05000220/LER-2012-002, Regarding Automatic Reactor Scram Due to Automatic Generator Protective Trip

Regarding Automatic Reactor Scram Due to Automatic Generator Protective Trip

ML12331A327
Person / Time
Site:	Nine Mile Point
Issue date:	11/19/2012
From:	Philippon M Constellation Energy Group, EDF Group, Nine Mile Point
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 12-002-00
Download: ML12331A327 (7)

LER-2012-002, Regarding Automatic Reactor Scram Due to Automatic Generator Protective Trip

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv)(B), System Actuation
2202012002R00 - NRC Website

text

Michel A. Philippon Plant General Manager P.O. Box 63 Lycoming, New York 13093 315.349.5205 315.349.1321 Fax CENG.

a joint venture of 0 C.nellioef,=on eof NINE MILE POINT NUCLEAR STATION November 19, 2012 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:

SUBJECT:

Document Control Desk Nine Mile Point Nuclear Station Unit No. 1; Docket No. 50-220 Licensee Event Report 2012-002, Generator Protective Trip Automatic Reactor Scram due to Automatic In accordance with 10 CFR 50.73(a)(2)(iv)(A), please find attached Licensee Event Report 2012-002, Automatic Reactor Scram due to Automatic Generator Protective Trip.

There are no regulatory commitments in this submittal.

Should you have questions regarding the information in this submittal, please contact John J. Dosa, Director Licensing, at (315) 349-5219.

Very truly yours, MAP/KJK

Attachment:

Licensee Event Report 2012-002, Automatic Reactor Scram due to Automatic Generator Protective Trip cc:

NRC Project Manager NRC Resident Inspector NRC Regional Administrator

ATTACHMENT LICENSEE EVENT REPORT 2012-002 AUTOMATIC REACTOR SCRAM DUE TO AUTOMATIC GENERATOR PROTECTIVE TRIP Nine Mile Point Nuclear Station, LLC November 19, 2012

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Nine Mile Point Unit 1 05000220 1 of 5

4. TITLE Automatic Reactor Scram due to Automatic Generator Protective Trip

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

I FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NA NA I

I FACILITY NAME DOCKET NUMBER 09 20 2012 2012 002 0

1 1 19 2012 NA NA

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)

El 20.2201(b)

E3 20.2203(a)(3)(i) 0l 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii)

N [1 20.2201(d)

[] 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

El 20.2203(a)(1)

El 20.2203(a)(4)

[E 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

10. POWER LEVEL

[] 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

El 20.2203(a)(2)(ii)

[I 50.36(c)(1)(ii)(A)

ED 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

El 20.2203(a)(2)(iii)

[E 50.36(c)(2)

El 50.73(a)(2)(v)(A)

El 73.71(a)(4) 100 El 20.2203(a)(2)(iv)

E3 50.46(a)(3)(ii)

[I 50.73(a)(2)(v)(B)

[1 73.71(a)(5)

El 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

[I 50.73(a)(2)(v)(C)

[I OTHER El 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

El 50.73(a)(2)(v)(D)

Specify in Abstract below or in C. INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

There were no inoperable components or systems that contributed to this event.

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES

All times below are approximate and occurred on 9/20/2012; 0922 -

The operator observes oscillations on the AVR causing the buck/boost meter to fluctuate.

The operator attempts to null the AVR, but was unsuccessful due to the oscillations.

0923 -

The AVR is removed from service, the generator trips and the reactor scrams.

0923 -

HPCI mode of operation initiates on low reactor water level.

0924 Reactor water level is restored above the low water level set point and HPCI system secured.

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED

None

F. METHOD OF DISCOVERY

This event was discovered by the operators when the annunciators for generator trip and RPS initiation of the reactor scram alarmed in the control room.

G. MAJOR OPERATOR ACTION:

On September 20, 2012, at 0922, the operator observed oscillations on the AVR causing the buck/boost meter to fluctuate. The operator attempted to null the AVR, but was unsuccessful due to the oscillations.

