Update: March 20, 2015
Yesterday i called the Hatch nuclear plant senior resident asking him about all their recent failures of the model 0867F SRVs. Could just leave a recording. You know you are in Siberia when the regional public relations person calls you back instead of the resident inspector.
He didn't have much information about the Hatch SRV events…but he did say something particular. There is no doubt he called region I officials and the higher level officials were coordinating the response. What the message the NRC wanted me to relay to the public:The failed SRV at Pilgrim had 57 cycles on it while a similar Hatch SRV has 3 to 4 cycles on it. Hatch operates their SRV's fundamentally different than Pilgrim.
I tried to probe this guy (he was a nice guy) asking him how Hatch operates their SRVs different than Pilgrim. I told him I was a license operator at Vermont Yankee. He responded back to me, Pilgrim uses their SRVs to control pressure while up at power while Hatch does not. You never know when these guys are playing dumb or are really dumb? Usually all NRC employees, no matter what the stripe, are particularly intelligent. I asked him twice what he meant by that, the response never changed.
If I had to translate what he said, I think he was trying to say during start-ups and particularly shutdowns and hard shutdowns, Pilgrim reverts as a normal operation path, especially when the main stream lines are closed, into using their SRVs as the means of cooling the core and pressure control in the vessel.
Is he saying all their shutdowns and hard shutdowns are causing damage to Pilgrims SRVs? Why are the SRV designs so delicate?
Typically in the worst accident possible (DBA), they cycle the SRV valves between 300 and 500 times in one accident…
I asked region I senior public affair official to respond to this in a phone message (Mrs. Srenci)
Did the NRC release this for the public meeting tonight?
PNO
Part 21 Event Number: 50900
Only the 0867F is under investigation.
The root cause of the potential test induced defect has not yet been confirmed as of the date of this report.
One of the four installed MS-SRVs may not have fully opened.
As-found steam testing of the affected MS-SRV did not duplicate this failure; the valve opened on demand.
We are working with all three (4) sites to identify appropriate precautions.
Rep Org: CURTISS WRIGHT FLOW CONTROL CO.
Licensee: CURTISS WRIGHT FLOW CONTROL CO.
Region: 1
City: EAST FARMINGDALE State: NY
County:
License #:
Agreement: Y
Docket:
NRC Notified By: JOHN DeBONIS
HQ OPS Officer: STEVE SANDIN Notification Date: 03/17/2015
Notification Time: 09:59 [ET]
Event Date: 03/17/2015
Event Time: [EDT]
Last Update Date: 03/17/2015
Emergency Class: NON EMERGENCY
10 CFR Section:
21.21(a)(2) - INTERIM EVAL OF DEVIATION
Person (Organization):
GLENN DENTEL (R1DO)
BINOY DESAI (R2DO)
PART 21/50.55 REACT (EMAI)
Event Text
INTERIM PART 21 REPORT - POTENTIAL TEST INDUCED DEFECT IN A 0867F MAIN STEAM SAFETY RELIEF VALVES
The following report was received from Curtiss - Wright via email:
"This letter provides interim notification of a potential test induced defect in a 0867F Series Main Steam Safety Relief Valves (MS-SRVs) manufactured and supplied by Target Rock (TR). The information required for this notification is provided below:
"(i) Name and address of the individual or individuals informing the Commission.
William Brunet
Director of Quality Assurance
James White
General Manager
Target Rock, Business Unit of Curtiss-Wright Flow Control Corporation
1966E Broadhollow Road
East Farmingdale, NY 11735
"(ii) Identification of the basic component supplied for such facility or such activity within the United States which may fail to comply or contains a potential defect.
Target Rock 0867F Series of Main Steam-Safety Relief Valves Manufactured by Target Rock. This is a 3-stage piloted valve consisting of a main valve (the 'Main') with an actuator mounted to it (the 'Topworks'). The 0867F is the latest generation of the 67F line of MS-SRVs, including the original 3-Stage and 2-Stage designs, and this product line has over 40 years of plant operational experience. Only the 0867F is under investigation. This is due to the differences between the 0867F design and the other designs.
