ML19345H544

Documents Basis for Containment Isolation Pressure Setpoint Reported in Item II.E.4.2 of NUREG-0737 Response Per NRC 810414 Telcon.Present 5 Psig Setpoint Considered Realistic & Appropriate

ML19345H544
Person / Time
Site:	Point Beach
Issue date:	05/07/1981
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.E.4.2, TASK-TM IEB-79-01B, IEB-79-1B, TAC-44877, TAC-44878, NUDOCS 8105210238
Download: ML19345H544 (2)

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WlSCORSin Electnc mm counn 231 W. MICHIGAN, P.o. 80X 2046. MILWAUKEE WI 53201 May 7, 1981 Oh Mr. Harold R. Denton, Director 9

f Uf *W Office of Nuclear Reactor Regulation D

U. S. NUCLEAR REGULATORY COMMISSION Washington, D. C.

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MAY 201981= y Attention: Mr. Robert A. Clark, Chief Operating Reactor Branch #3 up p3 Gentlemen:

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9 DOCKET NOS. 50-266 AND 50-301 CONTAINMENT PRESSURE SETPOINT NUREG-0737 ITEM II.E.4.2_

POINT BEACH NUCLEAR PLANT UNITS 1 AND 2 During a telephone conversation on April 14, 1981, Mr. Mel Fields of your Staff requested that Wisconsin Electric Power Company document the basis for the containment isolation pressure setpoint reported in Item II.E.4.2 of our NUREG-0737 response dated December 23, 1980. The position clarification in NUREG-0737 directed that the containment setpoint pressure which initiates containment isolation be reduced to the minimum compatible with normal operation. This setpoint should be far enough above the maximum observed or expected pressure inside containment during nonnal operation so that inadvertent containment isolation does not occur during normal opera-tion from instrument drift or fluctuations. A margin of 1 psi above the maximum expected is considered, according to the NUREG, to be adequate.

Any other proposed value must be justifigd.

Point Beach Nuclear Plant Technical Specification 15.3.6.B speci-fies that containment internal pressure sfiould be maintained between 3 psig and -2.0 psig.

If not, the condition shall be corrected or the reactor rendered subcritical. Specifications for the containment high pressure actuation for the safety injection system requires a setting limit of <6 psig. The containment design pressure of 60 psig would not be exceeded if the internal pressure before a major loss-of-coolant accident were as much as 6 psig (Point Beach Nuclear Plant FSAR 14.3.4) which corresponds to the existing Technical Specification limit. The actual setpoint for high con-tainment pressure actuation of safety injection and containment isolation is 5 psig so that a possible instrument drift of 1 psig high would not result in a Technical Specification violation.

Instrument drifts.of up to 2 psig have been observed in the past for the current containment pressure instruments. The instrument accuracy Id 81052.10235

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Mr. Harold R. Denton May 7, 1981 a

of 1/2% of the 60 psi range results in a I.3 psi error band. Containment O

pressure has exceeded 2 psig during normal plant operation.

In order to prevent spurious actuations of the safety injection system, a nominal setpoint of over 4.3 psig (2 psig + 0.3 psig + 2 psig) is required. It should be noted that other channel error bands have not even been considered.

Our present 5 psig setpoint provides a 1 psig margin to the 6 psig Technical Specification limit. The 3.0 psig Technical Specification limit requires corrective operator action and NRC notification. During normal plant operation, there are no normally open or automatically opened containment release paths, either gaseous or liquid, except for a two-inch containment atmosphere monitoring and pressure equalization line. This line is isolated by containment signals including safety injection.

We consider our present 5 psig setpoint to be realistic and appropriate. The basis for this setting is adequately supported.

We would note further that we are in the process of trying to change the existing containment pressure transmitters to comply with IE Bulletin 79-018. We are also adding high range pressure transmitters in compliance with Item II.F.1.4 of NUREG-0737. When the replacement transmitters have been installed and evaluated, we may reconsider the necessity for adjustment of the containment isolation setpoint pressure.

Very truly yours,

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G A.

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C. W. Fay,' Director Nuclear Power Department Copy to: NRC Resident Inspector Point Beach Nuclear Plant

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