PNO-IV-88-078, on 880923,util Plans to Begin Scheduled Outage to Inspect Bottom Mounted Instrument (Bmi) Tubes.On 880506, Util Reported That Review of Eddy Current Test Data on 58 Bmi Thimble Tubes Revealed Wear on 19 Thimble Tubes

PNO-IV-88-078:on 880923,util Plans to Begin Scheduled Outage to Inspect Bottom Mounted Instrument (Bmi) Tubes.On 880506, Util Reported That Review of Eddy Current Test Data on 58 Bmi Thimble Tubes Revealed Wear on 19 Thimble Tubes

ML20154N415
Person / Time
Site:	South Texas
Issue date:	09/23/1988
From:	Holler E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-88-078, PNO-IV-88-78, NUDOCS 8809290297
Download: ML20154N415 (2)

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September 23, 1988 >

, PRELIMINARY NOTIFICATION OF_ EVENT OR UNUSUAL OCCURRENCE -- PN0-IV-88-78 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: Houston Lighting & Power Co. Licensee Emergency Classification:

South Texas Project, Unit 1 Notification of Unusual Event Bay City, Texas ~ ~ Alert DN: 50-498 ~~~ Site Area Energency General Emergency X Not Applicable

SUBJECT:

PLANNED OUTAGC T0 INSPECT BOTTOM MOUNTED INSTRUMENT (BMI) TUBES At approximately 6 p.m. (CD1) on September 23, 1988, Houston Lighting & Power Company (HL&P) plans to begin a scheduled outage to inspect the BMI tubes at South Texas Project, Uni 1 (STP-1). During the outage, which is anticipated to last 14 days, HL&P will conduct eddy current tests on the Bhl tubes to determine wear.

On May 6,1988, HL&P reported that a review of eddy current test data on the 58 bottom mounted instrument thimble tubes at STP-1 revealed wear on 19 thimble tubes. Significant wear (greater than 25 percent of the wall thickness) was found on five thinble tubes. The significant wear was in the area of the floi.

limiters and ranged from 28 percent to 59 percent. An additional 14 thimble tubes exhibited wear as follows: 5 - 12 percent, 2 - 15 per:ent, 1 -

16 percent, 5 - 20 percent, and 1 - 25 percent. The minimum detectable wear is 10 percent.

These thimble tubes allow nt Jtron detectors to be inserted into the reactor core to provide :: detailed map of core power. Flow induced vitrations are believed to cause thimble tube wear which could lead to leakage of reactor coolant into the containment sump.

During the outage, HL&P will also install marual isolati;>n valves on the thimble tubes and conduct other routine maintenance and surveillance testing activities.

Preoperational testing continues at Soutn Texas Proje:t, Unit 2 (STP-2). STP-2 is approximately 98 percent complete and HL&P appears to be an Schedule for a projected fuel loading in December 1988.

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

1his information has been ( mfirmed with a licensee representative.

The state of Texas will be informed.

CONTACT: t'. Holler FTS: 728-8287 I

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9/23/88 9/23/88 p {

8309290297 880923 PDR Ite PNO-IV-88-078 PNU

.- PNO-IV-88-78 DISTRIBUTION:

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

Chairman Zech EDU TUU LDT(Trans only)

Con.n. Roberts 0IA OGC Com. Carr NL PA FAX: INP0 Com. Rogers ES O! NSAC SECY NMSS RRI CA NRR NRC OC POR SLITP LICENSEE (Reactor Lic.)

OGC-H GPA /

ACRS 5520: 'f/0/38 0 //' 774-REGIONS & HQ DISTRIBUTION:

NRC0CA LEAD 0P Please deliver)

Chairman Zech Com. Roberts Com. Rogers Com. Carr ACRS SECY CA POR OGC GPA NRC0CA/0CAPN (Please make internal distribution for OCA)

INRC02/0RDAZ (Please make internal distribution for PA, AE0D, ARM, 0GC-MNB offices)

INRClll2/BEREAN (Diease mke internal distribution for NRR offices)

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NRCRMP/0!DW (Please make internal aistribution for 01 office)

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