05000346/LER-1997-001, :on 970122,nuclear Instrumentation Declared Inoperable & Incapable of Performing Safety Functions.Caused by Small Shift in Degraded Bottom Linear Amplifier.Power Range Bottom Linear Amplifier Replaced

:on 970122,nuclear Instrumentation Declared Inoperable & Incapable of Performing Safety Functions.Caused by Small Shift in Degraded Bottom Linear Amplifier.Power Range Bottom Linear Amplifier Replaced

ML20135B112
Person / Time
Site:	Davis Besse
Issue date:	02/21/1997
From:	Kraemer C, Lash J TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-97-001, LER-97-1, NP-33-97-001, NP-33-97-1, NUDOCS 9702280091
Download: ML20135B112 (4)

LER-1997-001, on 970122,nuclear Instrumentation Declared Inoperable & Incapable of Performing Safety Functions.Caused by Small Shift in Degraded Bottom Linear Amplifier.Power Range Bottom Linear Amplifier Replaced

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(1)
3461997001R00 - NRC Website

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TOLEDO EDISON A Centerior Energy Company EDISON PLAZA 300 MADISON AVENUE TOLEDO. OHIO 43652-0001 NP-33-97-001 Docket No. 50-346 License No. NPF-3 February 21, 1997 United States Nuclear Regulatory Commission Document Control Desk Washington, D. C.

20555 Ladies and Gentlemen LER 97-001 Davis-Besse Nuclear Power Station, Unit No. 1 Date of Occurrence - January 21, 1997 Enclosed please find Licensee Event Report 97-001, which is being submitted to provide 30 days written notification of the subject occurrence. This LER is being submitted in accordance with 10CFR50.73(a)(2)(i)(B).

l very truly yours, n LA

/

J s H. Lash Plant Manager Davis-Besse Nuclear Power Station CAK/dlc Enclosure cc:

Mr. A. B. Beach Regional Administrator

/

USNRC Region III V

7 Mr. Stan Stasek

/s DB-1 NRC Sr. Resident Inspector Utility Radiological Safety Board 9702280091 970221 l

PDR ADOCK 05000346 l

I S

PDR N

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150 0104 C>e2)

EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS 0

INFORMATION COLLECTIO 50.0 HRS. FORWARD LICENSEE ET7ENT REPORT (LER)

COuMENTS REGARDiuG N REQUEST:

UnDEN ESTIMATE 10 Tse iNFoRMATiON AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF (See reverse for required numtwr of digits / characters for each block)

MANAGEMENT AND DUDGET, WASHINGTON, DC 20503.

F ACILITY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

Davis-BeSSe Unit Number 1 l

05000 - 346 1 OF 3 TITLE (4)

Nuclear Instrumentation Inoperable in Excess of Technical Specification Action Statement Requirements EVENT DATE (5)

LER NUMilER (6)

REl' ORT NUMilLR (7)

OlllER l ACILillLS INVOLVED (8)

SLQULN ilAi kEVblON 1 ACILilY NAML DuaET NL MBLR MOND{

DAY

, YEAR YEAR NUMBE R NUMBLR MONTH DAY YEAR 05000

'* * * ^"'

01 22 97 97

-- 001 --

00 02 21 97 05 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR (: (Check one or more) (11)

MODE (9) 1 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b) 1 POWER 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

LEVEL (10) 100 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vis)

OTHER 20.405(a)(1)(iii) x 50.73(a)(2)(i) 50.73(a)(2)(viii)(A)

(Simcdy n Atswt 1

20.405(a)(1)(iv) 50.73(a)(2)(ti) 50.73(a)(2)(viii)(B) t*im amm text, 20.405(a)(1)(v) 50 73(a)(2)(iii) 50.73(a)(2)(x)LICENSEE CCHTACT FOR THIS LER (12) a%ME TELEPHONE NUMBER (include Area Code)

