ML13333A367

Updates Status of Commitments Re Operating Functions & Plant Mods of Fire Protection Program.Discusses Safe Shutdown Casualty Procedure,Spurious Valve Actuation & Hydrogen Seal Oil Area Fire

ML13333A367
Person / Time
Site:	San Onofre
Issue date:	05/15/1979
From:	Buskin K SOUTHERN CALIFORNIA EDISON CO.
To:	Ziemann D Office of Nuclear Reactor Regulation
References
TAC-48143, NUDOCS 7905230514
Download: ML13333A367 (3)

Text

Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN May15, 1979 TELEPHONE

MANAGER, GENERATION ENGINEERING 213-572-1401 Director, Office of Nuclear Reactor Regulation Attention:

Mr. D. L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors Washington, D. C. 20555 Gentlemen:

A C ULATnR DOCKET FILE COPY

Subject:

Docket No. 50-206 Fire Protection Program Review San Onofre Nuclear Generating Station Unit 1 As a result of the recent SCE/NRC meetings and correspondence which were part of the Fire Protection Program Review for the San Onofre Nuclear Generating Station Unit 1, a large number of commitments have been made with respect to operating functions and plant modifications. A review of these commitments has identified the need for submittal to the NRC of an update of the status of these commitments and to identify any deviation from the commitments which may have occurred in the interim.

The required update concerns three different areas of review; (1) the casualty procedure to be implemented following loss due to fire of the equipment located in the 4160 V switchgear room or the lube oil reservoir area, as identified in our letter dated October 18, 1978, (2) the evaluation of spurious valve actuation, as identified in our letter dated October 18, 1978, and (3) the evaluation of the effects of a fire in the hydrogen seal oil unit on the structural steel of the turbine building, as identified in our letter dated January 11, 1979. An update to these items is required due to changes which were necessary for implementation of the commitment or due to the acquisition of new information, the details of which are provided as follows:

1. Interim Safe Shutdown Casualty Procedure By letter dated October 18, 1978, the casualty procedures for safe shutdown following a fire in the 4160 V switchgear room or the lube oil reservoir area, were provided as Enclosures 7 and 8. The procedural steps which were incorporated into Emergency Operating Instruction S-3-5.28 differed somewhat from the original procedural steps identified in the October 18, 1978 letter. The changes were necessary for the functional implementation of the steps described in the procedures and are described below.

7905230 51 q

0 Mr.

D. L. Ziemann, Chief Mayl5, 1979

a. The original procedures identified the need to locally remove power to certain equipment in order to avoid spurious actuation which could affect safe shutdown. As a result of further evaluation, however, it was determined that it would not be feasible to remove power locally to all the non-required equipment. Therefore, the method identified was to remove all normal sources of power to the station by directing the system dispatcher to isolate the 220 kV and 138 kV switchyard at San Onofre Unit 1 from all incoming sources, and by taking operator action to assure that the diesel generators are not operating, and the battery sources to non-required equipment are disconnected. The required shutdown equipment would be powered from 480V switchgear #2 which can be energized by the recently installed emergency power supply (from Japanese Mesa Substation).

It has now been identified that the above described method for removing non-required power from the station may result in grid instabili ties on the San Diego Gas & Electric system since complete isolation of the switchyard would disconnect the SCE grid from the San Diego Gas & Electric grid.

In order to avoid the possibility of disrupting the SDG&E system, we are in the process of revising the procedural steps for removing the normal off-site sources of station power. Instead of having the system dispatcher perform the switchyard isolation, the Plant Equipment Operator (PEO), as a part of his Fire Brigade Duties, will travel to the switchyard and manually open the Plant Circuit Breakers, their associated DC control, and the Bus Disconnects. The other procedural steps will remain the same. The basis for revising the procedural steps are two-fold:

(1) it is estimated that power isolation can be accomplished in a shorter time, and (2) the PEO can isolate the station from offsite sources but leave the switchyard energized. By not deenergizing the switchyard, the SCE intertie to the San Diego Gas & Electric grid will not be lost thereby removing the possibility that grid instabilities might be created affecting the emergency offsite power source to 480V switchgear #2 which is supplied from the San Diego grid. Once the procedural steps are revised, a "walk through" will be accomplished to verify that it can be implemented.

b. The time available to restore normal reactor coolant pump seal cooling was indicated to be 20 minutes in the original procedures.

A more rigorous calculation has recently been performed which indicates that the available time is actually greater than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, which provides more time available to perform operator actions.

c. It was indicated in the original procedure that the normal air compressor KlB would be used to supply compressed air to required equipment. It has now been determined that the control circuitry for the compressor loader-unloader may be affected by the postulated fire. In such a case, the diesel driven air compressor will be used. Since sufficient time is available to perform the required equipment alignment, the use of the diesel driven air compressor will not affect the safe shutdown of the plant.

Mr. D. L. Ziemann, Chief Mayl5, 1979

d. The Emergency Operating Instruction S-3-5.28 as changed by Items a (first paragraph), b, and c was implemented and a "walk through" was performed as committed in our letter dated October 30, 1978.

2. Spurious Valve Actuation Evaluation The spurious valve actuation evaluation provided as Enclosure 6 to our letter dated October 18, 1978 includes a description of operator actions to locally remove power from certain equipment not required for safe shutdown. As described, in Item 1.e above, this method of power removal will not be implemented. The evaluation also provided the failure modes for the valves included in the analysis. Further evaluation of the failure modes has resulted in the need to update the following items of.

a. Page 1, CV544 fails open on loss of air with no affect on results.

b. Page 6, CV100A fails open on loss of air with no spurious movement to unfavorable position and no affect on results.

c. Page 8, CV276 fails closed on loss of air with no affect on results.

d. Page 11, FCV1112 fails open on loss of power or closes on loss of air with no affect on results.

e.

Page 11, FCV1102A fails closed on loss of air with no affect on results.

f. Page 11, FCV1102B fails open on loss of air with no affect on results.

3. Hydrogen Seal Oil Area Fire By letters dated January 11, 1979 and March 1, 1979, we committed to supply the NRC staff with an evaluation to determine the potential for damaging the structural steel of the turbine building in the vicinity of the hydrogen seal oil unit should a fire occur in this area. The evalua tion was also to determine the potential for damaging equipment required for safe shutdown in the area, should the building be damaged and fail.

Based on the assumptions that the oil from the turbine lube oil system is feeding the fire and the fire continues to burn unmitigated until all of the oil is consumed, it has been determined that the conservatively assumed unmitigated fire will not affect the structural integrity of the turbine pedestal nor any of the individual structural systems surround ing it. The fire will therefore not impact any required equipment in the area due to structural collapse.

If you have any questions or desire further information, please contact me.

Very truly yours,