ML20147C281

Presents Info Re Proposed Mod to Assure High Pressure Injection Flow to Reactor Core Following a Small Break,As Requested by NRC

ML20147C281
Person / Time
Site:	Rancho Seco
Issue date:	10/09/1978
From:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Reid R Office of Nuclear Reactor Regulation
References
NUDOCS 7810120027
Download: ML20147C281 (2)

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[$SMUDSACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S street, Box 15830, Sacramento, California 95813; (916) 452 3211 October 9, 1978 Director of Nuclear Reactor Regulation -

Attention: Mr. Robert W. Reid, Chief Operatinq Reactors, Branch No. 4 U. S. Nuclear Regulatory Comission Washington, D. C. 20555 Docket No. 50-312 i Rancho Seco Nuclear Generating Station, Unit No.1

Dear Mr. Reid:

The Sacramento Municipal Utility District has reviewed your letter of. September 26, 1978 requesting information relative to our proposed modification which will assure adequate high pressure injection flow to the reactor core following a small ~ break. The District still intends to modify Rancho Seco Unit No.1, as described in our letter to you of July 20, 1978 This modification eliminates any need 'for operator action following a small break beyond that which has previously been assumed and incorporated in appropriate operating procedures.

Each of the four (4) high pressure injection lines contains flow indication which alarms in the control room on high flow which could be indicative of a high pressure injection pump approaching runout conditions.

As a precautionary measure, the control room operator throttles the injection valve in that line until the alarm clears. It is possible to prethrottle these injection valves so that a high flow alarm would never be received and flow requirements for all sizes and locations of breks would be satisfied.

However, the District does not feel that it is desirable to do this since this would cause a reduction in flow, which is not necessary in most instances.

We wish to emphasize the point that the modification, as described in our July 20, 1978 letter, does not require any operator action to initiate adequate high pressure injection flow to each injection line and that operator action to prevent the possibility of pump runout is only required for larger size breaks and is the same as has always been assumed for Rancho Seco Unit No. 1.

On August 11, 1978 the Babcock & Wilcox Company submitted a letter to Mr. S. A. Varga of the NRC justifying the simplified input method for the F0AM analysis which was incorporated into their Small Break Analysis of

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Mr. Robert W. Reid October 9, 1978 July 18,1978. The District has reviewed this justification and finds it applicable to Rancho Seco linit No. I and therefore concludes that your approval of this analysis to also be applicable to Rancho Seco Unit No.1 Sincerely yours,

. , 7)t<t7b ,at J. J. Mattimoe Assistant General Manager and Chief Engineer