ML20249B423
| ML20249B423 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/19/1998 |
| From: | Nunn D SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20249B424 | List: |
| References | |
| NUDOCS 9806230082 | |
| Download: ML20249B423 (3) | |
Text
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SOUTHf RN CAlliORNIA EDISON o-'8 ' t x -
6 Vice President An (Dl504 INTLRNATIOML* Company June 19, 1998 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket Nos. 50-361 and 50-362 Proposed Technical Specification Change Number NPF-10/15-491 RCS Temperature Reduction and Volumetric Minimus Flow Rate San Onofre Nuclear Generating Station Units 2 and 3 i
Enclosed are Amendment Application Number 179 to Facility Operating License NPF-10, and Amendment Application Number 165 to facility Operating License NPF-15, for the San Onofre Nuclear Generating Station, Units 2 and 3, respectively. The Amendment Applications consist of Proposed Technical Specification Change Number (PCN)-491 which is provided in Enclosure 1 to this letter.
PCN-491 is a request to revise Technical Specification (TS) 3.4.1, "RCS DNB (Pressure, Temperature, and Flow) Limits."
Specifically the Proposed Change includes the following:
1)
A reduction in the minimum primary Reactor Coolant System (RCS) cold leg tem)erature (T,,ib)evels.
from 544 F to 535 F between the 70% and 100% rated tiermal power j
2)
A conversion of the specified RCS minimum flow rate from a " Mass" (i.e., Ibm /hr)toa" Volumetric"(gpm)flowbasis.
3)
Elimination of the maximum RCS flow rate limit.
The RCS temperature is being reduced to minimize further steam generator tube degradation and can thus be viewed as an improvement in safety.
Specifying the TS minimum flow rate in volumetric units will result in consistency of the TS minimum flow rate limit with both the measured flow and theCESECcomputercodeusedfortheSanOnofreUnits2and3 safety / accident 4
analyses of record.
Elimination of the maximum RCS Total Flow Rate is being proposed because 1) it is not a limiting Departure from Nucleate Boiling Ratio (DNBR) criterion (as flow increases the margin to DNBR increases), 2) other ABB Combustion Engineering (ABB CE) units do not have an upper flow limit to DNBR, and 3) actual Reactor Coolant Pump (RCP) flow output is physically limited to values well below the approximately 120% of RCS design basis minimum total flow rate at which core uplif t could become an operational issue. Consequently, the P. O. Ika 128
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Document Control Desk maximum RCS Total Flow Rate has no real safety significance and is being removed.
In addition to the amendment applications and the supporting evaluations, the Southern California Edison Company (SCE) and ABB CE are currently performing other engineering evaluations related to the effect of intended future operation at lower temperatures on the original Nuclear Steam Supply System design. These engineering assessments will evaluate the structural response due to specified faulted conditions (Loss of Coolant Accident (LOCA) blowdown loads) as well as effects of revised inputs to the Containment response from postulated line breaks. Operational issues will also be addressed, including procedures, control systems setpoints, simulator changes and operator.
training. These evaluations and associated updates of design documents are being performed in accordance with 10 CFR 50.59 and will be completed prior to implementation of 'the proposed license amendment.
In the course of this work, if any unreviewed safety questions are discovered the resolution will be submitted to the NRC for review.
SCE requests this amendment be issued effective as of its date of issuance, to be implemented within 30 days from the date of issuance. SCE will be ready to operate-at the requested lower RCS temperature following the Cycle 10 refueling outage for each unit. Because SCE strongly believes-in the importance of reducing the RCS operating temperature to reduce the steam generator tube degradation, SCE requests approval of these amendment applications on or before January 26, 1999.
NRC approval on or before January 26, 1999 will allow adequate time for implementation to support operating at the reduced temperature on return to service following the Unit 2 Cycle 10 refueling outage, currently scheduled for February 25, 1999.
If you would like additional information regarding this Proposed Technical Specification Change, please let me know.
Sincerely, 1
\\
Enclosure.
cc:-
E. W. Merschoff, Regional Administrator NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV.
-J. A. Sloan, NRC Senior Resident-Inspector, San Onofre Units 2 & 3 1
J. W. Clifford, NRC Project Manager, San Onofre Units 2 and 3 S. Y. Hsu, Department of Health Services, Radiologic Health Branch l
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ENCLOSURE AMENDMENT APPLICATIONS 179 AND 165 (PCN-491) l