ML17297A558

Forwards Draft SER Input for Dc Power Sys.Requests Schedule for Response to Open Issues within 7 Days.W/Exception of Items Discussed,Dc Current Power Sys Is Acceptable

ML17297A558
Person / Time
Site:	Palo Verde
Issue date:	06/16/1981
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
References
NUDOCS 8107140838
Download: ML17297A558 (20)

Text

"7 JUN >6 taN Docket Nos.

STN 50-528/529/530 Mr. E. E. Van Brunt, Jr.

Vice President - Nuclear Projects Arizona Public Service Company P.

O.

Box 21666 Phoenix, Arizona 85036 51 STR IBUT ION Docket File NRC PDR Local PDR'ELD LB¹3 Rdg File RLTedesco FMiraglia JKerrigan JLee ISE (3)

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ACRS (16)

NSIC TERA TIC

SUBJECT:

DRAFT SAFETY EVALUATION REPORT (SER)

INPUT FOR DG POWER SYSTEMS Enclosed is a draft SER input for the direct current power systems for Palo Verde, Units-il, 2 and 3.

This was the first SER input prepared which incorporated the results of the Independent Design Review (IDR) concept in our review process.

It should be noted that the IDR approach has elimi-nated the need for the issuance of /is and g2s and has resulted in an SER for direct current power systems containing only two minor open issues as follows:

l.

Battery and battery charger alarms.

2.

gualification of Class 1E direct current equipment for operation at the equalizing charge voltages.

The results of our evaluation were previously discussed with members= of your staff.

Within 7 days after receipt of this letter, please provide a schedule for responding to these open issues.

Please contact us ifyou have any additional questions on this matter.

Sincerely,

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g obert L. Tedesco, Assistant Director for Licensing

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 JUN 16 1981 Docket Nos.

STN 50-528/529/530 Mr. E. E. Van Brunt, Jr.

Vice President - Nuclear Projects Arizona Public Service Company P.'.

Box 21666 Phoenix, Arizona 85036

SUBJECT:

DRAFT SAFETY EVALUATION REPORT (SER)

INPUT FOR DC POWER SYSTEMS Enclosed is a draft SER input for the direct current power systems for Palo Verde, Units 1, 2 and 3.

This was the first SER input prepared which incorporated the results of the Independent Design Review (IDR) concept in our review process.

It should be noted that the IDR approach has elimi-nated the need for the issuance of qls and g2s and has resulted in an SER for direct current power systems containing only two minor open issues as follows:

1.

Battery and battery charger alarms.

2.

gualification of Class lE direct current equipment for operation at the equalizing charge voltages.

The results of our evaluation were previously discussed with members of your staff.

Within 7 days after receipt of this letter, please provide a schedule for responding to these open issues.

Please contact us if you have any additional questions on this matter.

Sincerely, cc:

w/enclosure Robert L. Tedesco, Assistant Director for Licensing Division of Licensing

'I

Mr. E. E. Van Brunt, Jr.

Vice President - Construction Projects Arizona Public Service Company P. 0. Box 21666

Phoenix, Arizona 85036 CC:

Arthur C. Gehr, Esq.

Snell 8 W'ilmer 3100 Valley Center

Phoenix, Arizona 85073 Charles S. Pierson Assistant Attorney General 200 State Capitol 1700 Hest Washington Phoenix, Arizona 85007 David N. Barry, Esq.,

Senior Counsel Charles R. Kocher, Esq., Assistant Counsel Southern California Edison Company P. 0. Box 800

Rosemead, California 91770 Margaret Walker Deputy Director of Energy Programs Economic Planning and Development Office 1700 West Washington Phoenix, Arizona 85007 P

William Primum Assistant Attorney General Bataan Memorial Building Santa Fe, New Mexico 87503 Resident Inspector Palo Verde/NPS U.S. Nuclear Regulatory Commission P. 0. Box 21324 Phoenix, Arizona 85001 les. Patricia Lee Hourihan 6413 S. 26th Street Phoenix, Arizona 85040

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SAFETY EVALUATION OF DIRECT CURRENT POWER SYSTEMS FOR PALO VERDE UNITS 1, 2

5 3 JUN 1S ling~

8.1 General Consideration The objective of our review is to determine that the electric power systems are designed in accordance with the requirements of the staff's acceptance criteria.

