ML20128B047
| ML20128B047 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 08/08/1974 |
| From: | Wachter L NORTHERN STATES POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-74-08, IEB-74-8, NUDOCS 9212030546 | |
| Download: ML20128B047 (4) | |
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NORTHERN OTATEC P'O W E R COMPANY Minneapolis, Minnesota 55401
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August 8, 1974
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1 Mr. J. G. Keppler, Regional Director Directorate of Regulatory Operations Region III United States Atontic Energy Cmmission 799 Roosevelt Road Glen Ellyn, Illinois 61073
Dear Mr. Keppler:
i-IOTTICELID NUCLEAR GENERATING PIAVT Docket No. 50-263 License No. DPR-22 In accordance with DRO bulletin No. 74-8, this rer: rc is submitted to inform you that ITE bb1ded Case Circuit Breakers, Type IE-3, are not used at the hbnticello Nuclear Ge:arating Plant.
Yours very truly, fYct&
L. s. Wachter Vice Pres.-Power Prod, f, Systan Operations IJW/nmn cc: J F O' Leary, Directorate of Licensing G Charnoff Minnesota Pollution Control Agency Attn: E A Pryzina File 4
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UNITED STATED el ATOMIC ENERGY ' COMMISSION
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g DIRECTORATE OF REGULATORY OPERATIONS r
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REGION 111
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GLE:N ELLYN, ILLINOls 60137 (312) 854-2o00 Northera States Peeer Coopeny Doeket No. 50-263 ATTN Mr. Lee Nachter Deshet No. 50-182-Vise Freefdent Doekst No. 50-306 Power Prodnetten and systen Operation 414 Niaollet Mall Minneapolis, Miemaaota 54401 Centlease The saalosed Dao Dulletia No. 74-9 "Defistemey in the General Riastria Model 4KV Magne-Blast Circuit Breakers," to bains sent to you relating asportenes with osas of these siromit breakers at Verasat Yoakas and Calvert Cliffe anclear facilities.
This inforesties any have applisability at your facility. Aatten on your part is identified in Bestima B of the analesed Bulletia.
Simanealy, Jesse C. Esppler Basional Direnter.
Eagleeurs:
Dmo Bulletin No. 74-9 bec: R0]iles iPK Central Files Local PDR PDR
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.b August 9, 1974 DRO Bulletin No. 74-9
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DEFICIENCY IN GENERAL ELECTRIC MODEL 4KV MAGNE-BLAST BREAKERS We have recently received information from the licensee of Calvert Cliffs Units 1 and 2 relating to circuit breaker malfunctions in engineered safety systems.
These circuit breakers, General Electric Model 4KV safety Magne-Blast are used extensively at both PWR and BWR facilities.
The malfunctions, which could negate operation of engineered safety system components, were attributed to an oversized roller trip bar and improper clearances of related guide holes and linkages.
We have also received information from the licensee of Vermont Yankee station describing an installation deficiency of the auxiliary switch assembly installed in the General Electric Model 4KV Magne-Blast circuit
-breakers. Although the circuit breakers are similar in model to the units used at Clavert Cliffs, they are of a different type and are used at both PWR and BWR facilities. Pertinent details relating to both problems are contained in Section A below, and the related action requested by this Bulletin is contained in Section B.
A.
, Description of Circumstances Calvert Cliffs Units 1 and.2 On several occasions in the past, there had been unexplained " trip open" operations of several 4KV circuit breakers. On each occasion, the anomaly occurred immediately following an attempt to close the circuit breakers. Investigatien into the problem disclosed that causes for failure were attributed to an oversized spring discharge roller bar located on the right side of the breaker cubicle and improper clearances in the roller bar guide hole and associated linkages. The purpose of the roller bar is to trip open the breaker unit in the event it is inserted into the breaker cubicle while in its closed position. However, the installed roller bars were found to be approximately 1/4" longer than the desigu length, causing interference with the breaker auxiliary switch linkage.
Approximately 116 circuit breakers of the make and model described herein and equipped with the faulty roller bars and the above mentioned clearance problem are used in the two nuclear units at the facility.
Because we are requesting that you determine whether or not the subject breakers are used or are planned to be used at your facility the following details are provided for your information:
Manufacturer: General Electric Company Auxiliary Switch Assemblies in MC-4.76 Horizontal Dravout l
Metal Clad Switchgear 1
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Vermont Yankee The licensee reported that while investigating a problem involving a station service water pump 4KV circuit breaker, an electrician noted that the breaker stationary auxiliary switch assembly rear mounting bolt had loosened and was disengaged from its mounting plate. The loose bolt is one of two bolts that assist in maintain-ing proper switch contact alignment. The loosening and disengage-ment of the tie bolt caused misalignment of the switch auxiliary contacts which could have rendered those contacts inoperable.
Inspection of similar switch assemblies installed in forty-seven 4KV circuit breakers at this facility found that all switch assemblies exhibited varying degrees of bolt loosening, Because we are requesting that you determine whether or not the e
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subject devices are used or are planned to be used at your facility, the following details are provided for your information:
Manufacturer:
General Electric Company Type: Metal Clad, M26 Switchgear (This switchgear has the auxiliary switch assembly mounted to it and may be used with a large number of different circuit breakers.)
B.
Action Requested It is requested that you determine whether safety related (Class IE) circuit breakers of the described makes and models are in-stalled at your f acilities and provide the R0 Regional Office with your findings within 20 days from receipt of this bulletin.
With regard to the problem at Calvert Cliff s Units 1 and 2, if the subject breakers are installed, please include in your response a description and r_he results of your program to determine if you have oversized rv11er trip bars installed and the scheduled com-pletion date of your corrective actions.
For facilities under construction, please inform us of your plans to assure that appropriate modification has been implemented in all safety related circuit breakers of the type described that have been or will be installed at your facility.
With regard to the Vermont Yankee problem, it is requested that you ascertain the bolt tightness conditions of the switch assembly in question and include in your respcase a description and the results of your inspection program concerning these matters.
It is also requested that you inform us of your plans regarding the long term verification of bolt tightness of the switch assemblics.
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