ML19289C679

Responds to 781128 Ltr Re Purging During Normal Operation. Need for Purging Has Been Limited,But It Is Essential That Capability of in-containment Activities at Power Be Maintained

ML19289C679
Person / Time
Site:	Point Beach
Issue date:	01/16/1979
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	Harold Denton, Schwencer A Office of Nuclear Reactor Regulation
References
TAC-44877, TAC-44878, NUDOCS 7901220097
Download: ML19289C679 (3)

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\s_,s) wisconsin Electnc voua couvany 231'A EST MICHIGMt MIL A AUKE E, WISCONSIN 53201 January 16, 1979 Mr. IIarold R. Denton, Director Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D. C. 20555 Attention: Mr. A. Schwencer, Chief Operating Reactor Branch 1 Gentlemen:

DOCKETS 50-266 and 50-301 CONTAINMENT PURGING DURING NORMAL PLANT OPERATIONS POINT BEACll NUCLEAR PLANT UNITS 1 AND 2_

This is in reply to your letter of November 28, 1978 in respect to containment purging during normal operation.

In that letter you cclled attention to events relating to containment purging w erations, and raised questions concerning possible failure of purge line valves, requesting we take certain alternative actions in response. You also requested that we review safety actuation signal circuits, incorporating manual override or bypass features to assure that overriding of one safety actuation signal does not also bypass any other safety actuation signal.

We regret that our reply has been delayed, but the nature of the matters raised in your letter involves substantial review and analysis, which we have been unable to complete. We are continuing to examine the issues raised in your November 28 transmittal, and will respond more fully at a later date. In the meantime, we present herewith our interim reply.

In respect to containment purging, we have found at Point Bec.ch that extended activities inside containment with a reactor at power or in hot shutdown are infrequent. Accordingly, the need for purging at our facility has been limited. Nevertheless, we believe it is essential that the capability of in-containment activities at power be maintained. This requires containment \ p purging if personnel exposures are to be minimized. N90% * .

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Mr. Ilarold R. Denton January 16, 1979 You suggested three options governing such containment purging activities. We have requested design and analytical data from the manufacturer of our purge isolation valves. Pending receipt of these data, we are unable to determine which of the options you offered would be appropriate to Point Beach. In the interim, we will continue to limit purging to the minimum necessary.

A brief description of the actuation system at Point Beach follows.

The containment purge inlet and outlet valves are automatically closed by a containment ventilation isolation signal.

The containment ventilation isolation signal is formed by an OR function of the following signals:

High Containment dadiation Safety Injection Manual Spray Manual Containment Isolation A reset or override function is provided on the containment ventilation isolation signal. If any of the above-listed input signals are continuously present and it is desired to open the centainment purge inlet and outlet valves, this can be done by pressing the reset button. The reset circuit contains a seal-in which prevents reactivation of containment ventilation isolation by another input signal as long as the original input is continuously present. As soon as the input signal is interrupted, the seal-in is dropped and any of the input signals will again generate the containment ventilation isolation signal. Thus, for example, if a high containment radiation signal is continuously present, the purge inlet and outlet valves could be opened by resetting the containment ventilation isolation signal. Under these conditions, a safety injection signal would not reclose the valves. The valves can be reclosed manually from the control room.

Presence of reset on the containment ventilation isolation signal is not presently annunciated.

Reset of the containment ventilation isolation signal does not affect any other signal. In particular, it does not affect actuation of the containment (fluid) isolation signal or the safety injection signal.

A review of past operating experience with the containment purge system verifies that the inlet and outlet valves have never been opened using the reset capability to bypass one safety actuation signal in order to open the valves. When the high radiation signal has been present, it has been adjusted upward from its initial conservatively low setpoint until it is cleared. The purge inlet and oatlet valves are opened by pushing the reset function and opening the valves. Should any safety actuation signal occur while the valves are open, they would close automatically.

This mode of operation will continue until the system can be modified, if required, to remove the bypassing of other safety actuation signals when the system is reset with an actuation signal present.

.e Mr. Ilarold R. Denton January 16, 1979 We will provide to you, in approximately 90 days, our review of the design of the remaining safety actuation circuits and a schedule for the development of any design or procedural changes planned to assure correction of any non-conforming circuits.

Very truly yours, Exec tive Vice President Sol Burstein