05000410/LER-2003-001, Regarding Oscillation Power Range Scram Due to a Power and Flow Perturbations Resulting from a Power Supply Failure

Regarding Oscillation Power Range Scram Due to a Power and Flow Perturbations Resulting from a Power Supply Failure

ML032810130
Person / Time
Site:	Nine Mile Point
Issue date:	09/22/2003
From:	Hopkins L Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NMP2L 2101 LER 03-001-00
Download: ML032810130 (5)

LER-2003-001, Regarding Oscillation Power Range Scram Due to a Power and Flow Perturbations Resulting from a Power Supply Failure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
4102003001R00 - NRC Website

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P.O. Box 63 Lycoming, New York 13093 I

Constellation Energy Group Nine Mile Point Nuclear Station September 22, 2003 NMP2L 2101 United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

Nine Mile Point Unit 2 Docket No. 50-410 Facility Operating License No. NPF-69 Licensee Event Report 03-001, "Oscillation Power Range Scram due to Power and Flow Perturbations Resulting from a Power Supply Failure" Gentlemen:

In accordance with 10 CER 50.73(a)(2)(iv)(A), we are submitting Licensee Event Report (LER)03-001, "Oscillation Power Range Scram due to Power and Flow Perturbations Resulting from a Power Supply Failure."

Very truly yours, Lawrence A. Hopkins Plant General Manager LAHIKLE/bjh Attachment cc:

Mr. H. J. Miller, NRC Regional Administrator, Region I Mr. G. K. Hunegs, NRC Senior Resident Inspector 2,.,

SJ59

NRCG FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 7-31-2004 Estimated burden per response to comply with this mandatory Information collection request 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are Incorporated Into the licensing process and fed back to Industry. Send comments regarding burden estimate to the Records Management Branch (T-6 E6). U.S. Nuclear Regulatory Commission. Washington, DC LICENSEE EVENT REPORT (LER) 20555-0001, or by Internet e-mail to bisltnrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202 (3150-0104). Office of Management and Budget. Washington, DC 20503. I a means used to Impose information collection does not display a currently valid OMB contrl number, the NRC may not conduct or sponsor, and a person is not required to respond to, the Information collection.

FACILITY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

Nine Mile Point, Unit 2 05000410 1 OF 4

TITLE ()

Oscillation Power Range Scram due to Power and Flow Perturbations Resulting from a Power Supply Failure EVENT DATE (S)

LER NUMBER (6)

REPORT DATE (7 OTHER FACILITIES INVOLVED (6)

MO DAY YEAR YEAR SEOUENTIAL REV MO DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO 05000 07 24 2003 2003 -

001 -00 09 22 2003 FACLITY NAME DOCKET NUMBER

- I 05000 OPERATING THIS REPORT IS SUBMfTED PURSUANT TO THE REQUIREMENTS OF 10 CFR I: (Check all that apply) (11)

MODE (9) 1 202201(b) 20.2203(a)(3)X1) 50.73(a)(2)(ii)(B) 50.73(a)(2)(0x)(A)

POWER LEVEL (10) 20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(ii) 50.73(a)(2)(x) 100 20.2203(a)(1)

_ 50.36(c)(1)(I)(A)

X 50.73(a)(2)(lv)(A) 73.71 (a)(4) j,'.

'i'20.2203(a)(2)()

50.36(c)(1)(I1)(A) 50.73(a)(2Xv)(A) 73.71 (a)(5) 20.2203(a)(2)(1l) 50.36(c)(2) 50.73(a)(2)(v)B)

OTHER 0

00 0

If t it0;4

_20.2203(a)(2)(iii)

_50.46(a)(3X11)

_50s.73(a)(2)(v)(C)

__ SpecifyIn Abstract below or In 20.2203(a)(2)(iv) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D)

(ff more space Is required, use additional copies of NUBC FR(2 366 (1N7)

I. Descriptlon of Event On July 24, 2003, at approximately 0550 hours0.00637 days <br />0.153 hours <br />9.093915e-4 weeks <br />2.09275e-4 months <br />, Nine Mile Point Unit 2 (NMP2) experienced a failure of instrument power supply C33-1<611, which caused a partial loss of power to feedwater control, main steam flow instrumentation, and reactor recirculation flow control. Prior to the failure of the power supply, two feedwater pumps and two recirculation pumps were operating. The loss of power to recirculation relays resulted in both recirculation pumps shifting from fast speed to slow speed. The reduction In flow caused reactor power to drop from 100 percent to approximately 45 percent. The reduction In core flow caused the reactor to enter the exit region of the power to flow map in which core instability is possible.

