEY - State : PA

Unit : [2] - RX Type : [2] W-3-LP

Event Date : 10/05/2015 Event Time : 08:15

Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(A) - DEGRADED CONDITION

Initial PWR : 0% Current PWR : 0%

Event Text

TWO REACTOR VESSEL HEAD PENETRATIONS COULD NOT BE DISPOSITIONED AS ACCEPTABLE

"On 10/5/2015, during the Beaver Valley Power Station Unit No. 2 (BVPS-2) refueling outage, while performing planned ultrasonic examinations (UT) on the 66 reactor vessel head penetrations, it was determined, that two penetrations could not be dispositioned as acceptable per ASME [American Society of Mechanical Engineers] Code Section XI in a Reactor Coolant System pressure boundary. The indications of a degraded condition, on these two penetrations, are not through wall, as no leak path was identified. The examinations are being performed to meet the requirements of 10 CFR 50.55a(g)(6)(ii)(D), and ASME Code Case N-729-1, to find potential flaws/indications well before they grow to a size that could potentially jeopardize the structural integrity of the reactor vessel head pressure boundary. All 66 reactor vessel head penetrations are scheduled to be examined during the current refueling outage.

"The plant is currently shutdown and in Mode 6. The reactor vessel head is not currently installed. Repairs are currently being planned and will be completed prior to startup.

"This is reportable, pursuant to 10 CFR 50.72(b)(3)(ii)(A) since the as found indications did not meet the applicable acceptance criteria referenced in ASME Code Case N-729-1 to remain in-service without repair.

"The NRC Resident Inspector has been notified."

http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2015/20151006en.html#en51453