ML17056B541

Summary of 911120 Meeting W/Util & Exide Electronics Re 75 k-volt Uninterruptible Power Supply Control Logic Power Supply at Facility

ML17056B541
Person / Time
Site:	Nine Mile Point
Issue date:	11/20/1991
From:	Brinkman D Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 9112020116
Download: ML17056B541 (14)

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Docket No. 50-410 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 November 20, 1991 LICENSEE:

FACILITY:

SUBJECT:

Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station, Unit 2 MEETING MINUTES REGARDING THE NOVEMBER 1, 1991, MEETING TO DISCUSS THE EX IDE ELECTRONICS 75 KVA UNINTERRUPTIBLE POWER SUPPLY CONTROL LOGIC POWER SUPPLY AT NINE MILE POINT 2 A meeting was held in the Maryland National Bank Building in Bethesda, Maryland with Niagara Mohawk Power Corporation (NMPC), Exide Electronics, and NRC staff representatives.

This meeting was requested by the Incident Investigation Team (IIT) to (I) further discuss the purpose of the internal batteries in the Exide 75 KVA uninter ruptib'le power supply (UPS) units at Nine Mile Point 2 and (2) to attempt to resolve technical disagreements between the IIT and NHPC reqarding the purpose of the internal batteries.

These technical disagreements were identified in the IIT briefing of the Commission on October 18, 1991, and in a letter dated October 23, 1991, to James M. Taylor, NRC, from B. Ralph

Sylvia, NMPC.

Enclosure 1 is a list of meeting attendees.

The IIT concluded that two factors were the direct causes of the UPS loss at NHP-2.

The first factor was a design deficiency internal to each UPS.

The second factor was the failure of the NMPC plant staff to perform appropriate preventive maintenance in that the internal batteries were dead and had not been replaced on a timely basis.

In its October 23, 1991, letter, NMPC expressed disagreement with these conclusions and suggested that Information Notice 91-63 and NUREG-1455 be revised to reflect NMPC's position that the root cause of the UPS loss was an improper design.

During the meeting, the Exide Electronics representatives stated that the UPSs were standard commercial grade products which were originally designed without the internal batteries.

The batteries were added when it was discovered that a

UPS would shut down and fail to transfer from the normal AC supply to the maintenance AC supply upon demand if cer tain single failures existed in the UPS logic.

The batteries were intended to supply power to the logic for up to 15 minutes in the event of single failures; however, the batteries were not intended to compensate for multiple failures within the UPS logic.

The Exide representatives also stated that with no failures in UPS logic, with the UPS logic receiving power from the inverter output, and assuming that the maintenance supply is of proper quality (correct frequency, voltage, phase angle, etc.), the UPS would transfer from its normal AC supply to the maintenance supply regardless of the condition of the internal batteries or even without the internal batteries present.

It was also determined that the internal batteries may be useful in maintaining logic power in the event of certain logic failures and for startup of the UPS when AC power is not available.

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Niagara Mohawk Power Corporation November 20, 1991 Prior to the meeting, the NRC Incident Investigation Team had developed a

series of questions regarding the UPS.

The questions (Enclosure

2) were provided to NNPC and Exide Electronics prior to the meeting.

NHPC and Exide Electronics provided oral responses to these questions during the meeting.

At the conclusion of the meeting, the NRC staff representatives informed the NNPC representatives that the NRC staff would respond in writing to Nr. Sylvia's letter dated October 23, 1991.

Enclosures:

1.

List of Attendees 2.

UPS guestions cc w/enclosures:

See next page Donald S. Brinkman, Senior Project Manager Project Directorate I-I Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation

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Mr. B. Ralph Sylvia Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station Unit 2 CC:

Mr. Mark J. Wetterhahn, Esquire Winston 5 Strawn 1400 L Street, NW.

Washington, D.C. 20005-3502 Mr. Richard Goldsmith Syracuse University College of Law E. I. White Hall Campus

Syracuse, New York 12223 Resident Inspector Nine Mile Point Nuclear Power Station P. 0.

Box 126

Lycoming, New York 13093 Mr. Gary D. Wilson, Esquire Niagara Mohawk Power Corporation 300 Erie Boulevard West

Syracuse, New York 13202 Hr. David K. Greene Manager Licensing Niagara Mohawk Power Corporation 301 P 1 a infiel d Road

Syracuse, New York 13212 Ms.

Donna Ross New York State Energy Office 2 Empire State Plaza 16th Floor

Albany, New York 12223 Supervisor Town of Scriba Route 8, Box 382

Oswego, New York 13126 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, Pennsylvania 19406 Char lie Donaldson, Esquire As s i s tant Attorney Genera 1

New York Department of Law 120 Broadway New York, New York 10271 Mr. Richard M. Kessel Chair and Executive Director State Consumer Protection Board 99 Washington Avenue

Albany, New York 12210 Mr. Martin J.

McCormick Jr.

Plant Manager, Unit 2 Nine Mile Point Nuclear Station Niagara Mohawk Power Corporation P. 0.

