05000245/LER-1996-049, :on 960524,EDG & Gas Turbine Generator Has Potential to Malfunction During Seismic Event.Caused by Original Design Deficiency.Relay Replacements Being Identified

:on 960524,EDG & Gas Turbine Generator Has Potential to Malfunction During Seismic Event.Caused by Original Design Deficiency.Relay Replacements Being Identified

ML20133G467
Person / Time
Site:	Millstone
Issue date:	01/10/1997
From:	Robert Walpole NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20133G460	List: 05000245/LER-1996-049, :on 960524,EDG & Gas Turbine Generator Has Potential to Malfunction During Seismic Event.Caused by Original Design Deficiency.Relay Replacements Being Identified 05000245/LER-1996-049-01, Forwards LER 96-049-01,documenting Event That Occurred at Mnps,Unit 1 on 960524,per 10CFR50.73(a)(2)(i) & 10CFR50.73(a)(2)(v).Util Commitments Listed
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, LER-96-049, LER-96-49, NUDOCS 9701160057
Download: ML20133G467 (4)

LER-1996-049, on 960524,EDG & Gas Turbine Generator Has Potential to Malfunction During Seismic Event.Caused by Original Design Deficiency.Relay Replacements Being Identified

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)
2451996049R00 - NRC Website

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d NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO.3150-0104 I4-95)

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FACluTY NAME 11)

DOCKET NUMSER 12)

PAGE (3)

Millstone Nuclear Power Station Unit 1 05000245 1 of 4 s

TITLE 44)

Emergency Diesel Generator and Gas Turbine Relays May Not Function During Seismic Event EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8) i MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FAC!UTY NAME DOCKET NUMBER NUMBER 05 24 96 96 049 01 01 10 97 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR I: (Check one or more) (11)

MODE (9)

N 20.2201(b) 20.2203(a)(2)(v)

X 50.73(a)(2)(i>

50.73(a)(2)(viii) j POWER 20.2203(aH1) 20.2203(a)(3hi) 50.73(a)(2)(ii) 50.73(a)(2)(x) j LEVEL (10) 000 20.2203(aH2Hi) 20.2203(aH3Hii) 50.73(aH2)(iii) 73.71 20.2203(aH2)(ii) 20.2203(a)(4) 50.73(a)(2Hiv)

OTHER 3

50.36(cH1 >

X 50.73(aH2)(y) specify in Abstract below 20.2203(a)(2)(iii) i or in NRC Forrn 366A 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (include Area Codel i

Robert W. Walpole, Nuclear Licensing Supervisor (860)440-2191 j

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO NPROS

^

i i

s SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR SUBMISSION f

YES NO (if yes, complete EXPECTED SUBMISSION DATE).

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On May 24,1996 at 0730 hours0.00845 days <br />0.203 hours <br />0.00121 weeks <br />2.77765e-4 months <br />, with the plant in a COLD SHUTDOWN condition, Design Engineering personnel determined that relays associated with the Emergency Diesel Generator (EDG) and Gas Turbine Generator had a j

potential to malfunction during a seismic event. The potential relay malfunction could have resulted in a lockout of the generators which then would have required a manual action to reset the protective (lockout) relays to restore the EDG and Gas Turbine. The relays were being evaluated under the ongoing USl A-46 program in response to Generic Letter 87-02. The relays were " low ruggedness" or bad actor relays as well as relays with inadequate seismic capacity. The relays are believed to be susceptible to contact chatter (momentary change of state) during the vibratory motion i

resulting from a seismic event. The cause of this event is associated to original design as relay performance during l

vibratory motion was not known or identified as a design issue. This condition was promptly reported under 10 CFR l

50.72(b)(2)(iii)(D) on May 24,1996, and is reportable under 10 CFR 50.73(a)(2)(v)(D) as a condition that alone could have prevented the fulfillment of the safety function of systems needed to mitigate the consequences of an accident.

a 1

Due to the historical inoperability of these systems, this event is also reportable under 10 CFR 50.73(a)(2)(i) as a condition prohibited by the plant's Technical Specifications. The safety consequence of this event is low since there were no seismic events. The relay evaluations are continuing and the relay replacements are being identified. The qualification of existing equipment, some of which are not addressed in EPRI NP-7147, is being researched through the manufacturer. The combination of replacement and definition of equipment capability will result in fully qualified re!avs beina in service.

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9701160057 970110 PDR ADOCK 05000245 s

PDR

FORM 366A U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

' FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION Millstone Nuclear Power Station Unit 1 05000245 NUMRER NUMBER 2 of 4 96

-- l 049 01 l

t TEXT (11more space is required, use additional copies of NRC Form 366A) 117) i 1.

Description of Event

i On May 24,1996 at 0730 hours0.00845 days <br />0.203 hours <br />0.00121 weeks <br />2.77765e-4 months <br />, with the plant in a COLD SHUTDOWN condition, Design Engineering i

personnel determined that relays associated with the EDG and Gas Turbine Generator had a potential to malfunction during an earthquake. This relay malfunction could have resulted in a lockout of the generators which would require manual action to reset the protective (lockout) relays and restore the EDG and Gas Turbine. The relays were being evaluated under the ongoing program in response to GL 87-02, " Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, USl A-46". The program i

reviews are being conducted in accordance with the " Generic implementation Procedure, Rev. 2" and the