The power supply failure also caused the loss of 3 out of 4 steam flow input signals to feedwater level control, which resulted in feedwater level control valve 2FWS-LV1 OA closing. Additionally, the power supply failure caused feedwater level control valve 2FWS-LV1OB to fail "as Is" at approximately 52 percent open. With 2FWS-LV1OB at 52 percent open and reactor power reduced, reactor vessel level began to increase. To keep reactor water level from increasing further, operators secured reactor feedwater pump 2FWS-P1 B. Upon securing feedwater pump 2FWS-P1 B a reactor recirculation flow runback occurred, reducing power to approximately 35 percent. A false low reactor vessel water level, resulting from the failed power supply, coincident with only one running feedwater pump (after securing the B reactor feedwater pump) satisfied the recirculation flow runback initiation logic. Approximately three minutes after the recirculation flow runback, Oscillation Power Range Monitor (OPRM) channels 1 and 4 detected power oscillations and initiated an automatic reactor scram (a period based algorithm scram) at approximately 0557 hours0.00645 days <br />0.155 hours <br />9.209656e-4 weeks <br />2.119385e-4 months <br />. At the time of the scram, reactor power was approximately 45 percent and core flow was approximately 28 percent.

All control rods fully inserted. After the scram, the turbine bypass valves were used to control reactor pressure. Post scram, operators took manual-electric control of 2FWS-LV1OA (from the control room) and used feedwater pump 2FWS-P1A to control reactor water level.

Troubleshooting determined that power supply C33-K611, a Lambda model LRS-54-24, had failed. A temporary power supply was installed in parallel with the failed power supply C33-K61 1 and power to control 2FWS-LV1 OB was re-established. Power supply C33-K611 is located in panel 2CEC-PNL612, along with power supplies C33-1<612 and C33-K613. All three power supplies were Lambda model LRS-54-24 and all three were replaced with auctioneering type Lambda model LZS-250-3. The auctioneering type power supply reduces the single point vulnerability.

II. Cause of Event

The cause of the power and flow perturbations leading to the reactor scram was failed power supply C33-K611. The power supply failed because of the age related failure of internal components and no specific preventive maintenance program activity to refurbish or replace the power supply. Power supply C33-K611 was manufactured circa 1985.

There was no specific preventive maintenance program activity to refurbish or replace the power supply. Contributing causes were the lack of power supply redundancy for important operational loads and inadequate distribution of loads on the power supply, i.e. the powering of 3 out of 4 main steam line flow instruments from one power supply. The significance of the load distribution is reduced by using the auctioneering type power supply.

NRC FORM 368A (1-2001)

NRb (If more space Ls requred, use addiffonal copies of NRC Form 366)

(17)

Ill. Analysis of Event This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a critical reactor scram.

Given the power supply failure, the feedwater system and recirculation system responded as designed.

All control rods fully inserted.

Reactor Core Isolation Cooling was available post scram but was not needed.

No Emergency Core Cooling Systems actuated or should have actuated.

A General Electric evaluation confirmed that Minimum Critical Power Ratio (MCPR) safety limit protection was provided by the OPRM reactor trip.

A probabilistic risk assessment of the event concluded that the estimated Conditional Core Damage Probability for the event was less than 1 E-6 and therefore, the event was not considered risk significant.

Based on the above, the event did not pose a threat to the health and safety of the public.

IV. Corrective Actions

1. Power supply C33-K611 and two additional power supplies (C33-K612 and C33-K613) were each replaced with an auctioneer style power supply, Lambda Model LZS-250-3.

2. Activities were initiated to replace non-safety related power supplies whose failure could result in a reactor scram or impact mission critical equipment, or cause a significant plant transient.

3. An engineering evaluation of load redistribution on power supply C33-K611 has been initiated.

4.

Power supply C33-K611 was added to the preventive maintenance program.

NRV (If more space Is requred, use add tonal copies of NRC Form 366A) (17)

V. Additional Information

1. Failed Components:

Lambda power supply, Model Number LRS-54-24, Manufacturer: Lambda Electronics

2.

Previous similar events

Licensee Event Report 89-024, "Manual Scram Due to Equipment Failure and Entry into Restricted Zone,'

documents the failure of a Lambda LRS-54-24 power supply on September 8, 1989. The cause of the reactor scram was identified as failure of the power supply. The cause of the power supply failure was not identified.

3.

Identification of components referred to in this Licensee Event Report:

Components IE Feedwater System Mainsteam System Turbine Bypass Oscillation Power Range Monitors Reactor Protection System Recirculation System Reactor Core Reactor Core Isolation Cooling System Instrument Power System Control rod Pump Valve Power Supply Reactor Vessel Panel Flow Indicator Relay MEE 805 System ID IEEE 803A Function SJ SB TG IG JC AD AC BN EE AC AD SB, TG, AD SJ, SB, AD, EE AD EE SB AD N/A N/A N/A N/A N/A N/A N/A N/A N/A ROD P

LCV, PCV, FCV RJX VSL PL Fl RLY