05000336/LER-1997-021-02, :on 970423,investigation Indicated That Burned Out Lamp Failed W/Internal Short Circuit.Caused by Inadequate Scope of Review in Response to NRC Info Notice 94-68.Engineering Evaluation Shall Be Performed

:on 970423,investigation Indicated That Burned Out Lamp Failed W/Internal Short Circuit.Caused by Inadequate Scope of Review in Response to NRC Info Notice 94-68.Engineering Evaluation Shall Be Performed

ML20141M029
Person / Time
Site:	Millstone
Issue date:	05/23/1997
From:	Joshi R NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20141M022	List: 05000336/LER-1997-021, Forwards LER 97-021-00,documenting an Event That Occurred on 970423,per 10CFR50.73(a)(2)(ii).Commitments Made within Ltr, Submitted 05000336/LER-1997-021-02, :on 970423,investigation Indicated That Burned Out Lamp Failed W/Internal Short Circuit.Caused by Inadequate Scope of Review in Response to NRC Info Notice 94-68.Engineering Evaluation Shall Be Performed
References
IEIN-94-068, IEIN-94-68, LER-97-021-02, LER-97-21-2, NUDOCS 9706040146
Download: ML20141M029 (3)

LER-1997-021, on 970423,investigation Indicated That Burned Out Lamp Failed W/Internal Short Circuit.Caused by Inadequate Scope of Review in Response to NRC Info Notice 94-68.Engineering Evaluation Shall Be Performed

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
3361997021R02 - NRC Website

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. NkE, FORM 366

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TickrrY umE m oocnET uumeEnizi PAoE m Millstone Nuclear Power Station Unit 2 05000336 1OF3 1

l TITLE m Non-QA lamps int,talled in the QA Category 1 Reactor Protection System EVENT DATE (5)

LER NUEIBER (6)

REPORT DATE (7) oTHER FACILITIES INVOLVED (8)

SE U AL E $ N MONTH DAY YEAR YEAR MONTH DAY YEAR U

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04 23 97 97 021 --

00 05 23 97 OPE 9ATING THIS REPORT IS SUBMITTED PURSUANT To THF. REoUIREMENTS OF 10 CFR 5: (Check one or more) (11)

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N 2o.2201(b) 20.2203(a)W(v) 50.73(a)(2)(i) 50.73(a)(2)(viii)

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X 50.73(a)(2)(ii) 50.73(al(2)(x)

LEVEL (10) 000 20.2203(al(2)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(iii) 73.71 R 2203(a)(2)(id 2o.2203(a)(4) 50.73(a)(2)(iv) oTHER 5.2203(a)(2)(iii) 50.36(c)(1) 50.73(a)(2)(v)

Specify in Abstract below 0

20.2203(a)(2)(iv) 50.30(c)(2) 50.73(a)(2)(vil) in NRC Form 366A

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LICENSEE CONTACT FoR THis LER (12)

NAME TELEPHOtd NUMBER 8 include Area Codel R. G. Joshi, MP2 Nuclear Licensing (860)440-2080 COMPLETE ONE LINE FoR EACH COMPONENT FAILURj TsCRIBED IN THIS REPORT (13)

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SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR

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(if yes, complete EXPECTED SUBMISSION DATE).

I A11STRACT (Limit to 1400 spaces,6.e., approximately15 single-spacedtypewnttenlines) (16)

On April 23,1997, an investigation was completed which indicated that a burned out lamp had failed with an internal short circuit. This investigation was initiated due to an April 8,1997, event in which a technician noticed a burned out lamp on channel B Low Reactor Ccolant Pump (RCP) Speed trip unit and an unusualindicator light configuration on the Reactor Protection System (RPS) BC matrix. The technician was preparing to per'orm a surveillance test at the time of discovery. When he rernoved the burned out lamp in the trip unit for the Low RCP Speed trip unit, the other l

lights returned to normal. The failed lamp was replaced with a new lamp. After furtherinvestigation it was postulated that had this failure occurred during operation, there is a possibility that the BC trip matrix could have been l

unavailable. The other five trip matrices were not affected and would have caused a trip if required. The investigation l

found that Non-QA lamps were being used in the RPS, a OA Category 1 system, contrary to system design ' oasis. At j

l 4.e time of discovery the unit was defueled.

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The cause of this event was an inadequate scope of review in response to NRC Information Notice 94-68: Safety Related Equipment Failures Caused by Faulted Indicating Lamps.

t As correctiv? action an engineering evaluation of low voltage lamp circuit design in safety related equipment which 3 -

was not reviewed as part of the Information Notice 94-68 response sha'i be performed. This evaluation will determine L

' i' lamp iso latiori is adequate or if a fault tolerant design exists. It will also evaluate possible interaction between OA end non-QA systems. This action will be completed before entering MODE 4 from the current outage.