" Supplement to GL 87-02: SSER No. 2," dated May 22,1992, as identified in the response to GL 87-02, Supplement 1, dated September 21,1992. The relays were " low ruggedness" or bad actor relays as well as relays with inadequate seismic capacity as defined in EPRI NP-7147-SL, " Seismic Ruggedness of Relays",

and EPRI NP-7148-SL, " Procedure for Evaluating Nuclear Power Plant Relay Seismic Functionality", the documents endorsed for relay capacity reviews. The relays are believed to be susceptible to contact chatter (momentary change of state) during the vibratory motion resulting from an earthquake. This condition renders both on-site power supplies inoperable. This condition was promptly reported under 10CFR50.72(b)(2)(iii)(D) on May 24,1996, as a condition that alone could have prevented the fulfillment of the safety function of systems needed to mitigate the consequences of an accident. The resolution of the relay issues for Millstone Unit No.1 is an ongoing effort. As stated in LER 96-003, dated February 12, 1996, Northeast Nuclear Energy Company (NNECO) intended to report all issues identified through the USl A-46 program in one final supplement to LER 96-003 by January 10, 1997. NNECO has subsequently determined that it would be more appropriate to submit separate LERs for the relay issue and the seismic anchorage issue.

l lI.

Cause of Event

The cause of this event is an original design deficiency as the dynamic behavior of relays during vibratory l

motion was not quantitatively known. The data which is now available is the result of the large population of components which have been subjected to dynamic testing using accepted test standards (IEEE C37.98 and 344-75). This discovery is entirely consistent with the promulgation of GL 87-02 which sought to review existing equipment in light of the great population of known earthquake performance records from testing and real earthquakes.

The cause of the event, after extensive investigation appears to center on the lack of knowledge of the impact of vibratory motion on the relays and a lack of test data to understand dynamic behavior. The only i

exception to this which has been identified is the relay, Model CFD, which was identified in IE Notice 85-

82. In our evaluations conducted in 1986, several CFD relays were evaluated and found to be acceptable, l

Subsequent to this evaluation, EPRI 7148 was published in December 1990, identifying the CFD relay as a Low Ruggedness Relay. This data, combined with the in cabinet amplification values given for use in the USI-A-46 evaluation change the conclusions reached previously regarding the suitability of the CFD relay.

j lit. Analysis of Event This event is reportable under 10CFR50.73(a)(2)(v)(D) as a condition that alone could have prevented the fulfillment of the safety function of systems needed to mitigate the consequences of an accident. Due to the historical inoperability of these systems, this event is also reportable under 10CFR50.73(a)(2)(i) as a condition prohibited by the plant's Technical Specifications. The on-site power supplies, EDG and Gas 1

• U.S. NUCLEAR REGULATORY CoMMISslON (4 95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER ((,)

PAGE (3)

YEAR SEQUENTIAL REVISION Millstone Nuclear Power Station Unit 1 05000245 NUMBER NUMBER 3 of 4 96 049 01 l

TEXT lif more space is required, use additional copies of NRC Form 366A) (17)

Turbine Generator are designed to start automatically on detection of an Loss of Normal Power (LNP) such as would result from a seismic event. The condition described in this report would have prevented the design function from being achieved without manual action to reset control circuits. In the case of the Gas Turbine, the protective circuitry would have resulted in a five minute lock out which can not be overridden by an j

operator action

l There were no safety consequences of this event as the relays have never been challenged by a seismic event and thus have never misoperated during runs of the EDG or the Gas Turbine. The relays which are not machine mounted, will perform all intended functions when not subjected to vibratory loads.

IV. Corrective Action

The relay evaluations are continuing and the relay replacements are being identified. The replacement relays l

will be qualified by current qualification methods to assure proper function during a postulated earthquake.

The qualification of existing equipment, some of which are not addressed in EPRI NP-7147 (i.e. no Generic Equipment Ruggedness Spectra are available) is being researched through the equipment manufacturer, General Electric. The combination of replacement and definition of equipment capability will result in fully qualified relays being in service. The inadequate relays will be replaced prior to startup for operating cycle 16.

The results of the entire A-46 program will be submitted to NRC within 6 months of completing RFO 15 as previously stated in LER 96-003-01 and committed to in the response to GL 87-02 Supplement 1 dated September 21,1992. This report will also summarize the relay replacements.

I V.

Additional Information

Similar Events LER 96-007 " Emergency Gas Turbine Generator and Emergency Diesel Generator Inoperable Simultaneously" This LER documents an event where the Emergency Gas Turbine Generator was determined to have been inoperable on several occasions due to a fuel oil forwarding pump being out of service while the EDG was also inoperable simultaneously for short periods of time for surveillance testing and maintenance. However, there were no seismic issues involved.

LER 96-003 " Seismic Deficiencies identified Through the USI A-46 Program" l

This LER documents a seismic deficiency with the EDG day tank anchorage discovered through a walkdown performed as part of the USl A-46 program. Also the vibration isolator support system of the turbine building secondary cooling water (TBSCCW) air coolers did not meet the seismic adequacy screening criteria. The EDG and TBSCCW were declared inoperable. The LER states that the evaluation of actions required to resolve USl A-46 program outliers was continuing.

LER 91-028 " Seismic Interaction on TBSCCW System" This LER documents that due to inadequate anchoring of room coolers, a seismic event could have resulted in loss of TBSCCW which in turn would have resulted in inoperability of EDG and

1. U.S. NUCLEAR REGULATORY COMMISSION to-95)

UCENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION Millstone Nuclear Power Station Unit 1 05000245 NUMBER NUMBER 4 of 4 96 049 01 l

TEXT (If more space is required, use additional copies of NRC Form 366A) til)

Feedwater Coolant injection System. As part of the corrective actions, it was stated that "the adequacy for all safety related electrical and mechanical equipment is scheduled to be reviewed under the upcoming USl A-46 inspection program.

This inspection program during its implementation will analyze all safety related component anchorage and ensure the correct number of anchor bolts are installed."

Manufacturer Data None l

WRC FORM 366A (4-95)