ML20207H415

Safety Evaluation Supporting Technical Solution to Address Operability & Reliability of Tdi Emergency Diesel Generators

ML20207H415
Person / Time
Site:	River Bend
Issue date:	07/16/1986
From:	NRC
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ML20207H414	List: ML20207H411 ML20207H415
References
NUDOCS 8607240308
Download: ML20207H415 (37)

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Enclosure SAFETY EVALUATION REPORT OF THE OPERABILITY / RELIABILITY OF EMERGENCY DIESEL GENERATORS MANUFACTURED BY TRANSAMERICA DELAVAL, INC.

1 INTRODUCTION AND BACKGROUND 1

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.

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I Concerns regarding the reliability of large bore, medium speed diesel gener-i

' ators manufactured by TDI for 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 event

, at Shoreham and at other nuclear and non-nuclear facilities employing TDI diesel generators. These deficiencies stemmed from inadequacies in design, manufacture l and quality assurance / quality control (QA/QC) by TDI.

In response to these problems, 11 (now 13) U. S. nuclear utility owners formed i

a TDI Diesel Generator Owners Group to address operational and regulatory issues relative to diesel generator sets used for standby emergency power. On

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March 2, 1984, the Owners Group submitted a proposed program to the NRC which, through a combination of design reviews, quality revalidations, engine tests and component inspections, was intended to provide an in-depth assessment of the adequacy of the respective utilities' TDI engines to perform their safety related function (

Reference:

TDI Owners Group, " March 2,1984, TDI Owners

, Group Program Plan").

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I TheOwnersGroupProgramPlaninvolvedthefollowingmaiorelements:

1 (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 Program.

(2) Phase II: Adesignreview/qualityrevalidation(DR/QR)ofalargesetof 1 important engine components to assure that their design and manufacture;

including specifications, quality control and quality assurance, and j operational surveillance and maintenance, are adequate.

l (3) Expanded engine tests and inspections as needed to support Phases I and j II. -

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'l The staff has previously concluded that the Owners Group Program Plan incorpo-rates the essential elements needed to resolve the cutstanding concerns relating to the reliability of the TDI EDGs for nuclear service (

Reference:

U.S. NRC l

0607240308 860716 PDR ADOCK 0D0004S0 1, S PDR 1 --, . _ . _ _ , _ _ . _ . _ _ _ - _ _ - , _ - _ ____ _ _

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Safety Evaluation Report, Transamerica Delaval Inc., Emergency Diesel Generator Owners Group Program Plan, Washington, D.C., August 13,1984).

The Safety Evaluation Report (SER) herein provides the staffs evaluation of the Owners Group findings and recommendations stemming from the program. Sub- 1 ject to the findings of this SER, the staff has concluded that a technical t resolution of the generic TDI emergency diesel generator issue is available. l This SER is also intended to provide guidance to NRC project managers and tech-nical reviewers on what must be done to technically resolve the TDI issue at each individual plant.

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2 EVALUATION The Owners. Group program and the Owners Group findings and recommendations stemming from this program have been reviewed by Pacific Northwest Laboratory (PNL) under contract to the NRC. PNL retained the services of several expert diesel engine consultants as part of its review staff. PNL has documented its findings in the following Technical Evaluation Reports (TERs):

o PNL-5600, " Review of Resolution of Known Problems in Engine Components for Transamerica Delaval Inc. Emergency Diesel Generators," December 1985.

o PNL-5335, " Review of Design Review and Quality Revalidation Report for the Transamerica Delaval Diesel Generators at Shoreham Nuclear Power Station Unit 1", October 1985. ,

o PNL-5444, " Review of Design Review and Quality Revalidation Report for

, the Transamerica Delaval Diesel Generators at Cemanche Peak Steam

. Electric Station Unit 1," October 1985.

o PNL-5718, " Review of Transamerica Delaval Inc. Diesel Generator Owners Group Engine Requalification Program - Final Report," December.1985.

The NRC staff worked closely with PNL in reviewing the Owners Group Program and findings therefrom and in preparing the above mentioned PNL reports. Subject to a few clarifications as identified in this SER, the staff concurs with the PNL conclusions and recommendations presented in the PNL reports. The PNL reports are incorporated into this SER by reference.

2.1 Technical Resolution of Phase I 2.1.1 General A Phase I of the Owners Group program consisted of identifying and resolving

- significant engine component problems that had potentially generic implications.

Through an extensive review of TDI and other engine performance data in both nuclear and non-nuclear applications, the Owners Group identified 16 such components:

o air start valve dapscrews o engine base and bearing caps o connecting rods ' o engine mounted electrical cable o connecting rod bearing shells o high pressure fuel injection tubing a crankshafts o jacketwaterpump o cylinder block o piston skirts o cylinder heads o push rods o cylinder head studs o rocker arm capscrews -

o cylinder liner:.* o turbochargers

• Combined with cylinder block in Owners Group evaluations.

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l The Owners Group recommended that problems with these components be resolved before the TDI engines were placed into service to support full power nuclear plant operation. To resolve the known problems with these components, the Owners Group contracted with Failure Analysis Associates (FaAA - Palo Alto, California) and. Stone & Webster Engineering Corporation (SWEC - Boston, Massa-chusetts) to perform extensive design reviews. Each component was addressed by these consultants in one or more design review documents. Each design review report includes, as appropriate, materials evaluations, load anc; stress analyses, fracture and fatigue analyses, and evaluations of required maintenance and sur-veillances Based on these reviews, the Owners' Group arrived at conclusions regarding the basic adequacy of the 16 components with known problems, and recommended actions that should be taken by the engine owners.

PNL's assessment of the Owners Group findings stemming from Phase I are docu-mented in detail in PNL-5600. Based on its assessment, PNL concluded that the Owners Group has established a technical basis for the utilities to qualify all of the components with known problems (i.e., Phase I components) for nuclear service. PNL has generally endorsed all of the Owners Group recommendations

.- pertaining to modifications and/or replacement, quality revalidation inspections, and maintenance / surveillance of Phase I components. In addition, however, PNL has recommended some additional actions in these areas beyond what the Owners

, Group has recommended. Details of PNL's findings and recommendations for each

_ of the Phase I components can be found in the following sections of PNL-5600.

Comoonent Section in PNL-5500 air start valve capscrews 4.1.4.2 auxiliary module wiring and terminations 4.2.4.3 DSR-4 connecting rods 4.3.4.3 DSRV-4 connecting rodt , 4.4.4.4 connecting rod bearing shells 4.5.4.2 b DSR-48 crankshafts:

Shoreham 1 4.6.5.3 River Bend 1 4.6.7.2 Other DSR-4 engines 4.6.8 DSRV-16-4 cylinder crankshafts 4.7.8.3 & 4.7.9 DSRV-20-4 cylinder crankshafts 4.8.5.6 cylinder block 4.9.5.2 cylinder heads 4.10.4.3 cylinder head studs 4.11.4.3 DSR-4 engine base and bearing caps 4.12.4.2 2-2 2_-__- - - .

