05000333/LER-2003-002
| James A Fitzpatrick Nuclear Power Plant | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3332003002R00 - NRC Website | |
FACILITY NAME 111 DOCKET (2) LER NUMBER (6) PAGE (3)
NUM BER
2 � OF � 5 James A. FitzPatrick Nuclear Power Plant 05000333 03 � 002 � 00 - Exentfiestription:
On August 19, 2003, while the plant was operating at 100 percent power, FitzPatrick was notified that three Safety Relief Valve (SRV) [S13] pilot assemblies removed at the end of Cycle 15 had as-found setpoints outside the allowable tolerance of 1145 psig +/- 34.3 psig (+/- 3%).
This allowable tolerance (1110.7 to 1179.3 psig) is required per Technical Specifications (TS) Surveillance Requirement (SR) 3.4.3.1. Two SRVs exceeded the high limit of 11793 psig and one SRV exceeded the low limit of 1110.7 psig.
The removed SRV pilots were tested at Wyle Laboratories during the period July 29 through August 5, 2003. The results from these tests were reported to FitzPatrick by Wyle Laboratories on August 19, 2003.
Test Results:
Pilot � Plant � Pass/Fail Serial � Valve � As-Found � (pass unless Number � Number � Setpnint � otherwise. noted) 1053 � 02RV-71B � 1140 1236 � 02RV-71H � 1197 � Fail 1191 � 02RV-71E � 1142 1087 � 02RV-71.1 � 1168 1111 � 02RV-71D � 1134 1239 � 02RV-71K � 1158 1045 � 02RV-71A � 1222 � Fail 1013 � 02RV-71C � 1104 � Fail 1235 � 02RV-71G � 1146 1051 � 02RV-71F � 1143 1110 � 02RV-71L � 1139 TS LCO 3.4.3 requires nine operable SRVs when in Modes 1, 2 or 3. Specifically, the TS states:
The safety function 0.1'9 SIRVs shall be OPERABLE.
Since three pilot valves exceeded the allowable setpoint range, this report is being made under 10 CFR 50.73(aX2Xi)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications...
Cauaa.rtf_Ement:
The cause of the two high out of tolerance pilot setpoints was determined to be corrosion bonding between the SRV pilot disc and seat [Cause Code 13]. With a bond forming between the pilot disc and seat, more pressure is needed to raise the pilot disc off the seat. Since the normal balance of pilot assembly spring force and steam pressure force necessary to lift the pilot disc corresponds to the nominal setpoint of the SRV, the pilot disc to seat bond results in a higher pilot setpoint.
[ � , FACILITY NAME (11 DOCKET (21 LER NUMBER (61 PAGE (3) sER 3 � OF � 5 James A. FitzPatrick Nuclear Power Plant 05000333 03 � 002 � 00 Cause of Event: (continued) An oxygen rich environment in the pilot assembly, due to the radiolytic breakdown of water to hydrogen and oxygen, causes the corrosion bonding. Oxygen accumulates in the area of the pilot disc because the pilot assembly is a high point on the main steam [S131 line.
The cause of the SRV testing low out of tolerance was determined to be sticking of the air operator stem in conjunction with the pilot diagnostic test that preceded the SRV test failure. The diagnostic test is performed to determine the presence of pilot disc-seat corrosion bonding. During subsequent troubleshooting, abnormal air actuator stem movement was observed, which indicated increased friction or "stickiness". This initial pre-test cycling of the operator pilot set spring, combined with the observed friction, prevented the pilot set spring from fully extending, creating a "preloaded" condition.
This preloaded condition reduced the overall steam pressure required for lifting the pilot disc, thereby causing the SRV to lift at a lower pressure. [Cause Code 13] On 3 subsequent tests of this SRV pilot, it lifted at 1142 psig, 1138 psig and 1142 psig, respectively. No pilot diagnostic test was performed immediately prior to these subsequent tests, which precluded the potential for a pilot set spring preloaded condition. Consequently, this performance is likely most representative of the setpoint during the operating cycle, because the potential for spring preloading would be precluded by the environmental vibration conditions.
Event Analysis; The SRVs provide overpressure protection for the Reactor Coolant Pressure Boundary (RCPB) as required by the ASME Boiler and Pressure Vessel Code. SRV pilots actuating at pressures higher than the required setpoint may be significant if adequate overpressure protection is not available.
