ML20039C095

LER 81-053/03L-0:on 811120,emergency Condensers 11 & 12 Were Isolated When Emergency Condenser Vent Radiation Monitor de-energized Due to Loss of Dc Motor Speed Control.Caused by Defective Silicon Controlled Rectifier.Rectifier Replaced

ML20039C095
Person / Time
Site:	Nine Mile Point
Issue date:	12/14/1981
From:	Patrou N NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20039C094	List: ML20039C093 ML20039C095
References
LER-81-053-03L, LER-81-53-3L, NUDOCS 8112280400
Download: ML20039C095 (2)

Text

nirw r v ru ' ' b4 O h. NUCLLAH HLbueAIONY LUMMIM 4VN (7 77)

LICENSEE EVENT REPORT

. CONTROL BLOCK: l l l l l } l (PLEASE PRINT CQ TYPE ALL RE7.UIRED INFL RMATIONI 1 6 M lN8 9lY lNUCENSEE

> lM lP l1 l@lb0 l 0 l - l 0 lUCENSE CODE 14 0l0 l 0 l 0 l - l 02hl 0 26l@ 4 NUMBER l 1 lTYPE UCENSL 1 lJo1 l 671CATl l@l b8 l@

CON *T loI11 8

5$RC l L @l0 l5 l0 l 0 l 0 l 2 l 2 l 0 @l1 l1 l 2l 0l 8 l 1 @l1 l; l1 l4 l8 l1 l@

7 60 61 DOCKET NUMSEe 68 69 EVENT DATE 74 7b RE PORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 10121 l Durine normal operation while preparing to remove #172 motor generator set from service l lc la l l for relay tehting, tt was noted that after placing the Motor Generator Set Function [

lo !4 l l Switch in the "UC Run pesiticn, speed control of the DC motor was erratic. This remove 4 ITTrl I the ability to synchrenhe between #172 motor generator set and #130 Instrument and l lotsJ ; Control Bus (ISC 130). Considering the redundancy in the loads normally powered from l g y [ #172 motor generator set, it was decided to de-energine the loads on #172 motor generatoy f a ls i i set and then pick up these loads on IGC 130. In doing so, one of two Emergency Condensey SYSTE M CAUhE CAUSE COMP. ~ VALVE CODE CODE SUSCODE - COMPONENT CODE SUBCODE . SUSCODE '

lo 19 l' lClE l@ { Blh #l A l@^ l~ Zl Zl ~*] Zl Z l Z l@ ' l Zlh 20W @ .

7 8 9 10 1' 12 13 18 19 SEQUEN7fAL OCCUR R E NCE REPORT REVISION

-EVENT YE AR REPoR 7 NO. CODE TYPE NO.

h "LE yj"&aiR'ROl

_ 21 8l 1l 22 l-l T3 24 l 0 l5 l3 l 26 l/l 27 l0l3l 3 h W

JO l-l 31 l 0l 32 KEN ' ACT ON ON PLANT ME HOURS SB i D FoR 6. SUPPLI R MANUFA URER lXl@lXl@

3J 34 l, Z ,JQ 3d W@ l 0 l0 l0 lo l { Q lNl@

36 37 40 41 42 l43Z l@ lZ l 9l 9l 9l@

44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h J i j o l l The cause of the isolation of #11 and #12 Emergency Condensers was due to system design l li li l l (emergency condenser isolation upon loss of power to any channel of the Emergency Con-  !

, 7 l denser Vent Radiation Monitors). Power was restored to the de-energized radiation l g,,3g l monitors and the steam isolation valves were re-opened, returning the Emergency Cooling l

ij4; ] System to its normal configuration. The loss of DC motor speed control was due to a l 7 8 9 80 STA  % POWER OTHE R STATUS DISCOV R DISCOVERY 0ESCRIPTION NA Operator Observation

11 l 5 l l E l@ l 0 l 9 l 9 l@l l lAl@l l ACTIVITY CO TENT RELEASED OF RELE ASE AMOUNT OF ACTIVITY LOCATION oF RELE ASE l i l o l l z _j @ l Z i@l _ NA l l NA l 7 6 9 10 1- 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCR4& TIONl @q j i l 7 l l 0 l 0 l 0 l@l Z l@j NA l PERSONNEL INJURIES NUMBE R DESCRIPT13N FTE-l 7 8 9 l 01010 l@l12 11 NA l 80 LOSS OF OR DAMAGE TO FACILf TV TYPE DESCRIPTtoN 200400 811214 PDR ADOCK 05000220 Q l2l@l 7 6 9 10 6

PDR NA 80 l

PU8ttCITY ISSUE D NRC USE ONLY

• i Fro l LN_j@ DESCRIPTION l NA 7 C 9 to l lllllllllllllI 68 69 80 E (315)343-2110, X1212 NAME OF PREPARER PHONE: {

LER 81-53 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (Cont'd.)

Vent Radiation Monitors in each loop of the Emergency. Cooling System was de-energized. By design, this caused the closure of normally open Emergency Cooling System Steam Isolation Valves, thus isolating #11 and #12 Emergency Condensers. This placed the plant in a limiting condition for operation per Tech. Specs. 3.1.3e. The Emergency Condensers remained isolated for approxi-mately 20 minutes, at which time they were returned to service using normal operating procedures. The safety significance of this event was minimized by several factors: (a) operator knowledge of system isolation at the time of occurrence; (b) the short length of time during which the system was isolated.

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (Cont'd.)

defective silicon controlled rectifier (SCR) in the speed control circuit which has subsequently been replaced and the motor generator set returned to service.

I n1: '

c,

• 4 f