ML19305B789

Supplemental LER 79-040/03L-1:on 791213,during Instrument Check,Variations in Suppression Pool Level Noted Between Reading on Control Room Panel 901-3 & Local Sight Glass, Exceeding Tech Specs.Caused by Crud on Sensing Lines

ML19305B789
Person / Time
Site:	Quad Cities
Issue date:	03/07/1980
From:	Kopacz J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19305B788	List: ML19305B787 ML19305B789
References
LER-79-040-03L, LER-79-40-3L, NUDOCS 8003200385
Download: ML19305B789 (3)

Text

NRC FCRM 366 U.S. NUCLEAR REGULATORY CoMMisSloN (7 771 UPDATE REPORT--

PREVIOUS REPORT DATE l-11-80 LICENSEE EVENT REPORT CONTROL BLOCK: l 1

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60 61 DOCK ET NUMB E R 68 69 EVENT DATE 74 75 REPORT QATE 80 EVENT DESCRIPTION AND PRCSABLE CONSEQUENCES h lo l2l l During routine instrument check, slight variations in the suporession pool level have i Fo tal I been noted between the reading in the control room, on panel 901-3, and tne local I l o l41 l sight glass. Due to these variations the Technical Specification 3.7.A.l b limit for l lo tel I suppression pool level was exceeded on December 13, 23, 28, 1979, and on January 8 l l 0 l6 l l and 9, 1980. Since the suppression pool temperature was moderate and because the l lo l7l l limits for suppression pool level are conservative, safe plant operation was not i 10181 l jeopardized. I 7 8 9 60 SYSTEM CAUSE CAUSE COMP. VA LVE CODE CODE SUSCODE COMPONENT CODE SUSCODE SUSCODE l0l9l 8

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h lijoll A partial blockage of the instrument sensing lines, due to postulated crud buildup, I lTTi l l reduced instrument response. Further investigation found a crack in the upoer I i ,121 I section of the local sight glass. The instrument lines were backflushed and the l gl instrument was recalibrated. The local sight glass was replaced. In each case the l 33141; suppression pool level was immediately restored to normal. l 7 8 9 80 ST S  % POWER OTHER STATUS IS O RY DISCOVERY 0ESCRIPTION lt l s l l El@ l 0l 9l 7lgl NA l lAlgl Operational Event l ACTIVITY CO TENT RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE Q J* @ l Z l@l NA l l NA l PERSONNEL EXPOS ES NUMSER TYPE DESCRIPTION NA l i l 7 l l 0l 0 l 0 l@l Z l@l l PERSONNE L INJURIES NUMBER DESCRIPTION g l0l0l0l@l NA l r

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1. LER NUMBER: LER/R0 79-40/03L-l .

II. LICENSEE NAME: Commonwealth Edison Company quad-Cities Nuclear Power Station Ill. FACILITY NAME: Unit One IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

On December 13, 1979, while on shift rounds, an equipment attendant checked the suppression chamber level at the local sight glass. The sight glass indicated a level of +.4 inchas.

The lower sensing line was then opened and the sight glass was drained. When this was done, the level then corrected to a level of -2.2 inches. During this time the control room Indication dorpped from -1/4 inches to -2.0 inches.

On December 23, 1979, the Unit One operator found the suppression chamber level above normal. By pumping water to the main condenser, suppression pool level was lowered to -1/2 inches by control room indication. An equipment attendant was then dispatched to verify the level at the local sight glass. The local sight glass indicated a suppression pool level of -2 inches.

On December 28, 1979, an instrument mechanic backflushed the sight glass sensing lines and calibrated transmitter 1-1626.

Following this work the suppression chamber level by local indication was found to be +2.25 inches.

On January 8, 1980 the Suppression Chamber level instrumentation appeared to be sensing level inaccurately. Level in this instance was found at the lower procedural limit and was immediately increased. The instrumentation was checked and as a result the final level was +2.5 inches. The water level was immediately restored to normal by removing water inventory.

On January 9, 1980 the suppression chamber level was found to be low. In this instance both the control room instrument and the local sight glass indicated -2.0 inches. Water was immediately added to correct the level.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE Minimal safety implications result from these occurrences.

The suppression pool level is maintained to assure total condensing of steam from a reactor blowdown at full power.

Due to a large factor of safety designed into the pressure suppression system, total steam condensing would result even with slightly higher or lower water levels. Therefore the system would have operated as designed.

Vll. CAUSE This instrumentation and associated sensing lines are subject to crud buildup from the suppression chamber water. This buildup caused partial blockage in the sensing lines and reduced the response of the instruments. Therefore, after the first two events, a recalibration of the transmitter gave the correct water level but did not clear the sensing lines.

Therefore, when the level changed, the instrument did not respond correctly.

A subsequent investigation found a crack in the upper section of the local sight glass. This is believed to have caused some deviation in the accuracy of the local level readings.

Vill. CORRECTIVE ACTION in each case the immediate action was to correct the suppression chamber level to within limits. A calibration check (QlS 1) of transmitter LT-1-1626 was then performed.

Upon reoccurrence, further investigation disclosed a partial blockage of the sensing lines. This was corrected by backflushing the sensing lines, on December 28, 1979 On January 15, 1980 when a crack in the local sight glass was found, the sight glass was replaced. The level was then monitored daily for seven days to verify conformance between the local sight glass and the control room instrument indication.

To improve the reliability of the transmitter, transmitter internals are to be replaced in the future. Parts are on order and will be installed on a simely basis.

The level transmitter is manufactured by Barton Instrument Company model 352. The new internals are to be Barton model 368-352.

The suppression pool level readings are currently being taken once a week at the local sight glass to assure conformance with the control room instrument.

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