05000346/LER-1992-001, :on 920210,both Channels of Containment H Analyzer Inoperable & TS 3.0.3 Entered.Caused by Breaker Malfunction.H Analyzer AC Input Breaker Replaced & Labeling & Access Control to Circuitry Improved
| ML20090H026 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/10/1992 |
| From: | Storz L, Turkal M TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| AB-92-0010, AB-92-10, LER-92-001, LER-92-1, NP-33-92-001, NP-33-92-1, NUDOCS 9203130232 | |
| Download: ML20090H026 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2) |
| 3461992001R00 - NRC Website | |
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Docket No. 50-346 License No. NPF-3 Itarch 10, 1992 United States l'uclear Regulatory Cotrmission Document Control Desk.
Vashf'igton, D. C.
20555 Centlement LF,R 92-001 Davis-Besso Nuclcar Power Station, 151t No. 1 Date of Occurrence - February 10, 1992 Enclosed please find Licennew Event Report 92-001, which is being submitted to provide 30 days written notification of the subject occurrence. This LER is being submitted in accordance with 10 CFR 50.73(a)(2)(1).
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Lotiis F. Storz Plant Manager Davis-Besse Nuclear Povet Station LFS/ed Enclosure cet Mr. A. Bert Davis Regional Administrator USNRC Region III Mr. V1111am Levis DB-1 NRC Sr. Resident Inspector 1
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On Februarv 10, 1992 at 1843, with the plant in Mode 1, it was discovered that both channis of the Containment Hydrogen Analyzer vere inoperanle.
Channe.1 2 of the Containment flydrogen Analyzer had been remsved from service for maintenance at approximately 0010 and the actinn statement for Technical Specification (TS) ~1.6.4.1, which allows operation for 30 days with ore inoperable hydrogen analyzer, was en;ered. At IP'O the E 91stant Shift Supervisor vas not itled that computer point A301, CTl?T H2 Chaanel 1, vas in the ahr n state.
An ir.vestigatior, was initiated sind the AC input breaker asrociated with Channel I was vetiffesd to be open.
is 3.0.3 vas entered at %43. The bteaker was closed at 1846 and TS 3.0.3 vas exited.
No power reduction occurred ehm to the r.hort time in T3 3.0.3.
The Channel i Containment Hydrogen Analyzer AC input breaker was replaced on February 20, 1992.
Amendment 168 to the Davis-Besse Operating 1.icus.:. vas 3
implemented on February 11, 1992.
This amendment revised TS 3/4.6.4.1 to address inoperability of both hydrogen analyzers.
An Operatfor.s Night Order vas issued on February 14, In92 which requires review of the ccmputer alaru list at least twice per shift with logging of this review and any actions taken ir response to compu'.er alaru. A review team has been formed to address possible improvements in the computer a.tarm system.
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On February 10, 1992 at 1843, with the plant in Mode 1, it vas discovered that both channels of the Containment Ilydrogen Analyzer (IK) were inoperable.
Cnannel 2 of the hydrogen analyzer had been removed from service for maintenance l
at approximately 0010 and the action statement for Technical Specification
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3.6.4.1, which allovs operation for 30 days _vith one inoperable hydrogen-l analyzer, was entered.
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A reviev of the computer alarm records vas initiated after a reactor operaior noted a belov scale _ reading on Containment Ilydrogen Analyzer Channel 1.
During ti.is reviev, it was discovered that computer point A3024 CTNT 112 Channel 1, had l
entered the alarm utate at 0852.
The Assistant Shift Supervisor-vas notified of j
this condition at 1830.
An investigation was faltiated and at 1843 the AC input breaker associated with Channel 1 vas verified to; be open. Technical i
Jpecification 3.0.3 vas entnred at 1843 because the action stateruent in Teen! N Specification 3.6.4.1 did not contain a provision for tw inoperable
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of the hydrogen analyzee. At.1046, the breaker vas closed, a channel performed which demonstrated the operability of Channel 1 of the r+
ocg r analyzer, and Technical Specification 3.0.3 vad-exited.. No pova,r
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n occurred because Technical Specification 3.0.3 was only in effect for it '
.inutes.
This event is being reported in accotdance with 10 CFR 50.73(a)(2)(.) as a
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i condition prohibited by the plant's technical specifications.
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i bppareat cause of occurrence:
The cause of this event was the inadvertent opening of_the Channel I hydrogen l
analyzer.AC input breaker while Channel 2 vas temoved from service. This required entry into Technical, Specification 3.0.3.since both channels of the-Containment Hydrogen Analyzer vere out of service and the action statement in.
I Tee huical Specification 3.6.4.1 did not contain a provision for two. inoperable channels of the hydrogen anal per.
