ML20029B042

LER 91-002-00:on 910126,automatic Actuation of Safety Injection Sys Occurred in One of Three Train C Trains.Caused by Inadequate Work Instructions for Maint Activity.Training Bulletin Issued & Supervisors counseled.W/910225 Ltr

ML20029B042
Person / Time
Site:	South Texas
Issue date:	02/25/1991
From:	Ayala C, Harrison A HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-002, LER-91-2, ST-HL-AE-3695, NUDOCS 9103050284
Download: ML20029B042 (6)

Text

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5 The Light company P.O. Itox 1700 llouston. 'li xas 77001 (713) 228 9211 llouston Lighting & Power ,

February 25, 1991 ST-llL- AE- 3 69 5 File No.: 026 10CFR50.73 r U. S. Nuclear Regulatory Conunission Attention: Document Control Desh E-Washington, DC 20555 South Texas Project Electric Cenorating Station Unit 1 Docket No. STN 50-498 Licensee Event Report 91-002 Regarding on Unplanned Safety injection Actuation Due to Less than Adequate Work Ingructions for a Mnintenance Activity Pursuant to 10CFR50.73, llouston Lighting & Power (llL6P) Company subrnits the attached Licensee Event Report (LER 91-002) regarding an unplanned safety >

injection actuation due to less than adequate work instructions for a maintenance activity. This event did not have any adverse impact on the health and safety of the public.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972 8628 or myself at (512) 972 7298.

h W. llarrison Manager Nuclear Licensing .

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Attachment:

LER 91-002 (South Texas, Unit 1)

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Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Cownission Associate General Counsel 611 Ryan Plaza Drive, suite 1000 llouston Lighting 6 Power Cortpany Arli"Ston, TX 76011 P. O. Box 61267 llouston, TX 77208 Coorge Dick, Project Manager U.S. Nuclear Regulatory Comrnission INPO Vashington, DC 20555 Records Center 1100 circle 75 Parkway J. 1. Tapia Atlanta, CA 30339 3064 Senior Resident inspector c/o V. S. Nuclear Regulatory Dr. Joseph M. llendrie Connissio. 50 Be11 port Lane P. O. Box 910 Be11 port, NY 11713 Bay City, TX 77414 D. R. Lacker 4 J. R. Newman, Esquire Bureau of Radiation Control Newman & Holtzinger, P.C. Texas Department of llcalth 1615 L Street, N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX 78756 3189 D. E. Ward /T. M. Puckett Central Power and Light Company P. O. Box 212)

Corpus Christi, TX 78403 J . C. Lanicr/M. B. Lee City of Austin Electric Utility Department P 0. Box 1088 Austin, TX 78767 R. J . Costello/M. T. Hardt City Public Service Board P. O. Box 1771 San Antonio, PX 78296 Revised 01/?9/91 L4/NRC/

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On January 26, 1991, Unit I was in itu third refueling outage with no fuel in the reactor vessel and the P.cactor Coolant System vented to atmosphere. At 0350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br />, during the first performance of a preventive maintenance (PM) work activity, an automatic actuation of the Safety Injection (SI) system occurred in one of three trains (Train C) as a result of less than adequate rh work instructions. All associated Eng: Decred Safety Features (ESP) equipment p operated as expected. The cause of the less than adequate work instructions was personnel error in that two supervisors failed to requir:. Idrther review of work instructions which they believed had potential f. causing an unplanned ESF actuation. Corrective actions include ir. .tivating the subject PM and the associated PMs for the other actuation trair4 in both Unirm. These PMr will be corrected prior to future use. Further cf _rective actions were taken to issue a trainit.:; bulletin to appropriate operations and esiutenance supervisors describing the event, and to counsel the two supervisors on the necessity of performing thorough reviews of procedures and woth instructions that have the potential to cause unplanned ESP actuations, A UtEE02&V1.t01

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On January 26, 1991, Unit I was in its third refueling outage with no fuel in the reactor vesael and the Reactor Coolant System (RCS) vented to atmosphere.

At 0850 hours0.00984 days <br />0.236 hours <br />0.00141 weeks <br />3.23425e-4 months <br />, an automatic actuation of the Safety Injection (SI) system I occurred in one of three trains (Train C) as a result of less than adequate preventive maintena,ce (PM) work instructions. Operations personnel verified.

. that actuated compenents operated as requirad, including HVAC fans and  ?

dampers, contaircent isolation valves, cooling voter systems and the Train C Si occumul.cor isolation valve. No water was actually injected into the reactor vessel since the Trs'n C SI system had been removed from service during this tint,. This equipment operated as expected and there were no adM tional actuations or consequences as a result of this unexpected Engineered Safety Peatures (ESP) partial acttwien. The NRC was notified of the unanticipated ESP actuation at 1225 hours0.0142 days <br />0.34 hours <br />0.00203 weeks <br />4.661125e-4 months <br /> ta Januaty 28, 1991.

