ML20151J912

PNO-OSP-88-004A:on 880406,calculated Unidentified Leak Rate of 1.09 Gpm Obtained,Exceeding Tech Spec Limit of 1 Gpm. Differential Pressure Transmitter Reactor Coolant Seal Return Line Isolated.Plant Currently in Mode 5 for Repairs

ML20151J912
Person / Time
Site:	Sequoyah
Issue date:	04/12/1988
From:	Richardson S NRC OFFICE OF SPECIAL PROJECTS
To:
References
PNO-OSP-88-004A, PNO-OSP-88-4A, NUDOCS 8804210211
Download: ML20151J912 (4)

Text

_ _ _ _ __-- -_

April 12, 1988 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PN0-0SP-88-004A 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 all that is known by the OSP staff on this date.

FACILITY: Tennessee Valley Authority Licensee Emergency Sequoyah Unit 2 Classification:

Docket No. 50-328 Notification of Unusual Soddy-Daisy, Tennessee Event Alert Site Area Emergency General Emergency ,

X Not Applicable l

SUBJECT:

UPDATE OF SEQUOYAH UNIT 2 APPROACH TO CRITICALITY This updates PN0-0SP-88-004 which discusses the Sequoyah Unit 2 approach to criticality. On April 6, while performing a surveillance on reactor coolant system water inventory, a calculated unidentified leak rate of 1.09 gallons per minute (gpm) was obtained, which is above the Technical Specification (TS) limit or' 1 gpm. The licensee declared an Unusual Event (UE) at 8:20 a.m. (EDT).

At 8:42 a.m. (EDT), the differential pressure transmitter on the No. 4 reactor coolant pump seal return iine, which was the suspected cause of the leakage, was isolated. Followup surveillance indicated that the unidentified leak rate 4

dropped to 0.48 gpm after isolation of the transmitter, which brought the leakage back below the TS limit. The UE was terminated at 5:45 p.m. (EDT).

The licensee issued a statement to the press on this occurrence at 11:00 a.m.,

on April 6. The licensee then determined that .30 gpm of the .48 gpm unidentified leakage was due to a primary to secondary leak in the No. 3 steam generator. The .30 gpm leak rate was determined by a special test to detect steam generator secondary side tritium content. Earlier radionuclide analysis had indicated no evidence of leakage. The licensee issued another press announcement at 11:30 p.m. (EDT) on April 6 concerning the primary to secondary leakage.

The licensee subsequently determined that it would be necessary to cooldown from hot standby to repair the steam generator tube leak. The plant is currently cooled down and in Mode 5, systems are partially drained, and access covers to the steam generators are open. Testing to find the source of the leak is expected to comence late on April 12. Current estimates of time for repairs and accomplishment of other work is at least two weeks.

The State of Tennessee has been informed.

The NRC startup staff is monitoring the licensee's actions related to these events.

CONTACT: S. Richardson 49-23286 8804210211 880412 PDR I&E O(

PNO-OSP-88-OO4 DCD 1E3Y

O of This PN is being issued for information purposes only.

This information is current as of 11:00 a.m. April 12, 1988.

DISTRIBUTION H Street MNBB OWFN NL ACRS ARM NRR RES AE00 OE Hqs Operations Office NMSS DCS OGC OIA 01 SP OSP ED0 DEDRO GPA ,

Regional Offices Chairman Zech Region I Commissioner Roberts Region II Commissioner Bernthal Region III Commissioner Carr Region IV Commissioner Rogers ,

Region V SECY 1 CA Sequoyah Resident Inspector Licensce: TVA 1 i

l l

April 12, 1988 PRELMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-0SP-88-004A This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The in:'ormation is as initially received without verification or evaluation, and is all tPyt is known by the OSP staff on this date.

FACILITY: Tennessee Valley Authority Licensee Emergency Sequoyah Unit 2 Classification:

3

, Docket No. 50-328 Notification of Unusual Soddy-Daisy, Tennessee Event Alert

- Site Area Emergency General Emergency X Not Applicable

SUBJECT:

UPDATE OF SEQUOYAH UNIT 2 APPROACH TO CRITICALITY This updates PH0-0SP-88-004 which discusses the Sequoyah Unit 2 approach to criticality. On April 6, while performing a surveillance on reactor coolant system water inventory, a calculated unidentified leak rate of 1.09 gallons per minute (gpm) was obtained, which is above the Technical Specification (TS) limit of 1 gpm. The licensee declared an Unusual Event (UE) at 8:20 a.m.. (EDT).

At 8:42 a.m. (EDT), the differential pressure transmitter on the No. 4 reactor coolant pump seal return lire, which was the suspected cause of the leakage, was isolated. Followup surveillance indicated that the unidentified leak rate dropped to 0.48 gpm after isolation of the transmitter, which brought the leakage back below the TS limit. The UE was terminated at 5:45 p.m. (EDT).

The licensee issued a statement to the press on this occurrence at 11:00 a.m.,

on April 6. The licensee then determined that .30 gpm of the .48 gpm unidentified leakage was due to a primary to secondary leak in the No. 3 steam generator. The .30 gpm leak rate was determined by a special test to detect steam generator secondary side tritium content. Earlier radionuclide analysis had indicated no evidence of leakage. The licensee issued another press announcement at 11:30 p.m. (EDT) on April 6 concerning the primary to secondary leakage.

The licensee subsequently determined that it would be necessary to cooldown from hot standby to repair the steam generator tube leak. The plant is currently cooled down and in Mode 5, systems are partially drained, and access covers to the steam generators are open. Testing to find the source of the leak is expected to comence late on April 12. Current estimates of time for repairs and accomplishment of other work is at least two weeks.

The State of Tennessee has been informed.

The NRC startup staff is monitoring the licensee's actions related to these events.

CONTACT: 5. Richardson 49-23286 p -

.p ..

This PN is being issued for informa' tion purposes only.

This ii) formation is current as of 11:00 a.m. April IE,1988.

DISTRIBUTION H Street MNBB 0WFN NL NF ACRS KF ES AE00 OE

- Hqs Operations Office NMSS s DCS OGC OIA 01 SP ,

OSP EDO DEDR0 GPA Regional Offices Chairman Zech Region 1 Commissioner Roberts Region II Commissioner Bernthal ..

Region III Commissioner Carr Region IV Commissioner Rogers Region V SECY CA ,

l Sequoyah Resident Inspector Licensee: TVA Y