After the scram, the operators verified all rods fully inserted. No other actions were required to support shutting down the reactor.

H. SAFETY SYSTEM RESPONSES:

All safety systems responded per design. There was no loss of offsite power to the onsite emergency buses, the HPCI system initiated as designed, and the ECCS systems were available, but not called upon to support the safe shutdown of the reactor.

II. CAUSE OF THE EVENT

The root cause of this event is that in 2003, a failure to follow the existing administrative procedure guidance for procedure change evaluations resulted in an inadequate review of the procedure change

and introduction of a latent error into the amplidyne operating procedure. The Design Engineering organization was not afforded a cross disciplinary review of the procedure to ensure the change in operating strategy was aligned with the design standards for the system. The procedure change had been implemented in an attempt to increase current flow through the amplidyne commutator brushes to reduce wear. The impact of operating with a 10-20 volt boost amplidyne output was not fully understood by personnel making the change. The procedure change did not address how voltage regulation would be affected when operating with a 10-20 volt boost prior to automatically or manually transferring to manual voltage regulation without nulling the amplidyne output.

The contributing equipment cause was due to degraded sub-components in the AVR control circuit.

The following degraded sub-components initiated the buck/boost meter oscillations and MVAR swings.

Degraded capacitor on the AVR card Erratic output of potentiometers A3P and A2P High resistance contact on the 90R control switch The NMP2 generator control system uses an Alterrex Excitation System which contains an Auto-tracking section that maintains the Manual Voltage Regulator within 2 volts of the Automatic Voltage Regulator; thus, NMP2 is not susceptible to the type of failure that occurred at NMP1.

This event was entered into the Nine Mile Point Nuclear Station (NMPNS) corrective action program (CR-2012-008673).

III. ANALYSIS OF THE EVENT

This event is reportable in accordance with 10 CFR 50.73 (a)(2)(iv)(A), as an event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph 10 CFR 50.73 (a)(2)(iv)(B). Both the RPS and HPCI system (an operating mode of the feedwater system) were actuated during this event. Both systems are listed in 10 CFR 50.73 (a)(2)(iv)(B).

Except for the failure of the AVR, there were no equipment failures associated with this event. All other plant systems performed per design. Plant parameters, other than the reactor water level, remained within normal values throughout the event. There was no loss of offsite power to the onsite emergency buses, HPCI initiated as designed, and the ECCS systems were available, but not called upon to support the safe shutdown of the reactor.

Had a design basis accident occurred coincident with this event, plant systems would have responded per design to mitigate the accident. Based on the above considerations, the safety significance of this event is very low, and the event did not pose a threat to the health and safety of the public or plant personnel.

This event affects the NRC Regulatory Oversight Process (ROP) Index for Unplanned Scrams. Due to this scram, the Unplanned Scrams Index value will be 1.6 compared to the Green-to-White threshold value of greater than 3. This reduction will not result in entry into the "Increased Regulatory (White) Response Band."

IV. CORRECTIVE ACTIONS

A.

ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

1. The degraded sub-components of the AVR were replaced. The plant was returned to full power on September 26, 2012. The voltage regulator was operated in manual and performance monitored, prior to returning the AVR to service.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

1. The operating procedure was revised to operate the amplidyne at null (zero volts) position.

2. The NMP1 AVR is scheduled for replacement in the NMP1 2015 refueling outage.

V. ADDITIONAL INFORMATION

A. FAILED COMPONENTS:

Sub-components in the AVR control circuit found degraded:

capacitor on the AVR card potentiometers A3P and A2P 90R control switch B. PREVIOUS LERs ON SIMILAR EVENTS:

None C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:

COMPONENT IEEE 803 COMPONENT IDENTIFIER IEEE 805 SYSTEM IDENTIFICATION Capacitor on AVR card Voltage Regulator Main Generator Exciter Main Generator System Main Generator Output Power System High Pressure Coolant Injection System Reactor Protection System D. SPECIAL COMMENTS:

CAP EC*

EXC N/A N/A N/A N/A TB TB TB TB EL BJ JC None