ML17146B115

Discusses Safety Concern Derived from 860522 Occurrence at Facility Re Common Mode Failures.Requests Info within 30 Days Re Actions Util Proposes to Address Safety Concern

ML17146B115
Person / Time
Site:	Susquehanna
Issue date:	01/14/1988
From:	Varga S Office of Nuclear Reactor Regulation
To:	Keiser H PENNSYLVANIA POWER & LIGHT CO.
References
NUDOCS 8801250476
Download: ML17146B115 (7)

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Docket No. 50-387/388 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 January 14>

1988 Mr. Harold M. Keiser Vice President Nuclear Operations Pennsylvania Power and Liqht Company 2 North Ninth Street Allentown, PA 18101

SUBJECT:

POTENTIAL OF COMMON MODE FAILURES AT SUSQUEHANNA, UNITS 1 5 2 RE:

Susquehanna Steam Electric Station, Units I and 2

It has come to our attention that in the current plant configuration, the Susquehanna Units I and 2 safety systems could experience excessive energy surges in electrical systems which could cause damage to or malfunction of the affected safety systems.

Our concern derives from an occurrence on May 22, 1986 when, while the "D" diesel generator was being tested, the field circuit of the diesel generator opened up as a result of a field wire separation from its terminating lug to the slip ring.

The failure caused a "flash" and a

ground field alarm on the "D" diesel generator, and also on "A", "B", and "C"

diesel generators.

A number of Plant Monitoring Systems (PMS) monitoring points were also lost.

The cause was traced to a small Unit 1 computer I/O cabinet fire which was subsequently fanned out.

As a result of the review of the information related to the May 22, 1986 occurrence, the staff has raised a concern that either unqualified or in some cases no isolation devices may exist on many of the Class 1E and Non-Class 1E interfaces at Susquehanna.

The staff finds that the diesel generator open field circuit event demonstrates the shortcoming in the use of analysis to justify inadequate isolation capability between Class 1E and Non-Class lE circuit interfaces.

Justification provided in your FSAR for the lack of isolation was based on an analysis that since only low energy can be derived from instrumentation circuits, the probability of these Non-Class 1E circuits providing a mechanism of failure to the Class IE circuits is extremely low.

The May 22, 1986 event demonstrates that analytical iustification for not installing qualified devices can not be relied upon.

The staff therefore concludes that:

1.

All Class lE/Non-Class 1E instrumentation and control interfaces, where qualified isolation devices do not exist, should be identified and qualified isolation devices installed.

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2.

During qualification testing of an isolation device, the maximum credible fault voltage/current to which the isolation device is exposed should be that which is available on both the input as well as the output of the isolation device.

3.

gualified isolation between neutron monitoring system interfaces and non-safety related plant equipment should be provided.

The staff is currently pursuing this issue with General Electric on several BWR plants and the resolution of this item will be applicable to Susquehanna Steam Electric Station.

Accordingly, please provide information on how the above staff conclusions would be addressed on the Susquehanna Units I and 2.

Please provide us, within 30 days from the receipt of this letter, information on what actions you propose to take to address the safety concerns identified by the staff.

Sincerely, Steven A. Vabga, Di ctor Division of Reacto rojects I/II cc:

See next paae

Mr. Harold W. Keiser Pennsylvania Power

& Light Company Susquehanna Steam Electric Station Units 1

8 2

CC:

Jay Silberg, Esq.

Shaw, Pittman, Potts 5 Trowbridge 2300 N Street N.W.

Washington, D.C.

20037 Bryan A. Snapp, Esq.

Assistant Corporate Counsel Pennsylvania Power 5 Light Company 2 North Ninth Street Allentown, Pennsyl vania 18101 Mr. E. A. Heckman Licensing Group Supervisor Pennsylvania Power 5 Light Company 2 North Ninth Street Allentown, Pennsylvania 18l01 Mr. Loren Plisco Resident Inspector P.O.

Box 52 Shickshinny, Pennsylvania 18655 Mr. R. J.

Benich Services Project Manager General Electric Company 1000 First Avenue King of Prussia, Pennsylvania 19406 Mr. Thomas M. Gerusky, Director Bureau of Radiation Protection

.Resources Commonwealth of Pennsylvania P. 0.

Box 2063 Harrisburg, Pennsylvania 17120 Robert W. Alder, Esquire Office of Attorney General P.O.

Box 2357 Harrisburg, Pennsylvania 17120 Mr. Jesse C. Tilton, III Allegheny Elec. Coorperative, Inc.

212 Locust Street P.O.

Box 1266 Harrisburg, Pennsyl vania 17108-1266 Mr.

W.

H. Hirst, Manager Joint Generation Projects Department Atlantic Electric P.O.

Box 1500 1199 Black Horse Pike Pleasantville, New Jersey 08232 Regi ona 1 Admini s tra tor, Regi on I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406

2.

During qualification testing of an isolation device, the maximum credible fault voltage/current to which the isolation device is exposed should be that which is available on both the input as well as the output of the isolation device.

3.

gualified isolation between neutron monitoring system interfaces and non-safety related plant equipment should be provided.

The staff is currently pursuing this issue with General Electric on several BWR plants and the resolution of this item will be applicable to Susquehanna Steam Electric Station.

Accordingly, please provide information on how the above staff conclusions would be addressed on the Susquehanna Units 1 and 2.

Please provide us, within 30 days from the receipt of this letter, information on what actions you propose to take to address the safety concerns identified by the staff.

Sincerely, cc:

See next page

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During qualification testing of an isolation device, the maximum credible fault voltage/current to which the isolation device is exposed should be that which is available on both the input as well as the output of the isolation device.

3.

gualified isolation between neutron monitori'ng system interfaces and non-safety related plant equipment should be provided.

The staff is currently pursuing this issue with General Electric on several BWR plants

- and the resolution of this item will be applicable to Susquehanna Steam Electric Station.

Accordingly, pursuant to 10 CFR 50.54(f) of the regulations, please provide information on how the above staff conclusions would be addressed on the Susquehanna Units l and 2.

Please provide us, within 30 days from the receipt of this letter, information on what actions you propose to take to address the safety concerns identified by the staff.

Sincerely, cc:

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