ML20054M117

Final Deficiency Rept Re Potential for Loss of Operability of Limitorque Motor Operator Models SMB-0-25 & SMB-000-5, Initially Reported 820108.All Electrical Terminals,Limit Switches & Torque Switch Bolts to Be Checked for Tightness

ML20054M117
Person / Time
Site:	Nine Mile Point
Issue date:	06/30/1982
From:	Rhode G NIAGARA MOHAWK POWER CORP.
To:	Starostecki R, Starosteki R, Staroteki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, CDR-82--1, CDR-82-00-01, NUDOCS 8207090267
Download: ML20054M117 (3)

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Y NIAGARA NUMOHAWK NSAGARA MOHAWK POWER CORPORAT10N/300 ERIE BOULEVARD WEST. SYRACUSE, N.Y.13202/ TELEPHONE (315) 474-1511 June 30, 1982 U.S. Nuclear Regulatory Commission Region I Attention: Mr. R. W. Starostecki, Director Division of Resident and Project Inspection 631 Park Avenue King of Prussia, PA 19406 Re: Nine Mile Point Unit 2 Docket No. 50-410

Dear Mr. Starostecki:

Enclosed is a final report in accordance with 10CFR50.55(e) for the deficiency regarding Limitorque motor operators. This condition was reported to your staff on January 8,1982 as a potentially reportable deficiency.

Very truly yours, NIAGARA M0 HAWK POWER CORPORATION t /_ b

$d d Senior Vice Pre ' dent PCF:ja Enclosure cc: Director of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. R. D. Schulz, Resident Inspector e i

._ O Niagara Mohawk Power Corporation Nine Mile Point Unit 2 Docket No. 50-410 Final Report for a Deficiency Under 10CFR50.55(e) Regarding Limitorque Motor Operators DESCRIPTION OF THE DEFICIENCY In 1981, Niagara Mohawk initiated an exploratory test program to assess the capabilities of Limitorque motor operators to withstand dynamic loads postulated inside a BWR containment. The Limitorque motor operators, Models SMB-0-25 and SMB-000-5, were tested. The following occurrences were noted during the tests:

1. Operator SMB-0-25 experienced excessive limit switch chatter which eventually resulted in a loss of operability during a vibratioE aging test performed in accordance with IEEE Standard 382-1980. The limit switch was determined to be defective by the manufacturer. A new limit switch was installed, and the test was repeated. The new limit switch also experienced excessive contact chatter throughout this test.

Testing, in accordance with IEEE Standard 382-1980, is not required to meet the criterion and bases stated in the PSAR or construction permit.

2. Operator SMB-000-5 experienced a loss of operability during an early stage of the dynamic load test. Examination of the operator revealed that all the screws holding various subassemblies of the limit switch were loose and one of the four limit switch rotors was broken. It was concluded that the breakage of the rotor was caused by the loose limit switch contact assembly.

These occurrences were discussed with the manufacturer. The manufacturer indicated a possibility of the screws becoming loose during shipment. The manufacturer recommended that all the screws be checked for tightness and that the limit switch contact be inspected and adjusted, if necessary, for proper contact pressure.

Two new operators were tested. A pretest inspection of the operators at the test laboratory revealed that several limit switch assembly screws in one operator were loose. Also, several limit switch contact subassemblies in both operators required adjustments for proper contact pressure. Prior to the start of the tests, all the screws were tightened and the limit switch contact subassemblies adjusted in accordance with the manufacturer's newly developed procedure s. The test results were satisfactory.

During a subsequent inspection of nine randomly selected Limitorque motor operators at the Unit 2 site, the following conditions were observed:

1. All nine operators have several loose screws in the limit switch assemblies.

2. Two operators have loose torque switch mounting screws.

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3. Limit switch and torque switch subassemblies in at least six

! operators will require adjustments in accordance with the manufacturer's newly developed adjustment procedure.

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4 Electrical terminals at the torque switches in two operators are loo se.

ANALYSIS OF SAFETY IMPLICATIONS Loose limit switch and torque switch assembly screws, improper switch contact

! pressure, and loose electrical ' terminals could cause misoperation of safety

. related equipment. Under a dynamic loading environment, such as during a i seismic event, each one of the above conditions could result in a possible r interruption in the valve control circuit. This interruption could cause the motor controller to drop out, resulting in an incomplete valve stroke. The J intended function of an active valve could thus be compromised.

CORRECTIVE ACTIONS .

4 The following corrective actions will be taken on all safety-related  ;

} Limitorque motor operators prior to plant operation:

i i j 1. All the electrical terminals will be checked for tightness. ,

i I 2. Limit switch and torque switch contact gaps will be adjusted in ,

accordance with the manufacturer's procedure.

i 3. Limit switch and torque switch screws and/or bolts will be tightened i 1 as follows:

Screw Diameter (In.) Torque (In.-Lbs.)

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1/4 110 1 5/16 150

The above measures were determined to be acceptable through a dynamic 2

test program and will correct improper limit or torque switch contacts, loose limit and torque switch screws, and loose electrial  :

j terminations in the safety-related Limitorque motor operators used at '

Unit 2.

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