Escalation of problems with Peach Bottom’s SRVs

Originally published on Nov 15, 2012

Nov 26: Doing a little work on this for a few days...

Nov 25: How come from a period of 8/01/2001 to 11/25/2003(8) compared to 8/01/2009 to 11/25/2011(23) there are 300% more BWR's safety relief valve license event reports from the same length of time.I did a search on these terms in NRC Adams document system... 

The two year period covers the typical 28 months to two year operating cycle....

Content search on "Safety Relief valve" and "LER". 

Do you think the NRC criteria for writing LER had loosened, tightened or stayed the same. I think it loosened.

Why are there more troubles today?  

Nov 18: LER2012001

"There were no previous similar LERs identified involving an ADS SRV inoperability due to failure of the actuator diaphragm thread seal."

Well, truth be told, in the 2003 dual plant trip with SRV failures, with the SRV pilot valve stem packing failure on the steam side, the steam leak from the main valve damaged the actuator diaphragm thread seal and the heated steam damaged the diaphragm preventing opening the valve by control room switch.

...Hmmm: "The six SRVs and the one SV were replaced with refurbished SRVs / SV for the 20th Unit 2 operating cycle."

"There were a total of seven SRVs and one SV initially removed for testing and replacement during the 1 9 th Refueling Outage."

So 6 out of 7 were failures...so a 86% failure rate...430% more failure than average... 

So this outage had 500% more SRV failures than expected and the alarms bells hadn't gone off? Licensee Event Report (LER) 3-07-01: 

(2007)A historical review of SRV as-found test set points indicates that approximately20% of valves tested over time do not meet the + 1% Technical Specification set point.

Unit 2  LER 2012001 event date 9/26/2012

Based on information received from a laboratory performing Safety Relief Valve (SRV) / Safety Valve (SV) as-found testing, Site Engineering personnel determined on 9/25/12 that SRV / SV setpoint deficiencies existed with six SRVs and one SV that were in place during the Unit 2 19th operating cycle. The SRVs / SV were determined to have their as-found setpoints outside of the Technical Specification allowable ± 1% tolerance. The six SRVs outside of their Technical Specification (TS) allowable setpoint range were within the ASME Code allowable ± 3% tolerance. The one SV outside of its TS allowable setpoint range also exceeded the ASME Code allowable ± 3% tolerance. The cause of the SRVs / SV being outside of their allowable as-found setpoints is due to setpoint 

SRV 71A 24 1143-1167 1121 -2.94%

SRV 71D 16 1124-1146 1118 -1.50%

SRV 71E 81 1124-1146 1103 -2.82%

SRV 71F 19 1124-1146 1116 -1.67%

SRV 71G 82 1134-1156 1127 -1.57%

SRV 71H 17 1134-1156 1111 -2.97%

SV 70B BL-1095 1247 - 1273 1303 +3.41%

10CFR 50.73(a)(2)(i)(B) - Condition Prohibited by Technical Specifications 'Technical Specification Limiting Condition for Operation (LCO) 3.4.3 requires that 11 of the 13 SRVs / SVs be operable during operational Modes 1, 2, and 3. Contrary to this requirement, six SRVs and one SV were found with setpoints outside of the Technical Specification setpoint requirements.

10CFR 50.73(a)(2)(vii) - Common Cause Failure of Multiple Trains being Inoperable - Six SRVs and one SV were considered inoperable as a result of exceeding their allowable setpoint range based on laboratory testing. Therefore, this occurrence is considered as a common cause failure of multiple independent trains being inoperable.

There were a total of seven SRVs and one SV initially removed for testing and replacement during the 19^th  Refueling Outage.

 That is a 100% failure rate and they don’t test all the rest of them...???

LER 2-10-03 reported two SRVs and one SV having their as-found setpoints in excess of the TS allowable + 1% tolerance. LER 3-07-01 reported two SRVs and one SV having their as-found setpoints in excess of the TS allowable ± 1% tolerance. LER 2-06-02 reported one SV having its as-found setpoints in excess of the TS allowable ± 1% tolerance. LER 3-05-04 reported a situation involving four SRVs having their as-found setpoints in excess of the TS allowable ± 1% tolerance.