ML20214E485

Paper 1.6, Emergency Diesel Generators Mfg by Tdi Problems, Their Resolutions & Lessons Learned

ML20214E485
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Issue date:	11/10/1986
From:	Berlinger C, Murphy E NRC
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PAPER NO. 1.6.

" EMERGENCY DIESEL GENERATORS MANUFACTURED BY TRANSAMERICA DELAVAL, INC.

PROBLEMS, THEIR RESOLUTION AND LESSONS LEARNED" l C. H. Berlinger and E. L. Murphy i United States Nuclear Regulatory Commission

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Washington, D.C. 20555

.o ABSTRACT m Emergency standby diesel generators manufactured by Transamerica

. Delaval, Inc, experienced a number of major problems during preopera-tional qualification testing at several U.S. nuclear sites. Most H -

notably ~these have included a complete fracture of a crankshaft, an

-o engine block f ailure, piston failures, and cracked and leaking cylinder I heads. These problems appear to stem from deficiencies in design and j manufacturing quality by the engine manufacturer. This paper discusses j some of the more significant problems experienced and actions taken by

the nuclear utility owners and the NRC to reestablish confidence in the l 3 reliability of these engines and to qualify these engines for nuclear

,i service.

4 8611240457 861110 PDR FOIA ELLI596-656 PDR 8

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1. Introduction and Background During the 1970s, many utilities ordered diesel generators from Transamerica Delaval, Inc. (TDI) for installation at nuclear plants in the USA. The first of these engines to become operational at an operating plant were at San Onofre Unit 1 in 1977. However, nuclear plant operating experience with TDI Emergency Diesel Generators (EDGs) remained very limited until preoperational test programs were commenced at Shoreham and Grand Gulf Unit 1 in the early 1980's.

Concerns regarding the reliability of large bore, medium speed '

diesel generators manufactured by TDI far application at domestic nuclear plants were first prompted by a crankshaft failure at Shoreham in August 1983. However, a broad pattern of deficiencies in critical engine components subsequently became evident at Shoreham and at other nuclear q and non-nuclear facilities employing TDI diesel generators. These 3 deficiencies stem from inadequacies in design, manufacture and quality g- assurance / quality control (QA/QC) by TDI.

In response to these problems, 11 (now 13) U.S. nuclear utility owners formed a TDI Diesel Generator Owners Group to address operational and regulatory issues relative to diesel generator sets used for standby i emergency power. On March 2, 1984, the Owners Group submitted a proposed d program to the NRC which, through a combination of design reviews, quality revalidations, engine tests and component inspections, was

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intended to provide an in-depth assessment of the adequacy of the respec-

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tive utilities' TDI engines to perform their safety related function [1].

1 The Owners Group Program Plan involved the following major elements:

1. Phase I: Resolution of known generic problem areas intended by the Owners Group to serve as a basis for the licensing of plants during the period prior to completion of Phase II of the Owners Group Prbgram.

g 2. Phase II: A design review / quality revalidation (DR/QR) of a large g set of important engine components to assure that their design i and manufacture; including specifications, quality control and i quality assurance and operational surveillance and maintenance, are adequate.

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3. Expanded engine tests and inspectibns as needed to support Phases I and II. ,

Under Phase I, the Owners Group has performed a comprehensive review of operating history of TDI Series DSR-4 engines in both nuclear and non-nuclear service for purposes of identifying significant problem areas.

The Owners Group has evaluated the causes of these problems and issued recommendations to the individual owners concerning actions they should take to resolve these problems including needed component upgrades or modifications, component inspections, and engine tests.

Phase II of the Owners Group Program has proceeded beyond known problem areas to systematically consider all components (approximately 150 to 170 component types per engine) important to the operability and reliability of the engines. Phase II is intended primarily to ensure that significant new problem areas do not develop in the future due to deficiencies in design or quality of manufacture. The Owners Group performed the Phase II design reviews and, as was the case for Phase I, recommended needed component upgrades and modifications and component

. inspections to validate quality of manufacture and/or assembly. A major element of the Phase II Program was the preparation of a comprehensive engine maintenance and surveillance program to be implemented by the

, individual owners.

