ML20245A085

PNO-ADSP-89-005:Investigation of Preoperational Testing Events on 890423-0505 Completed.Events Caused by Valve Misalignment & Inoperability of Borg-Warner Swing Check Valves.Rev of Reassembly Procedures Proposed

ML20245A085
Person / Time
Site:	Comanche Peak
Issue date:	06/15/1989
From:	Livermore H, Lyons J Office of Nuclear Reactor Regulation
To:
References
PNO-ADSP-89-005, PNO-ADSP-89-5, NUDOCS 8906210063
Download: ML20245A085 (3)

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June 15, 1989

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE FN0-ADSP-89-05

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

FACILITY: Licensee Emergency Classification:

TU Electric Notification of Unusual Event Comanche Peak Unit 1 Alert Docket No. 50 445 Site Area Emergency Glen Rose, Texas General Emergency X Not Applicable

SUBJECT:

IN0PERABILITY OF MULTIPLE BORG-WARNER PRESSURE SEAL, SWING CHECK VALVES IN THE AUXILIARY FEEDWATER SYSTEM An Augmented Inspection Team (AIT) has completed the investigation of the preoperational testing events of April 23 and May 5,1989, which resulted in the blowdown of multiple steam generators thragh stuck open auxiliary feedwater check valves to the condensate storage tank. A Confirmation of Action letter concerning required actions and material evidence preservation of the subject components was sent to the applicant on May 5, 1989. The AIT team followed the applicant's response to these events including the evaluation of precursors, the evaluation of root cause analysis, development of permanent corrective action, and evaluation of potential damage to piping, supports, and penetrations.

Specifically, the inadvertent steam generator blowdowns through the stuck open AFW discharge check valves resulted in the intrusion of high temperature secondary water into the AFW supply lines and localized damage to AFW piping and supports. The operational conditions which caused each occurrence were determined to be a valve misalignment combined with the inoperability of each of the eight 4-inch Borg-Warner swing check valves located on the AFW motor-driven and turbine-driven pump discharge lines to the steam generators.

Subsequent to these events, the applicant formed a task team in order to address the technical issues and generic implications. Additionally, the applicant has been working closely with the vendor in establishing the definitive cause of the check valve failures. Information indicates that the primary contributor to the valve disc hanging up under the seat ring for the 3 and 4-inch pressure bonnet check valves was an inconsistency between the factory assembly technique and the procedures specified in the Borg-Warner operation and maintenance manual provided to the applicant. In particular, the valve reassembly procedures specify that the threaded retainer ring be installed in the valve body and bottomed out thus causing the disc assembly to hang too low in the valve body. This process coupled with the axial play in the disc arm bushing allowed the check valve disc to hang up under the valve seat ring. See the attached drawing.

The proposed corrective actions currently include revising the reassembly procedures to allow for backing out the bonnet retaining ring a predetermined amount, thus centering the disc on the seat ring. This revised reassembly technique will be both statically and dynamically tested by the applicant to ensure proper cheek valve operation.

8906210063 990615 /

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Valve reassembly and testing schedules are under development by the applicant and are expected to be accomplished within one or two weeks. The applicant expect no effect on the projected fuel load date of October 2, 1989.

Concurrent with the above described events, the AIT team has reviewed recent test failures of the Borg-Warner bolted bonnet check valves in the service water system and the containment spray system. The failure mechanisms for these check valves does not appear to be directly related to the check valve deficiencies associated with the AFW system backleakage events.

The AIT team expects to exit on June 16, 1989 and issue a team report the following week.

Enclosure:

Drawing CONTACT: H. Livermore J. Lyons (817) 897-1500 (301) 492-3305 DISTRIBUTION:

One White Flint North MNBB Regions Mail To: DCS(IE34)

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