"(iii) Identification of the firm supplying the basic component which fails to comply or contains a defect.
Target Rock, Business Unit of Curtiss-Wright Flow Control Corporation
1966E Broadhollow Road
East Farmingdale, NY 11735
"(iv) Nature of the defect or failure to comply and the safety hazard which is created or could be created by such defect or failure to comply.
As we understand it, the Pilgrim Station recently manually opened the Target Rock Main Steam Safety Relief Valves (MS-SRVs) as part of cooling down the reactor following a loss of offsite power. One of the four installed MS-SRVs may not have fully opened. As-found steam testing of the affected MS-SRV did not duplicate this failure; the valve opened on demand. However, the valve did not re-close as expected. Internal inspections found damaged parts in the main stage subassembly that could potentially affect the ability of the MS-SRV to operate as designed.
We are investigating potential root causes for this damage. However, we are still unable to determine if a specific defect exists. GE SIL-196, Supplement 17 determined Main Spring relaxation was caused by 'extreme dynamics encountered during limited flow testing . Valve dynamics under full flow conditions (i.e. discharge not gagged) are much less severe than those under limited flow conditions.' These extreme dynamics, under limited flow test conditions, are the focus of our investigation. Specific areas of investigation include;
a) Testing of materials to verify they are consistent with our material specifications,
b) evaluation of differences between the 0867F and earlier designs, and
c) evaluation of the differences between different limited flow test loop configurations and test procedures
"(v) The date on which the information of such defect or failure to comply was obtained.
The Pilgrim event occurred on January 27, 2015. As-found testing occurred on February 2, 2015.
"(vi) In the case of a basic component which contains a defect or fails to comply, the number and location of these components in use at, supplied for, being supplied for, or may be supplied for, manufactured, or being manufactured for one or more facilities or activities subject to the regulations in this part.
While we have yet to determine if a specific defect exists, the following plants were supplied 0867F MS-SRVs:
- Pilgrim (Model 09J-001) Quantity Shipped = 8
- Fitzpatrick (Model 09H-001) Quantity Shipped = 4, Quantity on order= 8
- Hatch 1 and 2 (Model 09G-001) Quantity Shipped= 24, Quantity on order= 12
The following plants will be supplied 0867F MS-SRVs:
- Hope Creek (Models 14J-001, 14J-002) Quantity on order = 7
"(vii) The corrective action which has been, is being, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action.
The root cause of the potential test induced defect has not yet been confirmed as of the date of this report. Therefore, no specific corrective actions have been initiated. Target Rock Problem Report 080 will document the corrective actions when they are determined and complete the 10 CFR Part 21 evaluation of the potential test induced defect. This determination will be based on further mechanical and material evaluations. TR anticipates completing these evaluations within 45 days; however, in the event the evaluations are not completed, TR will forward another interim report within 45 days.
"(viii) Any advice related to the defect or failure to comply about the facility, activity, or basic component that has been, is being, or will be given to purchasers or licensees.
We are working with all three (4) sites to identify appropriate precautions.
"(ix) In the case of an early site permit, the entities to whom an early site permit was transferred.
Not applicable.
"Should you have any questions regarding this matter, please contact Michael Cinque, Director of Program Management at (631 ) 293-3800."