Box 32

Lycoming, NY 13093 Mr. Joseph F. Firlit Vice President - Nuclear Generation Nine Mile Point Nuclear Station Niagara Mohawk Corporation P. 0.

Box 32

Lycoming, New York 13093

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ENCLOSURE I ATTENDANCE LIST November I, 1991 Meeting to Discuss Exide 75 KVA UPS Control Logic Powe~ Supply at NMP-2 Name Donald S. Brinkman Jack E. Rosenthal Denny Ross D. J.

Hess Rudi Machi'lek Michael Grady John Hockoday B. Ralph Sylvia Carl Terry Anil K. Julka Bob Crandall W. David Baker Frank Ashe Thomas J.

Pohida Roger Woodruff Penny Bender Kim Hills John Kauffman Tlt'le Senior Project Manager IIT Team Leader Dep. Dir. AEOD Dir. Customer Support Dir. Sr. Staff Consultant Hgr. Tech Support Sr.

Tech Specialist Executive Vice President VP-Nuclear Engineering Supervisor-Electrical NHP2 NMP2 UPS System Engineer Program Dir.-Licensing NMP2 Electrical Engineer IIT Member Sr. Reactor Systems Eng.

Reporter Reporter IIT Member Organization NRC/NRR/PDI-I NRC/AEOD NRC/AEOD Exide Elec Exide Elec Exide Elec Exide Elec Niagara Mohawk Niagara Mohawk Niagara Mohawk Niagara Mohawk Niagara Mohawk SELB/NRR SICH/NRR OEAB/NRR States News Service Associated Press NRC/AEOD/ROAB

ENCLOSURE 2 October 29, 1991 Mr. B. Ralph Sylvia Exec. Vice President-Nuclear

¹iagara Mohawk Power Corporation 301 Plainfield Rd.

Syracuse, New York 13212

SUBJECT:

UPS QUESTIONS

1. What is the tcchnical basis for the power supply fail (PSF) setpoint being specified as 16.S volts? How frequently has this setpoint voltage been verified through measurement, and appropriately adjusted, in the past?

How frequently willthis setpoint be verified and adjusted in the future?

2. What is the Kl, K2, K3, and KS relay transfer time? How is this verified and monitored7

3. What wouM result ifone af the 2Q volt power supply outputs was suddenly lost without functional batteries7

4. Are thete any fuses associated with thc 20 volt power supplies? Ifyes, what would result ifone of the fuses open circuitcd?

5. What is the designed rise time of the inverter output voltage?

What is the time required

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for the inverter output voltage to rise from 2S VAC to 96 VAC? During this time period the 20 volt power supplies could be receiving power from the invcrter output; willthe power supply output voltage degrade during the rise time of the inverter?

6. What is thc mniimum DC voltage required to operate the shunt trip for CB1, CB2, and CB32 What is the current required at this minimum voltage? Willthe current bc availablc?

7. What time is xequhed to open CB3 and close CB4 after the circuitry has made this decision?

What is the sequence of the static switch and circuit brealur (CB3 and CB4) action?

For what time duration must thc circuitry be functional to control the static switch?

8. At what DC input voltage (from the power supplies) do the +S V and +12 V voltage regulators loose the ability to maintain their specified output voItages?

Plot the output voltage and current capability of the regulators for an input voltage ranging from 0 to 20 volts. What is the minimum voltage and current required out of thee regulators to power the various components?

9. How 1oag does it take to sense a degraded invertcr output voltage?

'Hats degraded voltage could be due to internal invcrtcr failures, or duc to faulty UPS unit loads.

10. What ate the postulated inverter failure modes?

11,.Provide copies of measurement data and oscilloscope traces for all tests performed on the UPS units aAer the event.

12. How long willthe batteries successfully power the UPS unit given the battery data sheets and the circuit drawings?

How is this time modified as a result of a unit trip?

Ts the battery current load greater during normal operation, after a module trip, or with all four breakers open?

13. How was maintenance and surveillance performed without the proper documentation?

14. Where is the UPS unit original equipment manual?

15, Dmin@ normal operating conditions, are the UPS umts configmed in the Auto-restart or Manual-restart mode?

16. What is the power source for the motors which operate CB3 and CB4? What is the minimum voltage and. current required from this source?

What is the time required for the motor to complete a full range of motion under the minimum voltage and current conditions?

POC: Tlmnas J. Pohida U.S. Nuclear Regulatory Commission 301<92~

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0 Niagara Mohawk Power Corporation November 20, 1991 Prior to the meeting, the NRC Incident Investigation Team had developed a

series of questions regarding the UPS.

The questions (Enclosure

2) were provided to NMPC and Exide Electronics prior to the meeting.

NMPC and Exide Electronics provided oral responses to these questions during the meeting.

At the conclusion of the meeting, the NRC staff representatives informed the NMPC representatives that the NRC staff would respond in writing to Mr. Sylvia's letter dated October 23, 1991.

Enclosur es:

1.

List of Attendees 2.

UPS guestions cc w/enclosures:

See next page Original Signed By:

Donald S.

Brinkman, Senior Project Manager Project Directorate I-I Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation DISTRIBUTION:

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