ML13331A445
| ML13331A445 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/18/1990 |
| From: | Nandy F Southern California Edison Co |
| To: | NRC/IRM |
| References | |
| NUDOCS 9006200493 | |
| Download: ML13331A445 (3) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 F.
R. NANDY TELEPHONE MANAGER OF NUCLEAR LICENSING June 18, 1990
>714) 587-5400 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 Supplement to Amendment Application No. 162 San Onofre Nuclear Generating Station Unit 1 We are in the final stages of preparing a supplement to Amendment Application No. 162 (AA-162). This supplement will revise the containment spray actuation (CSA) setpoint allowable value and clarify discrepancies in the amendment application in response to your letter dated September 12, 1989. Submittal of this supplement was delayed, as previously discussed with Mr. J. E. Tatum of the NRC staff, because the analyses performed as the basis for the CSA setpoint have identified an unresolved issue related to a 2*F increase in the peak containment temperature. As a result, submittal of a supplement to AA-162 must be rescheduled to December 15, 1990.
Background
Amendment Application No. 162, which was submitted on December 29, 1988, requested a revision of the Appendix A Technical Specifications to incorporate new Limiting Conditions for Operation (LCOs) and Surveillance requirements for the containment spray actuation instrumentation. This revision was provided in response to an open item from Systematic Evaluation Program Topic IV-10.A, "Testing of Reactor Trip System and Engineered Safety Features, Including Response Time Testing."
After our original submittal of AA-162, you requested additional information by letter dated September 12, 1989, regarding the LCO action statements and the containment spray actuation system setpoint allowable value. To provide the requested information regarding the allowable value for the containment spray actuation system trip setpoint, several analyses were performed. These analyses are discussed below.
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Document Control Desk June 18, 1990 Setpoint Calculation A setpoint calculation was performed to evaluate the effects of instrument uncertainty on the CSA instrumentation. The results of this calculation show that with a trip setpoint of 10.0 psig the allowable value should be 11.2 psig. Using these values and accounting for the effects of instrument delay in a worst case accident, the CSA signal will be generated before containment pressure reaches 15 psig.
Accident Analyses Since CSA actuation may be delayed until containment pressure reaches 15 psig, we investigated both our Loss of Coolant Accident (LOCA) analysis and our Main Steam Line Break (MSLB) analysis which had previously assumed CSA at 10 psig.
We found that the LOCA analysis is not sensitive to a small delay in the CSA.
The MSLB analysis, however, could be sensitive to a small delay in CSA.
We therefore performed an MSLB analysis assuming that CSA was delayed until containment pressure reaches 15 psig. The results of this analysis show the peak accident pressure is essentially unchanged, but the peak containment atmosphere temperature increased from 391.5 0F to 393.3oF.
Although this temperature increase was considered negligible, a review of the environmental qualification documentation of components required to function during an MSLB event was necessary.
Environmental Qualification A partial review of the environmental qualification documentation showed that most components inside containment are qualified based on the LOCA environment. This is in accordance with the evaluation provided in our June 30, 1982 letter and the NRC's assessment in the November 30, 1982 safety evaluation report which concludes that the LOCA environment is appropriate for the qualification of presently installed equipment. Subsequent issuance of the environmental qualification rule, 10 CFR 50.49, requires that the most severe environment be used for qualification of any new components which are required to function following a design basis accident. This would require new components required to function for an MSLB to be qualified to the MSLB environment for San Onofre Unit 1.
In our partial review of the environmental qualification documentation, we did not identify any components required to be qualified to the MSLB environment that would be affected by this increase in MSLB temperature. Since it is not possible to perform a direct comparison of the increased MSLB temperature with the LOCA environment in the environmental qualification data package, we will perform a review of each package. Our review will be performed as a part of the Environmental Qualification Improvement Program (EQIP).
It is our assessment that the slight increase in MSLB peak temperature resulting from the increased CSA setpoint will have no impact on any component required to operate following an MSLB.
Document Control Desk June 18, 1990 Resolution The EQIP was developed as a part of the corrective actions for Licensee Event Report (LER 2-89-012) concerning San Onofre Unit 2. The scope of this review has been expanded to cover San Onofre Units 1 and 3 as well.
The EQIP will be resolving a number of documentation issues by closely reviewing each package and updating them as required. As part of this program improvement for Unit 1, a review will be done to determine if the slight temperature increase has any effect on the equipment required to operate following an MSLB. If this review identifies any components which are affected by the temperature increase, evaluations will be performed to demonstrate acceptability as a part of the Unit 1 EQIP. The EQIP will be completed for San Onofre Unit 1 before the end of the Cycle 11 refueling outage.
Schedule Since resolution of AA-162 is on the Cycle 12 FTOL schedule, we feel it is acceptable to reschedule submittal of this supplement until after the Cycle 11 refueling outage when the EQIP will be completed for San Onofre Unit 1.
Accordingly, we will submit a supplement to AA-162 by December 15, 1990.
If you have any questions please call me.
Very truly yours, cc:
J. B. Martin, Regional Administrator, NRC Region V C. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3