ML20205B469

Responds to 850730 Request for Addl Info Re Util 850415 Application for Proposed Amend 128 to License DPR-54, Changing Tech Specs Re Interruption of Emergency Onsite Power Source.Info Re Onsite Power Source Testing Encl

ML20205B469
Person / Time
Site:	Rancho Seco
Issue date:	09/06/1985
From:	Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Stolz J Office of Nuclear Reactor Regulation
References
RJR-85-443, TAC-57587, NUDOCS 8509120091
Download: ML20205B469 (8)

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g.uu. 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 CAltFORNIA RJR 85-443 September 6, 1985 DIRECTOR OF NUCLEAR REACTOR REGULATION ATTN J F STOLZ, CHIEF OPERATING REACTORS BRANCH 4 U S NUCLEAR REGULATORY COMMISSION WASHINGTON D C 20555 DOCKET N0. 50-312 LICENSE N0. DPR-54 PLJPOSED AMENDMENT NO. 128 REQUEST FOR ADDITIONAL INFORMATION This letter is in response to your request for additional information dated July 30, 1985, concerning Proposed Amendment No. 128. The proposed technical specification changes contained in our letter dated April 15, 1985, address diesel generator _ testing requirements.

The purpose of Proposed Amendment No. 128 is to revise Technical Specification 4.6.2A3 in order to provide a more definitive method of satisfying the NRC requirement to interrupt the emergency onsite power source. This requirement is discussed in Enclosure II of a letter from J. J. Mattimoe to R. W. Reid, dated August 1, 1980 (Attachment 1). NRC Position 3: Onsite Power Source Testing, Part C, states: " Verifying that on interruption of the onsite sources, the loads are shed from emergency buses in accordance with design requirements and that subsequence loading of the onsite sources is through the load sequencer."

The District's response to Part C was Technical Specification 4.6.2A3 which reads:

" Simulating a loss of offsite power in conjunction with a safety features actuation signal, and verifying that on diesel-generator trip, the load shedding circuitry operates properly and the diesel restarts on the auto-start signal, and by verifying proper operation of the automatic load sequencing circuitry.

The diesel generator will be operated for at least 5 minutes in this condition."

However, the current emergency power system design does not allow the intent of Position 3, Part C to be readily met by applying the surveillance test method prescribed in Specification 4.6.2A3. Due to the design of the diesel generator control circuit, the diesel cannot be " tripped" without the control circuit locking it out and preventing an automatic restart. The local or remote emer-gency stop pushbutton picks up the diesel shutdown relay which seals in and shuts the diesel down. The diesel does not go to idle speed for 15 minutes to cooldown, which occurs with a normal shutdown. This places unwarranted stress on the diesel. The shutdown relay must be reset manually using the local " reset" push-button before the diesel will restart. Without defeating the diesel control circuit, we have tried to meet the intent of this Technical Specification by calling for a normal diesel shutdown and automatic restart.

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In dictating the testing requirements, the NRC does not require the diesel to be tripped. Instead, the NRC calls for an ". interruption of onsite sources" which only implies that-the onsite source of power be removed from the Nuclear Service Bus. We can accomplish this by tripping the diesel generator output breaker without calling for a diesel stop. However, this can only be done if

- there is no SFAS. signal in effect which blocks manual tripping of the diesel generator output' breaker.

Per POSITION 3 on page 4 of Attachment 1, the NRC does not require that the onsite source of power be interrupted in conjunction with an SFAS signal. After satisfying the requirement to simulate loss of offsite power in conjunction with an SFAS signal, we can reset-the SFAS before tripping the diesel output breaker.

Based upon the above discussion, the District proposed to move Specification 4.6.28 to 4.6.2C. This allowed Specification 4.6.2A3 to be revised and renumbered as 4.6.28. Proposed Specification 4.6.28 reads as follows: " Simulating a loss of offsite power and verifying that on interruption of the emergency power sources the loads are shed from the nuclear services buses in accordance with design requirements and that subsequent' loading of the emergency power source is through the automatic load sequencing circuitry. The diesel generator will be operated for a least 5 minutes in this condition."

SAFETY EVALUATION JUSTIFYING CHANGE Proposed Amendment No. 128 meets all the NRC requirements with respect to onsite power source testing in a manner that is consistent with the emergency power sys-tem design. Previously, Technical Specification 4.6.2A3 called for an interruption of onsite AC power by simulating a loss of offsite power in conjunction with a safety features actuation signal. However, the only way this can be accomplished is to initiate either an engine overspeed fault, a generator differential current fault or a ground overcurrent fault since all manual and automatic shutdown trips are blocked by the safety features actuation signal. Following an automatic shutdown by any of the three aforementioned emergency trips, the diesel engine controls will have to be manually reset before an automatic start can be initiated.