SRV-3B Safety Relief Valve Declared Inoperable Dueto Leakage and Setpoint Drift
Licensee Event Report 2013-002-01
Event date 01 20 2013LER: 2013 002 01Report Date 1 31 2014On Sunday January 20, 2013, at 2050 hours with the reactor at 100% core thermal power (RMSS in RUN), PNPS declared SRV-3B inoperable and entered Technical Specification (TS) 3.6.D.2 requiring an orderly reactor shutdown such that reactor coolant pressure is less than 104 psig within 24 hours. On Monday January 21, 2013, at 1300 hours (16 hrs and 10 minutes) reactor coolant pressure was lowered to less than 104 psig. SRV-3B had been declared inoperable consistent with PNPS procedures that state an SRV is inoperable if the first stage pilot thermocouple temperature is 350 F below its baseline temperature. This LER Supplement provides the determination of cause for the leakage. The cause of the SRV leakage was that the natural frequency of the pilot assembly was close to a resonant frequency of the valve assembly when installed on the PNPS main steam line, that had failed to be considered in the design of the SRV. A contributing cause was wear and looseness of parts in the main stage of RV-203-3B.The reactor was depressurized and a new pilot valve assembly was installed on SRV-3B. On January 22, 2013, at 1015 hours reactor restart was commenced. On January 24, 2013 at 0312 hours 100% core thermal power was achieved.This LER also reports the as-found setpoint of one SRV pilot valve tested was less than the minimum pressure required by TS 3.6.D.1.This event had no impact on the health and/or safety of the public.BACKGROUND:As background, the pressure relief system includes four (4) SRVs and two (2) spring safety valves (SSVs). During Refueling Outage (RFO-1 8), in April/May, 2011, the four SRVs were replaced with Target Rock Model 0867F 3-stage SRVs. The SRVs discharge through their individual discharge piping, terminating below the minimum suppression pool (torus) water level. The four SRVs are installed on the main steam piping in containment between the reactor pressure vessel and the flow restrictors.The 3-stage SRV contains a pilot (also called the first stage), a second stage, a main stage, and an air operator.To monitor these valves for leakage, Pilgrim installed thermocouples at the pilot (first stage), at the second stage, on the tailpipe near the valve (4.5' to 6' away), on the tailpipe far from the valve (-20' away) and at the pilot bellows. Procedure 2.2.23, "Automatic Depressurization System", provides guidance for interpreting the thermocouple data and determining valve operability based in part on testing performed by Target Rock.Subsequent to installation in RFO-1 8 and prior to this event, Pilgrim experienced minor second stage pilot valve leakage from SRV RV-203-3C on May 18, 2011 and November 25, 2011. Also, on December 26, 2011, SRV RV- 203-3D first stage pilot valve experienced leakage while operating at full power. The SRV was declared inoperable and the plant was shutdown on December 26, 2011 in accordance with TS 3.6.D.2 and RV-203-3C was replaced entirely, and the RV-203-3D pilot assembly was replaced (LER 2011-007-00).EVENT DESCRIPTION:On Sunday January 20, 2013, at 2050 hours with the reactor at 100% core thermal power (RMSS in RUN), PNPS declared SRV-3B inoperable and entered Technical Specification (TS) 3.6.D.2 requiring the initiation of an orderly reactor shutdown such that reactor coolant pressure is less than 104 psig within 24 hours. On Monday January 21, 2013, at 1300 hours (16 hrs and 10 minutes) reactor coolant pressure was less than 104 psig. SRV-3B had been declared inoperable consistent with PNPS procedures that state an SRV is inoperable if the pilot stage thermocouple temperature is 350 F below its baseline temperature.While at full power, indication of a steam leak across the first stage pilot of RV-203-3B was identified. The leakage was evaluated and in accordance with criteria specified in procedure 2.2.23, specifically, if the pilot stage thermocouple temperature is 35 degrees F below its baseline temperature (with a smaller decrease at the second stage thermocouple) and cannot be explained by a corresponding downpower, the SRV is inoperable. The safety relief valve was subsequently declared inoperable and the Limiting Condition for Operation (LCO) for Technical Specification (TS) 3.6.D.2 was entered. Per TS 3.6.D.2 the plant was shutdown and reactor coolant pressure was below 104 psig within 24 hours.CAUSE:The SRVs were purchased new, installed, and tested for the first time in April/May 2011 during RFO-1 8.Following an extensive investigation, it was determined that the cause of the SRV leakage was that the natural frequency of the pilot assembly was close to a resonant frequency of the valve assembly when installed on the PNPS main steam line. This was not considered in the Entergy specification or the Target Rock design of theEXTENT OF CONDITION:This condition potentially applies to all four three stage SRVs that were installed in RFO 18. During Cycle 19 operation, Pilgrim has observed leakage from RV-203-3B, 3C, and 3D.
