ML20040H291

Interim Deficiency Rept Re Capability of Limitorque Motor Operators to Withstand Dynamic Loads,Initially Reported 820108.Problem Still Under Investigation.Next Rept by 820630

ML20040H291
Person / Time
Site:	Nine Mile Point
Issue date:	02/03/1982
From:	Rhode B NIAGARA MOHAWK POWER CORP.
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8202180048
Download: ML20040H291 (3)

Text

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M V NIAGARA * '

R UMOHAWK NIAGARA RIONAWK POWER CORPORAT10N/300 ERIE BOULEVARD WEST, SYRACUSE, N.Y.13202/ TELEPHONE (315) 4741511.

4 February 3, 1982 Of fice of Inspection and Enforcement Region I s Attention: Mr. R. W. Starostecki, Director @ q)

Division of Resident and Project Inspection U. S. Nuclear Regulatory Commission # #

9 631 Park Avenue 6 # h @O.'^

- King of Prussia, PA 19406 p} I.fQ2/ ,,

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Re: Nine Mile Point Unit 2 Sg Docket No. 50-410  % [ply4 g

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Dear Mr. Starostecki:

Enclosed is an interim 30-day report in accordance with 100FR50.55(e) for the oeficiency regarding Limitorque motor operators. This condition t,as reportea to your staf f on January 8,1982 as a potentially reportable deficiency. A final report will be submitted by June 30, 1982.

Very truly yours, NIAGARA M0 HAWK POWER CORPORATION

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e ld K. Rhode Vice Presi ent System Project Management PM:ja Enclosure cc: Resioent Inspector DOC o!hoo4o Y

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-e e Niagara Mohawk Power Corporation Nine Mile' Point Nuclear Station - Unit 2 Docket No. 50-410 Interim Report for a Potentially Reportable

, Deficiency Under 10CFR50.55(e)

Regarding Limitorque Motor Operators Description of the Deficiency l

Niagara Mohawk Power Corporation initiated an exploratory test program to assess the capabilities of Limitorque motor operators to withstand dynamic loads postulated inside the 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 experienceo excessive limit switch chatter and this condition eventually resulted in a loss of operability during a vibration 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 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 and recommended that all the screws be checked for tightness and also that the limit swtich 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 proceoures. The test results were satisf actory.

During a subsequent inspection of nine randomly selected Limitorque motor operators at the Nine Mile Point - Unit 2 site, the following conoitions were ob served:

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1. All nine operators have several loose screws in the limit switch a ssemblie s.

2. Two operators have loose torque switch mounting screws.

3. Limit switch and torque switch subassemblies in at least six operators will require adjustments in accordance with the manuf acturer's newly developed adjustment procedure.

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

The problem is still being investigated and a final report, including the corrective action to be taken and an analysis of safety implications, will be submitted by June 30, 1982.

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