The staff has concluded that the Owners Group Program Plan incorporates the essential elements needed to resolve the outstanding

, concerns relating to the reliability of the TDI EDGs for nuclear service f [1]. The staff expects to complete its final evaluation of the Owners

- Group findings and recommendations stemming from this program in the Fall of 1985. In the interim, the staff has concluded that issues warranting g priority attention have been adequately resolved at several plants such

-g that the TDI EDGs will provide reliable service through at least the

-g first refueling outage (by which time the staff will have completed its j overall review). This finding has permitted the staff to proceed with

.S issuance of operating licenses for these plants and has generally been 3 based on (1) actions taken by the Owners Group and the individual owners 4 to resolve known problem areas, (2) implementation of an acceptable engine maintenance and surveillance program, ard (3) incorporation of 1 plant Technical Specification requirements and operating procedures which h ensure that the engines will not be operated in an overstressed condition.

l J Section 2 of this paper focuses on several of the known problem I areas considered under Phase I of the Owners Group Program and describes l how these problems have been resolved to the satisfaction of both the owners ind the NRC staff. Section 3 of this paper focuses on the role lh r

of periodic maintenance and surveillance in ensuring the continued reliability / operability of tN TDI engines for the life of the plant, and also addresses certain testing and operational consiriarations.

3 2.0 Some Significant Problem Areas and their Resolution 2.1 Crankshafts for TDI Model DSR-48 Engines TDI Model DSR-48 engines (used at Shoreham and River Bend) are 8 cylinder inline engines with a 3500 kw nameplate rating and a 3900 kw 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> overload rating. The Shorehan crankshaft failure in August 1983 occurred in the emergency diesel generator (EDG) 102 engine during a two hour overicad test at 3900 kw. At the time of the failure, the affected engine had been run for a total of 671 hours0.00777 days <br />0.186 hours <br />0.00111 weeks <br />2.553155e-4 months <br />, including 254 hours0.00294 days <br />0.0706 hours <br />4.199735e-4 weeks <br />9.6647e-5 months <br /> at loads 2 3500 kw and 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> at loads > 3900 kw. Crankshafts in the Shoreham EDG-101 and EDG-103 engines were subsequently inspected and also found to contain severe cracks.

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. Subsequent investigation by Failure Analysis Associates, Inc.

(FaAA), a consultant for the subject utility and also later for the Owners Group, revealed the failures to be fatigue related, caused by torsional vibration. Independent analyses performed by FaAA established that the crankshaft had been overstressed relative to the Diesel Engine Manufacturers Association (DEMA) standards [2].

The original crankshafts at Shoreham that had 11 inch diameter ,

crankpins with 1/2 inch fillets were replaced with new crankshafts having

_ 12 inch diameter crankpins with 3/4 inch fillets. Independent analyses performed by an expert consultant to Pacific Northwest Laboratories (PNL)

• on behalf of the NRC indicated that the crankshafts did not meet DEMA at 3500 kw for combined orders. PNL and the NRC staff concluded that there was insufficient evidence to either approve or disapprove the replacement crankshafts for operation at engine loads at or above the 3500 kw E nameplate continuous rating. However, PNL and the NRC staff concluded M that unlimited fatigue life for the crankshafts could be demonstrated by

{ testing one of the Shoreham engines for 107 engine stress cycles (about 6 750 hours0.00868 days <br />0.208 hours <br />0.00124 weeks <br />2.85375e-4 months <br />). That test would be conducted at a load at or above the maximum emergency service load which could be placed on the engines

.h during a design basis event. The test load would be designated the g

3 " qualified load" for the engine. Successful completion of such a test j would be considered sufficient by PNL and the NRC staff to demonstrate g that the " qualified load" is below the fatigue endurance limit [3].