Two analyses are used in determining the adequacy of overpressure protection; the RCPB Overpressure Analysis and the Anticipated Transient Without Scram (ATWS) analysis. The RCPB Overpressure Analysis is performed each fuel cycle based on the worst case anticipated transient with nine SRVs opening at an analyzed Upper Limit pressure of 1195 psig, and two SRVs out of service. Additionally, the current ATWS analysis was performed using the worst case ATWS with two SRVs out of service and the other nine opening at setpoints derived from Cycle 13 as-found test results. Review of the Cycle 15 test results has determined that the associated worst case setpoints are bounded by both of the above analyses.
The out-of-tolerance condition reported by this LER did not compromise overpressure protection for either analyzed event.
Thus, the current analysis demonstrates satisfactory results with two SRVs failing above the setpoint range and one SRV failing below the setpoint range.
The safety significance of this event is therefore minimal because the system safety function would have been achieved in accordance with the assumptions made in the design basis safety analysis.
FACILITY NAME 1) DOCKET (2) LER NUMBER (6) PAGE 43) yEAR SEQUENTIAL piumgER 4 � OF � 5 James A. FitzPatrick Nuclear Power Plant 05000333 03 � 002 � 00 Extent ardidillan:
All of the SRVs are susceptible to setpoint drift due to pilot disc to seat bonding. This is an industry issue that has been the subject of both NRC and BWROG generic assessment. In general, FitzPatrick SRV pilot performance has improved over the past few cycles, as indicated by a reduced number of out of tolerance high pilot test failures from each group of pilot assembly tests. However, failures due to the generic industry issue continue to occur.
The BWROG recommended modification to provide pressure switch actuation of the SRVs was operational during Cycle 15. This modification provides an electric actuation of SRV pilot valves based upon a pressure switch setpoint. This provides a diverse, redundant method of SRV actuation, which overcomes the pilot disc-seat bonding effect. As such, this modification will mitigate and limit the extent of condition to one part of a diverse SRV actuation methodology.
The SRV pilot that tested low out of tolerance due to sticking of the air operator stem is considered a unique case, as there is no industry evidence of a previous occurrence of an air operator corrective Actions! stem sticking.
Corrective Actions Completed Prior to this Report:
1. All SRV Pilots were removed from the plant during Refuel Outage 15 (October 2002) and replaced with newly refurbished and test certified pilots for Cycle 16.
2. The BWROG recommended modification to provide pressure switch actuation of the SRVs was operational during Cycle 15 when these valves were in service.
3. All SRV pilot assemblies are tested and replaced each operating cycle.
Corrective Actions for this Event:
1. Ensure Pilot #1013 air actuator is refurbished, and the affected air operator stem and body are replaced, as part of the pilot rebuild prior to certification testing. This action will be completed prior to Refuel Outage 16 (October 2004). OAF CR-2003-04321-CA-05) (Scheduled Completion Date 0711512004) 2. Discontinue performance of the pilot diagnostic test as part of as-found setpoint testing. This test no longer provides useful information and has the potential to bias pilot lift test results. This action will be completed prior to the next SRV pilot assembly tests. OAF CR-2003-04321-CA-06) (Scheduled Completion Date 06115/2004) safaty_systemandlimaiialluregeykya This event did not result in a safety system functional failure as defined by NEI 99-02, Revision 2.
FACILITY NAME (1) DOCKET (2) LER NUMBER (6) PAGE (3)
MAMA
NumBER 5 OF James A. FitzPatrick Nuclear Power Plant 05000333 03 002 00 .
allnilaLEXEDIX.
1. JAF LER-01-005 "Safety Relief Valve Setpoint Drift," August 17, 2001.
2. JAF LER-99-003 "Safety Relief Valve Setpoint Drift," March 16, 1999.
3. JAF LER-98-002 "Safety Relief Valve Setpoint Drift," April 9, 1998.
Failed Component ItIantlfIcatlent Manufacturer: Target Rock Corporation Model Number: 7567F-10 NPRDS Manufacturer Code: T020 NPRDS Component Code: Valve FitzPatrick Component ID: 02RV-071A, C & H References
- 1. JAF Condition Report CR-JAF-2003-04321. associated cause analyses and Wyk Laboratories Notice of Anomalies Number 1 for Entergy Purchase Order 4500524037.
2. GE-NE-A42-00137-2-01 rev 1, 'ATWS Overpressure Analysis for FitzPatrick,' dated July, 2003.