ML19337A485

Forwards Positions Re Degraded Grid Voltage & Protection of Reactor Containment Electrical Penetrations,Developed During Review of Fsar.Requests Date of Response

ML19337A485
Person / Time
Site:	Zimmer
Issue date:	09/12/1980
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Borgmann E CINCINNATI GAS & ELECTRIC CO.
References
NUDOCS 8009290086
Download: ML19337A485 (8)

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Docket No. 50-358 SEP 121980 Mr. Earl A. Borgmann Vice President - Engineering Cincinnati Gas & Electric Company P. O. Box 960 Cincinnati, Ohio 45201

SUBJECT:

STAFF POSITIONS ON DEGRADED GRID VOLTAGE AND PROTECTION OF REAC CONTAlf01ENT ELECTRICAL PENETRATIONS As a result of meetings with La Salle, the lead plant being reviewed for the utility owners of near-term boiling water reactors, it was brought to our attention that staff positions addressing degraded grid voltage and pro-tection of reactor containment electrical penetrations were not transmitted to you during the NRC staff review of the Zimmer ?SAR. To correct this oversight, we are transmitting the enclosed positions.

Please advise us when you will respond to the enclosure.

Sincerely, H CC Robert L. Tedesco Assistant Director for *.icensing Division of Licensing

Enclosure:

As stated cc w/ enclosure:

See next page 6

8009290 086 1

Mr. Earl A. Borgmann Vice President - Engineering Cincinnati Gas & Electric Company P. O. Box 960 Cincinnati, Ohio 45201 F

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cc: Troy B. Conner, Jr., Esq.

Dr. Frank F. Hooper Conner, Moore & Corber 1747 Pennsylvania Avenue, N. W.

School of Natural Resources University of Michigan Washington, D. C.

20006 Ann Arbor, Michigan 4B109 Mr. William J. Moran General Counsel g

Charles Bechhoefer, Esq., Chairman Atomic Safety & Licensing Board Panel Cincinnati Gas & Electric Company U. S. Nuclear Regulatory Ccamission P. O. Box 960 Washington, D. C.

20555 Cincinnati, Ohio 45201 Mr. William G. Porter, Jr.

Mr. Glenn O. Bright Porter, Stanley, Arthur Atomic Safety & Licensing Board Panel and Platt U. S. Nuclear Regulatory Commission 37 West Broad Street Washington, D. C.

20555 Col'umbus, Ohio 43215 Leah S. Kosik, Esq.

3454 Cornell Place Mr. Steven G. Smith, Manager Engineering & Project Control Cincinnati, Ohio 45220 a

Dayton Power & Light Company P. O. Box 1247 W. Peter Heile, Esq.

Assistant City Solicitor Dayton, Ohio 45401 Room 214, City Hall J. Robert Newlin, Counsel Cincinnati, Ohio 45220 Dayton Power & Light Company Timothy S. Hogan, Jr., Chairman P. O. Box 1247 Board of Commissioners Dayton, Ohio 45401 50 Market Street 1

,t Mr. James D. Flynn, Manager Clermont County Licensing Environmental Affairs Batavia, Ohio 45103 Cincinnati Gas &-Electric Company John D. Woliver, Esq.

P. O. Box 960 Clermont Ccunty Community Council Cincinnati, Ohio 45201 Box 181

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Mr. J. P. Fenstermaker Batavia, Ohio 45103 i

Senior Vice President-Operations r

Columous & Southern Ohio Mrs. Mary Reder i

Box 270, Rt. 2

l F'ectric Company 216 North Front Street California, Kentucky 41007 s

Columbus, Ohio 43215 Dale D. Brodkey David Martin, Esq.

Assistant Attorney General U

Office of the Attorney General Division of Environmental Law 209 St. Clair Street Office of Attorney General 2

First Floor 209 St. Clair Street Frankfort, Kentucky 40601 Frankfort, Kentucky 40601 i

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i Mr. Earl A. Borgmann cc: Andrew B. Dennison, Esq.

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i Bataviay Ohio 45103 Robert A. Jones, Esq.

3 Prosecuting Attorney of Clermont County, Ohio 154 Main Street Batavia, Ohio 45103 j

Resident Inspector /Zimmer

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i U. S. Nuclear Regulatory Cominission P. O. Box 58 New Richmond, Ohio 45157 4

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i Enclosure Wm. H. Zimmer Nuclear Power Station Unit 1 Sucolemental Staff Positions Docket No. 50-358 1.

