ML20071M418

Final Deficiency Rept Re Beloit Power Sys Failure to Tighten Stud W/Hex Nut Bolts on Shaft Spider Assembly to Torquing Specs.Initially Reported on 820423.Overrun Assembly Design Revised to Require Soldering Nut to Bolt

ML20071M418
Person / Time
Site:	Seabrook
Issue date:	09/20/1982
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE, YANKEE ATOMIC ELECTRIC CO.
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, SBN-326, NUDOCS 8209270117
Download: ML20071M418 (3)

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h IPUBLIC Ccmpanyof New SERVICE Hampehre 1671 Worcester Road Framingham, Mossochusetts 01701 (6171 - 872 - 8100 j September 20, 1982

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SBN-326 T.F. Q 2.2.2 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 Attention: Mr. Richard U. Starostecki, Director Dtvlsion of Resident and Project Inspection Re f e re nces: (a) Con 1truction Permit CPPR-135 and CPPR-136, Docket No s. 50-443 and 50-444 (b) Telecon of August 20, 1982, J. DeVincentls (YAEC) to Walter Baunack (NRC Region I)

Subject:

Final 10CFR50.55(e) Report; Misappilcation of Torquing Equipme nt by Beloit Power Systems

Dear Str:

On August 20, 1982, a reportable 10CFR50.55(e) Ltem was reported

[Re f e re nce (b)] regarding the possible misapp1Leation of torquing equipment on the d Lesel generator shaf t to rotor spider f astener. This Ltem was formally reported to the NRC by Belolt Power Systems (BPS) by letter dated April 23, 1982.

The following information is provided per 10CFR50.55(e)(3) and Ls considered to be the final report on this item.

DESCRIPTION OF DEFICIENCY Diesel generator sets manufactured with a Colt engine and BPS generators (frame size IX only) may have a loose stud / nut combination on the shaf t spider assembly. The re a re fourteen 3" studs with hex nuts to secure the generator shaft spider to the ro t o r. "he bolts were to be tightened to 4000 f t. Ibs.

torque by BPS. On a D-G set for another project, Colt performed 2 recheck of torque values to verify operation of torquing equipment used in the shop. It was founi that one bolt was not loaded at all, and three other bolts were only about thirteen pe rcent tight. BPS had provided Colt with documentation inlicating that bolting had been tightened per shop spectf tcations. This indicates a possible misapplication of torquing equipment.

8209270117 820920 DR ADOCK 05000 g

l United Statoo Nuclear Reguistory Co1 mission Ssptember 20, 1982 Attention: Mr. Richard W. Starostecki Page 2 ANALYSIS OF SAFETY I?iPLICATIONS Colt engineers have determined that for this valve failure mode, extreme overcooling with attendant risk of engine damage could occur with low raw water supply temperatures. The Seabrook D-G sets will utilize the Service Water System for removing heat f rom the Engine Jacket Cooling Water System.

The jacket water heat exchangers are designed to provide jacket cooling water a t 1100 with 900 service water, based on rated load operation. At reduced load, and with colder service water, a control valve malfunction could indeed cause overcooling in the engine, and a possible engine f ailure could constitute a substantial safety hazard. However, it is expected that this type of valve malfunction would be detected and corrected during periodic testing and maintenance operations.

CORRECTIVE ACTIONS When this problem was first reported, the overrun assembly design called for the nut to be staked in place. The design was revised by Robertshaw Controls to require soldering the nut to the bolt. This design change was not backfitted to previously manufactured overrun assemblies, so that some assemblies with the staked construction were supplied for nuclear plant D-G sets after the design change was made.

Colt has advised Robertshaw that the solder used to secure the nuts may be af fected by certata corrosion inhibitors used in Jacket Cooling Water Systems. Robertshaw, therefore, has determined that overrun assemblies att11 zing swagged locking should be installed as replacements in all suspect D-G sets.

Procedures for the replacement of the overrun assemblies and documentation sign-off sheets are being prepared. Information relative to availability of replacement assemblies is also being developed. The replacement parts will be supplied by Robertshaw on a no-charge basis. The parts shipments will be accompanied by instructions, and sign off sheets.

Af ter replacement work is done, the completed sign-off sheets will be returned 1 to Robertshaw and Colt, so that close-out actions can be recorded and reported to NRC.

ANALYSIS AND EVALUATION If the control valve malf unction described above was undetected and/or uncorrected, overcooling of the diesel engine could occur, with attendant risk of engine damage. Ilowever, this type of valve malfunction would be evident during periodic testing of the D-G sets, and appropriate corrective action would be taken.

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United States Nuclear Regulatory Commission September 20, 1982 Attention: Mr. Richard W. Starostecki Page 3 The corrective actions described by Colt and Robertshaw wLil preclude

. potentLal problems resulting from malfunction.of the overrun . assembly in the thermostatic valves. Installation of the replacement assemblies provided by -

Robertshaw will eliminate this potentLa1 problem.

j Very truly yours, i

YANKEE ATOMIC ELECTRIC COMPANY

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J. DeVincentls l Project Manager ALL/4d i

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