ML13330B453
| ML13330B453 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/13/1989 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TASK-06-07.B, TASK-6-7.B, TASK-RR NUDOCS 8901190028 | |
| Download: ML13330B453 (6) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M. 0. MEDFORD TELEPHONE MANAGER OF i'
o o(818) 302-1749 NUCLEAR REGULATORY AFFAIRS January 13, 1989 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Amendment Application No. 159, "ESF Switchover from Injection to Recirculation Mode Modification" San Onofre Nuclear Generating Station, Unit 1 By letter dated October 4, 1985, regarding the Systematic Evaluation Program (SEP)Topic VI-7.B, "ESF Switchover from Injection to Recirculation Mode," SCE committed to install an automatic trip feature during the Cycle 10 Refueling Outage in the Safety Injection System to trip the Safety Injection and Feedwater pumps on a low-low Refueling Water Storage Tank (RWST) level.
The automatic termination of high flow safety injection upon a low-low RWST level will ensure that sufficient water inventory exists to prevent the potential cavitation of the Charging and Refueling Water Pumps during the realignment from safety injection to recirculation following a LOCA. Additional information regarding the design details of the trip feature was requested by the NRC to support the staff review of the subject amendment request. The purpose of this letter is to provide more design and implementation information on the Safety Injection and Feedwater pump trip on a low-low RWST level.
Six safety-related pressure switches, three per train, will be mounted as Seismic Category A on the anchor ring of the RWST to function as level switches. These level switches conform to IEEE-323-1974 and IEEE-344-1975 standards. Each train of safety injection/feedwater pump circuits will have a channel, which is electrically independent and physically separated. Output contacts of these level switches will be configured to provide the two out of three coincident logic to automatically trip the feedwater and safety injection pumps upon a low-low RWST level signal and a concurrent Safety Injection Signal (SIS).
Thus, failure of a single level switch will not prematurely terminate the safety injection. Memory relays will be provided to ensure that the low-low RWST level trip capability is not disabled by the expected manual block/reset of the SIS that may take place prior to reaching a low-low RWST level post-LOCA.
Stainless steel piping will be added to the existing RWST single instrument nozzle to maintain train separation of the level switches by providing 1.9 11.?-C)2
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Document Control Desk January 13, 1989 separate taps and root valves.
Each level switch will have individual isolation and drain valves for the purposes of maintenance, calibration, and testing. Cables from the RWST level switches to the 4160V switchgear associated with the safety injection and feedwater pumps will be routed through new conduits and junction boxes. All conduit penetrations through floors and walls will be adequately sealed to maintain their assigned fire barrier rating. In addition, the cables connecting the RWST level switches to the switchgear are qualified to meet the harsh post-LOCA and MSLB environment, including HELB in the areas through which they are routed.
The switches are in a mild post accident environment during the injection phase. The switches, therefore, need not be qualified for the post-LOCA environment. This has been evaluated for 10 CFR 50.49 (b)(2) and found acceptable.
Internal electrical modifications at the 4160V switchgear cubicles consist of the installation of relays, test switches, and indicating lights to modify pump control circuits to provide two out of three low-low RWST level trip logic to the safety injection and feedwater pump motors circuit breakers.
Each train of level switches will actuate front panel mounted auxiliary relays on the corresponding safety injection and feedwater pump breakers. Test switches will be installed below these auxiliary relays which will be connected in parallel to the level switches for surveillance testing of the low-low RWST level auxiliary relays and 2 out of 3 low-low RWST level trip logic in accordance with Technical Specification criteria.
The RWST control room level indication is provided by a pneumatic indicator LI-950. Auxiliary Board Annunciator Window Number 7, which is initiated by level switch LS-69, alerts the operator to low-low RWST level.
The existing level indicator LI-950 will be relocated to the left; the redundant safety-related level indicator LI-3020 will be installed on Control Room Board C09 for proper train orientation. Two reset switchlight modules on the same control panel will be added to reset the two out of three low-low RWST level trip circuit after the sequencer is reset and the system has returned to normal.
Each module will have split indication consisting of an amber light to indicate "arming" of the trip logic and a white light to indicate pump trip on the low-low RWST level.
In addition, an annunciator window for each train on the auxiliary board in the Control Room will provide an alarm when any one of the level switches corresponding to that train is actuated.
The RWST level setpoint for Safety Injection and Feedwater Pump trip has been analyzed. The setpoint analysis takes into account the time-dependent single active failures and their impacts on Safety Injection/Feedwater Pump flow rates, charging, containment spray, operator action times, and other related criteria. The automatic setpoint is similar to the setpoint for the manual switchover from injection to recirculation mode and is 20%
indicated level, equivalent to approximately 50,000 gallons of water in the RWST.
Document Control Desk January 13, 1989 The load rejection trip test at 4,300 kW was performed successfully to verify the Diesel Generator Number 2 capability to withstand rejection of increased load without tripping. This load rejection test satisfies the present surveillance requirement in Technical Specification Section 4.4.F, as well as the surveillance requirement in Proposed Change Number 186 under NRC review. Hence, the retest of the diesel generator load rejection will not be necessary upon NRC approval of the proposed change. Similar tests for Diesel Generator Number 1 will follow upon completion of maintenance and surveillance testing of Diesel Generator Number 2. Additional details regarding these tests will be provided to the NRC as indicated in the telephone discussion of January 13, 1989, as soon as they become available.
Enclosed are draft revised System Description drawings for Safety Injection and Containment Spray Systems, SD-S0l-580-I-1-1 and SD-S0l-580-III-1-0, and feedwater and safety injection pump elementary diagrams, 5149858 and 456370, for information only to aid the staff review. If you have any question regarding this subject, please call me.
Very truly yours, Enclosures cc: C. M. Trammell, NRR Project Manager, San Onofre Unit 1
- 3. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3
Enclosures
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