ML13322A956
| ML13322A956 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/16/1980 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8106120379 | |
| Download: ML13322A956 (4) | |
Text
Southern California Edison Company P. 0.
BOX Boo 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER, NUCLEAR ENGINEERING (213) 572.1401 AND LICENSING May 16, 198
Director of Nuclear Reactor Regulation Attention:
Mr. D.M. Crutchfield, Chief Operating Projects Branch 5 Division of Project Management U.S. Nuclear Regulatory Commission Washington, D.C.
20555 CMIO Gentlemen:
Subject:
Docket No. 50-206 Additional Information for Amendment Nos. 89 and 90 San Onofre Nuclear Generating Station Unit 1 The subject amendments to Provisional Operating License No. DPR-13 have been submitted for NRC review and approval during the past few months.
Since that time, the NRC has requested clarification on certain aspects of Amendment Nos. 89 and 90.
The purpose of this letter is to supply the additional information necessary to complete the NRC review of these amendments.
By letter dated March 31, 1980, Amendment No. 89 was submitted and consisted of Proposed Change No. 89 to the San Onofre Unit 1 Technical Specifications.
Proposed Change No. 89 is a request to revise the existing Technical Specifications to require limiting conditions for operation Based, on control rod misalignment and to specify the surveil lance requirements necessary to assure compliance. Th-e safety analysis references a Westinghouse Proprietary report entitled, "Verification of Rod Misalignment Technical Speci fication, San Onofre Unit No. 1, Southern California Edison Company," dated March 1980, which was included as Enclosure
- 2. Pursuant to 10CFR2.790(b), it is requested that the report of Enclosure 2 to our letter dated March 31, 1980, be withheld in whole from public disclosure. This request is made for the reason that the report contains proprietary information, the public disclosure of which would adversely p1
Mr. D.
May 16, 1980 affect the competitive position of Westinghouse Electric Corporation. The Foreward to Enclosure 2 to our letter dated March 31, 1980, includes a reference to the basis for designating the material proprietary as identified by marginal notes to the standards in Section 8 of the affidavit of R.A. Wiesemann of record "In the Matter of Acceptance Criteria for Emergency Core Cooling Systems for Light Water Cooled Nuclear Power Reactors (Docket No. RM-50-1)" at transcript pages 3706 through 3710 (February 24, 1972).
By letter dated April 4, 1980, Amendment No. 90 was submitted and consisted of Proposed Change Nos. 91 and 92 to the San Onofre Unit 1 Technical Specifications.
Proposed Change No. 91 is a request to modify the existing Technical Specifications to describe the offsite power sources to the station, which will be operational at the completion of the cutover to the new switchyard which is under construction in conjunction with San Onofre Units 2 and 3.
As a result of inquiries made by members of the NRC Office of Inspection and Enforcement, Region V staff, regarding D.C. power for switchyard relays, the following information provides clarification to assist the NRC staff in their review of Proposed Change No. 91.
Specifically, the NRC Region V Staff members questioned whether our evaluation provided under Item II.A.2 for this change in cluded failure considerations involving the D.C. bus which is the source of power for relays on the SCE side of the switchyard.
As indicated in Chapter 8 of the San Onofre Units 2 and 3 FSAR, which is referenced in Proposed Change No. 91 as the source of a detailed description of the new switchyard, the D.C. bus located in the SCE relay house is the source of power for relays which operate equipment on the SCE side of the switchyard. Conversely, the D.C. bus located in the SDG&E relay house is the source of power for relays which operate equipment on the SDG&E side of the switchyard. Item II.A.2, of the Safety Analysis for Proposed Change No. 91 indicates that an automatic forced deenergization of a switchyard bus due to 220 kv system or bus faults was also determined to be a minor contributor to the probability of occurrence of the loss of offsite power accident. This determination was based on a review of SCE 220 kv system history from 1962 to the present including both substations and gen erating station switchyards. The occurrence of a deener gization of 220 kv buses due to any cause was investigated.
Mr. D.
May 16, 1980 This included the deenergization of the 220 kv bus due to faults on an associated D.C. bus for breaker relay power supply.
In no case was this type of fault the cause of an automatic forced deenergization of a 220 kv bus.
Therefore, while not explicitly discussed in our evaluation of the loss of offsite power event, the conclusions reached in Item II.A.2 of the Safety Analysis for Proposed Change No. 91 included failure considerations involving D.C. Buses.
It should also be noted that as a result of the evaluation of the offsite power sources, to San Onofre Unit 1, which was conducted in response to your request by letter dated August 8, 1979, from Mr. W.P. Gammill regarding, "Adequacy of Station Electric Distribution Systems Voltages",
it was determined that a fault on the D.C. bus in the SCE relay house will not result in the loss of offsite power since the switchyard breakers fail as is on loss of D.C. power.
The results of that evaluation are included as Enclosure 2 to our letter dated May 1, 1980.
Item II.A.2 of the Safety Analysis for Proposed Change No. 91 also indicates that the simultaneous loss due to system or bus faults of two buses within a 220 kv switch yard was not observed. This statement refers to the data for switchyards associated with generating stations where indeed no such failures were recorded in the data from 1962 to the present. If the data base is extended to include the infor mation for 220 kv switchyards associated with substations, there does exist a record of two such instances which occurred between 1962 and the present among the approximately 70 sub stations in the SCE system. Even with the substation data included, the statement of Item II.A.2 which indicates that the double bus loss is a smaller contributor to the probability for loss of offsite power, than the loss of a single bus, remains valid.
We hope that this information assists the NRC staff in their review of the subject amendments.
If you have any questions or desire additional information, please contact me.
Very truly yours, cc:
L. Miller, NRC Resident Inspector
Mr. D. M. Crutchfield Operating Projects Branch 5 28 Division of Project Management AYED FOR U.S. Nuclear Regulatory Comm.
- 3. o Washington, DC 20555 CC<.
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