05000445/LER-1998-001, :on 980110,discovered Entry Into TS 3.0.3 When Feedwater Isolation Valves Were Declared Inoperable Due to Low Nitrogen Pressure.Caused by Degraded Elastomer Seal. Restored Nitrogen Pressure
| ML20202D287 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/09/1998 |
| From: | Flores R, Terry C, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-98-001, LER-98-1, TXX-98032, NUDOCS 9802170037 | |
| Download: ML20202D287 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(1) |
| 4451998001R00 - NRC Website | |
text
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Log
- TXX-98032 7UELECTRIC File # 10200 Ref. # 10CFR50.73(a)(2)(1) c. t.c.wery senter m rentsens a principaixwirer opm February 9. 1998 U. 5. Nuclear Regulatory Comission
,Etn : Document Control Desk Washington. DC 20555 SUBJECT: COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) UNIT 1 DOCKET NOS. 50-445 CONDl:10NS PRD,41BITED BY TLMICAL SPEClflCATIONS LICENSEE EVENT REPORT 445/98-001-00 1
Er. closed is Licensee Event Report (LER) 93 001-00 for Comanche Peak rteam Electric.
Ste* ion Unit 1. " Entry into Technical Spec't) cation 3.0.3 When Feedwater Isolation v lves Were Declared inoperable Due to Low Nitrogu PrMsure."
a This communication contains no new licensing basis commitments regarding CPSES Unit 1.
Sincerely.
h $. W lg-C. L, Terry i
9002170037 980209 By:
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PDR ADOCK 05000443 Roge fD. Walker S
PDR Manager. Regulatory Affairs 08:ob I
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Mr. E. W. Merschoff. Region IV 3
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Residert Inspectors. CPSES i
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l ABSTRACT (Umit to 1400 e, paces. I e., at yoximately 15 single-spaced typewritten lines) (16)
On January 10, 1998, at approximately 1:48 a.m. during the performance of partial stroke test of feedwater isolation valves (FWlVu), the Plant Equipment Operators (utihty, non-licensed) discovered that feedwater Isolation Valve (Ells:(ISV)(SJ))
1-HV-2134 and 2 HV-2137 had low nitrogen pressure. The Shift Manager (utility, licensed) declared that both FWlVs 1-HV 2134 and 1-HV 2137 were inoperable. As such, the requirer,ients of Technical Specification 3.0.3 applied. Concurrent with the determination to enter Technical Specification 3.0.3, Maintenance personnel proceeded to charge the accumulators with nitrogen. The nitrogen pressure was corrected within the Technical Specification at approximately 1:52 a.m., on January 10, 1998, and Technical Specification 3.0.3 was exited.
The low nitrogen pressure for FWlV 1 HV 2134 was caused by a leak on a nitrogen solenaid valve and on the nitrogen cylinder head. The low nitrogen pressure for FWly 1 HV-2137 was caused due to a leak on a nitrogen solenoid valve. Immediate corrective action was to restore the nitrogen pressure to declare the FWlVs operable. The leak rate on 3 HV 2134 was reduced and work is planned to replace elastomer parts fcr this valvo. The solenoid valve on 1-HV-2137 has been replaced to prevent recurrence.
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DESCRIPTI(SLOF THE REPORTABLE EVENT A.
REPORTABLE EVENT CLASSIFICATION
Entry into Technical Specifications 3.0.3.
B.
PLANT OPERATING CONDITIONS PRIOR TO THE EVENT On January 10, 1998, Comanche Peak Steam Electric Station (CPSES) Unit I was in Mode 1. Power Operation, at approximately 100 percent power.
C.
STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT On January 10,1998, at approximately 1:48 a.m. during the performance of partial stroke test of feedwater 1501ation valves, the Plant Equipment Operators (utility, non-licensed) discovered that Feedwater Isolation Valve (Ells:(ISV)(SJ)) 1-HV-2134 and 2 HV 2137 were inoperable due to low nitrogen pressure.
D.
NARRATIVE
SUMMARY OF THE EVENT INCLUDING DATES AND APPROXIMATE TIMES At approximately 1:00 a.r on January 10, 1998. Plant Operators were performing ASME Section XI partial stroke tests of Feedwater Isolation Valves (FWlV)
(Ells:(ISV)(SJ)). A Plant Equipment Operator (utility, non-licenced) was stationed at the feedwater isolation valves. The partial stroke tot was performed on 1-HV 2134 for Steam Generator 1-01 (Ells;(SG)(AB)), a low pressure alarm was received in the control room when the valve partially closed, and the alarm cleared when the valve reopened. The Plant Equipment Operator reported normal conditions at the valve, sirce this was the expected response to the partial stroke test. The partial stroke test was performed on valve 1-HV-2135 for Steam Generator 1-02, and the expected response was observed. The test was performed on valve 1 HV 2136 for Steam Generator 1-03, and the expected response was observed. The test was then performed on valve 1 HV 2137 for Steam Generator 1-04, and the low pressure alarm did not clear when the valve reopened and the Plant Equipment Operator at the valve reported hearing the sound of a nitrogen leak. Technical Specification Action Statement 3.7.1.6 was entered. Maintenance personnel (utility, non licensed) were contacted to recharge the accumulator for valve 1-HV-2137. As the Maintenance personnel was setting up to recharge the a.
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v..un ma..-..w.a m w.ec e ac re ww tm accumulator for 1 HV 2137, the low pressure alarm for valve 1 HV 2134 was received and when the Maintenance personnel connected the presture gage to 1 HV.
