ML19309A528

Forwards Response to IE Bulletin 79-27, Loss of Nonclass IE Instrumentation & Control Power Sys Bus During Operation. Loss of Power to Any Instrument Bus Will Not Affect Ability to Go to Safe Shutdown

ML19309A528
Person / Time
Site:	Point Beach
Issue date:	02/29/1980
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-276, NUDOCS 8003310401
Download: ML19309A528 (3)

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WISCONSIN Electnc com come 231 W MICHIGAN. P 0. BOX 2046. MilwAUKfI WI 53201 February 29, 1980 Mr. James G. Keppler, Regional Director Office of Inspection and Enforcement Region III U. S. NUCLEAR REGULATORY COMMISSION 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

DOCKET NOS. 50-266 AND 50-301 REPLY TO IE BULLETIN 79-27 POINT BEACil NUCLEAR PLANT Your letter of November 30, 1979, forwarded IE Bulletin 79-27, " Loss of Non-Class I-E Instrumentation and Control Power System aus During Operation". Attached is our reply to IE Bulletin 79-27. If you have any questions on the attached material, do not hesitate to contact us.

Very truly yours,

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C. W. Fay, Director Nuclear Power Department Attachment Copy to: NRC, Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20555

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ATTACHMENT DOCKET NOS. 50-266 AND 50-301 REPLY TO IE BULLETIM 79-27 POINT BEACH NUCLEAR PLANT 1.- There are four singic phase 120 volt instrument buses at the Point Beach Nuclear Plant that could possibly affect the ability to achieve cold shutdown. Two of these are inverter powered from safeguards batteries, one is powered from a safe-guards diesel generator on loss of offsite nower and the fourth is powered from offsite power by a non-safeguards bus that can be manually transferred to a safeguards diesel generator if desired. The two buses that are not inverter powered normally receive power through motor generator sets which have been installed to ride through voltage transients.

An alternate power source with manual transfer is provided for each bus at its 120V breaker panel which is in the control room. The plant computer is not required for either power operation or cold shutdown of the plant and is not powered by any of these four instrument buses.

a) An annunciator is provided on the main control board in the control room. The legend on the annunciator is " Instrument Bus Voltage or MG". This annunciator is activated by loss of power or high voltage to any of the four buses or loss of output from either of the MG sets if powered. If an alarm condition occurs, the annunciator flashes and an audible alarm sounds until it is acknowledged, at which time the annunciator remains lighted until proper power is restored to the-bus. Also on the main control board is a matrix of color-coded indicator lights representing instrument channel bistable status. A light will be lighted when the associated bistable is in the tripped condition.

Since the channels fail to the tripped condition on loss of power, loss of an instrument bus would cause an entire row of these indicator lights thus, indicating which bus has lost power.to become lighted,ddition

. In a to the above two indications of the loss of an instrument bus, on top of each of the 120 volt bus breaker panels in the control room are two lights which indicate availability of power from the respective normal and alternate power supplies to each bus. These lights are arranged such that they are all simultaneously observable from one position in the control room.

b) Loss of power to any instrument bus will not affect the ability to go to safe shutdown. The design basis

, for the Point Beach Nuclear Plant is hot shutdown, not cold shutdown. Since achievement of cold shutdown

. can be accomplished over a relatively long time, power can be easily restored to the afflicted bus prior to proceeding to a cold shutdown condition.

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c) There are no proposed design modifications resulting specifically from these reviews and evaluations. As a result of proposed requirements of NUREG-0578, NUREG-0585, Regulatory Guide 1.97, NUREG-0623, and NUREG-0660, it is anticipated that additional instru-mentation loads will be added to the buses. It is further anticipated that some of the buses will be upgraded and loads redistributed among the buses. The timetable for this effort will be based on the require-ments of the referenced documents.

2. The emergency procedures at the Point Beach Nuclear Plant specifically address loss of offsite power and possible instrument failure or instrument error. The emergency procedures were recently rewritten as a result of our participation in a Westinghouse Owners' Group on procedures.

Loss of offsite power and possible instrument failure or instrument error were considerations emphasized in making

. these revisions.

a) The alarms and indicators provided in the control room enable the operator to very rapidly identify a loss of power on an instrument bus. This specific identi-fication is part of his training and it is not appropriate for inclusion in each emergency procedure.

b) Each of the emergency procedures contains a note that the listed symptoms are monitored in most cases by more than one instrument channel. The redundant channels should be checked during the evaluation of plant condi-tions to ensure instrument failure or instrument error does not cause faulty diagnosis, c) The methods for restoring power to an instrument bus are provided in a separate procedure, " Shifting of Instrument Supply Bus Feeders".

No proposed design modifications or administrative controls resulted from this review of the procedures.

3. No design modifications or administrative controls have been proposed as a result of the re-review of IE Circular No. 79-02.

Automatic transfer to the alternate power supply is not used for these instrument buses.

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