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Apparer.i Cause of Occurrence (Continur4d):
The it. advertent opening of the Channel I hydrogen analyzer AC input breaker can j
mont probably be attributed to a malfunction of the breaker.
Maintenance
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personnel vere at the hydrogen analyzer cabinet when the breaker opened, llo t h channels of the hydrogen cnalyzer are located in this cabinet, separated by a metal barrier. The maintenance personael had the doors to each side of the 6
cabinet open in order to compare tne-configuration of Channel 2 circuitry _to that of Channel 1.
During thir comparison, the channel 1 breaker box cover appeared loose and vas touched to determine if this was the case.
Due to the levt.1 of noise in the area, the trippin cf the breaker vould not have been auhble. Vhlie opening of the-breaker could be due solely
'.o mechanical shock induced by the maintenance personnel, it is balleved that their actior.s would I
not have been sufficient to jar the breaker c;en. This scenario is supported by a pi elous incident, tr Jenuary 1992, when the breaker was inexplicably found open during performance of i,i channel calibration prior to returning Channel 1 to i
service.
Dusing the review of this event, it vas detetmined that enhancements to tne control room alatm System tre warranted.
Anomalics entst in the computer alarra i
system which contribute to the number of continuous and extraneous computar alatme.
In addition, neither the screen disple.y ot the hardcopy printout of the computer alarms ptovides-nn indication of which alatms are associated with r
Technical Specification equipment.
This makes it mte dif ficult for the l
operators to determine the appropriato v.ction for each alarm. As a tresult of j
thene problets, the confidenca of operations personnel in the computer alarm i
I system has been reduced.
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A y l,ysis_of Occurrence the safety significance of this event i.v ainimal. There were no plent transients or automatic or manually initiated safety system responses during the approximately nine hours when both channels of the hydrogen analyzer vere inoperable.
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^"915 h 0I. 03Sjy,33ns,g (Con t inued):
The hydrogen analyzers are designed to monitor containment atmosphere.
Opetability of the conte *nment analyzers ensures that jndication of containment hydrogen concentration iri available following a loss 0,f ec>olant act.ident (LOCA).
Ilad a I.0CA occurred during the period when both hydrogen analyzers vere inoperable, the Post Accident Sampling System (IP) could have been used to determine containment hydrogen concentration.
In addition, it is estiinated that. if no operator actian is taken to initiate the hydrogen illution system (BB). it would take approximately 21 days af ter a design bash accideat fot the hydtogen concentiation to reach three percent and approximately ?? days to teach combuM ible levels.
On January 16, 1992, the flRC issued Amendment 168 to the Davis-Besse operating License. This amendment revised Technical Specification Section 3/4.6.4.1 by adding an additional action statement, applicable when both hydrogen annlyrers nre inoperable, which allows 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to return one of the two inopernble hydrogen analyzers to operable status before initiating a plant shutdovn.
Although Amendment 168 vas issued. Toledo Edison had not yet imple m ted the change.
Amendment 168 vas implemented on February 11, 1992.
Corrective Action
l The channel I hydrogen analyret AC input breaker was replaced on Februnty 20, 1992. Testing was conducted on the terrioved breaker, hovever, inappropriate breaker operation could nct be reproduced.
Due to the confi ptation of the hydrogen analyrer circuitty, vith both channels in a single cabinet better labeling and a m ss control vill be established to reduce the potential of inadvertent operation. The hydrogen analyzer cabinet is now locked with access contiolled by the Shift Supervisor. The ability to sepatately lock each channel vill t'e provided by June 1,1992.
In addition, labeling vill be enhanced to provide channel indication on each cabinet door and labeh for tic AC input breakers.
The labeling enhan;ements vill be completed by April 30. 1962.
An operations Night order was icsued on February H, 1992 vhich requires review of th> computer alarme list at least twice per shift with logging of this teview and any actions taken in response to computer alarms.
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correttive Action (Continued):
A review team has been formed to addtess possible linprovements in the computer
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alatm system. The tirst meeting of tnis team was held on February 20, 1992.
It is expected that this team vill recommend improvements which will make identification of significant computer alatms easier for control room operators.
4 The team is enpected to provide an edited list of :omputer points to be monitored by the Control Room CRT by-June _1.
1992.
This vill delete a numhet of unneteasary poluts and greatly improve on the nuisance" f actor experienced by the operators.
final results of the computer alarm system improvements ate exputted by December 1. 1992 for management review.
F'allut e Da ta:
LF.P. 90-12 is the only other report in the previous tve years which involved entry into Technical Specification 3.0.3.
In that instanen, Technical Specification 3.0.3 was entered as a result of two inoperable containment radiation monitors (IL).
The root cause and corrective actions discussed in LER 90-12 are not applicable to this event.
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