A E In response to the NRC staff position, a 107 cycle test was d completed for the Shoreham EDG-103 engine which established 3300 kw as the qualified load level for the Shoreham engines. Subuquent NDE j - inspection of the crankshaft confirmed the absence of cracks at critical fillet and oil hole locations, and provided the basir, for approving e operation of these engines at loads up to 3300 kw.

I Although the River Bend engines were identica; to the Shoreham 3 engines", the River Bend diesel generator set torsional characteristics R were found to be somewhat different from those at Shoreham due to 9 differences in their flywheels and generators. Based on the 107 cycle hG tests conducted at Shoreham, the River Bend engines were approved for a qualified load of 3130 kw; a load which produces comparable crankshaft

C stresses as those in the Shoreham engines operating at 3300 kw [4].

f Plant Technical Specifications and. engine operating procedures at l Shoreham and River Bend have been revised to ensure that the qualified

! load levels at the respective plants will not be exceeded in future .

I service.

2.2 Crankshafts for TDI Model DSRV-20 Engines San Onofre 1 is the only U.S. plant with TDI DSRV-20 engines. This model is a 20 cylinder engine in a " Vee" configuration with a continuous rating of 8800 kw. After over 1190 starts and 1275 hours0.0148 days <br />0.354 hours <br />0.00211 weeks <br />4.851375e-4 months <br /> of running time, inspections performed as part of the Owners Group program revealed i

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. linear indications in the vicinity of the oil holes in various main bearing journals. The indications were subsequently removed by either increasing the diameter of the oil holes or by modifying the entry radius to the oil hole.

Analyses by FaAA, and torsiograph testing established that the San Onofre crankshaft stresses were well within DEMA allowables at rated load. However, transient torsiograph testing and subsequent analysis

. revealed that, under startup and coastdown conditions, stresses can be developed which exceed the endurance limit and which could therefore lead to crack initiation. The level of stress was determined by FaAA to be

. dependent on the type of startup (rapid starts produce the maximum stress) and the angular position of the crankshaft prior to a rapid i start [5].

R n FaAA analyses and PNL analyses performed on behalf of the NRC staff f~ have indicated three closely spaced criticals occurring at 217, 240, and 264 RPM, respectively, which provide a possible explanation for the sensitivity of stress to fast starts. In this situation the vibrations r

i initiated by the first critical could still be " ringing" when the shaf t hits the next critical, and be once again augmented by the third critical f

d' leading to large vibrational amplitudes.

• 't A fracture mechanics analysis by FaAA determined that crack depths g up to 18 mils deep could be tolerated before the cracks would be subject

~j to rapid propagation under steady state cyclic stress conditions. FaAA concluded that if the oil hole regions are inspected using NDE techniques sufficiently sensitive to detect 10 mil cracks, then the number of start-stop sequences to propagate a crack from 10 to 18 mils should establish the effective life of the crankshafts. Based on predicted crack growth rates, FaAA conservatively recommended that the crankshafts should be

.i inspected at intervals of 50 start-stop sequences.

The NRC st ?f and its PNL consultants have not yet completed their y final evaluation of the FaAA findings and recommendations. In the interim, however, the staff has authorized operation of San Onofre 1 to q'l its next refueling cycle [6] based on the fact that (1) all of the

,h observed cracks were removed during the previous outage, (2) the

'f crankshafts will be reinspected at the next outage, and (3) the engines 2 ,

will not be operated above 4500 kw. ,

2.3 Connecting Rod Bearing Shells Connecting rod bearings in TDI Series DSR-4 engines consist of two half-shells assembled into each connecting rod. The half-shells are fabricated from aluminum-6% tin (Alcoa alloy B850) and are electroplated on the inner surface with a lead based babbit to form the bearing surface on the connecting rod journal.

