PNO-IV-88-041, on 880512,operators Noted Disagreement Between Tygon Tube Rv Level Indicator & New Indicator Just Installed.Cause Unknown at Present.Water Removed,Bringing Rv Level Indicator Into Relative Agreement

PNO-IV-88-041:on 880512,operators Noted Disagreement Between Tygon Tube Rv Level Indicator & New Indicator Just Installed.Cause Unknown at Present.Water Removed,Bringing Rv Level Indicator Into Relative Agreement

ML20154D085
Person / Time
Site:	Waterford
Issue date:	05/13/1988
From:	Chamberlain D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-88-041, PNO-IV-88-41, NUDOCS 8805190039
Download: ML20154D085 (2)

D

'. May 13, 1988 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-IV-88-41

[

.This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region IV staff on this date.

FACILITY: Louisiana Power & Light Co. Licensee Emergency Classification:

Weterford #3 Notification of Unusual Event Killona, La. Alert DN: 50-382 Site Area Emergency General - Emergency

, X Not Applicable

SUBJECT:

LOSS OF SHUTDOWN COOLING t

At about 4:55 a.m. (CDT) on May 12, 1988, the licensee was draining the reactor coolant system (RCS) to establish a reactor vessel (RV) level low enough to allow work on the steam generators and reactor coolant pump seals. At that time the plant was in Mode 6 (Refuelir.g) with the core refueled with a mix of new fuel and partially spent fuel. While draining the RCS the operators noted disagreement between the tygon tube RV level indicator and the new digital RV level indicator which had just been installed and was under test. Water was found in the normally dry reference leg of the digital instrument. The cause is unknown at this time.

The water was removed, thus bringing the RV level indicators back into relative apparent agreement with the tygon tuce indication.

At 6:15 a.m. the "A" Train shutdown cooling pump (LPSI A) began to cavitate at an indicated tygon tube level of about 18 feet. The licensee started the high pressure safety injection pump (HPSI A) and raised RV level about three l l

inches. At that point, shutdown cooling suction was shifted to LPSI B and flow restored. LPSI A was vented and then shifted back into service, thereby restoring the original shutdown cooling lineup. The licensee apparently did not consider a level indication problem to exist; however, the new digital RV level indicator was checked by maintenance personnel prior to recommencing RV draining operations. During the above sequence, RCS temperature rose from about 89 to 92 degrees F.

At approximately 9:15 a.m. the licensee resumed draining of the RV. At about 9:30 a.m. the licensee noted a discrepancy between the tygon tube and the digital RV level indicators. Draining was secured at that time.

At 9:39 a.m. the LPSI A pump began to cavitate. Again, RV level was raised slightly using HPSI A and cooling flow was quickly shifted to LPSI B. RV level was then questioned, as it was not normal to get cavitation at the level indicated by the tygon tube, which was indicating 17 feet. The new RV level instrument was indicating about 13 feet at this time. The operators apparently ignored the new digital RV level instrument and relied solely on the tygon tube.

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QN0-IV-88-41 A detailed inspection and evaluation by licensee engineering personnel  :

revealed an unwanted loop seal in the tygon tube. The tygon tube had apparently been rerouted with excess tubing coiled up, creating the loop seal. The tygon tube was then shortened and rerouted. Final level was confirmed at about 13 feet, which is below the center line of the RV hot leg nozzle. This level could cause cavitation of the LPSI pumps due to vortexing.

The licensee has since restored RV level to about 13 feet 6 inches, which is required in support of the steam generator and reactor coolant pump work.

The NRC will notify the State of Louisiana.

Neither the licensee nor the NRC plans to issue a press release.

Region IV received notification of this occurrence by the resident inspector at 8:00 a.m. CDT on May 13, 1988. Region IV has informed NRR.

This information has been confirmed with a licensee representative.

CONTACT: D. Chamberlain (FTS 728-8249)

DISTRIBUTION:

H. St. MNBL OWF MAIL: DCS (Original IE 34)  :

Chairman Zech KEUU EDU UUT-(Transonly)

Comm. Roberts 0IA OGC Comm. Bernthal ARM FAX:

INPO Comm. Carr NL PA NSAC Comm. Rogers RES 01 RRI ,

SECY NMSS NRC OC CA NRR LICENSEE (Reactor Lic.)

PDR SLITP OGC-H GPA ACRS 5520: 5/13/88 4 2:30 p.m. ~

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REGIONS & HQ

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