ML20151H011

IE Info Notice 81-33, Locking Devices Inadequately Installed on Msivs. W/O List of Recently Issued Info

ML20151H011
Person / Time
Issue date:	11/09/1981
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:
References
IEIN-81-33, NUDOCS 8107230036
Download: ML20151H011 (3)

Text

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• NS No.: 6835

' > ccession No.:

8107230036 IN 81-33 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 November 9, 1981 IE INFORMATION NOTICE NO. 81-33: LOCKING DEVICES INADEQUATELY INSTALLED ON '

MAIN STEAM ISOLATION VALVES Description of Circumstances:

During recent NRC inspections at the Grand Gulf Nuclear Station, Unit 1 (MississippiPowerandLightComgany),andHartsvilleNo.AlNuclearPlant (Tennessee Valley Authority), 26 Main Steam Isolation Valves (B21-F022 and 821-F028) manufactured by Atwood and Morrill Company, Inc., were inspected and were found to be deficient in installation of the locking plates.

These valves are fitted with locking plates which prevent rotation of hexag-onal nuts caused by vibration after they are tightened to the studs (part no. 26 Figure No. 1). A tab of the locking plate is bent during installation to engage the flats of the hexagonal nuts ( Figure No. 1, part nos. 26, 28 and 33).

The purpose of these studs is to couple the shaft from the air operator to the valve stem. Failure to bend these locking plates properly around the hexagonal nuts could cause the stroke of the valve stem to be lengthened resulting in the inability to properly open or clo'se the valve.

At the facilities mentioned above, these locking plates failed to engage the flat of the hexagonal nuts. Since these locking plates are installed at the manufacturer's plant, licensees have generally not been inspecting to verify that the locking plates are installed properly. Therefore, unless the licensee is required to perform valve rework on stem stroke adjustments in accordance with the Atwood and Morrill Instruction Manual, reverification of the valve-related work would not normally be performed.

This IE information notice is provided as an early notification of a potentially significant matter that is still under review by the NRC staff. InIftheNRC evalu-interim, ation so indicatos, further licensee action may be requested.

we expect that licensees will review this information for applicability to their facilities. We suggest that licensees with these Atwood and Morrill valves verify that the locking platas are bent sufficiently to engage the flats of the hexagonal nuts and perform their locking function.

No written response to this information notice is requested. If you need additienal information, please contact the Director of the appropriate NRC Regional Office.

Attachments:

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