.2134 the pressure was below the limit for valve operability. This placed two accumulators below the pressure for operability.
At approximately 1:48'a.m., January 10, 1998,- the Shift Manager (utility, licensed) declared that both FWlVs 1 HV 2134_and 1 HV 2137 were inoperable. As
- - such, the requirements of Technical Specification 3.0.3 applied, Concurrent with the detemination to enter Technical Specif1 cation _3.0.3, Maintenance personnel proceeded to charge the accumulators with nitrogen. The nitrogen pressure was corrected within the Technical Specification at approximately 1:52 a.m...on January 10, 1998, and Technical Specification 3.0.3 was exited.
E.
- - THE HETHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE OR PROCEDURAL OR PERSONNEL ERROR On_ January 10, 1998,'at-approximately 1:48 a.m. during the performance.of partial stroke test of feedwater isolation. valves, the Plant Equipment Operators (utility, non licensed) discovered that Feedwater Isolation Valve (Ells:(ISV)(SJ)) 1-HV 2134 and 2 HV 2137 were inoperable due to low nitrogen pressure, The Reactor Operator (utility. licensed) observed the low nitrogen pressure alarm annunciator.
C(MPONENT OR SYSTEM FAILURES A,-
FAILURE MODE, HECHANISH, AND EFFECT OF EACH FAILED COMPONENT The elastomer seal on FWIV 1-HV 2134 was degraded and caused the nitrogen to leak. The. low nitrogen pressure for FWlV 1-HV 2137 was caused due to a leak on a nitrogen solenoid valve.
B, CAUSE OF EACH COMPONENT OR SYSTEM FAILURE The elastomer seal on FWlV 1 HV-2134 was degraded and caused the nitrogen to leak. The. low nitrogen pressure for FWIV 1-HV-2137 was caused due to a leak on.-
a nitrogen solenoid valve. There were no system failures associated with this event.
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SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMPONENTS WITH-HULTIPLE FUNCTIONS The degraded elastomer seal did not involve failure of components with multiple
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D.
FAILED COMPONENT INFORMATION
4 1 HV 2134 Part Name: Elastomer Seal Part No. : N/A Manufacturer: Borg Warner 1.HV-2137 Part Name: Nitrogen Solenoid Valve SV4
- - Part No. : 38878 3 Manufacturer:-Borg Warner III. AtlALYSIS OF THE EVENT-A.
SAFETY SYSTEM RESPONSES THAT OCCURRED Not applicable - no safety system responses occurred as a. result of this event, B.
DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY
- - Roth FWlVs_were inoperab1e for 4 minutes.
- - C.
"lV CONSEQUENCES AND-!HPLICATIONS OF THE EVENT Yhe MJin Feedwater isolation Valves (FWIVs) are containment isolation valves.
To meat valve stroke time requirements, a pressurized nitrogen accumulator increases the rate of valve closure.
Operntion-of these valves is credited in several of the FSAR Chapter 15 accident analyses of secoadary induced overcooling events. The FWlVs are also credited mm
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..-- -,- -w n for mitigation of mass releases to containment in the event of a feedline or steamline break. Specific valve stroke times are assumed in the accident analyses.
Additionally, the Main Feedwater Control Valves (MFCVs) and Main Feedwater Control Bypass Valves (MFCBVs) provide redundant containment isolation and feedwater isolation functions to the FWIVs. The MFCVs and MFCBVs have the same stroke time requirements and close upon receipt of the same signals as the FWIVs. All required surveillances associated with the MFCVs, in accordance with the IST program, were current and satisfactory.
If a transient occurred that required the operation of the FIVs, the operation of the FCVs would have been sufficient to complete the feedwater isolation function, even with the lower-than-design nitrogen cover gas pressure on the affected FWIVs. Furthermore, based on the as found condition TU Electric believes that FWIVs would have closed after the MFCVs closed, thereby maintaining an adequate level of redundancy in the main feedwater isolation function. Therefore, the reported condition had no impact on the health and safety of the public.
IV,
CAUSE OF THE EVENT
The low nitrogen pressure for FWlV 1-HV-2134 was caused by a leak on a nitrogen solenoid valve and on the nitrogen cylinder head. The low nitrogen pressure for FWIV 1-HV-2137 was caused due to a leak on a nitrogen solenoid valve.
V.
CORRECTIVE ACTIONS
Immediate corrective action was to restore the nitrogen pressure to declare the FWIVs operable. The leak rate on 1-HV-2134 was reduced and work is planned to replace elastomer parts for this valve. The solenoid valve on 1-HV-2137 has been replaced to o
prevent recurrence.
VI.
PREVIOUS SIMILAR EVF ES There has been a previous similar event that pertains to FWIV nitrogen accum lator prcssure, and was reported pursuant to 10CFR50.73 (LER 446/94-009). However, the causes for that e ant was sufficiently different such that the corrective actions for
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Nacra,mmA3on the previous event would not have prevented this event. Additionally, a review of
- - a determinatior that; these valves are subject to leakage which requires occasional recharging, however, not in all cases did the 1? ntified-leakage render the FWlV -
3 iinoperabl_e or. lead into entry into Technical Specification 3.0.3.
Nonetheless.-the
- - nitrogen leakage for the FWIVs are tracked and evaluated by Plant Engineering for maintenance requirements.
- - VII, ADDITIONAL INFORMATION
- The times listed in the report are approximate and Central Standard-Timec 1
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