ML19317G973
| ML19317G973 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/19/1977 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| TAC-10968, NUDOCS 8004020633 | |
| Download: ML19317G973 (5) | |
Text
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NRC acetu 195 u.s. NUCLt:AR GE r.ULATOT.Y COF WloN DOCKET NUM BE C d'o - 311
,rsi NRC DISTRIBUTION roR PART 50 DOCKET MATERIAL O'
ATEoF oCUMENT Mr. Robert Reid SMUD 7-19-77 Sacramento, Calif.
95813 DATE RECEIVED
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J.J. Mattimoe 7-22-77 BCETTE R ONoToRizEc PRoe INPUT FORM.
NUMBER oP COPIES RECEIV.ED 2t RiolNAL Q([NCt.ASSIFIE D OCorv
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. Response to NRC Requeat for Info. regard--
ENCLOSURE ing Encl L of NRC to SMUD' ltr dated 6-3-77 entitled Safety Eval C, Stat.hment'of Sta'ff Positions relathvem to the Emergency Power Systems for Operating Reactors.....
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1 (- .~ gsuuo SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 s street, Box 15830, sacramento, California 95813; (916) 452-3211 July 19,1977 .[.J.il2 Director of Nuclear Reactor Regulation [,Y ' ',,.r g. qO Attention: Mr. Robert W. Reid, Chief /' kI b f) #'3) l'LOL Operating Reactors, Branch 4 6 U. S. Nuclear Regulatory Comission J A } ] ';; 7 7 y Washington, D. C. 20555 .{ n, ww c m (--,1
- e. ~, e. 3 Docket No. 50-312
\\'.C- .E' Rancho Seco Nuclear Generating
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Station, Unit No.1 qf
Dear Mr. Reid:
Please refer to your letter of June 3,1977 wherein you requested that the District compare the current design of the emergency power systems at the Rancho Seco Unit No.1 nuclear generating plant with the staff positions stated in Enclosure 1 of your letter and: (1) propose plant modifications as necessary to meet the staff positions, or (2) provide a detailed aralysis which shows that our facility design has equivalent capabilities and protective features. Enclosed with this letter are 40 copies of our response to your request for information. l Sincerely yours, .'. )>tJta J.' J. Mattimoe Assistant General Manager and Chief Engineer J Enclosures %; h'.;rf' C27=4 2 'i ELECTRIC SYSTEY SERVING MORE THAN 600.003 'N THE hfART GF CalifOPN+A j
( ) SACRAMENTO MUNICIPAL UTILITY DISTRICT RANCHO SECO NUCLEAR GENERATING STATION, UNIT NO. 1 RESPONSE T0: NUCLEAR REGULATORY COMMISSION REQUEST FOR INFORMATION REGARDING ENCLOSURE 1 0F NRC TO SMUD LETTER DATED JUNE 3, 1977 TITLED SAFETY EVALUATION AND STATEMENT OF STAFF POSITIONS RELATIVE TO THE EMERGENCY POWER SYSTEMS FOR OPERATING REACTORS i J July 19,1977 /
y- ) NRC REQUEST FOR INFORMATION 4 NRC POSITION 1: The NRC requires a second level of voltage protection for the onsite power system including coincidence logic meeting certain stated criteria. PRESENT RANCHO SECO UNIT 1 DESIGN: The existing Rancho Seco undervoltage transfer scheme does not include a second level of voltage protection with coincidence logic. The existing scheme utilizes a single undervoltage relay to initiate the transfer of the 4160-volt safety features buses from the normal offsite power supply to the emergency diesel generator. A modification is scheduled for this year's annual refueling shutdown to add an over-voltage protective relay. Other than the above stated factors, we consider that the existing design meets the intent of the stated design requirements of the NRC's Position No. 1. However, in that we are proposing to modify the existing design as stated below a detailed comparison analysis is not presented. PROPOSED MDDIFICATION: The District proposes to modify the existing scheme to provide the NRC's required second level of voltage protection including the coincidence logic trip circuit requirements. The District further proposes to install this modification during the 1978 refueling shutdown which would be approximately during the period of August-September 1978, if plant operating load levels proceed as planned. The proposed modification would be designed to meet the design and performance criteria guidelines contained in the NRC's Position No.1. NRC POSITION 2: The NRC requires that the current system designs automatically prevent load shedding of the energency buses once the onsite sources are supplying power to all sequenced loads on the emergency buses. The design shall also include the capability of the load shedding feature .] be automatically reinstated if the onsite source supply breakers are tripped. EXISTING RANCHO SECO UNIT 1 DESIGN: The existing Rancho Seco design complies with this requirement; conse-quently, no changes are proposed. The existing scheme functions as follows:
f. .. 1. Upon reaching the voltage setpoint a contact of the voltage sensing relay closes energizing a set of load shedding relays. 2. The load shedding. relays perform the following functions: A. Trips the normal offsite supply breaker to the safety features 4160-volt buses. B. Trips the load breakers on the 4160-volt buses. C. Sets up the load sequencing timing circuit. D. Starts the emergency diesel generators. 3. When the diesel driven generator reaches the required voltage, it's circuit breaker will automatically close connecting it to the 4160-volt bus, and the step loading sequence will automatically comence if a safety features actuation signal exists. 4. An auxiliary "b" contact from the generator circuit breaker opens to disable the load shedding feature of the circuit. Consequently, the voltage sensing relay cannot re-initiate the load shedding feature of the scheme so long as the generator circuit breaker remains closed. 5. Should the generator circuit breaker be opened for any reason the load shedding and loading sequences would be re-initiated as described in Items 2 and 3 above providing that the 4160-volt bus voltage was at or beyond the voltage sensing relay setpoint after the breaker opened. NRC POSITION 3: The NRC requires that the Technical Specifications include a test requirement to demonstrate the full functional operability and indepen-dence of the onsite power sources at least once per 18 months during shutdown.
RESPONSE
A review of the existing Technica1' Specifications and proposed changes relative to the NRC's requirement contained in Position No. 3 have not been completed. A separate submittal will be made at a future date regarding this item. i l l l}}