The purpose of the PM was_to verify time delay relays for SI reset. and RCS letdown isolation timin6 and to verify the Actuation Train C fifteen volt power supply. There are no specliic requirements for performing this test since failure modes could neither cause nor ptovent ESP actuation 4 The ,

system engineer had requested development of the PM as a good practic(. The FM was approved e December 11, 1990, along with five similar PMs for the other trains of both Units, and was beit.g performed for the first tim 9. The i PM instructions succeasfully tested the Si reset time delay relay buc aid not adequately control the conditions necessary to restore the system to its "as found" condition. Since the Unit was shut down, instrumentation channels were providing SI actuation signals to the Solid State Protection System (SSPS) logic. These logic signals were blocked initially as expected. As written,

< the PM instructions mistakenly clearnd all the blocks. resulting in the unexpected actuation.

The PM program requires review and approval of work instructions by a-respon:tble division authority-(RDA) within the Maintenance Department, The RDA for this PM,'an Instrumentation & Control (160) Techetical Supervisor, requested a technical review by the SSPS System Engineer. The SI reset time delay relay had been tested during a previous refueling outage as part of a design change activity using similar work instructiens contained within a work request. The RDA approved the PM without further review since the instructions were based upon a previous, successful work activity and had been f reviewed by the SSPS system engineer.

On January 25, 1991, the RDA and another 160 Technical Supervisor discussed the potential for an unplanned actuation during the first_ performance _of this-PM activity. Both agreed that the risks associated with performing the PM were minimal since the system engineer had reviewed tho instructions and the Unit was in a safe condition such that an unplanned actuation would have no .

safety consequences. However, the reportability of an ESP actuation was not considered at the time, They also agreed the risk could be further reduced A1/tER028U1.t01 gegromu ma

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t5rt ta m an= e w =v ano,. ama som DESCRIPTION OF EVENT: (cont'd) by ensuring that knowle('geable individuals participated in the first perfortnance of this PM. The latter supervisor directed the FM on the '

following day with a qualified 160 technician. Due to the complex nature of SSPS logic and the abnormal condition created by the relay test, these individuals were unabic to detect the error in the PM instructi'ans while performing the PM. Furthertnore, the complexity of SSPS circuitry is such that control room operators must rely on the expertise of the 16C Technical ,

Supervisors and the system engineer for evaluation of this type of activity.

The FM prograin requireroents were re-examined by rnanagement and found to be adequate for controlling this type of activity. The two supervisors, who are responsible for 160 PM development and implementation, are knowledgeable of the equipment (SSPS) and of the necessity of performing an adequate review of work instructions. Neither supervisor believed the work instructions were

, fully adequate, and both had are opportunity to require further review prior to th. first performance of the PM.

This PM could have been performed successfully had no SI signals been present.

While the PM correctly specified performance in plant modes 5 or 6, no i requirement to clear false Si signals was considered neenssary since the SSPS logic was blocked and the inctructions were not intended to clear the logic-

• block.

The FM prograin includes a continuous optimization process which includes a feedback snechanism used to identify necessary changes to improve PM coordination with plant conditions and irr: prove implementation of PM's. PM  :

feedback forros are prioritized, scheduled, and tracked co completion.

CAUSE OF EVENT: f The ESF actuation was caur.ed by less than adequate preventive maintenance work instructions during the first performance of a new activity. The cause of the less than adequate work instructions was personnel. error in that two supervisors failed to require further review of instructions which they believed had potential for an unplanned ESP actuation.

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ANALYSIS OF EVENT:

Inadvertent actuation of an Engineered Safety Feature is reportabic pursuant to 10CTR50.73(a)(2)(iv). While any inadvertent ESP actuation is undesirable, the safety rnignificance of this event was minimal as the plant was shut down with fuel

• removed frota the reactor core, and there was no safety injection flow to the reactor  ;

core. Had this event occurred with the reactor at power, there would have been no i adverse safety consequences or irrp11 cations as all safety systems responded as

, expected. This event did not result in any adverse safety or radiciogical concerns 5 nor did it threaten the safety of the public at any time.

l CORRECTIVE ACTION:

The following corrective actions are being taken as a result of this event:

1. . The PMs have been deactivated for the associated actuation trains in both Units.

These PMs will be corrected prior to future use. No additional PHs are planned for the Solid State Protection System.

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2. The two 16C supervisors have been courtseled on the necessity of performing thorough reviews of procedures and work instructions having the potential for unplanned ESF actuations prior to the first petformance of a work activity.

3. A training bulletin was . issued to appropriate operations and maintenance supervisors describing this event and reemphasizing the need to ensure the-adet.uacy of maintenance instructions regardless of plant mode or conditions.

ADDITIONAL INFORMATION:

No. component failurea occurred during this event or were discovered during this event, and there have been no previous unplanned Engineered Safety Teatures actuations as a result of less than adequate preventive maintenance work instructions. .

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