5 1 Campentnt Section in PNL-5600 DSRV-4 engine base and bearing caps 4.13.4.2 fuel oil injection tubing 4.14.4.2 jacket.watirpump 4.15.4.3 piston skirts .

type *AE 4.16.3.3 modified type AF 4.16.4.3 type AH 4.16.5.3

• type AN 4.16.6.3 push rods 4.17.4.3 rocker arm capscrews 4.18.4.3

.- turbochargers 4.19.4.3 ,

Subject to clarifications and exceptions as discussed in Section 2.1.3 of this

, SER, the_NRC staff has concluded that the PNL findings and recommendations in

- the aforementioned sections of PNL-5600 should be implemented for TDI engines in nuclear service in addition to the findings and recommendations of the Owners Group. ,

2.1.2 Components that Warrant Special Emphasis PNL has also concluded that its findings and recommendations pertaining to seven of the above components warrant special emphasis in terms of needed load restrictions and/or maintenan'ce/ surveillance to ensure their satisfactory ser-vice. Table 2.1 provides a list of those components deemed by PNL to require special emphasis. Supporting details are provided in PNL-5600. Licensing considerations relative to any necessary load restrictions are discussed in Section 2.1.3. Special emphasis for the maintenance / surveillance actions referred to in Table 2.1 will be assured by incorporating these actions as

license conditions (see Section 2.1.3 of this SER).

2.1.3 Clarifications, Exceptions, and Licensing Considerations Pertaining to PNL Recommendations in PNL-5600 Subsections 2.1.1 and 2.1.2 above have provided an overall perspective on the  ;

NRC staff position concerning the PNL findings and recommendations in PNL-5600.

Thissubsectionprovidesclarificationsand/ordiscussionofsomeofthePNL i findings and recommendations where deemed to be necessary by the staff. In addition, this subsection discusses the licensing considerations which pertain to some of the P'NL recommendations; namely those which PNL finds merit special l emphasis (see Section 2.1.2 above). l Subsequent to issuance of PNL-5600 in December 1985, the Owners Group transmit- l ted Revision 2 to the Design Review / Quality Revalidation (DR/QR) report by l letter dated May 1, 1986 from J. B. George, Chairman, TDI Owners Group, to H. R. Denton, Director, Office of Nuclear Reactor Regulation, NRC. Revision 2 2-3  !

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Table 2.1 Components requiring engine load limits and/or special routine maintenance and surveillance Engine Special caintenance load and Components limited surveillance required Crankshaft DSR-48 Yes Yes DSRV-20 Yes* Yes Cylinder Block DSR-48 (Shoreham) No Yes OSRV-16 (Comanche Peak) No Yes Cylinder Heads No . Yes

. Connecting Rods DSRV engines, 1-7/8 inch bolts Yes Yes .

DSRV engines, 1-1/2 inch bolts No Yes Piston Skirts Type AF Yes Yes Turbocharger No Yes

• Limitations on engine testing have been established to minimize crankshaft torsional stresses during startup transients.

is basically a revision to Appendix II of the DR/QR report dealing with generic and site-specific maintenance matrices. The background to Revision 2 is dis-cussed in additional detail in Section 2.3.1 of this SER. However, for purposes of this discussion it should be noted that Revision 2 includes revisions to a number of earlier Owners Group technical positions which were endorsed and

, adopted as part of PNL's findings in PNL-5600. Furthermore, Revision 2 of the 3 DR/QR report was prepared and issued after the Owners Group had received and reviewed PNL-5600. Accordingly, Revision 2 is, in part, the Owners Group re- ,

sponse to PNL-5600. Additional Owners Group comments pertaining to PNL-5600 l

, were provided in a separate letter from the Owners Group (J. George, Owners Group, to H. Denton, NRC) which was also dated May 1, 1986. The staff has reviewed Revision 2 of the DR/QR report and the Owners Group comments and, as discussed in this subsection, has revised certain findings relative to the PNL findings and recommendations in PNL-5600, as appropriate.

2.1. 3.1 Engine Overhaul Frequency The Owners Group had recommended an engine overhaul inspection to occur at approximate 5 year intervals in the original versions of the DR/QR Appendix II maintenance / surveillance (M/S) program issued for most plants. Th'is position was endorsed by PNL in PNL-5600. This recommendation was consistent with TDI's recommendation which assumes that the engines are in fairly continuous service during this period (about 7000 operating hours). However, since the diesels 2-4

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1 are relied upon to provide only a standby source of power with periodic test requirements of limited duration, actual engine service time will only be a small fraction of what it would be in continuous duty service. For this reason, the Owners Group now proposes in Revision 2 of the DR/QR report that a complete engine overhaul be performed at approximate 10 year intervals; namely that one engine / unit be disassembled and inspected at the refueling outage occurring prior to 1,0 years and the second engine at the refueling outage following ten years. For plants with three engines, the third engine would be disassembled and inspected during the second refueling outage after 10 years. In addition, the Owners Group now proposes a one-time inspection to be performed at about 5 years. The one-time 5 year inspection will generally involve the same compo-nents as the 10 year overhaul inspections; however, only a sample of some types of components (typically 25%) would be inspected.

The staff concurs that there is reasonable basis to conduct the major engine overhauls at 10 year intervals rather than 5 year intervals as originally pro-posed based on (1) the comprehensive design review / quality revalidation effort conducted for each of the engine components, (2) the limited number of operat-

.- ing hours for engines in nuclear standby service, and (3) the fact that a sample inspection of major engine components will be performed on a c,e time basis following 5 years of service. Therefore, the staff concludes that the engine overhaul frequency proposed in Revision 2 of the generic DR/QR Appendix II M/S 1 program is acceptable in lieu of the 5 year frequency endorsed by PNL in PNL-5600.

2.1.3.2 Air Start Capscrews PNL has endorsed the Owners Group recommendations that capscrew length be verified as part of the DR/QR process for each engine, and that the capscrews be torqued in accordance with Stone & Webster and TDI recommendations as dis-cussed in Section 4.1.3.2 of PNL-5600. The latter recommendation has been incorporated by the Owners Group as part of the DR/QR Appendix II maintenance matrix (i.e., installation procedures per TDI Service Information Memorandum (SIM) 360).

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2.1.3.3 Auxiliary Module Wiring and Terminations lA PNL has endorsed and adopted the Owners Group recommended inspections, replace-ments, etc. , as discussed in Section 4.2.4.3 of PNL-5600.

