ML19291C471

LER 79-040/03L-0:on 791213,during Routine Instrument Checks, Variations Between Control Room Panel & Local Sight Glass Readings Caused Suppression Pool Level to Exceed Tech Spec Limit.Caused by Partially Blocked Instrument Sensing Lines

ML19291C471
Person / Time
Site:	Quad Cities
Issue date:	01/11/1980
From:	Kopacz J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19291C470	List: ML19291C469 ML19291C471
References
LER-79-040-03L-03, LER-79-40-3L-3, NUDOCS 8001240464
Download: ML19291C471 (3)

Text

NRC FORM 3G6 ,

U. S. NUCLEAR REGULATORY COMMISSION (7 77)

LICENSEE EVENT REPORT CONTROL BLOCK: l l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATloN) 1 6 7

0 1 8 9 l 1 l LLICENSEE l a l CODE A l D l141 l@l 15 01 O! O!LfCENSE - 0l 0l O! -l 0 l O l 026 lh!264 l 1LICENSE NUMdER l 1 l TYPE l 1 ! 1J0 lh!57 CAT bd l@

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60 61 DOCKET NUVB ER 68 69 EVENT DATE 74 75 REPOHT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 I Durina rnutine instrument checks. slicht variations in the suncressinn nnni level l lo l3 l l have been noted between the readino in the control ronm. nn panel 901-3. and the 1 o 4 l local sight class. Due to these variations the Technical Specification 3.7.A.1.b l o s I limit for suppression pool level was exceeded on December 13, 23, and 28, 1979 l o s Since the suppression pool temperature was moderate and because the limits for supp- l o 7 i ression pool level are conservative, safe plant operation was not jeopardized. I O H l  !

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_ 21 W 23 24 26 '7 4 28 M 30 ' 31 32 TAKEN A TO ON PLANT MET HOURS 22 SB IT FO b 8. SUPPt.l E R MANLFACTU EH l33E [gl34F [g l35Z lg l36Z l g l0 l 0l 0l 31 l

40 l Y [g di l Yg 42 l Ngl Bl 0l 8l 0lg 4J 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS g! A partial blockage of the instrument sensing lines, due to postulated crud buildup, l ji ;ij [ reduced the response of the instrument. Corrective action was to backflush the I

,  ; g instrument lines and recalibrate the instrument. In each case the suppression pool

, , level was immediately restored to normal by adding or removing water inventory. A l l

, , g Supplemental report will be submitted when additional corrective actions have been 7 8 9 Completed. 80

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. POWER OTHE R STA TUS ISCC RY DISCOVERY DESCRIPTION Operational Event t 5 l E @ l 0l 9l 7l@l NA l l A l@l l ACTIVITY CO TENT RELEASED CF RELE ASE AYOUNT OF ACTIVITY LOCATION OF RELE SSE i 6 Zl @ [Z_j@l NA l l NA l 7 8 9 to 11 44 45 80 PERSONNEL E (POSURES NUV8E R TYPE

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NA L_LLI dsuE81 l lll lll[ll l lll 7 8 9 10 68 69 SG s NAME OF PREPARER PHONE: *

1. LER HUMBER: Ler/R0 70-40/03L-0

11. 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 inches.

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 dropped 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 -l/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.

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. -

1794 244

Vll. 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 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 timely basis.

This problem is still beign investigated and a supplemental report will be submitted when additional corrective actions have been completed to resolve this problem.

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

1794 245'

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