05000333/LER-2000-015-02, Re Containment Leakage Rate Exceeds Authorized Limits
| ML021910376 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 07/02/2002 |
| From: | Ted Sullivan Entergy Nuclear Northeast |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| JAFP-02-0130 LER-00-015-02 | |
| Download: ML021910376 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3332000015R02 - NRC Website | |
text
A-Entergy Entergy Nuclear Northeast Entergy Nuclear Operations, Inc.
James A. Fitzpatrick NPP P.O. Box 110 Lycoming, NY 13093 Tel 315 349 6024 Fax 315 349 6480 T.A. Sullivan Vice President, Operations-JAF July 2, 2002 JAFP-02-0130 United States Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, D.C. 20555
Subject:
Docket No. 50-333 LICENSEE EVENT REPORT: LER-00-015-02 (DER-00-05158)
Containment Leakage Rate Exceeds Authorized Limits
Dear Sir:
Revision 2 of this report provides an update of corrective actions planned to improve MSIV performance.
There are no commitments contained in this report.
Questions concerning this report may be addressed to Mr. John Hoddy at (315) 349-6538.
Very truly yours, TAS:JH:jrh Enclosure cc:
USNRC, Region I USNRC, Project Directorate USNRC Resident Inspector INPO Records Center (L-'
Abstract
On October 18, 2000, following completion of Local Leak Rate Testing (LLRT) of valves 29AOV-80D (inboard) and 29AOV-86D (outboard) Main Steam System isolation valves (MSIVs), it was determined that the Primary Containment Type B and Type C as-found running total minimum-pathway leakage rate had exceeded the maximum allowable limit of 320 standard liters per minute (SLM) specifiedin Technical Specifications (TS)
Section 6.20. When leak tested in combination (applied test pressure between the inboard and outboard MSIV),
test results demonstrated seat leakage in excess of 320 SLM. At the time of the testing, the mode switch was in the REFUEL position while the plant was conducting Refuel Outage 14.
The excessive leakage rate of inboard MSIV 29AOV-80D was attributed to valve disc to seat misalignment. The excessive leakage rate of outboard MSIV 29AOV-86D was attributed to seat scoring in the valve seat area, as a result of debris caught between the sealing surfaces.
The failed valves were repaired and retested satisfactorily prior to plant startup. An equipment failure evaluation was performed for the valves that failed testing. An operability review was performed to support operation through the remainder of the operating cycle. Additional valve modifications and improvements, and improved outage work management controls are being planned to enhance MSIV performance and test accuracy.U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL IREVISION James A. FitzPatrick Nuclear Power Plant 05000333 NUMBER NUMBER 2
OF 7
00 015 02 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
EIIS Codes in [ ]
Event DLrqription The plant entered Refuel Outage 14 on October 6, 2000. Type C Local Leak Rate Testing (LLRT) activities on the Primary Containment [NH] penetrations and isolation valves commenced shortly after plant cooldown in accordance with Technical Specifications (TS) Section 6.20, Primary Containment Leakage Rate Testing Program,,. On October 18, 2000, following completion of LLRTs of the Main Steam System [SB] Main Steam isolation valves (MSIVs) 29AOV-80D (inboard) and 29AOV-86D (outboard), it was determined that the Primary Containment Type B and Type C running total minimum pathway leakage rate had exceeded the maximum allowable limit of 320 standard liters per minute (SLM) specified in the Technical Specifications (TS). When leak tested, test results demonstrated gross seat leakage.
TS Section 6.20.A requires that peak Primary Containment internal pressure for the design basis loss of coolant accident (Pa) is 45 pounds per square inch gauge (psig). The maximum allowable Primary Containment leakage rate (La) at Pa shall be 1.5 percent of Primary Containment air weight per day. The maximum TS allowable leakage per day equates to 320 standard liters per minute (SLM).
Test methods for the combined test of the MSIVs require that pressure be applied between the inboard MSIV and the outboard MSIV. For the individual test of outboard valve 29AOV-86D, the Main Steam Line upstream of inboard MSIV is filled with water. During the fill evolution, excessive water leakage occurred past the valve seat of 29AOV-80D. Due to this excessive leakage through inboard MSIV, the "D", inboard MSIV was classified as having gross leakage. Inboard valve leakage was due to the inboard valve disc assembly not being properly aligned with the valve seat.
After draining the inboard Main Steam Line, combined testing of the inboard and outboard MSIVs indicated leakage exceeding the ability of the test equipment to achieve test pressure. The test volume could not be pressurized by the leak rate monitor, which has a 400 SLM maximum flow rate. Leakage observed at vents located upstream of the inboard valve and downstream of the outboard valve indicated excess leakage through both valves. This resulted in declaring the outboard valve as having gross seat leakage. Combined leakage of the inboard and outboard MSIVs was in excess of 400 SLM.
