ML13330B351
| ML13330B351 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/15/1988 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML13322A028 | List: |
| References | |
| TAC-68439, NUDOCS 8807210099 | |
| Download: ML13330B351 (3) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (18) 302-1749 AND LICENSING July 15, 1988 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Supplement to Amendment Application No. 153 San Onofre Nuclear Generating Station Unit 1 By letter dated June 22, 1988, Amendment Application No. 153 was transmitted to the NRC. That application consisted of Proposed Change No. 190 which increased the diesel-generator load limit from 4500 kW +/- 5% to 5250 kW +/- 5%. As a result of the NRC's review of this proposed change, additional information is necessary to support the review and a supplemental change to the proposed change is necessary.
Provided as enclosures to this letter are the following documents which support the NRC staff's review.
- 1. The Design Calculation for the Emergency Diesel Generator Loading, DC-1809, Revision 2, dated June 17, 1988
- 2. Letter to Mr. David Pilmer of SCE from David 0. Harris of Failure Analysis Associates regarding the Analysis of Piston Skirt Integrity on Delaval Diesel Engines dated June 15, 1988
- 3. A report entitled "The Influence of Reduced Peak Firing Pressure on the Fatigue Performance of Modified AF Piston Skirts at San Onofre Unit 1", by Failure Analysis Associates dated July 1988.
- 4. Supplemental Change to Proposed Change No. 190 (Amendment Application No. 153).
SCE met with the NRC on July 11, 1988 to discuss the resolution of NRC concerns resulting from the review. During those discussions, a number of issues were addressed. These are discussed in the following paragraphs.
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Document Control Desk July 15, 1988 During the review of the diesel generator loading calculation it was noted that the horsepower required for the feedwater and charging pumps was greater than the motors' rated horsepower. An evaluation of the motors operating in an overload condition will be provided to the NRC on July 19, 1988. If this evaluation results in any change to the diesel generator loading calculation, this will be reflected in a revision to the calculation prior to startup. In order to support the data that has been provided in the design calculation, pump and motor operating data will be obtained during plant operation following return to service. Data such as flow rate, differential pressure, temperature, motor current, voltage and power will be obtained if possible.
In some cases, such as the safety injection pumps, the data will be based on miniflow since the pumps are not normally operated and the system configuration precludes such operation under conditions representative of the design conditions. This information will be provided to the NRC within 60 days of return to service.
Prior to return to service from the current mid-cycle outage oil holes 8 and 9 on Diesel Generator No. 1,.and 9 and 10 on Diesel Generator No. 2 will be inspected.
Since the last inspection in January, 1986, Diesel Generator No. 1 has incurred 155 starts and Diesel Generator No. 2 has 122 starts.
This is larger than the previous assumption that there would be approximately 50 starts between inspections. The choice of two oil holes was concluded to be adequate to indicate whether or not new fatigue damage has occurred in the crankshafts. Based on previous analysis and inspection results, other oil holes have a lesser propensity to initiate cracking than the ones chosen. At the next refueling outage and each refueling outage thereafter, inspections will be performed of oil and dowel pin holes 8 through 12 in both diesel generators.
All starts for testing and surveillance of the diesel generators will be performed as slow starts (> 24 seconds), with the exception of the Technical Specification requirement for SISLOP testing which is a fast start performed every 18 months and any other fast starts required for specific maintenance
-involving the fast'-start capability. Enclosure 4 provides the supplemental technical specification which addresses the starting of the diesel generators.
SCE will replace the diesel engine pistons (modified AF) with AE pistons during the next refueling outage which is scheduled before the end of 1988.
All of the piston skirts were inspected during the 1984 or 1986 refueling outages. Since the inspections, the diesel generators have been run at the administratively controlled tech spec load of 4500 kW. Prior to this, the diesel generators would have been tested at loads up to 6000 kW. The testing at the lower load would have produced lower stresses on the pistons than result from running at 6000 kW. The piston skirts may initiate cracking under the loading conditions experienced during surveillance testing at either 4500 kW or 5250 kW; however, previous experience including analysis and destructive examination of pistons at the Shoreham plant indicates that the fatigue crack initiation will arrest at depths which would not affect the operability of the pistons. An analysis of the piston skirts for a load of 5250 kW is provided in the report prepared by Failure Analysis Associates (Enclosure 3).
Therefore operability of the modified AF piston skirts is not a concern for the remaining time until the pistons are changed out.
Document Control Desk July 15, 1988 In review of existing surveillance and inspection controls for the diesel generators it is noted that a diesel generator load limitation of 4725 kW has been imposed through NRC and SCE correspondence relating to the.Design Review and Quality Re-validation (DRQR) effort. SCE's letter dated July 9, 1987 provided comments on the NRC draft safety evaluation report on the operability/reliability of the SONGS 1 diesel generators. As indicated therein, crankshaft and piston skirt inspections will be performed if the diesel generators are loaded beyond 4725 kW. The level of inspection and additional actions required are commensurate with the degree and duration of exceeding the load limit. In accordance with the revised load limit of 5250 kW +/- 5%, inspections and other actions will be based on exceeding 5512 kW versus 4725 kW.
Amendment Application No. 153 was submitted as an exigent change. The return to service of the unit is scheduled for July 31, 1988. It is necessary that this additional information be included in the review, and approval of the amendment is obtained by July 20, 1988. This will allow time for procedural revisions and testing of the diesel generators at the increased load limit prior to Mode 4 entry. Therefore, the amendment application should be reviewed as an emergency change since a delay in the review and approval process will result in a delay in the return to service schedule.
If you have any questions regarding this matter, please let me know.
Very truly yours, Enclosures cc: J. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3