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Inspections performed subsequent to the crankshaft failure in the Shoreham EDG-102 engine revealed that one upper bearing shell from the EDG-102 engine and three upper shells from the EDG-103 engine were cracked through the thickness of the shells. One of the cracked shells from engine EDG-103 had actually fractured into two pieces although it had not affected the operability of the engine up to the time it was discovered.

Analyses of the failed bearing shells indicated that they were of the proper composition and ultimate strength. Metallurgical and analytic evaluation suggested that three factors contributed to the observed cracking: 1) the geometry of the connecting rod and bearing shell was

such that a small unsupported length of bearing shell occurred at its

extreme end; 2) the calculated peak oil pressure was 29,700 psi, which 3 exceeds the 26,000 psi commonly used in normal industrial practice; and i 3) edge loading of the bearings resulted in the concentration of the

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operating loads on the unsupported bearing ends. In addition, scanning j electron microscopy of the fracture surface of one of the cracked bearings revealed voids approximately 0.020 to 0.030 inches in diameter

]g that appeared to be the initiation site for the cracks [7].

l New 12 inch diameter bearings were installed in the Shoreham engines

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consistent with the 12 inch diameter crackpin journals of the replacement j crankshafts. The new 12-inch bearing eliminated the unsupported length

.3 of the bearing shell. Although the edge loading condition was not j" changed in the new design, the Owners Group analysis showed that the larger 12-inch diameter journal reduced the maximum tensile stress to 50%

• of the value in the original 11-inch design. Stress distributions in the s 13-inch bearings used in TDI Model DSRV-16-4 and DSRV-20-4 engines are 5 , approximated by those calculated by the Owners Group for the 12-inch

, . . bearings used in the DSR-48 engines. Acceptance criteria were developed p by the Owners Group, based on fracture mechanics analyses, concerning

.d maximum allowable void sizes in the aluminum bearings which could be tolerated without degrading their fatigue performance. The Owners Group I

j has recommended that each owner perform a radiographic inspection of all

.g connecting rod bearings to ensure compliance with these criteria.

i Application of these criteria have led to the replacement of numerous i* bearing shells at a number of plants.

2 2.4 Engine Block ,

Cracks have been reported in cylinder blocks of both TDI DSR-4 (in-line) and DSRV-4 (" Vee") engines in nuclear and non-nuclear applications. Numerous " ligament cracks", which are vertical cracks extending between the cylinder counterbore and an adjacent cylinder head stud hole, had been observed on the top surfaces of all three Shoreham engine blocks prior to March, 1984. In March, 1984, a " stud to stud" crack vas initially observed in engine EDG-103 which extended vertically (from the block top) between adjacent stud holes of adjacent cylinders to a depth of 1.50 inches.

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In April 1984, engine EDG-103 experienced an abnormal load excursion while being operated at full load (3500 kw). Subsequent to the load excursion, engine EDG-103 was subjected to a 3900 kw overload test. At a point less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> into the test, a crack was observed to extend from a stud hole at the top of the block to approximately 5 inches down the front of the block. The engine was shutdown and subsequent inspection revealed additional stud to stud cracks. The original stud to stud crack first observed in March 1984 was determined to have grown

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. to a depth of 3.9 inches. The owner elected to replace the block for the EDG-103 engine. Subsequent metallurgical tests and photomicrographs established that whereas the block material for EDGs 101 and 102 at

, Shoreham exhibited the appearance and ultimate tensile strength of normal gray cast iron, Class 40, the material of the original EDG-103 block was found to be of a degenerate (Widmanstaetten) graphite composition with an P ultimate tensile strength much inferior to that of typical gray cast iron, Class 40.

k At the Owners Group recommendation, other utility owners have also g checked their blocks for similar degenerate graphite microstructure. To y date, only one other block (at Washington Nuclear 1) has been found with g this microstructure and is being replaced.

