ML20010E220

Interim Deficiency Rept Re Failure of Limitorque Limit Switch Rotors & Torque Switches,Originally Reported on 810713.Investigation of Cracking Problem Underway.Next Rept by Oct 1981.Also Reported Per Part 21

ML20010E220
Person / Time
Site:	Susquehanna
Issue date:	08/27/1981
From:	Curtis N PENNSYLVANIA POWER & LIGHT CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
REF-PT21-81 10CFR-050.55E, 10CFR-50.55E, PLA-915, NUDOCS 8109030213
Download: ML20010E220 (4)

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ggjfj Pennsylvania Power & Light Company Tv o N. rth Phnth Street

• Anento An. PA 18101 + 215 / 770 5i51 r j Norman W. Cortis , _ . , ,

Vice PicsrJont Engincenng & Construction-NucIcar 2i5 / 770-5381 oJ \

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August 27, 1981 [h s

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r tir. Boyce H. Grier i f b ..' iS[J J g j Director, Region I ( # pf* g.

Nuclear Regulatory Commission 0,\ Uf A

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631 Park Avenue /\f /

King of Prussia, PA 19406 h SUS?UEHIsNNA STE/J4 ELECTRIC STATION INTERIM REPORT OF A POTFMTIALLY REPORTABLE DEFICIENCY INVOLVING LI'4ITORQUE LIMIT SWITCH ROTORS AND TORQUE EWITCHES EIb 100450/100508 FILE NOS. 821-10/840-4 PLA--915

Dear Mr. Grier:

This ]?tter serves to provide the Commission with an int. arim report c f a potentially reportable deficiency involving the failure of Limitorque limit sw;tch rotors and torque switches. The condition involves cracking of the gray plastic type material which is the main constituent in these components.

The problem was originally reported by telephone to Mr. L. Narrov of :1RC Region I by Mr. A. Sabol of PP&L on July 23, 1981. Durir.g that conversation, Mr. Narrow was 3dvi;ed that the condition was considered potentially reportable u: der the provisions of 10 CPR 50. 55 (e; .

The condition (cracks in the gray material) weaNm the components and can lead to eventual failure by breakage. The attachment to this lotter contains a description of the problems, the cause investigation and corrective action presently underwa'/, and the safety impact that exi<:ts. PP&L NCR #81-338 and Bechtel NCR #6020 currently identify the deficiency.

Since the details of this report provido ir.f orma t ion relevant to the reporting reqdirements of 10 CFR 21, this cocresponc'ence is considered to al~o discharge any formal responsibility PP&L may hrre in compliance thereto.

We expect to issue a final report on this condition in Octnber, 1981.

Very truly yours,

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". W. Curtis 4

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Vice President-Engineering & Construction-Nuclear gj FLW:sab 8109030213 01082' Attachment

{DrtADOCK 05000337 POR

Mr. Boyce H. Grier -

2- August 27, 1981 ,

l cc Mr. Victor Stello (15 copies)

Director-Office of Inspection & Enforcement U. S. Nuclear Regulatory Commissior' l Washington, D.C. 20555 Mr. G. Mcdonald, Director (1)

Office ot Management Information & Program Control U. S. Nuclear Regulatory Commission Washington, D.C. 20555

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Mr. Gary Rhoads U. S. Nuclear Pequlatory Commission P.O. Box 52 Shicks)inny, PA 18655 1

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ATTACHMENT TO PLA-915 Subject Limitorque Limit dwitch Rotors and Torque Switches (Gray Material)

Descriotion of Potential Problem The limit switches on the Limitorque valve operators are valve position switches, which are used for the control of the valve operatcr a:d for indication of valve position. The torque switches are used for the control of the valve operatur when valves are required to be opened or closed to predetermined values of torque, or as a backup to the limit switch.

A problem has been identified with lbnit switch rotors and torque switches, both inside and outside of primary containment, whose bodies are made of a gray material.

Cracks have been found which extend half way through the gray material limit switch rotor, weakening it to the extent that it is eacily broken. Similarly, torque switches have exhibited large cracks in the gray material around the mounting screws and have been known to fail at the pir. on the rotor shaft which engages the adjustment cams on the torque switches. The pins have been shearing off, thus disabling the switch.

Cause PP&L Engineering does not have conclusive evidence as to the cause and nature of the cracks. This is being investigated 1 ch Limitorque Corporation.

PP&L Engineering must evaluate the data that Limitorque Corporation provides and the results of a site inspection program (see " Corrective Action" below) before a cause can be determined.

Safety Impact The torque and lbmit switches are used to control safety related system valve I operations. Failure of these valves to operate could have affected adversely the j safety of operation of the nuclear power plant.

Although the extent of the cracking problem is not yet defined, it has been determined that this condition is potentially reportable under the requirements of 10 CFR 50.55(e).

Corrective Action Limitorque Corporation has been sent a letter (PLE-961 dated 7/9/81) which

$dentifies the problem and requests them to determine the cause, scope and corrective action for the cracking problem.

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. i ATTACR4ENT TO PLA-915 i

An inspection of Limitcrque valve operators, which contain the gray material limit switch rotors and torque switches, is currently being performed to detemine the extent of the cracking problem. Preliminary results indicated that 17 of th<. first 60 gray rotors checked had noticeable cracks. A Limitorgt'e reprer.entative visited the jobsite during the week of July 20, 1981 to review the problem.

The initial corrective action by the Integrated Startup Group is to replace all gray material limit switch rotors and the cracked torque switches with corpenents made of a different type and color material which is suitable for this application. The final report is expected to be issued by October 30, 1981.

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