The acceptance criteria are comprised of the applicable General Design Criteria (GDC) of Appendix A to 10 CFR 50 as listed below.

Additionally, we have listed those Regulatory Guides that amplify, clarify, and/or provide further guidance in the application of the General Design Criteria.

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0 CC 17 18 Electric Power Systems Inspection and Testing of Electric Power Systems Sharing of Structures,

Systems, and Components Environmenta]

and Missile Design Bases Design Bases for Protection Against Natural Phenomena X

REGULATORY GUIDES 1.6

1. 32 1.75 1.81 Independence Between Redundant Standby (onsite)

Power Sources and Between Their Distribution Systems Criteria for Safety Related Electric Power Systems for Nuclear Power Plants Physical Independence of Electric Systems Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plant I

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The direct current power system provides, (1) the alternating current offsite and onsite emergency power systems with control power as required, (2) power to the four inverters of the Class lE vital instrumentation and control alternating current power subsystem and (3) motive and control power to selected safety-related equipment.

Our review of the direct current Power system for Palo Verde nuclear generating station was based on the information provided in the FSAR, in the transcript of the Independent Design Review (IDR) conducted on May 8, 1980 for the Palo Verde Nuclear Generating Station (PVNGS) Direct Current Power Systems by Arizona Public Service Company with their consultants and architect engineer (The NRC involvement in the IDR was that of an observer/participant}.

and in the documentation of the resolution of the open items (requests for additional information) generated by the IDR; the IDR transcript and related followup documentation was trans-mitted to the NRC by the PVNGS letters dated June 30, 1980, Sept.

4, 1980, Sept.

18, 1980 and Oct. 14, 1980.

Evaluation Four Class 1E 125 volt direct cur rent subsystems (A thru D) are provided for each unit.

The direct current subsystems A and B provide control power for redundant alternating current load groups 1

(subsystems A and C) and 2 (subsystems B and D) respectively.

These subsystems also provide vital instrumentation and control power for channels A and B respectively, of the reactor trip system, engineered safety features actuation system (ESFAS),

and diesel generators A

and B respectively.

The direct current subsystems C and

'D provide vital

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instrumentation and control power for channels C and D respectively, for the reactor trip system, ESFAS and other safety-related loads.

Each of the four Class lE direct current power subsystems consists of one 125 volt battery, one battery charger supplied with 480 volt alternating current power from the above cited associated load group, and one distribution panel.

Each load group additionally contains a backup battery charger which can be manually connected to direct current subsystems A or C for load group 1, and B or D for load group 2, respectively.

The transfer mechanism is mechanically and electrically interlocked to prevent both direct current subsystems from being simultaneously connected to the backup battery charger.

This transfer mechanism will be reviewed in detail during our drawing review to ascertain that the r edundant direct current subsystems cannot be connected to the backup charger simultaneously.

We will report our concerns, if any, on this item in a supplement to this report.

There are also two non-Class lE direct current power systems provided for each unit, one for control loads and one for power loads.

The non-Class 1E direct current power system provides power for non-Class lE loads.

Each system con-sists of a 125 volt battery, battery charger and a direct current distribution panel.

A spare battery charger is provided which can be connected to either system.

Based on our review, we have determined that these non-Class lE direct current systems are indep'endent of the Class 1E direct current system.

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Some non-safety related loads. are supplied from the Class lE direct current system, however, these circuits are routed and separated in accordance with the requirements of Regulatory Guide 1.75.

Me find this acceptable.

The Class 1E batteries,

chargers, and direct current switchgear are located in separate rooms of the seismic Category I control building which provides pro-tection from the effects of tornadoes, tornado missiles and floods.