M t* Based on the results of strain gage tests and calculations using j two dimensional analytical models, FaAA has reported [8] that for a material exhibiting minimum acceptable tensile strength, initiation of g " ligament cracks" is predicted to occur after accumulating operating 4 hours at high load and/or engine starts to high load. Ligament cracks j are not a significant concern in-of-themselves; however, such cracks do i result in increased stress and thus increase the potential for crack g- initiation between the stud holes of adjacent cylinders. Such " stud to stud" cracks are considered to be more serious than ligament cracks since they can potentially degrade the overall mechanical integrity of the block and its ability to withstand piston firing pressures.

An FaAA cumulative damage analysis has indicated that given the g existence of ligament cracks and the absence of stud to stud cracks prior to a loss of off-site power / loss of coolant accident (LOOP /LOCA) event, c-

• even if a stud to stud crack were to initiate during such an event, the

. crack would not propagate sufficiently during the ever.t to impair the 2 operability of the engine. FaAA has recommended that blocks be periodically inspected for ligament cracks. For blocks with ligament cracks, FaAA has recommended that the absence of " stud to stud" cracks be confirmed by eddy current inspection subsequent to any period of

. operation above 50% of rated Icad. The NRC staff has required that these recommendations be incorporated into the engine maintenance and surveillance programs for each plant [3],[4].

2.5 Piston Skirts Piston skirts in the two piece piston design for the TDI R-4 series engines have been undergoing an evolution since their original introduc-tion in 1970. This evolution has been largely in response to problems identified during service experience with nuclear and non-nuclear applications.

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Early TDI DSR-4 engines employed type AF piston skirts. In response to problems with type AF skirts relating to the use of spherical washers in the stud boss attachment region, TDI introduced " modified" type AF skirts and type AH skirts. The modified type AF skirts incorporated machining modifications (primarily as a field retrofit) to the stud boss attachment region to permit use of a double stack of Belleville washers.

Pistons of this design were provided by TDI to a number of nuclear plants.

During an early inspection at Shoreham, all " modified" type AF skirts were observed to contain linear indications in the skirt-to-crown attachment bosses which were later confirmed by metallurgical examination ,

to be fatigue cracks. Similar indications were later found in " modified" AF skirts at Grand Gulf Unit 1. Experimental and analytical evaluations by the Owners Group indicated that although fatigue cracks may initiate

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p if the engines are operated near full rated load, the cracks will not continue to grow after they have moved out of the highly stressed region b

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near the boss [9]. The Owners Group concluded that the modified AF piston skirts are adequate for service provided that they are inspected 8 for cracks prior to use, and periodically thereafter.

The Owners Group findings notwithstanding, the modified AF piston i skirts at Shoreham, Grand Gulf Unit 1, and at other plants have been y replaced with an improved piston skirt design, type AE, discussed below e [3],[10]. To date, San Onofre Unit I has been the only plant to seek NRC d approval to operate with " modified" AF pistons installed. NRC approved use of modified AF skirts at San Onofre for one refueling cycle based Q upon a number of considerations including (1) that 25% sample inspection h'

revealed no evidence of cracks, (2) that the San Onofre engines will not be operated above 4500 kw which correspond to a cylinder firing pressure of about 50% of the firing pressures at normal rated load conditions for

? TDI DSR-4 engines, and (3) that similar piston skirts at a non-nuclear facility in Homestead, Florida have operated for more than 107 cycles (750 hours0.00868 days <br />0.208 hours <br />0.00124 weeks <br />2.85375e-4 months <br />) at loads comparable to those at San Onofre with no evidence

[V of cracks during subsequent inspections [6]. The staff expects to reach 1: a final conclusion in the Fall, 1985, regarding the acceptability of the y San Onofre pistons for use beyond the next refueling outage.

l-l b. TDI engines at a number of other nuclear plants were initially lN supplied with type AH pistons skirts. This skirt was manufactured from L type AF casting patterns which were modified to accommodate in the "as cast" skirt the aforementioned machining modifications to convert type AF skirts to " modified" type AF skirts. Owners Group analyses [11]

indicate that type AH skirts may initiate cracks in the stud boss region .

l under transient thermal conditions associated with engine start-ups prior to reaching steady state conditions. As in the case of the modified type AF pistons, however, the Owners Group predicts that any cracks will not propagate beyond the stud boss region. Nonetheless, type AH skirts at plants seeking near term operating licenses (Comanche Peak Unit 1 and Perry Unit 1) have been replaced with the improved type AE skirts as a i conservative measure.

