Etats-Unis : Calvert Cliffs : Technical specification required shutdown due to RCS pressure boundary instrument line leakage

21 juillet 2012

Fuite de liquide primaire sur une ligne qui contrôle la pression de la pompe de refroidissement du réacteur (0.8 gpm soit environ 183 litres/heure). Le réacteur est en cours d’arrêt.

Available in english only.

Facility : CALVERT CLIFFS - Region : 1 State : MD - Unit : [1] [ ] [ ]

Event Date : 07/21/2012 - Event Time : 12:10

Emergency Class : NON EMERGENCY

50.72(b)(3)(ii)(A) - DEGRADED CONDITION

Event Text TECHNICAL SPECIFICATION REQUIRED SHUTDOWN DUE TO RCS PRESSURE BOUNDARY INSTRUMENT LINE LEAKAGE

"[Calvert Cliffs Nuclear Power Plant] CCNPP U1 identified RCS Pressure Boundary Leakage from the instrument line to 1-PDT-123A, 11A reactor coolant pump differential pressure transmitter. Technical Specification 3.4.13, Action B was entered and requires that the Unit be placed in Mode 3 within 6 hours and Mode 5 within 36 hours. [The licensee has] initiated plant shutdown in accordance with this Technical Specification. Therefore, this is reportable under 10CFR50.72(b)(2)(i) Plant Shutdown Required by Technical Specifications. This is also reportable under 50.72(B)(3)(ii)(A) as a material defect in the primary coolant system that cannot be found acceptable under ASME Section XI, IWB-3600 or ASME Section XI, Table IWB-3410-1."

The leak is from an instrument line which monitors reactor coolant pump differential pressure. It is for monitoring purposes only. The leak rate is currently about .08 gpm. The licensee has begun power reduction of the unit and is currently at approximately 73% rated thermal power. The recovery plan is to complete the unit shutdown and then enter containment and repair the leak.

The leak is believed to be coming from the same instrument line that was reported to be leaking on July 17, 2012 (see EN #48116). At that time, power was reduced to approximately 10% and a containment entry was made. At that time it was believed that the leak had been isolated and full power operations were resumed. Based on containment sump pump run times and another containment entry, it was determined that the leak apparently had not been isolated.

The licensee notified the NRC Resident Inspector.

https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20120723en.html

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