ML18037A446

Proposed Tech Spec Amend Diesel Generator Maint Insp Frequency Change Engineering Evaluation Rept.

ML18037A446
Person / Time
Site:	Browns Ferry
Issue date:	03/12/1993
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18037A445	List: ML18037A444 ML18037A446 ML18037A447
References
NUDOCS 9309080151
Download: ML18037A446 (12)

Text

BROWNS IiEARF NUCLEAR PLANT PROPOSED TI".'CIINICALSPLi CIIiICATION AMENDMENT DIESEL GENERATOR MAINTENANCEINSPECTION PRZQ UZWCF CF1ANGE ENGINLiX<RING.EVALVATIONRL<'PORT Prepar by D te

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I PROPOSED TECHNICAL SPECIFXCATXON AMENDMENT

=HNGXNEHRXNG EVALUATION OF CFIANGH XN DIESEL GENERATOR MAXNTENANCE XNSPECTION TABLE OF CONTENTS Page 1.0 Xntroduction 2.0 Proposed Technical Specification Revision 2.1 Description 2.2. Justification 0 Page 2,o f 6

PROPOSED TECHNXCAL SPECXFXCATXON AMENDMENT ENGINEERING EVALUATXON OF CHANGE XN DIESEL GENERATOR MAXNTENANCE XNSPECTXON 1.0 Introduction Browns Ferry Nuclear Plant has eight diesel generators (DG) which are shared between three units. Four .DGs are used primarily for Units 1 and 2, and the remaining four are used primarily for Unit 3'. . The DGs are manufactured by the ElectroMotive Division of General Motors -and consist of a single EMD model 20-645-E4 engine driving an EMD A20 generator rated at 2600 kW (3250 kVA) continuous.

Browns Ferry Nuclear Plant Technical Specification 4.9.A.l.d currently requires each diesel generator be given an annual inspection in accordance with instructions based on the manufacturex's recommendations. As a result, each of the eight diesel generatoxs used as emergency power supplies must be xemoved from service every 12 months for a period of 4 to 7 days to perform these vendor required tasks. The average outage time for . the last seven perfoxmances of annual maintenance was'10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. This results in increased diesel generator unavailability during the times the diesels may be most needed.

The maintenance performed on the DGs are based primarily on EMD Maintenance Xnstructions (MX) 1728 and 1742. As stated in the introduction to .MI 1742, these instructions are "intended to serve as a 'guide when establishing maintenance schedules that will meet the particular requirements of individual operations, and planned economic life of the engine and associated equipment." The MX further states "Because operating requirements for, this equipment can vary from standby, to periodic, to continuous usage, the maintenance procedures must be modified to suit individual requirements."

Clearly, EMD recognized the diverse applications their engines would be used in, .and did not intend to establish any definitive maintenance requirements.

The EMD MIs are divided into three sections. The first section specifies maintenance to be performed before and after each start. The second and third sections specify maintenance performed on a "calendar time" basis and "running time" basis respectively. Due to the extremely limited xun times on the BFN diesels (each diesel averages about 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> a year), our maintenance is based on the first two sections. The "calendar time" section gives maintena'nce to be performed every day, week, month, three months, six months, year, two years, three years, six years, and twelve years. BFN Technical Specifications. mention " 'only the annual maintenance requirements.

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PROPOSED TECHNXCAL SPECXFXCATION AMENDMENT ENGXNEERXNG EVALUATXON OF CHANGE XN DXESEL GENERATOR MAXNTENANCE XNSPECTXON 1.0 Xntroducti.on (cont)

II Recent nuclear industry initiatives have sought to balance high diesel generator reliability with low diesel unavailability. To achieve this, it, is necessary to evaluate all maintenance and testing performed on. the diesels with respect to its effectiveness in increasing reliability.

Generic Letter 84-15, Proposed Staff Actions To Xmprove and Maintain Diesel Generator'eliability, was one document intended to aid in improving diesel reliability. This was important in that it recognized the detrimental effects of excessive diesel generator testing, especially

'ocument those which utilize cold fast. starts (one in which the diesel starts from standby conditions and accelerates to full speed within 10 seconds without the use of a preheat and prelube period), as the chief contributor to diesel engine wear in emergency power applications. As a result of this, BFN implemented a diesel reliability program and reduced the number of cold fast starts to once every 184 days and as required by the emergency load acceptance tests performed each outage.

One of the industry . groups working on improving DG reliability is the EMD MKW Power Systems Ownersconsists Group (EMD of Owners Group). The EMD Owners Group representatives of 23 nuclear utilities which utilize EMD manufactured diesel generators, as well as representatives of General Motors ElectroMotive Division (EMD), the manufacturer of the diesels, and MKW Power Systems, the nuclear supplier of EMD parts and services. The group was formed to utilize. the experience of the users of this type diesel engine and act as a clearinghouse of this information.