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i-Another piston design, type AN, has been found by the Owners Group to be unsuited for nuclear standby service [11]. Although geometrically similar to type AH and modified AF pistons, many type AN pistons have experienced relatively high levels of residual stress due to differences in thermal treatment received by these pistons. Although many AN pistons have reportedly been operated satisfactorily for extended periods, there have been numerous reports of cracks including instances of actual breaking of the piston skirt into numerous pieces with catastrophic

- a consequences to the engine (non-nuclear). Accordingly, AN piston skirts at Catawba Unit I have been replaced with type AE skirts [12].

. The AE piston skirt design was introduced by TDI in 1982 to

". alleviate problems with the AN design. It incorporates an increased stud p boss thickness (relative to " modified" AF, AH, and AN piston skirts) and J a stress relief to relieve residual stresses believed to have been i ~

responsible for the observed cracking in AN skirts. Owners Group U analyses indicate stress levels to be substantially reduced over earlier

% skirt designs. Furthermore, operating experience provides considerable M confidence that this design will provide adequate service. Two type AE 41l pistons were run in a TDI test engine for 622 hours0.0072 days <br />0.173 hours <br />0.00103 weeks <br />2.36671e-4 months <br /> at 514 RPM and at a ji peak firing pressure 20% higher than in TDI engines in nuclear service.

The 622 hours0.0072 days <br />0.173 hours <br />0.00103 weeks <br />2.36671e-4 months <br /> of operating time corresponds to 9.6 x 108 stress cycles.

r* Subsequent inspections revealed no cracks. In addition, type AE pistons

• were installed in the Shoreham EDG-103 engine during the 746 hour0.00863 days <br />0.207 hours <br />0.00123 weeks <br />2.83853e-4 months <br /> endurance test (107 stress cycles) at 3300 kw discussed earlier in F Section 2.1. Again, subsequent inspection revealed no evidence of crack initiation.

2.6 Cylinder Heads Numerous instances of cracks and leaks in TDI cast steel cylinder

, heads have been reported in both nuclear and non-nuclear application.

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From an operability standpoint, the major concern is that cracks in the jacket water passages can result in the leakage of water into the g

m affected cylinder when the engine is in a standby mode. If an attempt is made to start an engine with water present in one or more cylinders,

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severe structural damage can result.

TDI cylinder heads have been classified by the Owners Group as belonging to one of three groups [13]. Droup I heads include all those cast prior to October 1978. Group II heads include those cast between October 1978 and September 1980. Group III heads include those cast after September 1980. The distinction among groups involves both design changes to facilitate better casting control and improvements in heat treatment and quality control. Most instances of cracked heads have involved Group I heads. Only five instances of cracks resulting in water leaks have been reported in heads of Groups II and III, and these have all been in marine applications. Most of these cracks were observed to have originated at the stellite-faced valve seats.

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i To minimize the potential for leaks, the individual utilities have inspected the cylinder head fire decks and valve seats for cracks pursuant to recommendations by the Owners Group. In addition the fire decks have been checked for proper thickness.

To further verify the absence of cracks which may allow water leakage into the cylinder, the staff has required that the surveillance program for TDI engines include provisions for air rolling of the engine .

at appropriate intervals with open cylinder cocks before and after each

- planned operation. The staff has concluded that such air rolls should be performed 4 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and again 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following any engine operation ,

and, thereafter, prior to any planned start [2].

