RBG-31618, Part 21 Rept Re Defect in Standby Diesel Engine Replacement Rocker Arm Assembly Supplied by Cooper Industries.Caused by Use of Oversized Casting.Rocker Arm Assembly & Corrector Rod Replaced & Exhaust Valve Stems Readjusted

Part 21 Rept Re Defect in Standby Diesel Engine Replacement Rocker Arm Assembly Supplied by Cooper Industries.Caused by Use of Oversized Casting.Rocker Arm Assembly & Corrector Rod Replaced & Exhaust Valve Stems Readjusted

ML20055C581
Person / Time
Site:	River Bend
Issue date:	10/13/1989
From:	Deddens J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
REF-PT21-89 RBG-31618, NUDOCS 9005250107
Download: ML20055C581 (4)

Text

.

.1.,.. . . . . - . ,

) , .

+ .

. O GULF ' STATES- UTILITIES . COMPANY RP/(R BE ND $1 ATiCat ,535104tCE Box M0 ST, F H ANCIS VILLE. LOutStAN A 70775 ME A CODi' 504 63f, eO94 346 8e61 t

October 13, 1989 RBG-31618 File Nos. G9.5, G9.25.1.2

$ $ & h(N U -S. Nuclear Regulatory Commission s Region IV- , j gj]g  ;

611 Ryan Plaza Drive, Suite 1000 I .

Arlington, TX 76011 , I h g&.s . ,- ...

Gentlemen:- .

e

. River = Bend Station - Unit IT Docket No. 50-458

^li .

' Pursuant-'to .the : requirements . = of 10CFR21.21(b)(2), Gulf States

. Utilities ~ Company-(GSU)-is submitting this written report. of a-defect in -a- standby diesel engine at River. Bend Station. The attached report provides the-information required by 10CFR21.21.

.Sincerel ,

f +

,~ '~

J. C. Deddens Senior Vice President River Bend Nuclear Group

'JCD/JEB/LAE M %f DyGRH/DNL/ch' 64 Attachment-cc: Officesof Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555-

.NRC Resident Inspector

-Post Office" Box-1051 St. Francisv111e, LA 70775 Mr. Alan ~Barich g Cooper Industries, Energy Services Group - h. l Post Office Box 2161 0akland, CA 94621- p {"

. - 9005250107 891013 /

PDR ADOCK 05000458 j -

S PDC

N i: .

O OL 4

ATTACHMENT Gulf States Utilities Company River Bend Station - Unit 1 -

Report of a Defect Per 10CFR21 3' Standby Diesel Engine Rocker Arm Assembly

1. Name and address of individual (s) informing the NRC.

Written notification is provided by this report from Mr. J. C. Deddens, Senior Vice President, Gulf States Utilities Company.

Address: Gulf States Utilities Post 0ffice Box 220 St. Francisville, LA 70775

2. LIdentification of the facility, the activity, or the Basic Component supplied for the facility or activity which fails to comply or contains a Defect.

The ; defect was found in a standby' diesel generator (Mark No. LEGS *EGIA) intake rocker arm assembly at River Bend Station - Unit 1.

3. Identification of the~ firm constructing or supplying the Basic Component which fails to comply or contains a Defect.

The -subject intake rocker arm assembly was supplied by Cooper Industries 1 Energy 1 Services Group, Enterprise Engine Services.

4. Nature of the Defect or failure to comply and the safety hazard which is created by'the Defect or failure to comply.

A replacement intake rocker arm assembly was found to be defective due to

-an oversized cesting. The assembly was placed in the Division I standby 1 diesel engine valve train, cylinder 1. After running the engine for a short time, the engine was shutdown due to excessive noise.

Investigation' determined that interference in the valve train was caused by an oversized casting. The interference- prevented the connector pushrod, which drives the exhaust rocker arms, from seating squarely in

,the socket' in the rocker arm, causing an incorrect exhaust valve adjustment. After running the engine, the misaligned connector rod chipped a piece from the edge of its pushrod socket, increasing the exhaust valve clearance to an out-of-tolerance value. Excessive valve train noise was caused by the impacting pushrod/ rocker arm / valve stem train.

i Page 1 of 3

> \

• The intake, intermediate, and exhaust rocker arms are metal castings.

When casting the rocker arms, cores are placed in the mold to provide through-holes where- the tappets will- be- installed. It has been determined that the probable cause of the casting defect is that the cores. shifted to one side, allowing more metal on the rear side than the forward side. The difference in location apparently could not be made up in final reaming of the tappet holes. The core shift did not reduce the casting thickness on the short side to an out-of-tolerance condition.

R The subject rocker arm and valve train are integral components -of the standby diesel engine, which is required to ensure a safe shutdown of the plant when normal power is not available. Thus, the rocker arm is a basic component. The defect, as described above, could have lead to a substantial safety hazard if it had not been found during initial testing following maintenance. With excessive valve clearance caused by the interference and chipped socket, the valve train'could be damaged to the point- of depriving the diesel of power from one cylinder. This could effect the unit's capability to maintain a stable load due to the unbalanced running condition. Other damage to the engine may also occur.

It is noted that at the time of original discovery of the problem, during a refueling outage, the subject diesel was not required to be operable per RBS Technical Specifications. Thus, the= safety hazard described in this report is based on evaluation of the condition. The subject rocker arm assembly was a replacement part and was not used in an " operable" diesel engine at RBS.

5. .The-date on which the information of the Defect or failure to comply was obtained.

The initial condition was found on April 10, 1989. Evaluation of the condition per 10CFR21 determined _ the condition to be reportable on October 13, 1989.

6. In the case of a Basic Component which contains a defect or fails to comply, the number and location of all the components in use at, supplied for, or being supplied for one or more facilities or activities subject to the regulations of 10CFR21.

The intake rocker arm is an integral part of the Division I standby diesel generator. There are eight intake rocker arms in each diesel engine. River Bend Station utilizes two diesel engines of the same manufacturer and model as described in this report. GSU is, by copy of this letter, notifying the manufacturer of the defect.

7. The corrective action which has been, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action.

Page 2 of 3

'l

q. . LO1 O

~

I ,

The initial corrective action taken was to replace the intake rocker arm and' connector rod. The exhaust valve stems and tappets were found to be undamaged. Readjustment of the valves' completed the rework. In addition, n' comment was added to the inspection and maintenance requirements for the valve train requiring that any time a new . intake rocker arm is- installed, an inspection be performed-to specifically verify casting-to-connector rod clearances, and to check the adjustment of the connector rod before the valve lash is adjusted.

8. .Any advice related to the Defect or failure to comply about the facility,-

activity, or Basic Component that has been, is being, or will be given to purchasers or licensees.

Not applicable.

Page 3 of 3

.-x----__ _-_ __ _ _ _ _ _ _ _ _ _ _ _ _ .