2.1.3.4 Connecting Rod Bearing Shells PNL has endorsed (PNL-5600, Section 4.5.4.2) the original Owners Group recom-mendation that the connecting rods be inspected, visually and dimensionally, at the outage which precedes 500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> by at least the sum of hours in a LOOP /LOCA event plus the expected number of hours between outages. The Owners Group is now proposing (see Revision 2 of DR/QR Appendix II M/S program) that these inspections be conducted for all bearings at each 10 year overhaul and a one time sample inspection after approximately 5 years (see Section 2.1.3.1 regarding overhaul frequency). As is discussed in Section 4.5.4.2 of PNL-5600, the staff believes that a 10 year inspection interval and a one-time 5 year in-spection of a sample of the bearings is consistent with accumulated operating experience, namely that the total number of operating hours between inspections 2-5

5 will be on the same order as what has been successfully demonstrated at Shore-ham and Catawba Unit 1. Based on this and subject to PNL's recommendation for a periodic oil contamination analysis, the staff concludes that the proposed inspection frequency revision of the DR/QR Appendix II M/S program is acceptable.

The staff has concluded that the DR/QR Appendix II matrix does not satisfac-torily address the need for periodic oil contamination analyses. The staff will require that this matter be addressed satisfactorily in the plant-specific maintenance programs.

PNL has suggested in Section 4.5.4.2 of PNL-5600 that cons'ideration be given by Duke Power Company to increasing the engine oil pressure for the Catawba engines to the level employed at Grand Gulf (about a 10% increase). This suggestion is offered by PNL as a possible means to prolong bearing life.

However, the staff concludes that the periodic inspections recommended by the Owners Group will provide for the timely detection of bearing wear before it could affect the operability of the engines. The staff therefore concludes

.- that the subject PNL recommendation for increasing engine oil pressure at Catawba should be implemented at Duke Power Company's discretion and is not a requirement.

1 PNL has also endorsed the Owners Group recommendation that the connecting red bearing shells be inspected radiographically to the acceptance criteria adopted by the Owners Group as part of the DR/QR program fur each plant. The staff concludes that this action should be implemented for all TDI units. PNL has also endorsed the Owners Group recommendation that such radiograph inspections be performed for all new replacement connecting red bearing shells. The staff notes that this latter reccmmendation has been incorporated into the DR/QR Appendix II M/S program, Revision 2.

Finally, PNL has suggested that the critical zone of radiography for new 12-inch bearings intended for use in TDI eight-cylinder engines be extended axially to the bearing ends (rather than beginning 1/4 inch from each end as recommended by the Owners Group). The Owners Group has taken exception to this suggestion in its letter dated May 1, 1986, providing comments. The Owners Group noted that design modifications made with the replacement 12-inch bearing shells and the 12-inch crankshaft addressed each of the ccnditions contributing to cracking of the original 11-inch bearings as indicated below; thus reducing the stress range level by a factor of 2.

(1) The geometry of the connecting rods and the bearing shells was changed to provide complete support to the bearing shell ends.

(2) The increase in# diameter to 12 inches reduced the peak oil film pressure.

(3) Although the edge loading was not affected, the two previous changes re-duced stresses caused by the edge loading to an acceptable level.

The staff agrees with the Owners Group that PNL's suggestion regarding the critical zone for radiography should not be required; however, the staff con-tinues to encourage utilities to follow PNL's suggestion.

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x 2.1. 3. 6 DSR-48 Connecting Rods PNL has recommended a number of periodic maintenance inspections in Sec-tion 4. 3.4. 3 of PNL-5600. With the exception that the major engine disassem-blies and inspections will be performed at the intervals described in Sec-tion 2.1.3.1 of this SER (rather than at 5 year intervals as recommended by PNL), the PNL recommendations have been incorporated as part of the generic DR/QR Appehdix II M/S program, Revision 2. The staff considers these periodic maintenance proposals to be acceptable.

The staff concurs with PNL that any rod eye not p aviously examined in accor-dance with the acceptance criteria recommended by FaAA should be examined u' sing an appropriate nondestructive technique at the first major engine disassembly.

No indications deeper than 0.04 inch should be allowed.

2.1.3.7 DSRV Connecting Rods PNL has made a number of recommendations concerning needed preservice (i.e.,

quality revalidation (QR)) inspections and periodic maintenance inspections as identified in Section 4.4.4.4.1 and 4.4.4.4.2 of PNL-5600, respectively. Many of those recommendations are actually Owners Group recommendations endorsed by

, PNL. With respect to preservice inspections, the NRC staff concurs with PNL's recommendations in Section 4.4.4.4.1 of PNL-5600, and concludes that these recommendations should be fully implemented as part of the DR/QR program.

Among these PNL reccmmendations is a suggestion that the two pairs of bolts above the crankpin be measured ultrasonically pre- and post-tensioning. In addition to the reasons cited by PNL, the staff considers that proper preload is critical to assuring the long term integrity of the DSRV connecting rods.

For this reason the staff concludes that baseline ultrasonic elongation measure-ments must be performed for all DSRV connecting rods either as part of the DR/QR (preservice) inspection or, in the case of operating plants, at first availability. In the latter case, first availability would include the 25%

sample inspection of the connecting rods after approximately 5 years and all connecting rods at the 10 year overhaul inspections (see Section 2.1.3.1).

With regards to the PNL r'ecommended periodic maintenance inspections in Sec-tion 4.4.4.4.2 of PNL-5600, the staff has found that the PNL recommendations

& have generally been incorporated as part of Revision 2 to the DR/QR Appendix II M/S program with certain modifications as discussed below.

(1) Revision 2 of the Appendix II matrix calls for major overhaul inspections at 10 year intervals and a one time sample inspection after about 5 years in lieu of the 5 year interval for major engine overhauls originally pro-posed by the Owners Group and endorsed by PNL in PNL-5600 (see earlier discussion in Se~ction 2.1.3.1 of this SER).

(2) TheDR/QRAppendixIImhintenancematrix, Revision 2,doesnotincorporate PNL's recommendation that if connecting rod bolt tension is found to be reduced to less than 93% of its initial value as measured during instal-lation, then the cause should be determined, appropriate corrective action should be taken, and the interval between checks of bolt tension should be reevaluated.

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(3) The DR/QR Appendix II maintenance matrix calls for a one time rather than the periodic checks recommended by PNL regarding the degree of surface contact at the serrated joint and the zero clearance condition between the link pin and link rod.

With respect to the first item above, the staff concludes that the proposed alternative inspection interval is acceptable. However, for DSRV connecting rods with 1-7/8 inch bolts, this finding would be subject to certain engine load restrictions. (Note that the Grand Gulf engines are the only TDI engines employing'l-7/8 inch bolts.) Alternatively, if the DSRV engines with connecting rods with 1-7/8 inch bolts are to be operated at loads in excess of this load limitation, these DSRV connecting rods shall be subject to a complete teardown and inspection at 5 year intervals. The staff's finding and the basis thereof is discussed in Section 2.1.3.7.1, below.