· On May 18, 2011 and November 25, 2011, SRV RV 203-3C second stage pilot valve minor leakage was observed. This condition did not cause inoperability of the valve. SRV RV-203-3C was replaced during the December 26, 2011 shutdown.· On December 26, 2011, SRV, RV-203-3D first stage pilot valve experienced leakage that exceeded the operability criteria while operating at full power. The plant was shut down as required by TS 3.6.D.2, RV 203-3C and 3D were repaired and the plant returned to full power operation. The cause of the pilot leakage was later determined to be a combination of the natural frequency issue and weakening of the pilot bellows spring. This bellows spring had a through wall failure during testing at an offsite test facility in March 2013. This failure was the subject of a Target Rock 10 CFR, Part 21 (Reference 1).· On January 20, 2013, Pilgrim experienced the event described in this Licensee Event Report, first stage pilot valve leakage of SRV, RV-203-3B. The plant was shutdown as required by TS 3.6.D.2. The pilot valve was replaced with a refurbished pilot and the plant was returned to full power operation.· On February 3, 2013, RV-203-3B first stage pilot valve leakage was identified while at full power. Reactor power was lowered to 80% and at 1000 psig pressure, the pilot was reseated. An Operability Determination with a compensatory measure was implemented to maintain the reactor power at 80% and reactor pressure at 1000 psig. An Operations Decision Making Issue (ODMI) was implemented to monitor and take corrective actions. During the forced outage on February 8, 2013, caused by a loss of offsite power due to a major winter storm, RV-203-3B first stage pilot valve was replaced with a new pilot valve and the plant was returned to power operation. The cause of the pilot leakage was determined to be a combination of the natural frequency issue and weakening of the pilot bellows spring. This bellows spring had a through wall failure during testing at an offsite test facility in March 2013. This failure was the subject of a Target Rock 10 CFR, Part 21 (Reference 1).The removed RV-203-3B pilot valve was sent to Wyle Laboratory for testing.As-found test results for the SRV, RV 203-3B pilot valve were:Pilot S/N SRV Position As-Found Deviation23 RV-203-3B 1112 psig (-)3.8%Technical Specification 3.6.D.1 requires the as-found setpoint to be within 1155±34.6 psig (1120.4 psig to 1189.6 psig). The as-found setpoint was less than the minimum pressure specification required by TS 3.6.D.1. This test result was entered into the corrective action program as a separate event, and is included in this LER since the condition was discovered within 60 days from the initial discovery of pilot leakage. Accordingly, this as-found value being out of Technical Specification setpoint is reported in this LER pursuant to 10 CFR 50.73(a)(2)(i)(B).· The third pilot on RV-203-3B began leaking on February 26, 2013. Leakage was controlled by reducing power and pressure per the ODMI. This pilot was replaced during the Spring 2013 RFO. The cause of the pilot leakage was that the pilot assembly had a natural frequency that was close to a resonant frequency of the valve assembly when installed on the PNPS main steam line.CORRECTIVE ACTIONS:The following corrective actions were taken to address this event related to leaking RV-203-3B:· The SRV-3B pilot was replaced with a refurbished and tested pilot.· PNPS Procedure was revised to reduce reactor power and pressure to stop leakage per an ODMI as described in "Extent of Condition."The following corrective actions are being taken to address the results of review of Extent Conditions:· To minimize the possibility of further pilot leaks, all currently installed pilots (and replacements if necessary until the long term corrective action can be taken) have been set at the high end of their allowed set pressure band.· The recommendations of the Target Rock 10 CFR, Part 21 are being followed.