05000346/LER-1980-078-03, /03L-0:on 801027,reactor Protection Sys Channel 1 Tripped on Shutdown/Bypass High Pressure Trip.Caused by Loose Solder Connection in Lead from Pressure Detector Element & Loose Lock Nut.Connection Repaired

/03L-0:on 801027,reactor Protection Sys Channel 1 Tripped on Shutdown/Bypass High Pressure Trip.Caused by Loose Solder Connection in Lead from Pressure Detector Element & Loose Lock Nut.Connection Repaired

ML19350A121
Person / Time
Site:	Davis Besse
Issue date:	11/26/1980
From:	Werner J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19350A117	List: 05000346/LER-1980-078, Forwards LER 80-078/03L-0 05000346/LER-1980-078-03, /03L-0:on 801027,reactor Protection Sys Channel 1 Tripped on Shutdown/Bypass High Pressure Trip.Caused by Loose Solder Connection in Lead from Pressure Detector Element & Loose Lock Nut.Connection Repaired
References
LER-80-078-03L, LER-80-78-3L, NUDOCS 8012020533
Download: ML19350A121 (3)

LER-1980-078, /03L-0:on 801027,reactor Protection Sys Channel 1 Tripped on Shutdown/Bypass High Pressure Trip.Caused by Loose Solder Connection in Lead from Pressure Detector Element & Loose Lock Nut.Connection Repaired

Event date:
Report date:
3461980078R03 - NRC Website

text

U.S. NUCLEAR REGULATORY COMMISSION 4RC F OIM 366 i7 77)

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8 60 61 DOCKET NUMBER ha 69 EVENT DATE 74 75 REPORT OATE 80 s

EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h l (NP-33-80-106) On 10/27/80 at 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br />, Reactor Protection System (RPS) Channel 1 l

o 2 ITTTl I tripped on a shutdown / bypass high pressure trip. Since the non-nuclear instrumentationi l 0141 I reactor coolant system (RCS) pressure input signal comes from RPS Channel 1, a chain ofl l o i s i l events occurred which caused RCS pressure to drop to 640 psig. The station entered thel l o ls l l action statement of T.S. 3.3.1.1, and the failed channel was placed in the tripped conf j o l 7 l l dition within one hour. There was no danger to the public or station personnel. There l l

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33 34 34 36 31 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l i l o l ]The cause was a loose solder connection in the lead coming from the pressure detector l j i j [ element. The lock nut on the pipe between the detector housing and amplifier housing I

lt g,,,,lvas loose. The housing had rotated with respect to each other putting a stress on thel g l wiring soldered connection. Apparently the housing had been bumped by construction l

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-106 DATE OF EVENT: October 27, 1980 FACILITY:

Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: -Reactor Protection System (RPS) Pressure Transmitter Failure Conditions Prior to Occurrence: The unit was in Mode 3 with Power (MWT) = 0 and Load (Gross MWE) = 0.

Description of Occurrence: On October 27, 1980 at about 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br />, the RPS Channel 1 pressure indication failed high causing RPS Channel 1 to trip on a shutdown / bypass high pressure trip. Also, because the non-nuclear instrumentation (NNI) reactor coolant system (RCS) pressure input signal was coming from RPS Channel 1, the following occurred: The pressurizer heaters turned off, the spray valve opened, and the power operated relief valve (PORV) received an open signal.

Since the PORV block valve, RCll, was closed, the PORV did not open.

Upon indication of decreasing RCS pressure due to the open spray valve, the operators manually closed both the spray valve and its block valve. RCS pressure dropped to about 640 pounds. The unit was placed in Action Statement 3 of Technical Specification 3.3.1.1 which required the failed RPS channel to be tripped within one hour. The channel was tripped in about 30 minutes.

Designation of Apparent Cause of Occurrence: The apparent cause of the occurrence was a loose solder connection found in the Channel 1 pressure detector signal lead coming from the pressure detector element.

Investigation revealed that the lock nut on the connecting pi,.a between the detector housing and the amplifier housing was loose, enabling one to be rotated with respect to the other.

This would put a rotational stress on the soldered connections.

There had been scaffolding installed near the detector during the refueling outage.

It appears that construction personnel may have bumped the housing on the detector or amplifier causing a weakening of the soldered connection.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. There was no release of primary coolant and pressure re-mained in the allowable operating band at all times.

Corrective Action

Within 30 minutes the NNI RCS pressure input signal was changed over to RPS Channel 2, thus restoring all NNI functions lost. Under Maintenance Work Order IC-720-80, the locknut was tightened, the broken pressure transmitter lead was discovered and repaired, a transeitter calibration and time response performed, and the channel returned to service, thus removing the unit from the action statement of Technical Specification 3.3.1.1.

All other containment pressure transmitter lock-nuts were checked tight, and none found loose.

RPS Channel 1 was declared operable at 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> on October 30, 1980.

LER #80-078 I

r TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION. UNIT ONE SUPPLDIENTAL INFORMATION FOR LER NP-33-80-106 PAGE 2 Failure Data: There ' ave been no previous failures of this type.

LER #80-078 i

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