With respect to item (2) abose, the staff concurs with the PNL recommendation in view of the critical importance of maintaining proper bolt tension and will require that this be incorporated as part of the maintenance / surveillance pro-

." gram for each plant. Although PNL has recommended that the 93% criteria should apply to bolt tension as determined from either torque measurements or ultra-sonic measurements of bolt stretch, the staff believes that only ultrasonic measurements are sufficiently reliable to compare with this criterion. The i staff notes that Revision 2 of the DR/QR Appendix II M/S program calls for ultrasonic measurements prior to each bolt disassembly. However, utilities should verify that their plant-specific programs also require that baseline ultrasonic measurements be taken following each assembly of the bolts.

Regarding item (3) above, the staff concludes that the proposed one time inspec-tions are acceptable in lieu of the periodic inspections recommended by PNL.

Regarding the link rod to link pin clearances, this check is intended to verify sufficient counterbore depth and thus periodic checks are unnecessary. Simi-larly, a one-time inspection of the degree of surface contact at the serrated joint will be sufficient to verify dimensional adequacy. However, licensee's should consider future checks of surface contact in the event that periodic inspections should reveal. excessive detensioning of the connecting rod bolts, fretting of the serrated surfaces, or other evicence of connecting rod distress.

> In sections 4.4.4.4.2 and 4.4.4.4.3 of PNL-5600, PNL has recommended that an

" appropriate nondestructive method" be employed for preservice and periodic inservice inspection of the bolt holes in the link rod box. The NRC staff concludes that the inspection method shall include either (1) the eddy current inspection method developed by FaAA for threaded carbon steel bolt holes (i.e. ,

FaAA Procedure: NDE 11.9, Revision 1) or (2) an alternative method shown to be equivalent to the FaAA eddy current procedure for purposes of discriminating small cracks in the threads.

- PNL could not reach a conclusion regarding the ability of the FaAA eddy current procedure to detect flaws as small as the 1/8-inch rejectable limit recommended by FaAA. Indeed, staff discussions with the PNL consultants indicate that there is little assurance that flaws of this size can be detected reliably. The staff concurs with PNL, however, that this element of uncertainty does not add significantly to the risk of a connecting rod failure. In addition to an eddy current inspection numerous other inspections of critical connecting rod asser bly attributes will be performed at periodic intervals in accordance with the 2-8

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DR/QR Appendix II, Pevision 2, schedule. The staff believes that these inspec-tions should provide timely evidence of a connecting rod assembly anomaly (e.g.,

inadequate bolt torques (or stretch), cracks, frettitg of the serrated joint etc.) prior to a. connecting rod failure.

As noted in: Table 2.1 of this SER and as discussed in detail in Section 2.2.1 of PNL-5600', PNL has concluded that periodic maintenance and surveillance actions pertaining to DSRV connecting rods warrant special emphasis in view of the mixed results of known non-nuclear service experience, the unknown level of conservatism in the Owners Group stress analysis of the connecting rods, and the difficulties inherent in inspecting threaded bolt holes. Accordingly, the staff will incorporate key maintenance / surveillance actions as license conditions

. for TDI facilities with DSRV connecting rods. Sample license conditions are provided in Appendix A of this SER.

2.1.3.7.1 Justification for Revised Inspection Interval for DSRV Connecting Rods As noted above in Section 2.1.3.7,'the TDI Owners Group has proposed a modi-fication to the'DR/QR Appendix II inspection matrix for the DSRV connecting rods. Revision 2 calls for connecting rod inspections during major overhauls

, at 10 year intervals and a one time only 25% sample inspection after about

. 5 years. This inspection schedule is in lieu of the 5 year interval for major overhauls originally proposed by the Owners Group and endorsed by PNL in PNL-5600.

The DSRV connecting rods in nuclear service include two basic designs which utili::e either 1-1/2 or 1-7/8 inch diameter upper connecting rod bolts, which thread into blind holes in the rod box just above the crankpin. In general, many DSRV connecting rods have accumulated up to 50,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of trouble-free operation at loads up to 80 to 85% of rated load. The reported failures in non-nuclear service of DSRV connecting rods, which involved both the 1-1/2 and 1 1-7/8 inch upper connecting rod bolt designs, have typically occurred after many thousands of hours of operation. The random nature of these failures suggest that these failures may be attributable to non-design related causes as discussed in Section 4.4.2 of PNL-5600; namely, inadequate bolt preload and/or insufficient locating dowel counterbore depth in the link. red or link pin.

Conservative 2-D stress analyses of the rod box were performed by the Owners Group's consultant, Failure Analysis Associates (FaAA) for both the 1-1/2 and 1-7/8 inch bolt designs. The 1-1/2 inch bolt design was found acceptable for service at rated engine loads with calculated stress levels below the fatigue j endurance limit. However, the stress levels calculated for the 1-7/8 inch bolt l design were slightly 'above the fatigue endurance limit. Also, the FaAA report recommended that periodic inspection of the 1-7/8 inch bolt holes be performed at intervals of 280 operating hours (approximately every 5 years) to ensure the timely detection of flaws before they propagate excessively.

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In the staff's judgment, based on the FaAA analysis and the relative shortness of the proposed inspection interval compared to the extended periods during whicn the DSRV connecting rods h' ave been operated without problems, the proposed 10 year inspection interval with a one time sample inspection after 5 years is acceptable for the DSRV connecting rods with 1-1/2 inch bolts. The staff cannot support a similar inspection schadule for the connecting rods having 1-7/8 inch 2-9

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bolts unless they are operated at loads below those for which the preponderance of operating experience is positive. Therefore, since many of these connecting rods have accumulated up to 50,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> at loads of up to 80 to 85% of rated load and since the proposed inspection intervals are very short compared to the extended periods over which the DSRV connecting rods have been operated without the staff will require that operation of DSRV engines with connecting problems, rods emplo ying 1-7/8 inch bolts (only Grand Gulf has engines falling into this category) be limited to 82% of rated engine load to ensure that the connecting rods are operated within the envelop of successful operating experience, if the inspection interval proposed in Revision 2 is utilized. Alternatively, if all connecting rods of this type (1-7/8 inch bolts) are disassembled and inspected at 5 year intervals as originally proposed by the Owners Group and endorsed by PNL in PNL-5600 rather than as specified in Revision 2 of the DR/QR Appendix II M/S program, the staff will not require a similar load restriction.

In summary, the staff finds that the preservice inspections recommended by PNL in Section 4.4.4.4.1 (PNL-5600) and the periodic maintenance inspections pro-y posed in Revision 2 of the DR/QR Appendix II M/S program are acceptable for the DSRV connecting rods having 1-1/2 inch diameter upper connecting red bolts.