2.7 Turbocharger Thrust Bearings TDI diesel generators in nuclear service employ turbochargers fl

- manufactured by the Elliot Company. Elliot Model 90 S are used for TDI Models DSR-48 and DSRV-16 and Elliot Model 65G for TDI Model DSRV-20.

K Turbochargers at several nuclear plants have experienced rapid deteriora-g tion and failures of the combination thrust / radial bearings. It was

% recognized that bearing and bearing lubrication systems inherent in the

$ turbocharger designs were not adequate to provide lubrication of the E bearing thrust pads and rotor thrust collars under fast startup E conditions to high loads. In response to this problem, the oil drip a system was modified to provide for increased flow toward the bearings at all times during engine standby. In addition, an auxiliary prelubrica-u tion pump was provided by TDI to direct a substantial oil flow to the j bearings immediately prior to all planned starts.

The Owners Group recommended that the owners maintain oil filtration at 10 microns or better and utilize spectrochemical and ferrographic oil l

analyses regularly as part of the preventive maintenance programs at

's their plants. The Owners Group has also recommended that one bearing be j inspected at a plant following an initial 100 starts of any nature.

!O Furthermore, any bearing experiencing 40 automatic starts without manual

. prelube should be inspected. Finally, the Owners Group has concurred i ..I l# with TDI recommendations for monitoring turbocharger rotor axial I

clearances. The Owners Group has emphasized the need not only to confirm lC that the clearance is within TDI/Elliot specifications but, also to trend lm any increase in clearance which may be indicative of thrust bearing

• l"" degradation [14]. -

l l 3. Maintenance and Surveillance, Testing, and Operational Considerations .

l l Periodic maintenance inspections and engine surveillance to be I

performed in conjunction with periodic engine tests will provide the primary means for monitoring the effectiveness of the Owners Group l program in resolving known problem areas and in validating the design

! and manufacturing adequacy of key engine components. In addition to a I confirmatory role, it is clear from the preceeding discussion of known l prob 4ms areas that periodic inspections and surveillance practices as l reccr' ended by the Owners Group or as required by the NRC are an integral l

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. .- 77 element of the technical resolution of these issues. In some cases (e.g., DSRV-20-4 crankshafts, engine blocks, cylinder heads, turbocharger thrust bearings), the initiation of cracks or abnormal wear during future service cannot be precluded on the basis of operating experience and/or analysis. Periodic inspections are, therefore, critical from the standpoint of assuring that any problems are identified and corrective actions taken on a timely basis.

The Owners Group has prepared a comprehensive set of maintenance and surveillance recommendations as part of the Design Review / Quality Revalidation Report prepared for each plant. These recommendations

. reflect Owners Group findings stemming from both its Phase I and Phase II efforts and also reflect review by the Owners Group of TDI Instruction

! Manuals, TDI Service Information Memos, and TDI correspondence on specific components. The staff believes that these recommendations should be followed by each owner in developing its plant-specific

- maintenance / surveillance program. In addition, each owner should implement an operational surveillance program to monitor and record key engine parameters while the engine is being operated. These include W temperatures and pressures at key locations in and about the engine. By

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monitoring and recording key engine parameters, trends in degradation can be detected, allowing timely preventive maintenance. The staff has y required that each owner commit to implementation of an acceptable maintenance and surveillance program prior to issuance of an operating license.

In Generic Letter 84-15, the NRC has encouraged utilities to propose p changes to the Technical Specifications to address staff concerns

, regarding the effects of frequent fast start tests on engine wear and tear for TDI and non-TDI engines alike. As one example, frequent fast start, fast load tests during preoperational testing was an aggravating

[ factor contributing to the rapid deterioration of the turbocharger thrust bearings in several TDI engines as a result of inadequate prelubrication.

Technical Specifications currently being prepared for River Bend specify that each surveillance test may be preceded by an engine prelube period.

