ML19263A716

LER 78-044/03L-0 on 781203:reactor Protection Sys Channel C T-cold Was Erratic & Read Approx 4 F Higher than Pressure Other Channels.Caused by Bad Delta T-thermal Margin/Low Pressure Calculator Mode Switch

ML19263A716
Person / Time
Site:	Calvert Cliffs
Issue date:	12/21/1978
From:	Davis S, Miernicki M BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19263A713	List: ML19263A712 ML19263A716
References
LER-78-044-03L-01, LER-78-44-3L-1, NUDOCS 7901020133
Download: ML19263A716 (2)

Text

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LICENSEE EVENT REPORT CONTROL BLOCK:

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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60 L l@l61 0l 5 l 0DOCKET l 0 l NUMBER 0 l 31 1 l 868l@l691 l 2EVENT 3 l 7 874l@l75 112 l 0 lDATE l 2 l 117 8l@

REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h O 2 l At 1537 on 12/3/78 and aoain at 1645 on 12/9/78. it was noticed that reactor i O a I protective system (RPS) Channel C T-cold was erratic and readino acorx. 4 i O 4 degrees higher than the other channels. Channel C T-cold was declared inon- 1 O s I erative and High Power, Themal Margin / Low Pressure and Axial Shape Index l l0 is i trips were bypassed per T.S. 3.3.1.1. Channel C T-cold was returned to 1 0 7 l service at 1717 on 12/3/78 for the first occurrence and at 1710 on 12/9/78 l O 8 I for the second occurrence. LER 78-44 continued on attached sheet.

E CODE S BC DE COMPONENT CODE SU8 CODE S E O 9 l I l A l @ W@ l E l@ I I l N l S l T l R l U l@ [_Sj@ l_Z_j @

7 8 9 10 11 12 13 18 19 20 LER EVENT YEAR REPORT O ODE N .

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33_ 34 35 36 37 40 41 42 43 44 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i O l Cause was determined to be a bad delta T-thermal maroin/ low nressure calculator i ri 1i-l 1 mode switch. For more details see attachment. I i 2 l l l

L'_1__l 1 Ln4_1 1 7 8 9 80 STA S  % POWER OTHER STATUS DIS RY DISCOVERY DESCRIPTION i s l E l@ l0 l 9 l012l@l13 NA l lB l@l Operator observation l 7 8 1 44 45 46 80 RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE 1 6 [Z_j @ W@l NA l NA PERSONNEL EXPOS ES NUMBER TYPE DESCRIPTION l- TT) l 0 0 l 0 l@l Zl@l NA l

' PERSONNEL INJUIES NUMBER DESCRIPTION W *l0l0l0l@l NA l AGE TO FACILITY g5 Or OR O Luoj l Zl@l NA l 7 8 9 10 80 ISSUE DESCRIPTION @ 790102oB3 ~RC use oNov .

M [N_j@l NA l lllllllllllllj 7 8 9 10 68 69 80 5 NAME OF PREPARER S . M. avis /M. J. Hiernicki psoyg 301-234_7942/7960 g

LER 78-44/31 DOCKET N0. 50-318 EVENT DATE 12/03/78 REPORT DATE 12/21/78 ATTACHMENT EVENT DESCRIPTION AND PROBABLE CAUSE: (CONT)

The diree redundant channels remained operable during the event. This is not a repetitive event.

CAUSE DESCRIPTION AND CCRRECTIVE ACTIONS: (CONT)

Discovered input voltage readings were high on T-cold and T-hot when the delta T-thermal margin / low pressure calculator mode switch was in the onerate position. External input readings were found to be normal when selected with switch. Discovered that when switch was cycled then placed in operate T-cold reacted normally but slowly increased 4 - 5 degrees higher than other channels. Cause was determined to be bad contacts in the switch. In both of the above instances switch was cleaned with freon and returned to service. New switch is on order (Grayhill 42A36-04-2-4N, rotary switch C4 decks) ). Installed switch will be replaced when new switch is received. -