ML20059L337

SER Granting Interim Relief for 1 Yr or Until Next Refueling Outage to Continue Current Testing Methods While Licensee Investigates Feasibility of Acceptable Alternatives

ML20059L337
Person / Time
Site:	Byron
Issue date:	09/14/1990
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20059L310	List: ML20059L305 ML20059L337
References
NUDOCS 9009260250
Download: ML20059L337 (3)

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SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION pVMP AND VALVE TESTING PROGRAM RELIEF REQUESTS COMMONWEALTH EDISON COMPANY BYRON, UNITS 1 AND 2 DOCKET N05. STN 50-454 AND STN 50-455

1.0 INTRODUCTION

By letter dated July 6,1990 Commonwealth Edison Company submitted two relief requests concerning the inservice pump and valve testing program for Byron, Units 1 and 2. Relief Requests VR-21 and VR-22 requested relief from the check valve exercising procedures of ASME Code, Section X1, IWV-3522.

2.0 DESCRIPTION

AND DISCUSSION Relief Request Number VR-21: The licensee has requested relief from the exercising procedures of IWV-3522 for the residual heat removal system check valves 1/2 RH8705 A/B and proposes to replace these valves every 10 years.

Licensee's Bases for Relief These check valves cannot be safely tested to open during normal operation or refueling outages because of backpressure from the Reactor Coolant System (RCS) on the check valve discharge piping. Also, flow rates cannot be verified.

Evaluation The check valves are designed to relieve any built-up pressure between motor operated pressure isolation valves, which separate the RCS from the Residual Heat Removal (RHR) pumps. The pressure build-up could cause the motor operated valves to bind. These check valves also serve as pressure isolation valves.

It is not apparent to the staff that a reasonable forward flow test of these valves cannot be performed. A review of the Byron, Units 1 and 2, Piping and Instrumentation Diagram (P&lD's) indicates that these check valves could be tested to open by imposing a delta P across them through an existing tap located between the motor operated valves. The flow rates through the check valves could be verified by appropriate pressure indication, knowledge of the 9009260250 900914 PDR 1 P ADOCK 05000454 = l pg -

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flow through the existing tap, or non-intrusive flow measuring techniques.

Comparison of this flow rate with the flow required for this valve to perform its safet Alter-natively,yusing function would meet non-intrusive the exercising diagnostic requirement techniques to verifyofthat IWV-3522.

valve disk is contacting the back stop can be a demonstration of full stroke capability of a valve. Imposition of immediate compliance would result in an extended outage .

which would be a hardship for the licensee due to the costs involved. Further,  !

any binding of the motor operated pressure isolation valves, which the check  :

valves serve to prevent, would be detected during the full stroke testing of these motor operated valves that is performed on a cold shutdown frequenc Therefore, interim relief may be granted pursuant to 10 CFR 50.55a(a)(3)(y.ii) for six months to continue current testing methods while the licensee investigates the possibility of acceptable alternatives.

Relief Request Number VR-22: The licensee has requested relief from the check valve exercising method requirements of Section XI, Paragraph IWV-3522, for the following valves in the safety injection system: 1/2 S18818A-D, 1/2 S18948A-D, and 1/2 S!8841 A and B. The licensee has proposed verifying the full-stroke capability of these check valves in pairs.

Licensee's Bases for Relief These valves are installed in parallel and full-stroke verification cannot be performed individually on each valve.

Evaluation A valid full-stroke exercise based on flow measurements requires that the flow through each valve be known. The licensee's proposed alternative does not individually verify the flow rate through each valve and cannot be considered a full-stroke exercise. The proposed testing would be considered successful after passing a minimum flow rate through the valves even though one or both valves could have degraded significantly. Therefore, the proposed testing does not meet the Code and is not a reasonable long term alternative to the Code.

The licensee shouls actively pursue the use of non-intrusive flow measuring or valve diagnostic techniques to demonstrate that either the flow through each valve in the ) air is approximately equal or that these valves swing fully open.

If, after a t1orough investigation, it is determined that the full-stroke capability of these valves cannot be demonstrated with diagnostic techniques then the licensee may consider valve disassembly and inspection. The NRC staff positions regarding check valve disassembly and inspection to verify the full-stroke open capability are explained in detail in Generic Letter (GL) 89-04, Attachment 1, item 2. The minutes on the public meetings on Generic Letter No. 89-04 regarding this staff position further stipulate that a partial stroke exercise test using flow is exsected to be performed after disassembled valve is returned to service. T11s post-inspection testing provides a degree of confidence that the disassembled valve has been reassembled properly and that the disk moves freely.

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An interim period of relief is necessary to give the licensee time to complete their investigation and the test procedures, imposition of imediate compliance would result in an extended outage which would be a hardship for the licensee due to the costs involved. Although the licensee's proposal, to exercise these parallel valves collectively does not individually verify the full-stroke capability of each valve and is not a reasonable long-term alternative to the Code required testing, it does provide assurance that the pair of valves tan perform their intended safety functions. Therefore,  ;

interim relief may be granted pursuant to 10 CFR 50.55(a)(3)(ii) for one year or until the next refueling outage, whichever is longer, to continue current tasting methods while the licensee investigates the feasibility of acceptable alternatives.

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