ML20153F755

Discusses 880826 Decision to Open Valve HV-20578 & Place Associated Flow Control Valve FV-20528 in Closed Position, Returning Redundant Flow Path to Steam Generator to Svc

ML20153F755
Person / Time
Site:	Rancho Seco
Issue date:	09/02/1988
From:	Keuter D SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Knighton G NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
AGM-NPP-88-491, NUDOCS 8809070452
Download: ML20153F755 (3)

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$SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT C 620*' S Street, P.O. Box 15830, Sacramento CA 9585'e1830.(916) 452 3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA AGM/NPP 88- 91 September 2, 1988 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 AUXILIARY FEEDHATER (AFH) TECHNICAL SPECIFICATIONS Attention: George Knighton At 1833 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.974565e-4 months <br /> on ALgust 25, 1988, AFH isolation valve HV-20578 was declared inoperable when it failed to open during surveillance testing. Limiting Condition for Operation 3.5.1.1, Table 3.5.1-1, Emergency Feedwater Initiation and Control (EFIC) System, Item 4.b was entered with the appropriate 7 day Action time clock initiated. OMrations personnel determined that since both AFH pumps were operable and an operable flow path was available to each steam generator, the Limiting Conditions for Operation as delineated in Technical Specifications 3.4.1.E and 3.4.2.F were satisfied.

3.4.1.E. Both auxiliary feedwater trains (i.e., pumps and their flow paths) are operable.

3.4.2.F. Both auxiitary feedwater trains (i.e., pumps and their flow path) are operable except that:

(1) Hith one auxiliary feedwater train inoperable, restore the train to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in hot shutdown within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and on decay heat cooling within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

(2) Hith both auxiliary feedwater trains inoperable, the reactor shall be made subcritical within four hours and the reactor shall be on decay heat cooling within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

On August 26, 1988, members of the Rancho Seco staff were consulted and at the Plant Review Committee meeting the decision was made to open valve HV-20578 and place the associated flow control valve FV-20528 in the closed position.

This change returned to service the redundant flow path to steam generator B since valve FV-20528 returns to the automatic control mode on EFIC initiation. Valve HV-20578 was returned to operable ste us on August 28, 1988, at 0751 hours0.00869 days <br />0.209 hours <br />0.00124 weeks <br />2.857555e-4 months <br />. Valves FV-20528 and HV-20578 were subsequently returned (

to their normal standby positions, h0 8809070452 000902 i\

PDR ADOCK 05000312 P put)

• CANCHo SECO NUCLEAR GENERATING STATION O 14440 Nn Cmes Road. Hera'd, CA 95038 9799.1209) 333 2935

. AGM/NPP 88-491 George Knighton The licensing design basis of the Auxiliary Feedwater System (AFHS) is to mitigate the consequences of undercooling events in the primary system. The AFH System, designed and installed as part of the original plant, was upgraded to meet the requirements of NUREG-0737 Item II.E.1.2, which states:

(1) The design shall provide for the automatic initiation of the AFHS.

(2) The automatic initiation signals and circuits shall be designed so that a single failura will not result in the loss of AFHS function.

NUREG-0800, Standard Review Plan, Section 10.4.9, Auxiliary Feedwater System (PHR) references and includes as an attachment Branch Technical Position ASB 10-1. Item B.4 of ASB 10-1 states:

The auxiliary feedwater system should be designed with suitable redundancy te offset the consequences of any single active component failure; however, each train need not contain re('undant active components.

Although Rancho Seco's AFH System 's designed to minimize overcooling of the Reactor Coolant System, this feature is not part of the system's licensing design basis. This function of the system is thus not required to meet single failure criterion.

The Safety Evaluation of Rancho Seco Emergency Feedwater Initiation and Control (EFIC) System Design, issued December 14, 1987, concluded on Page 26 that the inoperability of one vector module (and thus either its associated two isolation volves or two control valves) is analyzed as stated by the NRC:

The staff has reviewed the operability requirements for EFIC system instrumentation, the required limiting conditions for operation (LCOs) and associated action statements for when operability requirements cannot be met, as listed in Table 3.5.1-1, "Instruments Operating Conditions," of the Rancho Seco Technical Specifications. Table 3.5.1-1 has been modified subsequent to proposed Amendment No. 152, Revision 2, as agreed to by both the staff and the licensee. In general, if one of the four EFIC system channels monitoring a parameter becomes inoperable, it must be restored to service within 7 days, or the reactor is to be placed in at least hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Although 7 days is longer than typically allowed by the Standard Technical Specifications (STS), the staff considers 7 days to be acceptable because even with an inoperable channel, the EFIC system will perform its AFH initiation and HFH isolation functions given a single failure. If a second EFIC system channel should become inoperable, one of the inoperable channels must be placed in trip, and one of the inoperable channels must be restored to service within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. If these conditions are not met, the reactor must be placed in at least hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. If more than two channels become inoperable, the reactor is to be brought to hot shutdown within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and to cold shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

. AGN/NPP 88-491

. George Knighton The loss of EFIC Channel C could result in the loss of control of both HV-20578 and HV-20581. Valve HV-20578 being inoperable and entering the EFIC Technical Specification is more conservative than this analyzed condition of loss of two valves.

The references presented above support the position that the redundant flow paths provided for each generator are a reliability enhancement, but are not required for compliance with the AFH Technical Specifications. Since the system flow control and isolation valves are part of the EFIC vector logic.

Technical Specification 3.5.1 is applicable in this case.

Members of your staff with questions requiring additional information or clarification may contact Steve Crunk at (209) 333-2935, extension 4913.

Sincerely, ,

a $%

Dan R. Xeuter Assistant General Manager, Nuclear Pc.wer Production cc: A. D'Angelo, NRC, Rancho Seco J. B. Martin, NRC, Halnut Creek