In addition, for connecting rods having 1-7/8 inch bolts if they are limited to operation at or below 82% of rated load, the same M/S program is also accept-

. able. However, if these engines are to be operated at loads greater than 82%

of rated load, the proposed modification to the DR/QR Appendix II M/S program is unacceptable and the staff will require that all connecting rods of this type be disassembled and inspected at 5 year intervals. Implementation of these requirements will provide timely identification of a connecting rod assembly anomaly (e.g., inadequate bolt torques (or stretch), cracks, fret-ting of the serrated joint, etc.) prior to a connecting rod failure.

The staff notes that the Grand Gulf Technical Specifications already limit engine operation to 82% of rated load due to earlier staff concerns regarding the load capacity of the DSRV crankshafts and AE piston skirts. As noted in Sections 2.1.3.11 and 2.1.3.19 of this SER, the staff has concluded that this interim load limitation is no' longer necessary and may be removed. If in ac-cordance with the above discussion, the licensee (Grand Gulf, Mississippi Power and Light) chooses to implement the proposed Revision 2 M/S program and

schedule, it must retain the 82% load limitation and, in addition, the staff

- will require that the licensee revise its engine operating procedures and train-ing as necessary to provide appropriate guidance and instruction to operators against operating the engines to in excess of 82% of rated load. Specific issues to be addressed are described in Section 2.1.3.10 of this SER. Finally, the staff will :equire that requirements for a contingency inspection of the connecting rods in the event that the engines are loaded beyond 82% be incor-porated as a licenseicondition.

2.1.3.8 Crankshafts - All TDI Models The staff notes that PNL-5600 does not address the subject of engine imbalance relative to the Shoreham DSR-48 crankshafts although this subject is addressed for the River Bend DSR-48 crankshafts, the DSRV-16 crankshafts, and the DSRV-20 crankshafts. As a matter of clarification, the staff believes that appropriate precautions should be taken for all engine models to prevent sustained engine operation in an unbalanced condition.

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With the exception of DSR-48 engines, the site-specific DR/QR Appendix II pro-grams, revision 2, call for monitoring cylinder exhaust temperatures and pres-sures for engine imbalance at each refueling. The staff believes this should also be applied for Shoreham. The staff notes that cylinder exhaust tempera-tures will also be monitored on an hourly basis (while engine is running) per Table 1 of the generic Appendix II program, Revision 2. It is implied in the table that'only maximum cylinder exhaust temperature is of interest (i.e., not to exceed 1050 F). The staff concludes that plant specific procedures should clarify that the hourly cylinder exhaust temperatures should also be monitored for engine imbalance.

2.1.3.9 DSR-48 Crankshafts - Shoreham and River Bend Sections 4.6.5.3 and 4.6.7.2 of PNL-5600 provide PNLs findings and recommenda-tions relative to the DSR-48 crankshaf ts at Shoreham and River Bend, respec-tively. These findings and recommendations have been fully addressed in the following SERs:

o Safety Evaluation Report related to the Operation of River Bend Station, Docket 50-548, NUREG-0989, Supplement 3, August, 1985.

o Safety Evaluation Report related to the Operation of Shoreham

. Nuclear Power Station, Docket 50-322, NUREG-0420, Supplement 9, December 1985.

DSR-48 crankshafts are among those components which the staff has concluded warrant special emphasis in terms of maintenance and surveillance. Key main-tenance inspections recommended by PNL have been incorporated as license con-ditions for Shoreham and River Bend. These include an inspection of the crankpin fillets and oil holes at each refueling cutage. The site-specific section of the DR/QR Appendix II M/S program, Revision 2, for River Bend now proposes that the crankshaft be inspected at each refueling, consistent with PNL's recommendation, through the third refueling. Assuming positive inspec-tion findings, these inspections would thereafter be performed at 5 year inter-vals. The staff' considers this proposal to be acceptable and consistent with PNL's recommendation that a reduced frequency of inspection could be considered after several refueling outages. riowever, it will be necessary to modify the

- existing license condition accordingly. .

The site specific section of the DR/QR Appendix II, Revision 2, M/S program for River Bend appears to only call for a one time inspection of the main journals after 5 years rather than periodic 5 year inspection as recommended by PNL. In contrast, the corresponding site-specific program for Rancho Seco does appear to call for a periodic 5 year inspection. The staff will continue to require that the River Bend main journal inspections be performed at 5 year intervals.

2.1.3.10 Other DSR-48 Crankshafts The staff concurs with PNLs recommendations in Section 4.6.8 of PNL-5600 con-cerning actions which should be followed to show that conclusions reached for Shoreham and River Bend are applicable to Rancho Seco and any other future DSR-48 engines. PNL has recommended, in part, that torsiograph test results and torsional stresses calculated from these results should be ccmpared with similar data from Shoreham and River Bend. The staff notes that the crankshaft 2-11

material properties as obtained from the material certification reports and fabrication history should also be compared to the Shoreham and River Bend data. All of the above data and data comparisons should be submitted for NRC staff review prior to placing the engines in nuclear standby service. Depend-ing on the outcome of these comparisons, further testing and analysis may be required by the staff to establish a " qualified" load capacity for the subject engines. -

Once a qualified load capability for the subject engines has been established satisfactorally, PNLs findings and reccmmendations for the Shoreham and River Bend crankshafts (i.e. , Sections 4.6.5.3 and 4.6.7.2 of PNL-5600) are applicable.

These findings and recommendations will be addressed by the staff in a manner similar to that for Shoreham and River Bend (see above referenced SERs).

Issues to be addressed by the staff include the following:

(1) Load testrictions must be incorporated into the plant Technical Specifica-tions to limit surveillance testing to loads not to exceed the engines

. " qualified" load.

(2) Engine operating procedures and training should provide proper guidance and instructions to operators against overloading the TDI diesel genera-tors above the qualified load. Specific issues include:

(a) No single operator error should cause the loading of more than one TDI engine in excess of its qualified load rating.

(b) Procedures and training in place should preclude operator action that would cause the TDI EDG load to exceed the qualified load.

(c) The training program should adequately address the technical concerns

. associated with the qualified load limit on the TDI EDGs.

(d) If a situation were to occur that would, for some unspecified reason, cause the EDG to exceed the qualified load, the procedures and training should provide the necessary guidance to reduce the load below the qualified load within one hour.

0- (e) Distinctive and unique instrumentation and alarms should be installed to warn operators when the engines are loaded above the qualified load.

(3) Requirements for contingency inspection of the crankshaft in the event that a diesel generator is overloaded above qualified load for some un-specified reasop will be specified as a license condition. A sample license condition is provided in Appendix A of this SER and was taken from the aforementioned River Bend SER.

