ML20247R387

Provides Evaluation of Effects of Neutron Radiation on Reactor Vessel Matls (Rvm) Using Methods in Rev 2 to Reg Guide 1.99,per Generic Ltr 88-11, NRC Position on Radiation Embrittlement of Rvms & Impact on Plant Operations

ML20247R387
Person / Time
Site:	Rancho Seco
Issue date:	03/29/1989
From:	Croley B SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Knighton G NRC, NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.099, RTR-REGGD-1.099 AGM-NTS-89-068, AGM-NTS-89-68, GL-88-11, NUDOCS 8904070307
Download: ML20247R387 (3)

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()sMun SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street, P.o. Box 15830. Sacramento CA 95852-1830,(916) 452 3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA l

AGM/NTS89-068 March 29, 1989 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Hashington, DC 20555 Docket No. 50-312 Rancho Seco Nuclear Generating Station License No. DPR-54 NRC POSITION ON RADIATION EMBRITTLEMENT OF REACTOR VESSEL MATERIALS AND ITS IMPACT ON PLANT OPERATIONS (GENERIC LETTER 88-11)

Attention: George Knighton Generic Letter 88-11 requested licensees to evaluate the effects of neutron radiation on reactor vessel materials using the methods described in Revision 2 to Regulatory Guide 1.99.

For Rancho Seco, calculations based on Regulatory Guide 1.99, Revision 2, resulted in the new values for plant heatup and cooldown limits shown in the attachment. The current heatup and cooldown limits are presented for information (also see Rancho Seco Technical Specification Figures 3.1.2-1 and 3.1.2-2). The present cooldown limits are more conservative than the new cooldown limits except in the 70*F to 80*F region. Since Reactor Coolant System (RCS) pressurization is not performed in this temperature region, the present cooldown curve in Technical Specifications is conservative in the region of applicability and will continue to be used until a Technical Specification Amendment is received.

The present Technical Specification heatup limit values are, in the region above 260*F, more restrictive than the new values; however, in the region below 240*F, the new heatup limit values are more restrictive than present Technical Specification values. The new heatup values'are based on no reactor coolant pump (RCP) operational restrictions during heatup. The District is evaluating the implementation of RCP operational restrictions at low temperatures to determine if additional heatup operational flexibility is possible. Any changes to the matup/cooldown values, as well the RCP operational restrictions assumaJ, will be submitted prior to return to operations following the Cycle 8 refueling outage.

8904070307 690329 M I PDR ADOCK 05000312 P PDC ,

A RANCHO SECo NUCLEAR GENERATING STATloN D 1444o Twin Cities Road, Herald, CA 95638-9799;(209) 333-2935

s George Knighton AGM/NTS89-068 A preliminary review of the current Technical Specification Low Temperature Overpressure Protection (LTOP) requirements, with the inclusion of the new heatup/cooldown values discussed above, concluded that the current LTOP values are acceptable. A more detailed review will be completed by the end of the Cycle 8 refueling outage to ensure the requirements of 10 CFR 50, Appendix G are addressed.

The District will, prior to leaving Cold Shutdown from the Cycle 8 refueling outage, incorporate the more restrictive portions of both the present and new heatup limit values (new values below 240'F, present values above 260*F) into plant procedures. The results of the evaluation for RCP operation restriction and any new heatup/cooldown values will be included in these procedural controls. This conservatism will be maintained until a Technical Specification Amendment is issued incorporating the new heatup and cooldown limits. A Technical Specification Amendment will be requested as part of the Improved Technical Specification Program submittal currently scheduled for October 1989.

Members of your staff with questions requiring additional information or clarification may contact Mr. Dave Swank at (209) 333-2935, extension 4920.

Sincerely, Bob G. Croley Assistant General Manager Nuclear Technical Services Attachment cc w/atch: J. B. Martin, NRC, Walnut Creek A. D'Angelo, NRC, Rancho Seco l

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, J Attachment AGM/NTS89-068 Page 1 of 1 i TECHNICAL SPECIFICATION LIMITS Rancho Seco Normal Heatup Present Values New Values Temperature Pressure Temperature Pressure

(*F) (osia) (*F) (osia) 70 355 70 299 146 355 150 299 f

230 528 240 528 260 528 260 528 263 630 265 692 339 1220 339 1394 397 2250 382 2250 L Rancho Seco Normal Cooldown Present Values New Values l

Temperature Pressure Temperature Pressure l (*F) (osia) (*F) (osia) 70 325 70 320 l 80 346 130 398 180 398 204 420 204 483 250 770 300 1313 331 1600 331 1854 363 2250 348 2250 l

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