ML20003B649

RO 50-336/81-8:as-built Hanger Review of Reactor Vessel Head Vent Piping Sys Determined Spring Can Type Hanger Was Installed Incorrectly,Resulting in Overstressing Socket Welded Joint.Spring Can Hanger Removed

ML20003B649
Person / Time
Site:	Millstone
Issue date:	02/17/1981
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
MP-2-4599, RO-50-336-81-8, NUDOCS 8102250092
Download: ML20003B649 (1)

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Reference:

Facility Operating License No. DPR-65 Docket No. 50-336 .

Reportable Occurrence 50-336/81-8 j

Dear Mr. Grier:

j This letter provides notification of Reportable Occurrence 81-8 pursuant to the requirements of Millstone Unit 2 Appendix A Technical Specifications, Section 6.9.1.8.i. The report concerns the discovery of conditions that require corrective measures or remedial action to prevent the existence or development of an unsafe condition. - ~

As a result of an as-built hanger review of the Reactor Vessel Head Vent Piping System, it was determined that a spring can type hanger was installed incorrectly. This system was modified extensively during the past refueling outage to install remotely operated head vent valves.

The hanger was located on 1"-ECD-5 (governing code ANSI B31.1), but the improper installation resulted in overstressing a socket welded joint of a 3/4" x l' tee in 1"-CCA-18 (governing code ASME Section III, Class 1).

Failure at the joint would have resulted in a non-isolable Reactor Coolant System leak. The stresses wert. reduced to less than allewable by recoving the spring can hanger and isolating then depressurizing the tee.

Repairs and/or modifications to the Head Vent System are being evaluated and will be completed during a fetr>re autage of sufficient length. In the interim, the head vent piping and specifically the overstressed joint will remain isolated and de;iressurized, o01

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0102250092 5

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Any further information will be provided in the two week report.

You n truly, j . -

NORTHEAST NUCLEAR ENERGY COMPANY h

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. Mroczka h' Station Superintendent

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