This is in accordance with the requirements of GDC 2 and GOC 4.

Each battery room is provided with a separate ventilation system.

The ventilation system is designed to preclude the possibility of hydrogen accumulation.

Each Class lE direct current subsystem, including batteries,

chargers, switch-gear and distribution equipment are physically separate and independent from its redundant counterparts.

Sufficient capacity, capability, independence, redundancy, and testability are provided in the Class lE direct current subsystems, to ensure the performance of safety functions assuming a single

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failure.

This is in accordance with GDC 17.

In addition, each of the four Class lE 125 volt direct current subsystems is designed to permit inspection and testing during plant operation and shutdown to assess the operability and continuity of the subsystems.

This is in accordance with the requirements of GDC 18.

During normal operation, the 125 volt direct current load is supplied from the battery chargers with the batteries floating on the system.

Upon loss of station alternating current power, the entire load is powered from the batteries until the power is restored by the emergency diesel generator or the offsite preferred power source.

Ho provisions exist for either manually or automatically trans-ferring loads between the redundant direct current systems.

This is in accordance with Regulatory Guide 1.6.

There is no sharing of direct current power sources between the units, which is in accordance with 10 CFR 50, Appendix A, GDC 5 and Regulatory Guide 1.81.

Based upon our review, we find P

that the direct current subsystems are independent.

Each Class lE battery has sufficient capacity to independently supply the required safety loads for two hours in the event of total loss of station AC power.

Each battery capacity is 25K greater than required.

This margin is in accordance with IEEE-450-1972 battery replacement criterion of 805 rated capacity.

Each battery charger has enough capacity to recharge the battery from its design minimum charge state, to the fully charged state within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> while simultaneously supplying the largest combined demand of various steady-state loads irrespective of the status of the plant during which these demands occur.

The battery chargers also have the capability to perform their required function if their associated battery is disconnected for any reason.

The above is in accordance with Regulatory Guide 1.32.

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Local and control room instrumentation is provided to monitor the status of the batteries and the battery chargers and to assure the continual operability of the Class 1E direct current power system.

These include the following:

Batter Instrumen.ation Ammeter for battery current indication Voltmeter for bus voltage indication Undervoltage relay for bus undervoltage alarm Ground detector relay Direct Current Control Center Control Room Batter Char er Instrumentation Ammeter for charger output current Voltmeter for charger output voltage Undervoltage relay to alarm on alternating current input low voltage Undervoltage relay to alarm on direct current output low voltage Overvoltage relay to alarm on direct current output high voltage Alternating current and direct current breaker position indication Output breaker (open) alarm Charger malfunction alarm including alternating current input low voltage, direct current output low voltage, direct current output high voltage, and output breaker open

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Me have reviewed the above status indications and alarms provided for the Class lE batteries and battery chargers and conclude that they do not fully meet our requirements.

Therefore, we require the applicant to provide the following additional alarms in the control room.

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(1)

Battery high discharge rate alarm to alert the operator that the loads are being supplied by the batteries and the batteries are discharging at an abnormal rate.

(2)

Battery breaker open alarm.

It is not clear from the information provided if the Class 1E direct current system is adequately qualified to preclude potential damage due to battery charger regulator failure {does not include built-in overvoltage shutdown protection) and that the Class 1E direct current equipment is qualified for operation at the equilizing charge voltages.

The above items will remain open until the applicant provides an acceptable response to satisfy our requirements.

We will report the resolution of these items in a supplement to this report.

In conclusion, the Class 1E portion of the direct current power and distribution system has sufficient capacity, capability, independence, redundancy and test-ability in accordance with GDC 17, is designed to permit testing and inspection in accordance with GDC 18, is located in a seismic Category I building and protected from tornadoes, tornado missiles and floods in accordance with GDC 2 P

and GDC 4 and there is no sharing of direct current power sources between the units in accordance with GDC 5.

Therefore, with the exception of the items discussed, above, we find the direct current power system to be acceptable.

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