ML17037B627

Letter Regarding a Requested Review of the Alarm and Control Circuitry for the Diesel Generators and an Enclosed Attachment Addressing Those Concerns

ML17037B627
Person / Time
Site:	Nine Mile Point
Issue date:	05/18/1977
From:	Rhode G Niagara Mohawk Power Corp
To:	Lear G Office of Nuclear Reactor Regulation
References
Download: ML17037B627 (12)

Text

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NRC DISTRIBUTION FoA RT 50 DOCKET MATERIAL o g26 PILE NUMBER TP e

Mr. George Lear FROM:

Niagara Mohawk Pwri Corp

Syracuse, New York Gerald K Rhode DATE OF DOCUMENT 73/18/77 DATE RECE)VP e

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'DO NOT REVdWB ENCLOSURE Consists of r'nfor<ation regarding reque'st'ed review of the alar'm and control circhitry for the dieSel-generators.

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ItrgCKNOWLEDGED PLANT NAME Nine Mile Point'Unit No.

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NIAGARA MOHAWK POWER CORPORATION NIAGARA~

MOHAWK SOO ERIC OOUI.KVARO WEST SYRACUSE H.Y. lS202 May 18, 1977

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Director of Nuclear Reactor Regulation Attn:

Mr. George Lear, Chief Operating Reactors Branch g3 U.

S. Nuclear Regulatory Commission Washington, D.

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.1 Re:

Nine Mile Point Unit 1 Docket No. 50-220 DPR-63 Gentlemen:

Your letter of March 28, 1977 requested a review of the alarm and control circuitry for the diesel generators at Nine Mile Point Unit 1

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The attachment to this letter addresses those concerns.

Very truly yours, NIAGARA MOHAWK POWER C RPORATION

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Rhode Vice President

- Engineering MGM/sz Attachment 77l430078

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DIESEL GENERATOR Alarm and Control Circuitry

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INTRODUCTION The automatic start sequence

.for. the diesel generators at Nine Mile Point Unit 1 is based on a-low voltage condition at the diesel generator power boards.

The following conditions could render the diesels incapable of responding to an automatic start'signal.

Loss of control voltage Insufficient starting air pressure Depleted fuel storage tanks Isolation switch in "local. start" position Normal supply breaker control switch locked out Failure to reset the overspeed trip device Failure to reset the crankcase pressure switch trip The wording on the annunciator windows that are associated with failure of diesel generator automatic start are as follows.

These are annunciated in the control room.

Diesel Generator 102 Standby Off Normal Diesel Generator 103 Standby Off Normal Diesel Generator 102 Start-Run Off Normal Diesel Generator 103 Start-Run Off Normal Each of these have many signals which would cause annunciation.

Signals which cause annunciation and have individual computer print-outs are as follows:

Diesel Generator 102 Standb Off Normal Diesel Generator 102 Engine Starting Control Circuit Voltage Fail Diesel Generator 102 Oil Temperature Low Diesel Generator 102 Fuel Oil Level Hi-Low Diesel Generator 102 Starting Air Pressure Low Diesel Generator 102 Fuel Pump Control, Circuit Voltage Fail Diesel Generator 102 Governor Control Circuit Voltage Fail Diesel Fuel Oil Tank Level 102-103 Low

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INTRODUCTION (Continued)

Diesel Generator 102 Start-Run Off Normal Diesel Generator 102 Overspeed Trip Operated Diesel Generator 102 Lube Oil Pressure Low Diesel Generator 102 Starting Fail Diesel Generator 102 600 RPM Lock Out Operated Diesel Generator 102 Engine Temperature High Similar annunciators exist for diesel generator 103.

Annunciator Diesel Generator 102 Start-Run Off Normal is also actuated by opera-tion of the field overcurrent relay.

This function does not have a

corresponding computer printout.

The following discussion concerns the ability of the diesel generators to respond to an automatic start sequence.

II.

DISCUSSION Automatic. Start Se uence If the diesel generator, during an automatic start

sequence, does not reach 200 RPM in five seconds, a reset in the control circuitry will result and another attempt to start the diesel will be made.

During the second starting attempt, 750 RPM must be reached in 2 minutes or a fast stop of the diesel generator will be initiated.

For this start

sequence, only two starting attempts are allowed.- If a successful start has not been accomplished during the second attempt, the diesel is tripped and locked-out.

A manual reset is then required of both the alarm circuit and the incomplete sequence circuit to permit initiation of another automatic start sequence and consequently another two attempts to start.

Isolation Switch The isolation switch is a two position selector switch per-mitting "Local Start" or "Remote Auto" modes of operation.

This switch is located on the diesel engine control.panel in the diesel generator room and has no alarm in the control room associated with it.

However, the switch has been modi-fied such that a mechanical restraint maintain's th'e switch in the "Remote Auto" position and requires procedural con-trol to place the switch in the "Local Start" position.

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DISCUSSION (Continued)

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Breaker Control Switch If the normal supply bpeaker control switch is in the locked-out position, initiatio'n of 'an'~automa'tic start sequence is not possible.

The only time that this switch is placed in the locked-out position is for routine switchgear main-tenance oi maintenance on the diesels.

Niagara Mohawk maintenance proceduxes and Technical Specifications des-cribe conditions for routine switchgear maintenance and operation'with an inoperable diesel generator.

Maintenance procedures at Nine Mile Point Unit 1 employ a "markup" procedure for taking equipment out of-service.

Pro-cedural control also exists for. placing equipment back into service.

Diesel Overs eed.Tri The diesel overspeed trip requires manual reset to permit completion of the automatic staxt sequence.

Crankcase Pressure Switch Tri The diesel engine has a mechanically-operated crankcase pressure switch to detect positive pressure in the crankcase.

Upon positive pressure, it operates to bypass oil going to the main bearings.

Bypassed oil returns to the crankcase.

This, in turn, results in an engine trip due to main bearing oil low pressure.

When this device operates, a local mechanical trip reset is required to allow automatic starting of the diesel generator.

Normal manual shutdown aftex test from either the local control station or the control room does not require a

reset to enable subsequent automatic operation.

The diesel will be ready for the automatic start condition.

III. MODIFICATIONS As a result of this investigation, the following modification will be made:

Replacement of the existing mechanical crankcase pressure switch with an electrical pressuxe switch.

The new switch will be installed to alarm in the emergency run condition only.

The positive cxankcase pressure trip function is not required during this mode of operation.

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