(4) The periodic inspections specified in the site-specific section of the DR/QR Appendix II, Revision 2, M/S program are the same as those for River Bend (see Section 2.1.3.9 o' this SER). The staff finds this program to be acceptable subject to the clarification discussed in Section 2.1.3.9 of this SER that the main journals inspections will be performed at 5 year intervals rather than on a one time basis. License conditions incorporat-ing key inspection items will be necessary. Sample license conditions are 2-12

i .

provided in Appendix A of this SER. These sample license conditions are similar to those established for River Bend.

Additional operating and maintenance practices as describcd in Section 4.6.6.4.1 of PNL-5600 may be necessary depending on the proximity of the harmonic speeds to the nominal engine speed of 450 rpm. At River Bend, fcr example, even though the' normal response to the 5th order harmonic (which is in resonance at 455 rpm) was found to be small, there was a concern regarding the potential for excitation of the 5th order under conditions of cylinder imbalance and slight overspeed. The staff finds that this issue should also be evaluated for Rancho Seco and any other future DSR-48 crankshafts.

2.1.3.11 DSRV-16 Crankshafts As discussed in Section 4.7.8.3, of PNL-5600, PNL has concludad that DSRV-16 crankshafts at Catawba, Comanche Peak, Grand Gulf, and Perry are adequate for loads of up to the full-rated load of 7000 kW assigned by the manufacturer,

. and to 110% of Tated load for the percentage of operating time allowed by the manufacturers. This conclusion may also extend to other DSRV-16 crankshaft

. subject to certain specified confirmations.

. Certain plants with DSRV-16 crankshafts (e.g., Grand Gulf, Catawba Unit 1) are

- currently restricted against operating beyond an engine load corresponding to a break mean effective pressure of 185 psi (about 5755 kW). These load limi-tations were discussed in supporting plant-specific SERs and were based in part on preliminary PNL estimates concerning the load capabilities'of these crankshafts. However, based upon PNL's final conclusions as given in PNL-5600, the staff concludes that these load limitations are no longer necessary based on crankshaft considerations alone. The staff will consider licensee proposals to delete these restrictions where applicable.

Site-specific sections of DR/QR Appendix II, Revision 2, M/S programs incorpo-rate the periodic crankshaft inspectior.s recommended by PNL in Section 4.7.8.3 with the exception that the crankpin and main journals would apparently be inspected only once after 5 years rather than at 5 year intervals. The staff believes that the crankpin and main journal inspections should be inspected

periodically to ensure that they are free of abnormal cracking or wear. How-ever, based on the fact that the DSRV-16 crankshafts exhibit somewhat smaller

~

stresses than the DSR-48 crankshafts, the staff concludes that an inspection frequency corresponding to the 10 year major engine overhaul schedule would be acceptable for the DSRV-16 crankshafts in lieu of the 5 year interval to be implemented for the DSR-48 crankshafts. The staff will require that such periodic inspections be incorporated as part of plant-specific M/S programs.

Finally, the staff concurs with PNL's recommendations in Section 4.7.9 of PNL-5600 regarding the actions which should be taken prior to operational ser-vice to ensure that DSRV-16 crankshafts are adequate for each site including torsiograph testing, checking of material certification reports and preservice crankshaft inspections.

2.1.3.12 Crankshafts, DSRV-20 A major benefit of the attention focused on the TDI diesels by the NRC staff and by the Owners Group as a result of the Shoreham crankshaft failure was the 2-13

discovery of cracks in the San Onofre crankshafts stemming from large transient stresses during engine startups and shutdowns. The staff believes that this finding prevented a major crankshaft failure which otherwise would have likely occurred at some point in the future.

The various operational restrictions recommended by the Owners Group and PNL are not considered sufficient to ensure that the transient stress levels have been reduced sufficiently to preclude initiation of additional cracks and ultimately.the potential failure of these crankshafts. For this reason, FNL -

has recommended that prompt action be taken to modify the engines as necessary to alleviate the transient torsional stresses. Pending completion of this effort, PNL has concluded that the crankshafts should be inspected at each refueling outage to ensure the timely detection and repair of any new cracks.

. The staff concurs with these recommendations. The staff believes that the de-sign margins against fatigue for the San Onofre crankshafts fall short of what is normally assumed to be the case for crankshafts in general; namely, that 4

,- crankshafts are adequate for infinite fatigue life for their intended service.

Apart from the San Onofre crankshafts, the DSR-48 crankshafts at Shoreham and River Bend are the most highly stressed TDI crankshafts from a fatigue stand-point in nuclear service. However, with the load restrictions which have been

_ imposed on these engines, the staff has concluded that the Shoreham and River Bend crankshafts have infinite fatigue life for their intended service. Peri-odic inspections of these crankshafts which are required by the staff are of a strictly confirmatory nature and provide added assurance that the crankshafts will not be subject to fatigue failure.

The staff and PNL concur with the reasonableness of the fracture mechanics anal-ysis performed by FaAA, and the conclusions drawn from the analysis; namely that 4 cracks would not be expected to propagate sufficiently to cause a crankshaft fracture prior to crankshaft inspections to be performed at each refueling out-age. The staff believes that this constitutes an adequate basis for continued use of the crankshafts for an interim period pending replacement or modifica-tion of the crankshafts to provide adequate fatigue resistance. The staff does not consider it appropriate however, to rely indefinitely on a accele-i - rated inspection schedule to compensate for a deficiency in cesign which makes L these crankshafts prone to fatigue crack initiation and propagation contrary P to normal industry practice and expectation. The staff concurs with PNL that the root cause of the cracking should be corrected to ensure the long term reliability of these engines.

The staff has requested (letter dated May 27,1986) that Southern California Edison Company commit to a program to correct the root cause of the cracking problem and will negotiate a, suitable schedule for completing this effort.

Pending appropriate modifications to correct the crankshaft cracking problem, the following issues must be addressed:

(1) The periodic inspections recommended by PNL in Section 4.8.5.6.2 of PNL-5600 have been incorporated into the site-specific section of the DR/QR Appendix II, M/S program, Revision 2. Key periodic inspection items i

will be incorporated as license conditions. Sample license conditions are 2-14

q , _

provided in Appendix A of this SER. These license conditions include pro-vision for prompt NRC notification in the event that cracks are found dur-ing these inspections. The staff concurs with PNL recommendations in Sec-tion 4.8.5.6.2 of PNL-5600 concerning the repairs and additional analyses-which should be performed in the event that cracks are found during future inspections. Depending on the outcome of this evaluation, the staff may requi,re that actions to correct the cracking problem be completed prior to plant restart.

(2) The plant Technical Specifications should be revised to limit diesel -

generator surveillance testing to 4500 kW 5%.

(3) Engine operating procedures and training should be revised as necessary to

, provide appropriate guidance and instruction to operators against over-loading the diesels beyond 4500 kW 5%. Specific issues to be addressed have been described earlier in Section 2.1.3.5 of this SER.