Cheryl A. Kraemer, Engineer - Licensing (419) 321-7153 COMPLETE ONE LINE FOR EACH COMPONEbT FAILURE DESCRIBED IN THIS REPORT (13)

CAUbb h)SILM COMPONENT MANLi-ACil kLk KEPOR'l Ahlb CAL'5E S WilM COMPONLNT MANUI ACTURLk REPOkIABLE TO NPRDS TU NPRDS j

X IG AMP B045 Y

1 SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MON T H DAY YEAH SUBMISSION YES X

NO DATE (15)

(if yes. complete EXPECTED SUBMISSION DATE)

ABSTRACT (Limit to 1400 spaces, i.e.,

approximately 1b single-spaced typewritten iines) (16)

At 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on January 22, 1997, with the Unit operating in Mode 1 at approximately 100 percent power, a Potential Condition Adverse to Quality Report (PCAQR) was initiated for NI-6 (power range nuclear instrument) reactor power imbalance signal. A Reactor Operator had noticed NI-6 (IG-AMP) imbalance to be reading more negative than expected..Upon investigation of this condition, NI-6 was determined to be in a degraded condition from 2151 hours0.0249 days <br />0.598 hours <br />0.00356 weeks <br />8.184555e-4 months <br /> until 2309 hours0.0267 days <br />0.641 hours <br />0.00382 weeks <br />8.785745e-4 months <br /> on January 21, 1997, and had shifted approximately 4 percent in the negative direction. A review of the degraded condition by Plant Engineerirg on January 23, 1997, determined that in its degraded condition, RPS Channel I which receives the NI-6 imbalance signal was inoperable and incapable of performing its intended safety function with respect to tripping on positive imbalance.

The initiating condition was that a degraded bottom linear amplifier caused a small shift of the indicated NI-6 reactor power imbalance and total power signal to RPS Channel 1.

The investigation revealed that the degraded condition existed for one hour and 18 minutes. Technical Specifications (TS) 3.3.1.1 allows an inoperable channel for no more than one hour.

This is being reported as a condition prohibited by the TS in accordance with 10 CFR 50.73 (a)(2)(i)(B). The power range bottom linear amplifier was replaced. An an enhancement, Licensed operators will be trained to make them more aware of instrument degradation of this nature by May 31, 1997.

a NRC FORM 366 (5 92)

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NRC FORM 306A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 I

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ESTIMATED BURDEN PER RESPONSE TO COMPLYWITH THIS LICENSEE EVENT REPORT (LER) l"!OT.*nEGMG" "'RL%e"OHE 0c^"MAuON U

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, TEXT CONTINUA.flON nEGUtATOsv COuuissiON. WASHINGTON,DC20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (31600104). OFFICE oF e

t MANAGEMENT AND BUDGET, WASHINGTON.DC20503.

1 F ACRJTY NAME (1)

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PAGE (3)

SEQUENHAL HEVISK)N Davis-Besse Unit Number 1 05000-346 97

--001 --

00 2 OF 3 TEXT (11more space is requ. red, use additoonal copies of NRC Form 366A) (17)

Description of Occurrence:

B At 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on January 22, 1997, with the Unit operating in Mode 1 at i

approximately 100 percent power, a Potential Condition Adverse to Quality Report (PCAQR) 97-0073 was initiated for power range nuclear instrument, NI-6.

It was discovered during shift turnover walkthroughs that the NI-6 reactor power imbalance signal was reading more negative than expected in comparison to the other 3 power range nuclear instruments,.

Investigation revealed that at 2151 hours0.0249 days <br />0.598 hours <br />0.00356 weeks <br />8.184555e-4 months <br /> on January 21, 1997, the NI-6 reactor power imbalance signal had shifted by approximately four percent in the negative direction and returned to a normal reading at 2309 hours0.0267 days <br />0.641 hours <br />0.00382 weeks <br />8.785745e-4 months <br /> on January 21, 1997. The NI-6 shift also caused the RPS l

Channel 1 total reactor power indication to shift upward approximately one percent. At the time of discovery, Reactor Engineering was consulted who determined that the imbalance signal was not an indication of the actual core condition and the core was operating normally.

l On January 23, 1997, upon review of PCAQR 97-0073, Plant Engineering issued an l

addendum to the PCAQR. The addendum reported that RPS Channel I was incapable of performing its specified safety function with respect to tripping on positive imbalance while the NI-6 reactor power imbalance signal was incorrect.

