ML20058Q402

Informs NRC of Potentially Generic Problem Experienced W/Westinghouse DB-50 Reactor Trip Breaker.Info Being Provided Due to Potential Generic Implications of Deficiencies in Westinghouse Torquing Procedues

ML20058Q402
Person / Time
Site:	Prairie Island
Issue date:	08/02/1990
From:	Parker T NORTHERN STATES POWER CO.
To:	Brach E Office of Nuclear Reactor Regulation
References
NUDOCS 9008220069
Download: ML20058Q402 (2)

Text

I' , }&

h. .

Northom Sistes Power Company f

414 Nicollet Mall A.1 gust 2, 1990 Minneapones. Minnesota 55401 1927 i Telephone (612) 330$5500 j l

Mr E W Brach, Chief Vendor Inspection Branch Office of Nuclear Reactor Regulat!.on  !

U S Nuclear Regulatory Commissisn  !

Washington, DC 20555 l

PRAIRIE ISLAND NUCLEAR CENERATING PLANT l Docket Nos. 50 282 License Nos. DPR 42 l

50 306 DPR 60 Potential Generic Problems With Refurbishment i of Westinghouse DB 50 Reactor Trin Breakers The purpose of this letter is to inform the NRC of a potentially generic problem experienced with a Westinghouse DB 50 Reactor Trip Breaker t. hat was recently refurbished by Westinghouse. ,

Northern States Power has been sending Prairie Island DB 50 reactor trip breakers to the Westinghouse Replacement Component Services Facility for refurbishment over the last three years. Six of the ten Prairie Island DB 50 Reactor Trip Breakers have been refurbished to date. During the receipt inspection of one of these refurbished breakers in February of this year, nine of the breaker's Pole Unit Retaining Bolts were found to be improperly torqued. The bolt torque appeared to be well outside the

. specifications as outlined by the Westinghouse technical manual for these breakers.

A Nonconform!ng Item Report was issued following discovery of the problem and the bolts were torqued to the value specified in the Westinghouse technical manual. The investigation that followed included an audit of the Vestinghouse Engineering control Instruction for the DB-  :

50 breakers. That instruction was found to be deficient in that it did not require bolt torque values to be recorded. The imestigation also raised a concern that the Westinghouse torque procedure did not adequately reference the torque specifications included in the technical manual for the DB 50 breakers.

Westinghouse acknowledged the findings of the Northern States Power investigation and committed to revising their Engineering Control Instruction procedure to include recorded torque values.

Northet' States Power has requested that Westinghouse issue a Technical Bulletin to other plants using DB 50 reactor trip breakers drawing attention to the torquing requirements described in the technical manual for the DB 50 breakers.

[,g ((@ ,

g2

! s 1 612.

! // r j

, o.

c

,-'.o. .. Mr E W Br:ch August 2, 1990 Page 2

. Northem States Power Company i

The Northern States Power evaluation of this problem concluded that the improperly torqued bolts on the subject reactor trip breaker did not constitute a significant asfety hazard at Prai.rie Island and thus was not reportable under 10 CFR Part 21. This letter is being provided for the informatien of the NRC Staff due to the potential generic impitcations of the deficiencies in the Westinghouse torquing procedures.

6 Please contact us if you have any questions or require any further information on this issue.

I gy,s Thomas M Parker Manager

• Nuclear Support Services s c: Regional Administrator - Region III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC ,

G Charnoff '

l 1

l l

i

.