9706040146 -770523 PDR ADOCK 05000336 s

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,NRC roHM 3ESA U.s. NUCLEAR REGulAl oRY COMMissioM (4 95)

UCENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER (6)

PAGE (3)

SEQUENTIAL REVislON YEAR NUMBER NUMBER 2OF3 Millstone Nuclear Power Station Unit 2 05000336 97

- 021 -

00 TLxT Uf more spect 's required. use additionalcopies of NHC form 366A) (11) l.

Description of Event

4 On April 23,1997, an investigation was completed which indicated that a burned out lamp had failed with an internal short circuit. This investigation was initiated due to an April 8,1997, event in which a technician noticed a burned out lamp and an unusual indicator light configuration on the Reactor Protection System (RPS) Channel B (BC matrix). The technician was preparing M perform a surveillance test at the time of discovery. When he removed the burned out lamp in the trip unit for the Low Reactor Coolant Pump (RCP) Speed trip, tha other lights r

retumed to normal. The failed lamp was replaced with a new lamp. After further investigation it was postulaLad t

that had this failure occurred during operation, there is a possibility thst the BC trip matrix could have been unavailable. The other five trip matrices were not affected and would have caused a trip if required. The investigation found that Non-QA lamps were being used in the RPS, a OA Category 1 (Cat-1) system, contrary to system design basis. At the time of discovery the unit was defueled.

This condition is being reported pursuant to 10 CFR 50.73(a)(2)(ii)(B) a condition that is outside the design basis of the plant.

II.

.C_ause of Event The cause of tnis everd was an inadequate scope of review in response to NRC Information Notice 94-68: Safety Related Equipment Failures Caused by Faulted Indicating Lamps.

111. Analysis of Event The RPS Channels provide the information to initiate protective action through bistable trip units. There are four independent, redundant measurement channels for each monitored parameter providing independent measurement of the same variable by each of the protective channels, A, B, C, & D. Each channel output is a bistable trip unit with three tnp relay contacts. These contacts are arranged in six logic matrices; AB, AC, AD, BC, BD, & CD, forming an "any 2 out of 4" coincidence trip logic for the four protective channels. Each logic matrix has 4 matrix relays which are normally energized. in parallel with each matrix relay is a lamp which is illuminated when the matrix relay is energized. Deenergizing the 4 matrix relays from any one of the 6 logic matrices results in a plant trip (Control Element Assemblies insert into the core). Thus, if one tr!p matrix fails to operate, any one of the l

remaining five can initiate a trip.

The shorted lamp in the channel B Low RCP Speed trip unit allowed power to reach the BC logic matrix relays through a circuit which was created by the shorted lamp. A pre;iminary review of the circuit shows the matnx relays would have about half of the normal voltage applied to them. This would not be enough voltage in pick up l

l the matrix relays. however, if they were energized (normal operating condition, deenergiza to trip)it may or may l

not be enough voltage to prevent the matrix relays from dropping out, when required, to produce a trip. A shorted lamp will affect only the matrix in which it is installed, and it would have no effect on the otner 5 matrices.

For the purpose of system analysis, the use of Non-QA lamps in the QA Cat-1 RPS could introduce multiple common mode failures where more than one channel or matrix could be affected. Since Non-QA lamps are used, single failure analysis cannot be used.

NRC FORM 3ffiA 14 95)

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,,NRctoRM 366A.

U.s. ftUCLEAR REGULATORY commission l

(4-96) i LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION i

FACILITY NAME (11 ooCKET LER NUMBER (6)

PAGE (3)

SEQUENTIAL REVIStoN YEAR NUMBER NUMBER 3OF3 Millstone Nuclear Power Station Unit 2 05000336

}

97 021 -

00 TEXT (11 more space is required, use aciditionalcopies of NRC form 366A) (11}

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The NRC issued information Notice 94-68 which identified safety related equipment fai! ares caused by faulted indicating lamps. In response to IN 94-68 Northeast Nuclear Electric Company (NNECO) conducted a review of safety related circuits for all three Millstone units. This review identified and corrected some indicating lamp designs which did not provide isolation of the lamp from the control circuit. However, at unit 2, this review only j

included the 120 volt AC and DC indication lamp circuits. The low voltage circuits (i.e. 28 volt) were not reviewed l

because the was no history of shorted lamps in these circuits and it was believed that the filament in the low l

voltage lamps were not large enough to fail and cause an internal short.

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In light of the fact that only one of the 6 matrices is affected by a failed lamp and this is the first known failure of its

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kind in a RPS, this is not considered to be a safety significant condition.

IV. Corrective Action

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As corrective action an engineering evaluation of low voltage lamp circuit design in safety related equipment which

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was not reviewed as part of the information Notice 94-68 response shall be performed. This evaluation will determine if lamp isolation is adequate or if a fault tolerant design exists. It will also evaluate possible interaction between QA and non-QA systems. This action will be completed before entering MODE 4 from the current outage.

V.

Additional information

Similar Events No previous similar events involving a lamp failure which could cause a channel or train failure to actuate were found.

Ensrgy Industry identification System (Ells) codes are identified in the text as [XX].

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NRC FofM 366A (4 96) 1