ML20147B180

Forwards Addl Info Re Use of Battery Chargers as Isolation Devices & Mod of Ics/Nni,Per 880211 Telcon

ML20147B180
Person / Time
Site:	Rancho Seco
Issue date:	02/19/1988
From:	Croley B SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Miraglia F Office of Nuclear Reactor Regulation
References
AGM-TA-88-054, AGM-TA-88-54, NUDOCS 8803020005
Download: ML20147B180 (4)

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$suun SACRAMENTO MUNICIPAL UTILITY DISTRICT C P. O. Box 15830, Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA gg1S1988 AGM/TA 88-054 U. S. Nuclear Regulatory Commission Attn: Frank J. Miraglia, Jr.

Associate Director for Projects 11555 Rockville Pike Rockville, MD 20852 Docket No. 50-312 Rancho Seco Nuclear Generating Station License No. DPR-54 USE OF BATTERY CHARGERS AS ISOLATION DEVICES AND ADDITIONAL INFORMATION ON ICS/NNI

Dear Mr. Miraglia:

The attached information confirms discussions with your staff on February 11, 1988, regarding the use of battery chargers as isolation devices and the modification of the ICS/NNI at Rancho Seco.

Please contact me if you have any questions. Members of your staff with questions requiring additional information or clarification may contact Mr. Masa Nakao at (209) 333-2935, extension 4916.

Sincerely,

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B. G. Croley, Acting Assistant General Manager, Technical and Administrative Services Attachments cc: G. Kalman, NRC, Rockville A. D'Angelo, NRC, Rancho Seco J. B. Martin, NRC, Walnut Creek 8803020005 880219 DI PDR ADOCK 05000312 DCD

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P [ l RANCHO SECO NUCLEAR GENERATING STATION O 1444o Twin Cities Road, Herald, CA 95638-9799;(209) 333-2935

- AGM/TA 88-054 b

ATTACHMENT 1 Telecon: SMUD/NRC, February 11, 1988.

Subject:

Justification for Use of Chargers as Isolation Devices.

Highlights of the Telecon

- Battery chargers H4BGA and H4BGB are Class 1.  ;

- Battery chargers are current limit type with maximum current limit of 110%.

Present current limit is set at 100%. i Battery chargers are tested per procedure EM.161 once every two years and  !

were last tested on November 2,1987.

- Each battery charger has a blocking diode in the' output circuit to prevent i reverse current flow. l i

- NRC accepted battery charger as an isolation device in M111 stone-3 (Ref.

Millstone-3, SER 8.3.3.3.9). Rancho Seco setup is similar to Millstone design (see Attachment 2 for comparison). j i

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. AGM/TA 88-054 ATTACHMENT 2 COMPARIS0N OF MILLSTONE-3 AND RANCHO SECO DESIGN USE OF BATTERY CHARGERS AS ISOLATION DEVICES H48GA AND H4BGB Hillstone Nuclear Power Position SMUD Position

1. Battery charger is Class IE and 1. Battery chargers H48GA & H4BGB are protected by two physically sep- Class IE. 480V feeder cable of arated circuit breakers, each charger from 480V SWGR bus to battery charger is protected by two breakers. One breaker is located in SWGR compartments; the second breaker is located in the battery charger cabinet.

2. DC output circuits routed in 2. DC output circuits from H4BGA & H4BGB dedicated conduits. are routed in dedicated conduits.

H4BGA - 102H4BGA AA 781601

- 102H4BGA AB 781600 H48GB - 102H4BGB A 781613

- 102H4BGB B 781614

3. Circuits from charger to the 3. Circuits from charger to the load loads are protected by a DC (DC Panel / Inverter) are protected by charger output breaker and main battery charger output circuit circuit and feeder circuit breaker, breakers.

4 Circuits from switchboard to 4 Circuits from Inverter to the loads the loads are physically and are physically and electrically electrically separated from separated from Class 1 circuits of Class 1 or associated circuit safety division.

of other safety division.

5. Testing of chargers demon- 5. Battery chargers are current limit strated its current limit- type and are presently set at 100%

ing capability, of the rating. Chargers were last tested on November 2,1987, to verify the 100% current limit.

.. AGM/TA 88-054 ATTACHMENT 3 ADDITIONAL INFORMATION - ICS/NNI ICS Module Replacement:

The District has replaced ICS and NNI static analog memory modules with analog memory modules that are programable upon restoration of power. This was accomplished by Engineering Change Notice ECN R-1217.

ICS/NNI Loss-of-Power Test:

The ICS/NNI Loss-of-Power Test, Special Test Procedure STP.664, has been revised to include provisions for testing the loading by the ICS on the NNI signals. When the ICS power is secured during testing, the NNI signals will be monitored (both before and after) to determine the loading effect. The affected ICS modules have been modified (by ECN R-1217) with the intent of precluding NNI signal loading.

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