Degraded Grid Voltage The Millstone, Unit 2 low grid voltage occurrence brought into focus the potential common mode failure of redundant safety-related electrical equipment that could result from a degraded grid voltage condition. This occurrence prompted the Regulatory staff to develop various positions to assure that the requirements of the Commission's General Design Criterion 17 will be satisfied with regard to making provisions to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electrical power supplies. These provisions for maintaining the independence between the offsite and onsite emergency power systems are emphasized in IEEE Standard 308-1974, " Criteria for Class lE Power Systems for Nuclear Power Generating Station," which states that the preferred (offsite) and the standby (onsite

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emergency) power supplies shall not have a common failure mode between them.

The positions that we have developed are being used in the evaluation of electrical power designs for operating plants, and construction permit and

, operating license applications. The position developed are summarized as follows:

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A.

In addition to the undervoltage scheme provided to detect loss of offsite power at the safety busses, we require that a second level of voltage protection for the onsite power system be provided with'a time delay and that this second level of voltage protection shall satisfy the following criteria:

a) The selection of voltage and time set points shall be determined from an analysis of the voltage requirements of the safety-related loads at all onsite system distribution levels; b) The voltage protection shall include coincidence logic on a per bus basis to preclude spurious trips of the offsite power source; c) The time delay selected shall be based on the following conditions:

(1) The allowable time delay, including margin, shall not exceed the maximum time delay that is assumed in the Final Safety Analysis Report accident analyses; (2) The time delay shall minimize the effect of short duration disturbances from reducing the availability of the offsite powersource(s);and (3) The allowable time duration of a degraded voltage condition at all distribution system levels shall not result in failure of safety systems or components; d) The voltage sensors shall automatically initiate the disconnection of offsite power sources whenever the voltage set point and time delay limits have been exceeded; e) The voltage sensors.shall be designed to satisfy the applicable requirements of IEEE Std. 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations"; and

f) The Technical Specifications shall include limiting condition for operation, surveillance requirements, trip set points with minimum and maximum limits, and allowable values for the second-level voltage protection sensors and associated time delay devices.

B.

We require that the current system designs automatically prevent load shedding of the emergency 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 to be auto-matically reinstated if the onsite source supply breakers are i: ripped.

The automatic bypass and reinstatement feature shall be verified during the periodic testing identified in Position 3.

C.

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; (2) simulating loss of offsite power in conjunction with an accident signal; and (3) simulating interruption and subsequent reconnection of onsite power sources to their respective buses. Proper operation shall be determined by:

a) Verifying that on 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 on the autostart signal, the emergency buses are energized with permanently connected loads, the auto-connected shutdown loads are

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energized through the load sequencer, and the system operates for five minutes while the generators are loaded with the shutdown loads.

c) Verifying that on an accident signal (without loss of offsite power) the diesel generators start on the autostart signal and operate on standby for five minutes.

d) Verifying that on loss of offsite power in conjunction with an accident signal the diesel generators start on the autostart signal, the emergency buses are energized with permanently connected loads, the auto-connected emergency (accident) loads are energized through 4

the load sequencer, and the system operates for five minutes while the generators are loaded with the emergency loads.

e) Verifying that on interruption of the onsite sources the loads are shed from the emergency buses in accordance with design require-ments and that subsequent loading of the onsite sources is through the load sequencer.

D.

The voltage levels at the safety-related buses should be optimized for the full load and minimum load conditions that are expected throughout the anticipated range of voltage variations of the offsite power source by appropriate adjustment of the voltage tap settings of the intervening transformers. We require that the adequacy of the design in this regard be verified by actual measurement and by correlation of measured values with analysis results. Provide a description of the method for making this verification; before initial reactor power operation, provide the documentation required'to establish that this verification has been accomplished.

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_ 2.

Protection of Reactor Containment Electrical Penetrations General Design Criteria 50 requires, in part, that reactor containment structures (electrical penetrations) be designed so that they can accommodate without failure the pressure and temperature conditions resulting from any loss-of-coolant accident.

In regard to electrical penetrations, Regulatory Guide 1.63 describes a method acceptable to the flRC for compliance with General Design Criteria 50.

Regulatory Guide 1.63 recommends that the electrical penetration assembly should be designed to withstand, without the loss of mechanical integrity, the maximum possible fault current versus time conditions that could occur given single random failures of circuit overload protection devices.

Regulatory Guide 1.63, Revision 1 was classified as a Category II review item by the Regulatory Requirements Review Committee meeting No. 60, March 27, 1977 for all applications not evaluated under Revision 0 to Regulatory Guide 1.63.

Pursuant with this Category II classification, it is our position that electrical penetrations at the Wm. H. Zimmer Nuclear Power Station be evalu-ated in accordance with Regulatory Guide 1.63, Revision 1.

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