Further, all surveillance tests, with the exception of once per 184 days,

, may also be preceeded by warm-up procedures and may also include gradual loading (> 150 seconds) as recommended by the manufacturer [4].

j , It has also been customary for plant Technical Specifications to require that monthly surveillance testing be performed at the nameplate

, engine rating specified by the manufacturer, with a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> overload test l

every 18 months. For the TDI engines, however, the staff is concerned that such testing could overstress certain components (such as DSR-48 crankshafts, for example) and thus, increase the potential for a premature failure during a lcss of offsite power event. Therefore the staff has required that surveillance testing not exceed the " qualified" load of such components as established on the basis of appropriate analysis, testing, and/or operating experience. However, surveillance testing must meet or exceed the maximum emergency load requirements (as specified in the plant FSARs) for a design basis LOOP or LOOP /LOCA event. In addition, the utility must have adequate operating procedures and operator training l to ensure that operators have proper guidance and instruction against overloading the diesels above the qualified load [3],[4].

,,.y References

[1] United States Nuclear Regulatory Commission (U.S. NRC), " Safety Evaluation Report, Transamerica DeLaval, Inc., Diesel Generator Owners Group Program Plan", Washington, D.C., August 13, 1984.

[2] Failure Analysis Associates (FaAA), " Emergency Diesel Generator Crankshaft Failure Investigation, Shoreham Nuclear Power Station, ,

"FaAA Report No. FaAA-83-10.2.1, Palo Alto, CA, October, 1983.

[3] U.S. NRC, " Supplemental Safety Evaluation Report, Shoreham Nuclear '

Power Station, Docket 50-322," Washington, D.C., December, 1984.

[4] U.S. NRC, " Safety Evaluation Report related to the Operation of

. River Bend Station, Docket 50-458", NUREG-0989, Supplerrent 3, Washington, D.C., (to be published in August 1985) y [5] FaAA, " Evaluation of Transient Conditions on Emergency Diesel

Generator Crankshafts at San Onofre Nuclear Generating Station j Unit 1," FaAA-84-12-14, Palo Alto, CA, April 1975.

[6] U.S. NRC, " Safety Evaluation Report, San Onofre Nuclear Generating Station 1, Reliability of TDI Diesel Generators, Docket No. 50-206, Washington, D.C., November 19, 1984.

1 4 [7] FaAA, " Design Review of Connecting Rod Bearing Shells for Transamerica Delaval Enterprise Engines, FaAA-84-3-1, Palo Alto, CA, March, 1984.

[8] FaAA, " Design Review of TDI R-4 Series Emergency Diesel Generator

! Cylinder Blocks and Liners", FaAA-84-5-4, Palo Alto, CA, June 1984.

[9] FaAA, " Investigation of Types AF and AE Piston Skirts", FaAA-84-2-14, Palo Alto, CA, May 1984.

4 [10] U.S. NRC, " Safety Evaluation Report related to be Operation of Grand Gulf Nuclear Station, Units 1 and 2, Docket Nos. 50-416 and 50-417", NUREG-0831, Supplement No. 6, Washington, D.C., August 1984.

[11] FaAA, " Investigation of Type AN and AH Piston Skirts," FaAA-84-10-30, .

j Palo Alto, CA, November 1984.

[12] U.S. NRC, " Safety Evaluation Report related to the Operation of ,

Catawba Nuclear Station, Units 1 and 2, Docket Nos. 50-413 and 50-414," NUREG-0954, Supplement 4, Washington, D.C., December 1984.

[13] FaAA, " Evaluation of Cylinder Heads of Transamerica Delaval Inc.

Series R-4 Diesel Engines," FaAA-84-5-12, Palo Alto, CA, August 1984.

[14] FaAA, " Design Review of Elliot Model 90G Turbocharger used on Transamerica Delaval DSR-48 and DSRV-16 Emergency Diesel Generators Sets", FaAA-84-5-7, Palo Alto, CA, July 1984.