Cawuse of Evant The excessive leakage rate of inboard MSIV 29AOV-80D was attributed to valve disc to seat misalignment. The excessive leakage rate of outboard MSIV 29AOV-86D was attributed to seat scoring in the valve seat area, as a result of debris caught between the sealing surfaces. No foreign material was found, however, it is believed the debris was washed across the seat during stroking evolutions.
Previous valve failure evaluations identified the need for valve modifications/enhancements, due in part to LLRT methodology and valve orientation. Improvements to valves 29AOV-80D and 29AOV-86D are identified in the
corrective actions
The cause and corrective actions for LLRT failures that significantly contributed to Primary Containment leakage during Refuel Outage 14 are identified in Table 1 of this report.U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION James A. FitzPatrick Nuclear Power Plant 05000333 NUMBER NUMBER 3
OF 7
00 015 02 TEXT (if more space is required, use additional copies of NRC Form 366A) (17)
Analysis of the Event
This report is being submitted in accordance with 10 CFR 50.73(a)(2)(ii), "Any event or condition that resulted in the nuclear power plant, including its principal safety barriers, being seriously degraded,, and in accordance with 10 CFR 50.73 (a)(2)(v), "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material."
The Primary Containment System has the capability to limit leakage during any of the postulated design basis accidents for which it is assumed to be functional such that offsite doses do not exceed the guideline values set forth in 10 CFR 100. Compliance with 10 CFR 50, Appendix J provides assurance that the Primary Containment including those systems which penetrate the Primary Containment do not exceed the allowable leakage rate specified in the TS.
Immediate actions were not required as the plant was in a shutdown condition and Work Orders were already in place to repair the valves. All MSIVs that exceeded the TS leak rate limit were rebuilt and successfully tested prior to startup from the Refuel Outage.
An upper bound on the leak rate through 29AOV-80D and 29AOV-86D could not be determined; therefore the potential dose consequences of this event could not be precisely quantified. A level 2 Probabilistic Risk Assessment was conducted to quantify/evaluate the safety significance of this event. This analysis determined that the change to Large Early Release Frequency (LERF) relative to the base case was 9.82 E-8 per reactor year. Therefore, this event is considered to have a low safety significance.
Fxtent of Condition At the conclusion of LLRTs, it was identified that as-found leakage rates for MSIVs 29AOV-80B, 29AOV-86B and 29AOV-86C had exceeded the Technical Specifications (TS Section 4.7.A.2.b, Surveillance Requirements, "Primary Containment") leakage rate acceptance criteria of =/< 11.5 scfh (5.422 SLM) per valve when tested at
=/> 25 psig. Therefore, valves 29AOV-80B and 29AOV-86B were also considered significant contributors to exceeding the maximum allowable Primary Containment leakage rate (La) of 320 SLM.
Other LLRT failures were evaluated. No additional penetration failures were identified during Refuel Outage 14 that significantly contributed to Primary Containment leakage.U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION James A. FitzPatrick Nuclear Power Plant 05000333 NUMBER NUMBER 4
OF 7
00 015 02 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
Corrective Actions
- 1.
Work Requests (WRs) were generated and repair activities were completed on MSIVs 29AOV-80B, 29AOV-80D, 29AOV-86B, 29AOV-86C and 29AOV-86D. Additionally, modification work, consisting of MSIV improvements/enhancements, based on previous valve failure evaluations and valve vendor recommendations, were completed on the following MSIVs:
29AOV-80D - Installation of guide pads to the valve body to control valve disc to valve body clearance and improve valve disc to seat alignment, and installation of a new ring/spacer configuration to aid in improving stem alignment and reduce stem galling.
29AOV-86D - Installation of hardened washers on valve bonnet to reduce torque transfer losses and eliminate bonnet leakage, installation of hardened washers on both ends of the live load spring to reduce torque losses for added packing pressure for better control of packing leakage, and installation of a new ring/spacer configuration to reduce stem galling. Additionally, a rebuilt/certified actuator was installed and the spring pack between the actuator and valve was rebuilt with new yoke guides and bronze bushings to reduce closing friction loads. The valve seat was refurbished.
- 2.
An operability review was performed to support operation through the remainder of the operating cycle, given the previous MSIV performance history and repair activities. This conclusion was supported by an independent evaluation performed by the NSSS vendor.
- 3.
Outage management work controls will be established to assure that the LLRT plan is followed. This will prevent failures, such as that for 29AOV-80B, which resulted from water being washed over the valve seat. (Scheduled to be Completed 10/05102)
- 4.
End-of-cycle LLRT testing will be performed early in RO1 5 to assess the effectiveness of modifications previously performed on those valves (29AOV-80B, 29AOV-80D, 29AOV-86D) which are currently fitted with upgrades planned for the remaining MSIVs. Test results will provide an accurate indication of the effectiveness of ongoing MSIV improvement efforts in addressing end of cycle failures of MSIV's to pass LLRT testing.
