ML20205T591

Safety Evaluation Supporting Requested Relief from Inservice Testing Requirements

ML20205T591
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	11/04/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20205T588	List: ML20205T585 ML20205T591
References
NUDOCS 8811140297
Download: ML20205T591 (3)

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UNITED STATES 8"

NUCLEAR REGULATORY COMMISSION o

h WASHING TON, D. C. 20555 y.....)

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REQUESTED RELIEF FROM INSERVICE TESTING REQUIREMENTS CONSUMERS POWER COMPANY BIG ROCK POINT PLANT DOCKET NO. 50-155

1.0 INTRODUCTION

By letter dated July 5, 1988, Consumers Power Company (the licensee) requested changes, among others to the Technical Specifications (TS) related to the inservice testi..; of cert-in Reactor Depressurization System (RDS) valves for Big Rock Point Plant.

Recognizing that the proposed TS changes deviate from certain ASME Code Section XI requirements, the licensee also submitted two relief requests for NRC review and approval.

2. 0 EVALUATION 2.1 Relief Request for RDS Depressurizing Valves Test Frequency The Code of Federal Regulations, 10 CFR 50.55a, requires, in part, that certain safety-related power operated valves (POVs) be tested in accordance with the ASME Code Section XI requirements.

Section XI, in turn, requires that these POVs be full stroke tested every three months, or each cold shutdown if quarterly testing is not practical, and after each repair and maintenance.

Previous TS for Big Rock Point Plant required that the RDS depressurizing valves be tested during each cold shutdown, but in no case these valves need be exercised more often than once every three months.

While the associated pilot valves were being full stroke exercised, the RDS depressurizing valves were only being partial stroke exercised because they discharge directly into containment.

That partial stroke exercise used compressed gas trapped in the spool between the system isolation valve and the depressurizing valve.

Evidence is available to show that the test is not adequate to demonstrate the operability of the RDS depressurizing valves and also that the test is a significant contributor to chronic pilot valve leakage.

Based on the evidence discussed above, the licensea proposed, and NRC approved, a change in RDS surveillance requirement 11.4.1.5.c.1 from a partial stroke test of the RDS depressurizing valves during each cold shutdown, but not required more often than once every 90 days, to a full stroke test each refueling outage.

The four depressurizing valves will be sent off site for full stroke, full pressure tests using live steam.

Justification, as well as relief from the Code requirement, are prerequisites under 10 CFR 50.55a for extending the test interval to refueling outages.

For that approval, based on the licensee's submittals, the staff concluded (1) that a full stroke test using system pressure could not be performed during any mode 8811140297 es1104 PDR ADOCK 0".000155 P

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9 of operation because the RDS valves for Big Rock Point Plant discharge directly to containment, (2) that there is no practical method available to perform the full stroke test on-site, and (3) that, during a regular cold shutdown, it is impractical to remove the valves for off-site testing.

To offset the impact of the longer test interval, the licensee will disassemble and visually inspect one depressurizing valve each refueling outage as a preventive measure.

If results i

of the inspection indicate corrective repairs to the valve are required, the licensee will disassemble and visually inspect additional valves to ensure the concern is not generic.

Based on the above discussion, the staff finds that the relief request to full stroke test the RDS depressurizing valves each refueling outage, in lieu cf quarterly or during cold shutdowns, is acceptable because more frequent testing is impractical and the full stroke testing, although less frequent, is a signif-icantly better alternative than the existing partial stroke testing.

2.2 Relief Request for RDS Depressurizing Valve Pilot Valve Testing Ouring the 1988 refueling outage at Big Rock Point Plant, the RDS depressurizing valve tops were modified and now have removable pilot valve assemblies.

The modifi ation consisted of installation of two isolation valves and a bolting flange between the depressurizing valve top and the pilot valve inlet, and another bolting flange between the depressurizing valve top and the pilot valve 1

outlet.

This modification provides physical separation and isolation of the pilot vaive assembly from the RDS depressurizing valve and therefore allows removal of the pilot valve assembly for repair while the plant is in power

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operation.

Based on the design modification to the RDS depressurizing valves, the licensee proposed, and NRR approved, the addition of surveillance requirement 11.4.1.5.d to Big Rock Point Plant TS as follows:

"Should a pilot valve be isolated from service and removed, the replacement pilot valve shall be functionally tested prior to installation and return to service." Since the pilot valve assembly is a separate entity from the RDS depressurizing main valve, any repair work performed on the pilot valve should not affect the operation and integrity of the main valve.

As such, post-maintenance testing of the pilot valve need only

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be done on the pilot valve and not necessarily on the main valve.

Therefore, the staff finds that relief from Section XI post-maintenance requirement in this instance is not necessary.

However, after installation, (1) the pilot valve solenoid electrical continuity should be rechecked, (2) the isolation valves between the pilot valve and main valve should be verified open, and (3) the pilot valve inlet bolting flange leakage should be checked by using system 2

operating pressure.

t Based on the above discussion, the NRC staff finds that the relief request to test only the pilot valve, rather than the entire RDS depressurizing valve, t

following repairs to only the pilot valve is acceptable, but that relief is unnecessary because a recently completed design modification made the pilot

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valve a separate component from the main RDS depressurizing valve.

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3.0 CONCLUSION

Based on the review summarized herein, we conclude that the relief granted and the alternative examinations imposed through this document provide reasonable assurance that the acceptable level of quality and safety intended by the ASME Code will be satisfied. We have determined that, pursuant to 10 CFR 50.55a(g)

(6)(i), granting relief where the inspection requirements are impractical is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest considering the burden that could result if the requirements were imposed on the facility.

Date:

November

• 4,1988 Principal Contributors:

J. Huang W. Scott