Indian Point Pressurizer Safety Valve: a 66% Failure Rate

 Safety Valves In Our Nuclear Power Plants Going Wild

 

These are the guys with all the scrams and shutdowns. 

Condition Due to Two Pressurizer Code Safety Valves Discovered Outside Their As-Found Lift Setpoint Test Acceptance Criteria"Indian Point Unit No. 3 Docket No. 50-286 DPR-64

On July 1, 2015, Engineering was notified by Wyle Laboratories that two of three Pressurizer {AB} Code Safety Valves (RC-PCV-464 and RC-PCV-468) {RV} removed during the spring 2015 refueling outage (RO) failed their As-Found lift set point test acceptance criteria (2411 - 2559 psig) . The As-Found set pressure testing acceptance criterion for operability is 2485 +/-3%. The SVs were .removed during the last refueling outage (RO) in the spring of 2015 and sent offsite for testing. Testing was performed within one year of removal as required by the Inservice Testing Program. Testing found SV RCPCV- 464 as-found lift pressure was 2573 (0.5% above the allowable As-Found *upper limit of 2559 psig), and SV RC-PCV-468 as-found lift pressure was 2379 psig (1.2% below allowable AS-Found lower limit of 2411 psig), which is outside their set pressure range acceptance criterion. The remaining SV lift tested satisfactorily. All three SVs were found with zero seat leakage. During the RO all three SVs were removed and replaced with certified pre-tested spare SVs. The SVs installed during the RO were As-Left tested to 2485 +/-1% with zero seat leakage in accordance with procedure 3-PT-R5A. Technical Specification (TS) 3.4.10 (Pressurizer Safety Valves), requires three pressurizer safety valves to be operable with lift settings set at greater than 2460 psig and less than 2510 psig. TS Surveillance Requirement (SR) 3.4.10.1 requires each PSV to be verified operable in accordance with the Inservice Testing Program. The condition was recorded in the Indian Point Energy Center (IPEC) Corrective Action Program (CAP) in Condition Report CR-IP3-2015-03710 and CR-1P3-2015-03708.

The pressurizer safety valves (SVs) are totally enclosed pop type, spring loaded, selfactuating 6 inch by 6 inch valves manufactured by Crosby Valve Company {C711}, Model HB-BP-86 Type E. The SVs are designed to prevent the system pressure from exceeding the system Safety Limit (SL) of 2735 psig, which is 110% of the design pressure.

The Cause of Event

The exact cause of failure of valves RC-PCV-464 and RC-PCV-468 is not known at this time. The most probable cause of By RC-PCV-464 lifting greater than 3% of its nominal setpoint was setpoint drift. The most probable cause of RC-PCV-468 lifting within less than 3% of its nominal setpoint was spring relaxation. The two valves that failed As-Found testing criteria (valve RC-PCV-464 and RC-PCV-468) will be disassembled and inspected to determine the cause of the failure.

They can't see the degradation at power. If they seen it, they would quickly have to shutdown per tech specs. No rush worrying about about if it is spring. Remember in Pilgrim, they damage the spring on the test stand. 

I think it is a plant design defect. If there were four safety valves, then they never would have crossed a tech spec shutdown. I guess only some required tech spec conservative shutdowns are applicable.   

TS 3.4.10 Condition B (Required action and associated completion time not met or Two or more pressurizer safety valves inoperable) required action B.l is be in Mode 3 in 6 hours and B.2 be in Mode 4 within 12 hours. This TS action was not performed and the actions of Condition B not implemented, the condition is a TB prohibited condition. In the UFSAR Chapter 14 analysis, the opening setpoint of the three PSRVs is assumed to be at +/-4% of the nominal 2485 psig value for applicable Chapter 14 transients…