ML19262A211

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Nonroutine 30-Day Rept 74-04 Re Deficiency in Design of Internals Handling Fixture Spherical Nut Retaining Device. Caused by Inadequate Design.Field Change FC-120 Initiated
ML19262A211
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 01/30/1975
From:
METROPOLITAN EDISON CO.
To:
Shared Package
ML19262A202 List:
References
74-04, 74-4, GQL-0709, NUDOCS 7910260553
Download: ML19262A211 (1)


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Three Mile Island Nuclear Statien Unit 1 (CC-1)

Docket Nc. 50-239 Cperating License Uc. OPE-50 Ucnrcutine 30-Day Report Th-Ch "otification of a Deficiency in Design of the Internals Handling Fixture Spherical Nut Petaining Device

1. Descrittien cf Deficienev During the preparaticn for plenum assembly re Oval frcm the reactor vessel at IXI-1, it was noticed thm: the spherical nut was not secured to the threaded red and could beccce unthreaded. The set screvs en the three assemblies were found to be either missing, loose, or cf the vrcng length.

As a result of review by Met-Ed's Corporate Technical Support Staff, this situation has been determined to constitute a design deficiency which is reportable in acccrdance with 6.7.2.b cf the TM:-l Technical Specifications.

2. Corrective tetien A design review undertaken by Met-Ed's centracter fcund that the criginal design for preventing the spherical nuts fres rotating relative to the threaded rods (i.e. , beccte unthreaded) was inadequate. The spherical nuts could be unthreaded during the adjusting procedure, leaving potentially inadequate thread engagement to suppcrt the weight of the internals.

The deficiency was fixed by Field Change FC-12C, which censisted cf drilling a hele in the threaded rod to ensure capture by the set screw and staking the set screw to ensure that the set screws veuld not back cut.

d 7910260-

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