Due to the indicated negative shift of imbalance, aetaal reactor core positive imbalance could have been greater than the Tech Spec allowable imbalance value without a corresponding trip of RPS Channel 1.

As a result, RPS Channel I would l

not have performed its intended safety function and the Channel was inoperable.

Technical Specification Table 3.3-1 Action 2 states that with one channel of RPS l

delta flux inoperable, power operation may continue provided that the inoperable l

channel is placed in either the bypassed or tripped condition within ene hour and that the quadrant power tilt is monitored at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

It was determined that the undetected NI-6 reactor power imbalance signal read incorrectly for approximately one hour and 18 minutes during which time the channel was not declared inoperable and placed in either the bypassed or tripped l

condition. This represents a condition that is prohibited by the plant's Technical Specifications and is reportable in accordance with 10 CFR 50.73(a)(2)(1)(B).

On January 31, 1997 at 1154 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.39097e-4 months <br />, NI-6 reactor imbalance signal to RPS Channel 1 once again shifted. The plant entered TS 3.3.1.1 Action Statement 2.

Troubleshooting analysis indicated that the power range NI-6 bottom linear j

amplifier was the faulty component. This component was reple :3 and TS 3.3.1.1 was exited at 0925 on February 1, 1997.

Since replacement of i.he bottom linear amplifier, this adverse condition has not recurred.

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NRC FORM 306A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMJ NO. 3150 0104 i

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F ACILITV NAME (1)

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LER NUMBER (6)

PAGE (3)

SEQUENTIAL HEVISION Davis-Besse Unit Number 1 05000-346 I

97

--001 -

00 3 OF 3 TEXT (It more space is required, use addittonal copses of NRC Form 366A) (17)

Apparent Cause of Occurrence:

The initiating condition was determined to be a degraded bottom linear i

amplifier. The amplifier degraded in such a manner as to cause a small shift in NI-6 indicated imbalance. This undetected condition existed for greater than the TS Action Statement Requirements.

Analysis of Occurrence:

There was minimal safety significance during this event. This degraded condition had no impact on actual core conditions or plant operations. The RPS is a four-channel system which requires only two channels to trip for initiation of a reactor trip. During the time of this event three of the four channels were operable and could have performed their intended safety function. Therefore, l

actual positive core imbalance would not have exceeded the Allowable Value limits l

of the Core Operating Limits Report (COLR). The bottom linear amplifier ouput shift causes both a negative shift in imbalance and indicated total power to increase which may cause the RPS channel to trip sooner than required.

l Reactor core conditions are monitored by plant operators frequently during the course-of shift operations. It is unlikely that the plant would have exceeded the imbalance limits given in the COLR.

Operation of the plant resulting in an i

i imbalance of the magnitude limited by the COLR would be more recognizable.

The power range nuclear instrument linear amplifiers have had acceptable l

reliability. Partial degradation of the linear amplifier causing a slight shift in indicated imbalance is not known to have occurred in the last nine years.

Corrective Actions

1 The power range bottom linear amplifier was replaced on February 1, 1997. As an enhancement, Licensed operators will be trained to make them more aware of instrument degradation of this nature by May 31, 1997.

i

?

FailureJata:

A review of License Event Reports (LER) submitted in the last two years disclosed no similar events that were caused by hardware degradation causing inoperability. Additionally, there were no LERs involving nuclear l

instrumentation in the last two years.

NP-33-97-001-0 PCAOR 97-0073 NftC FORM 366A (5-92)