(4) Require.ments for contingency inspection of the crankshaft in the event that the crankshaft is loaded beyond 4500 kW 5% for some unspecified reason will be specified as a license condition. A sample license condi-tion specifically applicable to the DSRV-20 crankshaft at San Onofre 1 has not been included in Appendix A of this SER, but should be developed in a 1 manner similar to that for River Bend. The license condition for contin-gency crankshaft inspections at River Bend is provided in Appendix A of this SER.

(5) The licensee for San Onofre 1 has proposed a change to the plant Technical Specifications to limit " fast" starts of the engines to once each refueling outage as recommended by PNL. Monthly surveillance tests are to be " slow" starts. PNL's understanding of what constitutes a " slow" start appears to be a least a 24 second start to rated speed (see Section 5.8.4.3 of PNL-5600). However, the proposed plant Technical Specification would permit any start duration exceeding 10 seconds to be considered a slow start. The staff concludes that the licensee should submit appropriate clarification to the. staff that the monthly slow starts will be at least 24 seconds in duration. The plant Technical Specification should be revised accordingly as soon as practical.

' (6) PNL recommendations in Sections 4.8.5.6.3 of PNL-5600 concerning precau-tions against operating the engine in an unbalanced condition and avoiding operation more than a few rpm above 450 rpm need not be incorporated as a license condition. However, these reccmmendations should be incorporated into appropriate plant operating and surveillance testing procedures.

~

2.1.3.13 Engine Block Although not specifically stated in Section 4.9.5.2 of PNL-5600, PNL and the NRC staff endorse the recommendations of the Owners Group consultant, Failure Analysis Associates, concerni.ng periodic inspection of the engine block for

" ligament" cracks, " stud-to-stud" cracks and " stud-to-end" cracks as identified in Failure Analysis Associates report no. FaAA-84-9-11.1, dated December 1984.

With the exception of Rancho Seco, the site-specific sections of the DR/QR Appendix II M/S program, Revision 2, references Section 02-315A of the DR/QR report which in turn references FaAA-84-9-11.1. The staff understands that the 2-15 i

omission of Rancho Seco from Appendix II was inadvertent and should be the same as for River Bend.

As noted in Table 2.1, the cylinder blocks are among those components for which the NRC staff and PNL have concluded warrant special emphasis from a maintenance /

surveillance standpoint. Accordingly the staff has concluded that the following periodic inspection of the cylinder blocks should be required as conditions of the licensh (see Appendix A, " Sample License Conditions"):

(1) Cylinder blocks should be inspected for " ligament" cracks, " stud-to-stud" -

cracks, and " stud-to-end" cracks as identified in FaAA-84-9-11.1. The inspection intervals should not exceed the intervals calculated using the l cumulative damage index model in the subject FaAA report. In addition, l inspection methods and procedures should be consistent with or equivalent to those identified in the subject FaAA report.

(2) In addition to inspections specified in the aforementioned FaAA report, blocks with "known" or " assumed ligament" cracks should be inspected at

. y each refueling outage in accordance with PNL's recommendations in Sec-tion 4.9.5.2 of PNL-5600 to determine whether or not cracks have initiated on the top surface exposed by the removal of two or more cylinder heads.

i1 In addition to the above inspection items to be incorporated as license condi-l tions, PNL has also recommended (1) visual inspections of the block under in-l tense light, (2) inspections for cracks in the liner bore and cam gallery, and (3) that magnetic particle and eddy current inspections be conducted per spec-ifications cited by PNL. Regarding item (1), the staff believes that these inspections are redundant to inspections which will be performed at periodic intervals as specified in the above mentioned FaAA report and to visual inspec-tions which will be performed for leaks on a hourly basis while the engine is running (see Table 1, DR/QR Appendix II, Revision 2). Thus, the staff will not require inclusion of such inspections in plant-specific maintenance /

surveillance programs.

I l

Regarding item (2), PNL and the staff have concurred with the Owners Group that such cracks would not be likely to propagate sufficiently to degrade the integrity of the block. The staff nonetheless believes that it is prudent to

- monitor these cracks at available opportunities should such cracks be known to exist. The staff concludes that plant specific programs should reflect this point.

Regarding item (3), the staff has not evaluated the specific merits of the PNL recommendation. However, licensees are, already required pursuant to NRC regu-lations and applicable industry standards to meet certain minimum standards for NDE inspections of safety related components. The staff concludes that licensees should consider PNL's recommendations on this matter and incorporate these recommendations into their program if and as deemed appropriate.

Regarding the block inspections to be performed in accordance with FaAA-84-9-11.1, the Owners Group has proposed a clarification that (1) for blocks with known or assumed ligament cracks, inspections will be performed for stud-to-stud cracks af ter any operation above 50% of rated load, (2) these inspections ~ may be per-formed using an eddy current probe or a borescope with heads in place, and 2-16

v (3) the inspections are to be performed within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after engine shutdown (Owners Group letter dated Hay 1, 1986, J. George, Owners Group, to H. Denton, NRC).

The staff believes the first clarification item above to be consistent with FaAA's recommendation which has been endorsed by PNL and which is acceptable to the staff. Regarding the second item, the NRC staff and its PNL consult-ants have previously found borescope inspections to be an acceptable alterna-tive to eddy current testing for the application indicated. (

Reference:

PNL-5600,'Section 4. 9.5. 2). The staff also finds the third clarification item to be acceptable.

PNL and the NRC staff concur with FaAA's conclusion that there currently exists no analytical basis for operation in cases where " stud-to-stud" or " stud-to end" cracks exceed 1.5 inches in depth. In addition, the staff will require as a condition of the license that it be promptly informed of any such cracks, re-gardless of depth. Further, the engine should not be considered to be operable for nuclear standby service until the proposed disposition and/or corrective

.~ actions have been approved by the NRC staff (see Appendix A, " Sample License Conditions").

. The NRC staff concurs with PNL's recommendation that any block with degraded microstructure (e.g. , Widmanstaetten graphite) should not be placed in nuclear standby service without thorough justification by the engine owner and' review by the NRC staff.

2.1.3.14 Cylinder Heads PNL has endorsed the recommendation of the Owners Group consultant, FaAA, that all cylinder heads be inspected as part of the quality revalidation inspection.

However, the Owners Group recommendation as expressed in plant-specific DR/QR reports recommends that a 25% sample inspection is sufficient for Group III heads (i.e., heads cast after September 1980). In an Owners Group letter to the NRC dated May 1, 1986 (J. George, Owners Group, to H. Denton, NRC), the Owners Group has stated that Group III heads are much less prone to manufactur-ing defects than Group I or Group II heads. The Owners group has further stated that Group III head castings have been subjected to magnetic partial inspec-L tions in accordance with TDI procedures ccmmencing April .1984. In addition, t'he machined surface of the fire deck was also subject to magnetic particle inspection during this same period. The staff notes that Group III heads cast during the period between September 1980 and April 1984 appear not to have re-ceived these inspections. However, based on good operating experience to date with Group III heads and subject to continued implementation of air roll tests as described below, the staff finds the proposed 25% sample inspection for Group III heads to be acceptable.

