ML13324A731
| ML13324A731 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/15/1985 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| GL-85-06, GL-85-6, NUDOCS 8510170179 | |
| Download: ML13324A731 (2) | |
Text
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e Southern California Edison Company P. 0.
BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER, NUCLEAR LICENSING October 15, 1985 (818) 302.1749 Director, Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Reduction of Risk from Anticipated Transients Without Scram (ATWS)
San Onofre Nuclear Generating Station Unit 1 On June 1, 1984, the Commission approved publication of a final rule, 10 CFR 50.62, regarding reduction of risk from ATWS events for light-water cooled nuclear power plants. In accordance with the requirement of Section 50.62(d) of this rule, each licensee must develop and submit a proposed schedule for meeting the requirements of the rule within 180 days after staff issuance of explicit quality assurance (QA) guidance for non-safety related equipment encompassed by the ATWS rule. The staff guidance was published on April 16, 1985 by Generic Letter 85-06. The purpose of this letter is to outline our plans and schedule to obtain full compliance with the requirements of the rule.
For San Onofre Unit 1, the ATWS rule requires equipment, which is diverse from the reactor trip system from sensor output to final actuation device, to automatically initiate the auxiliary feedwater system and initiate a turbine trip under conditions indicative of an ATWS. This equipment must be designed to perform its function in a reliable manner.
Provisions for automatic initiation of auxiliary feedwater were installed as part of the TMI upgrades for San Onofre Unit 1. The equipment which performs this function is completely independent (from sensor output to the final actuation device) from the Reactor Protection System (RPS).
Low steam generator level is utilized as the initiating parameter so that diversity from the RPS is provided. The equipment which automatically initiates auxiliary feedwater is primarily safety related. Portions of this system utilize controls grade equipment which will be upgraded to safety related during the upcoming refueling outage.
Various methods to initiate a turbine trip under conditions indicative of an ATWS are currently being reviewed. It is our plan to evaluate the methods proposed by Westinghouse for independent and diverse initiation of a turbine trip and implement the design which is best suited for San Onofre Unit 1. Completion of-the NRC staff review of the proposed 9510170179 851015 K
PDR ADO3CK 500206
Director October 15, 1985 Westinghouse methods will be a necessary prerequisite to final implementation of a plant modification. Any significant delay in completion of the staff review may impact the proposed schedule as described below. Regardless of which method for implementation is chosen, the resultant configuration will provide the necessary independence from the RPS and will satisfy the requirements of the ATWS rule.
It is expected that the equipment necessary to initiate a turbine trip as discussed herein will be installed and functioning prior to return to service from the refueling outage for Cycle X, which corresponds to the second refueling outage following publication of the rule. This implementation schedule was determined by the ILS process.
As indicated in our ILS Plan submitted August 29, 1985, regulatory required modifications would be included in Schedule A and receive higher priority than previously scheduled items in Schedule B. In order for the ATWS modification to be implemented by Cycle X, it may be necessary to defer some other Cycle X task currently listed in Schedule B. We will inform you should this become necessary.
If you have any questions or desire additional information, please let me know.
Very truly yours,