· The only PNPS pilot with a bellows spring from the same material and heat treatment certifications as the failed bellows was removed from the plant. Detailed metallurgical analysis did not identify any intergranular cracks such as those identified in the failed bellows.· PNPS has ordered new pilot assemblies with enhancements designed by Target Rock to raise the natural frequency of the pilot and make it more resistant to steam system vibration (References 2 and 3).These pilots include the bellows replacement recommended by the 10 CFR, Part 21. PNPS plans to install these pilots during the spring of 2015 RFO.SAFETY CONSEQUENCES:The leaking SRV pilot valves and the plant shutdown to repair the SRV in accordance with Technical Specification 3.6.D.2 posed no threat to the public health and safety.All leakage from the valve was collected in plant systems, the suppression pool (torus), and processed in accordance with normal station practices.Pilgrim has installed temperature monitoring to provide sufficient indication of SRV leakage to ensure that timely actions can be taken to ensure that the plant is maintained in a safe condition. Procedure 2.2.23 provides the instructions and guidance for interpreting and responding to SRV temperature indications. Based on these instructions, the plant was shutdown. The SRV would have been able to respond if needed to meet its core coolingor reactor pressure vessel over protection functions. As a result, the plant safety was maintained. The risk of operating with a leaking SRV is characterized by an increased chance of having an inadvertently opened SRV with increased chance of that valve failing to reclose.Assuming the plant operated for 24 hours with this condition, this results in a change in core damage frequency of less than 1.OE-7. The impact of setpoint drift (0.8% below the 3% tolerance) is considered to be bounded by delta change in core damage frequency of less than 1.OE-7.PREVIOUS EVENTS:Prior to Cycle 19, there were no leakage or setpoint drifts occurrences with three stage safety relief valves since the new design was installed in April/May, 2011, during Refueling Outage 18 for all four safety relief valves.During Cycle 19, Pilgrim observed minor leakage from the second stage pilot valve of RV-203-3C. Also, first stage pilot valve leakage was observed from RV-203-3D which was confirmed, plant was shutdown as required by TS 3.6.D.2, and first stage pilot valve was replaced. This event is described in LER 2011-007-00. During the outage for RV-203-3D, the entire RV 203-30 was replaced with a new valve assembly.The industry has experienced numerous instances where SRV leakage has occurred at other plants with other Target Rock Model three stage safety relief valves.OE33766 - Three Stage Safety Relief Valve Pilot Leakage just below Normal Operating Pressure - Plant Hatch. The plant Hatch installed the same model 3-stage SRVs in Unit 2 in April 2011. Hatch experienced numerous pilot leaks during 2011. On some occasions, leakage was reduced by power and/or pressure reductions. Hatch Unit 2 had some success through power and/or pressure reductions and operating for several months after reseating the first stage pilot valve through power and/or pressure reductions.OE26394 & OE26892 - Planned Shutdown due to a three stage Safety Relief Valve Leak - Peach Bottom Unit 3OE32805 - Safety Relief Valve Temperature Phenomenon – FitzpatrickOE34730 - Target Rock 3 Stage Main Steam SRV Bore to Seat Misalignment - Limerick 2OE19219 - Plant Shutdown Due to Increasing Tailpipe Temperature - Duane ArnoldREFERENCES:1. Target Rock Letter NID#13307, "10 CFR Part 21 Report, Notification of a Defect, Bellows Failure," June 17, 2013.2. Target Rock Technical Evaluation of Replacement Items TERI 075, "Technical Evaluation of Pilot Assembly 304095-1 Replacing Pilot Assembly 303977-1 for 0867F-001," Target Rock, Revision A, January 14, 2013.3. Target Rock Letter SRP1 3003, "Enhancements to Primary Pilot Design," Target Rock, January 21, 2013.4. Condition Report CR-PNP-2013-0378, Safety Relief Valve RV-203-3B, Pilot Leakage.
No comments:
Post a Comment