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UNITED STATES ATOMIC ENERGY COMMISSION osascTon ATs or nrous.Avony oran ATION, nsoson e
' 631 P ARK AVENUE KING OF PRUS$1 A, PENNSYLVANI A 19406
'JAN 171974 y
Jersey Centesi Pouer & Light Company Decket see. 50-219 Attentions Mr. I. R. F1mfreak, Jr.
50-363 Vise Prealdest - Someentsen
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Mam a== Avenue at Funeh Earl Boed Morristoun, Ese Jersey 07960 1
.Omntlemes:
A letter to the Directorate of Lisemaing, from the Vermont Yaakes Nealear Peeer Corporaties, dated Descober 27, 1973, was recently placed in the Public Deesment Room. The subject matter diesessed la that letter is felt to have possible applisability to your plant and, j
asserdingly, I have emeleoed a espy for year informaties.
Sincerely, 4
a El' den J. Brunner, Chief Reacter Operations Branch Reeleeure
- 1. Copy"of letter from the Yermont Yankee Nuclear Feeer Corporaties, 27,1973 p()- 73-3y) dated December ee Mr. J. T. Carrell, Plant Seperistendent bec: RO Fil DR en ral File PDF Loc PDR NS:.C DT".E Stat of New Jersey Reg Rdg Rm h
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PICTifRE INDEX A.
Breaker in open p~osition 1.
Stationary auxiliary swite'h 2.
Switch operating shaft 3.
Switch operating linkage
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4.
Breaker operating plunger B.
Breaker in closed position 1.
Breaker operating plunger C.
Typical breaker in compartment 1.
Breaker closed D.
Typical breaker in compartment.
1.
Breaker opened 9
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VERMONT YAhElc NUCLEAR POWE ) CORPORATION l
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ie SCVENTY SCVCN OROVC STHCCT RurLAso, VEltMONT 03701 VYV-3109
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g x,37 VERNON. VERMONT oS354 l
December 27, 1973 i
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Director Directorate of Licensing United States Atomic Energy Commission l
Washington, D.C.
20545 l
REFERENCE:
Operating License DPR-28
. Docket No. 50-271 Abnormal Occurrence No'. A0-73-34 Gentlemen:
l As defined by Technical Specifications for the Vermont Yankee
'Nuc. lear Power Station. Section 6.7.B.1, we are reporting the following Abnormal occurrence as A0-73-34.
On December 17, 1973, while investigating a reported probicm involving the "A" Station Service Water Pump 4 KV breaker, an cicetricia'n noted the fact that th'e breaker stationary auxiliary switch assembly' rear mounting tie bolt had loosened and was disengaged from its mounting plate.
This bolt serves to assist in maintaining proper switch contact alignment.
The loosening and subsequent backing out of the tic bolt caused some misalignment of the switch auxiliary contacts which would have rendered those contacts inoperable had the breaker operated.
This failure is not considered to be an abnormal occurrence, but is merely referenced to detail appropriate background information.
As a result of this incident, an investigation of all forty-seven (47) 4 KV breakers was initiated.
This investigation, which was completed on December 19, 1973, indicated that all 4 KV breakers exhibited varying degrecs of boly loosening.
Due to the fact that some breakers are associated witti safety related systems, it was determined that this condition was in violation of Technical Specifications, Section 1.A.4 in that it could have resulted in one or more engineering safety feature failures which could have caused ~or threaten to cause that feature or component to be incapabic of performing its. intended function as defined in'the Technical Spccifications.
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"5 Directorate of Licensing December 27, 1973 Page 2 Tightening of all loose switch tie bolts was initiated immediately i
up'on discovery and completed by 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on December 19, 1973. The l
reactor was operating at approximately 68% power at the time of this incident.
Of a total of forty-seven (47) switchgcar units (Cencral Electric Metal-clad, Type 106) at vermont Yankee, forty-three (43) contain 1200 amp., Cencral Electric tbgne-Blast circuit breakers, style AM-4, 16-250-8HB, and the remaining four (4) units contain 3000 amp., Magne-Blast circuit breakers, style AM-4, 16-350-1H.
All switchgear units are equipped with stationary auxiliary switches which are referenced in Concral E1cetric Company Instruction and Renewal Parts Manual CEH-1802R, Metal-Clad Switchgcar, Figure 45A.
l
'l The Plant Operations Review Committeo.(PORC) concluded that a possibic cause of bolt loosening could be' attributed to improper bolt tightening during factory assembly.
This possibility is supported by the fact that the switch must be pre-wired prior to being mounted to the front mounting plate. At this time, the rear mounting tie bolt and cou1d' percib1' be e tcricched uhdn 18.somewhat diffien1r en caa
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performing a final quality check.
An additional possible cause could l
be due to breaker operation.
During breaker closure, the switch is operated by the breaker operating plunger through mechanical linkage.
l When the breqker is tripped, the switch is again operated in the reverse direction by'a spring which has been held under tension by the' breaker operating plunger.
The operation of thc' switch in either direction is, of course, rapid and pronounced and might possibly contribute to a problem of this nature.
PORC determined that as a result of this incident, all 4 KV I
switchgcar stationary auxiliary switches should be inspected in threc l
months (which would be coincidental with approximately three breaker operations).
If a similar condition is found to be developing at that. time, the committee will undertake whatever further corrective action is required to assure resolution of the probicm.
In addition, a completo inspection of all breaker associated devices should bc conducted during cach plant refueling outage.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATIOh
- W B.W. Riley Plant Superintendent WFC/kbd 8
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