- 5.
Additional valve modifications and improvements are planned to be installed during RO1 5 for specific MSIVs to enhance performance (See Tables 1 and 2). Since the planned actions incorporate all applicable LLRT failure corrective actions, where planned activities require valve disassembly, regularly scheduled periodic LLRT testing will be completed only after work completion and prior to start up from RO15. (Scheduled to be Completed Before Startup from R015)U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET 12)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION James A. FitzPatrick Nuclear Power Plant 05000333 NUMBER NUMBER 5
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00 015 02 TEXT (If more space is required, use additional copies of NRC Form 366AJ (17)
Additional Information (cont'd)
A.
Previous Similar Events
LER 98-013 and LER 96-012 reported Primary Containment accumulated leakage in excess of maximum allowed by the TS.
B.
Failed Components:
Component:
Manufacturer:
Model:
Type:
29AOV-80B, 80D, 86B, 86C, and 86D Main Steam Line Inboard and Outboard Main Steam Isolation Valves Edward Valves, Inc.
1612 JMMNY 1250 psi, 24 inch, Globe (flite-flow)
C.
Applicability to NEI 99-02, Rev. 0. "Regulatory Assessment Performance Indicator Guideline."
This event is considered a safety system functional failure in the context of NEI 99-02, Rev. 0.
0 FACILITY NAME (1)
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James A. FitzPatrick Nuclear Power Plant 05000333 1
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Table 1 - Corrective Actions Scheduled for R015 for MSIVs Failing LLRT During R014 Failure Mechanism Additional Valve Improvements Component Effect Failure Mode (see notes below) and Modifications 29AOV 8B Internal Loss of Sealing Improper Operation, No further corrective action is
- - 8 Leakage Integrity Particle Accumulation required (RO 14 action is considered 29AOV-80D Internal Loss of Sealing Out of Alignment effective). As a long-term Leakage Intert enhancement, however, hardened n
Lwashers will be installed above and 29AOV-86D Internal Loss of Sealing Scored Seat below packing liveload (29AOV-80B Leakage Integrity and 29AOV-80D).
External Loss of Pre-load Improper Design, Replace disc stem, disc as needed, 29OV8B ekae(Packing)
Improper Assembly, and change stellite junk ring to (Packin) LMechanical Cycling carbon steel junk ring spacer. Install External Loss of Pre-load Improper Design, hardened body/bonnet stud washers 29A0V-86C Leakage (Packing)
Improper Assembly, and packing liveload washers.
Mechanical Cycling.I Notes:
Improper Operation:
Particle Accumulation:
Out of Alignment:
Scored Seat:
Improper Design:
Improper Assembly:
Mechanical Cycling:
Valve was cycled open prior to completing LLRT, causing particulate laden water to wash over the valve seat due to the abnormal system line-up.
Particles on the seating surfaces prevented full metal to metal contact, thereby causing an air test failure.
Caused by valve being in a 30 degree off vertical position; actuator and spring force insufficient to ensure full metal to metal contact in seating surfaces without additional guiding.
Caused by debris traveling across seating surfaces, driven either by fluid motion over seat or by valve disc motion.
Further analysis was not performed, as the material that scored the seat was not found when the valve was disassembled.
Stem is guided at packing gland junk ring (stellite interface with 17-4 pH stainless steel stem); cycling the valve over time causes scoring, which removes packing material and reduces packing preload; increased scoring can lead to galling.
Involved the sequencing of the packing replacement. An upgraded sequence has been developed.
With stem scoring and low packing pre-load, mechanical cycling provided the sliding force needed to degrade the packing pre-load to a failure condition.
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YEAR SEQUENTIAL I REVISION James A. FitzPatrick Nuclear Power Plant 05000333 NUMBER NUMBER 7
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Table 2 - Additional MSIV Modifications and Improvements Scheduled for R015 Component Valve Improvements and Modifications 29-AOV-80A Addition of hardened washers to body/bonnet joint and packing liveloads.
Replace Stellite junk ring with carbon steel spacer.
Installation of additional weld-in body guides.
Installation of bronze spring flange bushings.
Replacement of stem and disc as needed.
Installation of upgraded spring pack (heavier springs).
29-AOV-80C Addition of hardened washers to body/bonnet joint and packing liveloads.
Replace Stellite junk ring with carbon steel spacer.
Installation of bronze spring dividers and spring flange bushings.
Replacement of stem and disc with upgraded design.
29-AOV-86A Addition of hardened washers to body/bonnet joint and packing liveloads.
Replace Stellite junk ring with carbon steel spacer.
Installation of additional weld-in body guides as needed.
Installation of bronze spring flange bushings.