TVA and Browns Ferry are attending members of this group.

Recent meetings of this group had discovered that several utilities implement different mai:ntenance schedules on their EMD diesels. The represented plants also have different Technical Specification requirements

. concerning diesel generators. The Technical Specification differences result primarily from the variety of nuclear unit suppliers and plant vintage. Xn order to attempt to standardize maintenance requirements on EMD diesels at nuclear'ites, to identify the type and frequency of maintenance required to assure high diesel reliability, and to identify maintenance practices which penalize diesel generator availability while not significantly contributing to increasing'eliability, the Owners Group formed a subcommittee to thoroughly investigate current maintenance practices. The subcommittee then drafted Page 4 of 6

PROPOSED TECFINXCAL SPECXFXCATXON AMENDMENT ENGXNEERXNG EVALUATXON OF CIIANGE'XN DXESEL GENERATOR MAXNTENANCE XNSPECTXON 1.0 Introduction (cont)

I a maintenance document which was reviewed and approved by all voting utility members of the EMD Owners Group. This document has been reviewed and concurred with by EMD and MKW Power Systems. A formal letter of concurrence was drafted by EMD to be given to the Owners .Group for use in allowing each plant member to revise their diesel maintenance'rograms.

2.0 Pro osed Technical S ecification TS Revision 2.1 Descri tion The proposed

'f TS amendment, current requirement PTS 93-01, will revise the TS 4.9.A.l.d to allow the inspection to be performed once every 24 months. The wording shall be as follows:

Each diesel generator shall be inspected in accordance with instructions based on the manufacturer's recommendations once every 24 months.

2.2 Justification BFN's current Technical Specifications are not specifically applicable to diesels in, nuclear service.

The vast majority of EMD engine experience is based on use as locomot'ives and in marine power. These applications require large amounts of operating time, harsh operating environments, and long periods of operation between starts. The diesels used in standby power applications operate for small periods between starts, typically two,hours, and operate in relatively mild environmental conditions. As a result, these

.applications do not require the same maintenance frequency to ensure required reliability.

The maintenance document written by the EMD Owners Group takes the maintenance recommendations given in MX 1728 and 1742 and addresses each one specifically for nuclear service. As .a result, some differences between the Owners Group document and the EMD MX's have emerged.

Nhile some requirements have been tightened, others have been relaxed. Specifically, the annual inspections given in the MX's have been changed to once each refuel cycle with the interval between inspections to be 18 to 24 Page 5 of 6

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PROPOSED TECHNXCAL SPECIFXCATXON AMENDMENT ENGINEERING EVALUATION OF CHANGE XN DXESEL GENERATOR MAXNTENANCE XNSPECTXON 2.2 Zusti fication (cont) months. The effect of thi's change on engine reliability is not significant since these inspections are wear related engine inspections, such as mechanical inspections and adjustments, filter replacements, cleaning of strainers and internal components, functional checks of alarms and timers, and inspection of the generator. With the implementation of the new inspection interval of once every two years, engine run time will have increased from 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> between inspections to 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. Even if engine operation is required for, extended times during these two years, it should be noted that the first maintenance required by EMD on a "running time" basis is at 500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> of operation. Based on th'is, it is apparent that the diesel may run for an addition 400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> (or 16 days) during this period without the need for any additional inspections. Since BFN has already reduced the most significant contributor to diesel generator wear by eliminating all unnecessary cold .fast starts, wear on the. diesels is expected to be minimum in the time periods between inspections. Xnspections performed on the. diesel generators, including recent annual, two year, three year, and six year inspections, have revealed no'significant wear on any of the diesel parts required to be inspected annually.

This Technical Specification revision is also supported by the fact that several plants of "the same

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type (BWR-4) and vintage as BFN also utilize EMD diesels and have different Technical Specification requirements concerning diesel maintenance intervals. Most notably .

was the recent amendment to Toledo Edison's Davis-Besse Nuclear Power Station's Technical Specification which extended the 18 month diesel generator. inspection during shutdown to a maximum inspection interval not to exceed 30 months. Davis-Besse uses the same type diesels used at BFN, EMD 20-645-E4 engines. Also, the latest proposed Standard Technical Specifications for BWRs contain no requirement to perform any inspections recommended by the diesel manufacturer.

Based on the justifications given, changing the annual inspection requirement to one inspection every operating cycle should ensure the diesels are maintained at the existing levels of high reliability while improving'he availability of the diesel generators to perform their intended safety functions.'age 6 of 6

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ENCLOSURE 2 EMD-PS OWNERS GROUP RECOMMENDED MAINTENANCE PROGRAM

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