Therefore, the exact method outlined in Technical Specification 4.6.2A3 cannot be applied due to the design of the emergency power system. As a result of this, the District requested NRC approval of Proposed Amendment No. 128 which meets the intent of Position 3 in a responsible and thorough manner.

N0 SIGNIFICANT HAZARDS CONSIDERATIONS The proposed changes provide a more meaningful method to assure that'onsite power source surveillance requirements are met. Therefore, operation of Rancho Seco in accordance with this Proposed Amendment:

1. does not involve a significant increase in the probability or consequences of an accident previously evaluated,

2. does not' create the possibility of a new or different kind of accident from any accident previously evaluated, and

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3. does'not involve a significant reduction in a margin of safety.

Theref , significant safety hazards are not associated with this change.

R. J. R ,>RIGUEZ l ASSISTANT GENERAL NAGER, NUCLEAR l Attachment i

Subscribed and sworn to before me _ _ . . . . . ~ ~ ~ . - -

this 6 4 day of Afff /zatv.v , 1985. OFFICIAL SEAL {

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Enclosure II SACRAMENTO MUNICIPAL UTILITY DISTRICT RANCHO SECO NUCLEAR GENERATING STATION, UNIT NO. 1 RESPONSE TO:

NUCIIAR 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 9

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.. Issued: July 19, 1977 Revision 1: August 1, 1980 I

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2. The load shedding relays perform the following functions:

A. Trip the normal offsite supply breaker to the safety features 4160 volt buses.

B. Trip the load breakers on the 4160 volt buses.

C. Set up the load sequencing timing circuit.

D. Start the emergency diesel generators.

3. When the diesel driven generator reaches the required voltage, its circuit breaker will automatically close connecting it to the 4160 volt bus, and the step loading sequence will automatically commence 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.

POSITION 3: ONSITE PokT.R SOURCE TESTING We require that the Technical Specifications include a test requirement to demonstrate the full functional operability and independence of the onsite power sources at least once per 18 months during shutdown.

The Technical Specifications shall include a requirement for tests:

(1) simulating loss of offsite power in conjunction with a safety injection actuation signal; and (2) simulating interruption and subsequent reconnec-tion of onsite power sources to their respective buses. Proper operation shall be determined by:

a) Verifying that one loss of offsite power the emergency buses have been de-energized and that the loads have been shed from the emergency buses in accordance with design requirements..

b) Verifying that on loss of offsite power the diesel generators start from ambient condition on the autostart signal, the emergency buses are energized with permanently connected loads, the autoconnected emergency loads are energized through the load sequencer, and the system operates for five minutes while the generators are loaded with the emergency loads.

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c) Verifying that on interruption of the onsite sources the loads are shed from emergency buses in accordance'with design requirements and that subsequence loading of the onsite sources is through the load sequencer.

RESPONSE TO POSITION 3 .

' Refer to Attachment I for a description of the Technical Specifi-cation modifications being considered by the District.

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, ATTACHMENT 1 t

4. SURVEILLANCE STANDARDS 4.1 OPERATIONAL SAFETY REVIEW (

TABLE 4.1-1 INSTRUMENT SURVEILLANCE REQUIREMENTS Add item 48 to Table 4.1-1.

. Channel Description Check Test Calibrate Remar'ks

48. Voltage Protection S Compare voltmeter readings

a. Undervoltage R R

b. Overvoltage R R

c. Time Delay R R S = Each Shift M = Monthly R = Once during the refueling interval 4.6 EMERGENCY PO'4R SYSTEM PERIODIC TESTING Specification Substitute 4.6.2 with the following:

4.6.2 During each refueling interval, a test of the diesel generators and emergency start circuits shall be performed to verify that these emergency power sources and associated equipment are operable by:

A. Simulating a lo::s of offsite power in conjunction with a safety injection actustion signal, and:

1) Verifying deenergization of the nuclear services buses and operation of the load shedding circuitry.

2) Verifying the diesel starts from ambient condition on the auto-start signal and energizes the nuclear services buses, and by verifying proper operation of the automatic load sequencing circuitry. The diesel generators will be operated for at least 5 minutes in this condition.

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'3) Verifying that on diesel generator trip, the load shedding circuitry operates properly and the diesel restarts on the auto-start signal, and by verifying proper operation of the automatic load sequencing circuitry. The diesel generator will be operated for at least 5 minutes in this condition.

B. ,

Load testing the diesel generators to SFAS capacity. ,

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