TXX-4835, Final Deficiency Rept CP-86-23 Re Potential Failure of P-10 Reactor Protection Sys Permissive.Initially Reported on 860403.Procedure ABN-703 Revised to Include Addl Info Re Problems Associated w/P-10 If Below 10% Power

Final Deficiency Rept CP-86-23 Re Potential Failure of P-10 Reactor Protection Sys Permissive.Initially Reported on 860403.Procedure ABN-703 Revised to Include Addl Info Re Problems Associated w/P-10 If Below 10% Power

ML20211D770
Person / Time
Site:	Comanche Peak
Issue date:	06/05/1986
From:	Counsil W, Keeley G TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
CP-86-23, TXX-4835, NUDOCS 8606130147
Download: ML20211D770 (3)

Text

T Log # TXX-4835 File # 10110 907.2 TEXAS UTILITIES GENERATING COMPANY SKYWAY TOWER . 400 NORTH OLIVE NTEEET. L.B. EI . DALLAS. TEXAS 78301 June 5, 1986

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Mr. Eric H. Johnson, Director Division of Reactor Safety and Projects g glE i l' U. S. Nuclear Regulatory Commission u A Jf, 611 Ryan Plaza Drive, Suite 1000 u Arlington, TX 76012

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NOS. 50-445 AND 50-446 P-10 PERMISSIVE SDAR: CP-86-23 (FINAL REPORT)

Dear Mr. Johnson:

On April 3,1986, we verbally notified your Mr. T. F. Westerman of a deficiency involving a potential failure of the reactor protection system permissive, P-10, to reset during power reduction to below the P-10 setpoint.

We have submitted an interim report logged TXX-4787, dated May 5, 1986. We have concluded that this deficiency is reportable under the provisions of 10CFR50.55(e). We anticipate completion of all corrective action by December 1, 1986.

Very truly yours, Yh W. G. Co nsil n5h l

By: . ,.

G. S. Keeley _

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Manager, Nuclea L _icensing JCH/arh Attachment ,

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Director, Inspection & Enforcement (15 copies)

U. S. Nuclear Regulatory Commission Washington, D.C. 20555 0606130147 860605 5 PDR ADOCK 0500 S

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ATTACHMENT P-10 PERMISSIVE DESCRIPTION The issue involves a potential malfunction of the reactor protection system permissive, P-10, to reset during power reduction to below the P-10 setpoint when one channel is in a tripped status and a single failure of one of the three remaining operable channels is assumed. The automatic unblocking of the permissive would not occur when the power is reduced below the P-10 setpoint.

An evaluation assuming that the trips are not functional revealed that no fuel failures would occur but the licensing basis in the FSAR might not be met.

However, it is a significant deficiency in the final design such that the design does not conform to the crittria in the FSAR. Corrective action is required to restore the intended safety function.

This deficiency applies to both Units 1 and 2.

SUMMARY

OF EVENTS Date Discussed: March 4, 1986, per vendor (Westinghouse) notice.

Date NRC Notified as Potentially Reportable: April 3, 1986.

Interim Report to NRC: May 5, 1986.

Date Determined Reportable: June 2, 1986.

, SAFETY IMPLICATION The potential malfunction is not a substantial safety hazard. It does not represent a loss of safety function to the extent that there is a major reduction in the degree of protection provided to public health and safety.

This is true because there are other reactor trips which would mitigate the

, event. Depending on the scenario, these include the power range high neutron flux trip (high setpoint), the over temperature N-16 trip, the over power N-16 trip, the power range high positive neutron flux rate trip, and manual trip.

Although the margin of the technical specification DNBR may be reduced, the DNBR never reaches the limit, thereby preventing fuel failures.

CORRECTIVE ACTION Operations Engineering has evaluated the problems and concerns associated with the permissive P-10 inoperability and has concluded the following changes to operations procedures will be made. The recommendations made by Westinghouse are listed below followed by the CPSES response.

, 1. If possible, when a Power Range Flux channel is determined to be I inoperable, place the affected P-10 bistable in a non trip condition I when operating at or following a reduction of power below 10% power.

l RESPONSE: Current design at CPSES does not allow the P-10 l bistable to be reset in a non trip condition without allowing other trips to be bypassed (109% Reactor Trip).

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ATTACHMENT P-10 PERMISSIVE (continued)

This in turn would violate Technical Specifications if performed. Therefore, this recommendation can not be performed and no further action is required.

2. When reducing power to below the P-10 setpoint, verify by observation of the existing control room bistable status lights, permissive status lights and associated alarms that the P-10 permissive properly changes state.

RESPONSE: Currently IP0-004A has the operator verify the bistable lights go out when power drops below 10%. To give the operator more guidance if the above is not met, the procedure will be revised to include a reference to ABN-703A (Power Range Channel Malfunction Procedure) in the case where the bistable lights above can not be verified.

3. If permissive P-10 is not and can not be placed in the appropriate status for the existing condition, place the plant in a condition such that the trips made inoperable by P-10 are not required to function. This may require plant shutdown followed by opening the reactor trip breakers and/or boration. Consideration should be given to existing procedures and Technical Specifications.

RESPONSE: Technical Specifications currently require P-10 to be operable with a minimum of 3 channels operable. With less than 3 channels operable, the plant is required to be shutdown within a specified period of time.

The procedure that currently discusses the power range channel inoperability is ABN-703. This procedure will be revised to include additional information concerning the problems associated with P-10 if below 10% power or if intending to go below 10% power.

i 4. Make all reasonable attempts to regain source range instrumentation as quickly as possible if the source range (s) are inoperable.

RESPONSE: ABN-701A (Source Range Instrumentation) will be revised to include a statement that will make the operator aware that source range instrumentation must be restored to service as quickly as possible.

i Operations Engineering has scheduled the above procedure revisions to be incorporated and approved by December 1, 1986.

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