05000368/LER-1980-091-01, /01T-0:on 801220,Channel B Instruments Indicated Low Refueling Water Tank Level.Caused by Frozen Level Transmitters.Replaced Fuse

/01T-0:on 801220,Channel B Instruments Indicated Low Refueling Water Tank Level.Caused by Frozen Level Transmitters.Replaced Fuse

ML19340D883
Person / Time
Site:	Arkansas Nuclear
Issue date:	12/26/1980
From:	Shively C ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19340D830	List: 05000368/LER-1980-091, Forwards LER 80-091/01T-0 05000368/LER-1980-091-01, /01T-0:on 801220,Channel B Instruments Indicated Low Refueling Water Tank Level.Caused by Frozen Level Transmitters.Replaced Fuse
References
LER-80-091-01T, LER-80-91-1T, NUDOCS 8101050501
Download: ML19340D883 (5)

LER-1980-091, /01T-0:on 801220,Channel B Instruments Indicated Low Refueling Water Tank Level.Caused by Frozen Level Transmitters.Replaced Fuse

Event date:
Report date:
3681980091R01 - NRC Website

text

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• • F,OM f DaTE 80 EVENT OESCRIPTION AND PROB ABLE CONSEOUENCES h 1o12i IDuring Mode 1 operation, while performing routine Refueling Water Tank i

to i31 l(RWT) level indication checks, it was observed that Channels A, C, & D 1

Io i. i were indicating)100% and Channel B was 82%.

Previous checks indicated I

t c i s t iaoproximatelv 94%

All ESFAS RWT Instrumentation channels beino declared I ie is i linoperable, the L.C.0. of Action Statement #9 per T.S. 3.3-3 Item 6b, i

10171 'T.5. 3.3.2.1 could not be satisfied.

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40 el di e3 se as CAUSE DESCR.PTION AND CORREC flVE ACTIONS m 1 The instrurent indication discrecancy was diagnosed as frozen RWT level I

I t i li l l transmitters due to lgor ambient temoerature.

The system heat tracing i

i. i 2 rl circuit was found de-enercized because the main line fuse was removed.

I lii si i The fuse was replaced and RWT level indication returned to operable status.

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LER 80-091/01T-0 (Continued) 10 initiated per T.S. 3.0.3; however, to meet the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> " time-clock" a manual Reactor trip was required at 30% power. Similar to LER's 50-368/79-001,79-002, 79-008,79-101.

Reportable per T.S. 6.9.1.8.b.

l 27 Investigation revealed fusible disconnect did not confom to design drawings.

Ramifications and long term corrective actions are being evaluated.

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1.

Reportable Occurrence Report No. 50-368/80-091 2,

Report Date:

12/26/80 3.

Occurrence Date: 12/20/80 a.

Facility: Arkansas Nuclear One - Unit Two Russellville, Arkansas 5.

Identification of Occurrence:

Operation of the unit with Engineered Safety Features Actuation System instrumentation subject to a Limiting Condition for Operation (LCO) per T.S. 3.3.2.1, T. S. Table 3.3-3 Item 6b (Refueling Water Tank level instrumentation) in a less conservative than the least conservative aspect of the LCO as established by Action Statement #9 (allowing one inoperablechannel).

Reportable per T.S. 6.9.1.8.b.

6.

Conditions Prior to Occurrence:

Steady-State Power X

Reactor Power 2168 MWth Ilot Standby Net Output 685 MWe Cold Shutdown Percent of Full Power 77 %

Refueling Shutdcwn Load Changes During Routine Power Operation Routine Startup Operation Mode 1 Routine Shutdown Operation Cther (specify) 7.

Description of Occurrence:

While perfoming' routine Refueling Water Tank (RWT) level indication checks, as required by T.S. 4.3.2.1.1, T.S. Table 4.3-2 Item 6b, it was observed that Channels A, C, & D were indicating a level of >100% and~ Channel B was indicating 82%.

The previous channel check readings ranged from 93 to 95% on all RWT level indications.

All EFSAS RWT instrumentation being declared inoperable, the LC0 and associated action statement could not be satisfied; therefore, a Reactor shutdown to Mode 3 operation was initiated per the requirements of T. S. 3.0.3.

To meet the I hour time clock, a manual Reactor trip was required at 30% power.

Reportable occurrence neport No. 50-368/80-091 8.

Designation of Apparent Cause of Occurrence:

Desi m Procedure X

t bbnufacture Unusual Service Condition Including Environnental Installation /

X Const ruction Component Failure X

(See Failure Data)

Operator Personnel Error X

Other (specif,c)

The instrument indication discrepancy was diagnosed as frozen RWT level transmitters due to 150F ambient temperature.

The system heat tracing (added per corrective action to previous occurrences) was found de-energized because of a missing power fuse in a fusible disconnect located in terminal box, 2TB-608.

9.

Analysis of Occurrence:

Investigation revealed that the installation of a fusible disconnect in the heat tracing circuit did not conform to the original design configuration.

The power fuse was apparently removed when an unrelated plant design change required that the RWT level sensing lines be re-rcuted due to space utilization requi rements.

The post design modification check out failed to reverify the operablility of the heat tracing circuitry.

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i-

able Occurrence Report do.

50-368/80-091 10.

Corrective Action

The short tenm corrective action was to replace the missing power fuse,. thaw the RWT level transmitter, and return the ESFAS Refueling Water Tank instrumentation to an operable status.

Luig term corrective actions are being evaluated.

II.

Failure Data:

Refueling Water Tank, frozen level transmitter, occurrences were reported in LER's 50-368/79-001,79-002, 79-008, and 79-101.

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