As noted earlier in Table 2.1, cylinder heads are one of the components which ,

PNL has concluded warrant special emphasis in the area of maintenance /  ;

surveillance. The key item in this area is PNL's recommendation in Section  ;

4.10.4.3 for periodic air-rolling of the engine with the cylinder. cocks open i to check for the presence of water in the cylinders. Except as noted for l Group III heads below, this item will be incorporated as a license condition l for all TDI engines (see Appendix A, " Sample License Conditions"). l 1

2-17

5 .

The Owners Group has proposed that the post-operational air roll tests recom-mended by PNL be discontinued af ter the first operating cycle provided all heads are Group III heads and subject to their continued leak free perform-ance up to that time. The staff finds this proposal to be acceptable subject to the following conditions: -

(1) Quality revalidation inspections have been completed for all cylinder heads.

(2) GroujiIII heads continue to demonstrate leak free performance. This should be confirmed with TDI prior to deleting air roll tests.

In its letter dated May 1, 1986, the Owners Group noted that air rolling of the engine can be performed only if the engine is placed in a maintenance mode -

and is not available to accept a start signal. The Owners Group stated its opinion that performing an air roll on an engine should not be considered as a Limiting Condition for Operation (LCO) of the plant. The staff does not agree with the Owners Group's opinion. It is the staff's position that if the engine is not available to accept a start signal, then the engine is technically inoperable and therefore the action statement nf Technical Specification 3/4.8.1 should apply. However, the subject action statement allows one hour before the

, other diesel (s) and other remaining AC sources must be demonstrated operable.

. Since the air roll test can be accomplished in less than one-half hour, the staff believes that the subject engine can be returned to operable status, thus terminating the action statement, before it is necessary to demonstrate the operability of the other diesel (s) and other AC sources.

Finally, as a point of clarification, the staff finds that the PNL reccmmended air roll tests should be performed except in cases when the plant is already in the action statement of Technical Specification 3/4.8.1. In other words, it is not the staff's intent that an engine should intentionally be put into a condi-tion where it cannot receive a start signal if the other diesel (s) or other ac sources are already inoperable.

PNL has recommended in Section 4.10.4.3 that cylinder heads with any through-wall weld repair of the fire deck should not be placed in nuclear standby ser-vice if the repair is performed from one side only (i.e., a " plug weld"). The

& staff concurs with this reccmmendation and concludes that it should be incor-parated into appropriate plant maintenance / surveillance procedures, but need not be incorporated as a license condition.

However, as documented in the staff's SER for Catawba Unit 2 (NUREG-0954, Supplement 5), the staff has approved a weld repair procedure for an injector boreasshownonTDEfrawing 102718, Revision 0. This weld repair consists of welding a plug into the head, stress relieving the weld and machining the injector port back side of the plug out such that the weld is a full penetra-tion weld. The full penetration weld eliminates the crack starter found in previous partial penetration weld repaired heads.

Regarding PNL's recommendations for alternative procedures and acceptance criteria in future cylinder head inspections, the staff has not specifically reviewed the merits of the PNL recommendations. The staff assumes that li-censees will follow apprcpriate regulatory and industry standards in performing NDE inspections. The staff concludes that licensees should consider PNL's 2-18

\ ~. _

recommendations on this matter and incorporate these recommendations into their programs if and as appropriate.

2.1.3.15 Cylinder Head Studs PNL has endorsed findings of the Owners Group consultant, Stone and Webster, regarding the adequacy of the cylinder head studs for nuclear service subject to installation of the studs in accordance with procedures identified in a letter from C. Ray, Chairman, TDI Owners Group, to the individual utility .

owners, dated September 24, 1984. The staff notes that DR/QR Appendix II, Revision 2, does not specifically address this point. The staff will require that utilities check to confirm that this point is addressed in plant-specific programs.

2.1.3.16 Engine Base - All Models The DR/QR Appendix II M/S Program incorporates PNL's recommendations in Sec-tion 4.17.4.2 of PNL-5600 except as discussed below. First the Owners Group

.- is now proposing a visual inspection of the base to take place at each 10 year overhaul rather than at each refueling outage as originally proposed by the Owners Group and endorsed by PNL. In addition, the Owners Group is now propos-ing that the base be inspected at each of the first three refueling outages

- except in cases where the licensee has confirmed that the base material micro-structure conforms to normal Class 40 grey iron. There have been relatively few instances of cracks in the engine base and those which have occurred have been generally attributable to inadequate bolt preloads and installation pro-cedures with only one case due to inferior quality of the casting. These in-stances do not involve inadequate design. For this reason plus the fact that the engine bases will have received a quality revalidation inspection the staff concurs with the proposed inspection interval in cases where previous inspec-tions have shown the blocks to be crack free. In cases where cracks have been found to exist (e.g., certain bearing saddles of the EDG 102 and EDG 103 en-gines at Shoreham), the staff believes that these cracks should be Soaitored for growth by magnetic particle or liquid penetrant inspection at alternate refueling outages as recommended by PNL. If no growth is evident after ten years, these inspections need only be performed at subsequent major engine overhauls.

. Finally, the staff believes that all the TDI owner utilities should check ea:h engine base for degenerate Widmanstaetten graphite. The basis for this finding is that several TDI engine blocks (which are also fabricated from Class 40 grey iron) have been found to exhibit this degenerate microstructure which substan-tially increases the motential for developing cracks. Should any engine base be found to contain t1is degenerate microstructure, this should be reported to the NRC together with a detailed assessment as to the adequacy of the affected engine base for nuclear standby service. The staff will evaluate the need for licensing action to address the degenerate microstructure on a case by case basis.

2.1.3.17 Fuel Oil Injection Tubing In Section 4.14.4.2 of PNL-5600, PNL reco'. mended in part that (1) replacement fuel oil injection tubing be fabricated from SAE-1010 steel rather than SAE-1008 steel and (2) the fuel lines be shrouded (note that these were also Stone and 2-19

/

Webster recommendations to the utility owners). The staff encourages utili-ties to follow these recommendations, but concludes that implementation should nonetheless be optional. The staff's findings on this issue is based on the

~ fact that although implementation of these items would provide added assurance of satisfactory performance, the fuel lines have been found to have adequate fatigue resistance by both the Owners Group and PNL. This finding of adequate fatigue resistance is, of course, subject to implementation of the Owners Group recommendations for preservice inspections, acceptance criteria, and maintenance / surveillance as documented in the plant DR/QR reports and the generic Appendix II, Revision 2, of the DR/QR reports. In addition, plant maintenance programs should include the manufacturer's instructions concerning the installation and inspection of the fuel line fittings if this has not al-ready been done (see Section 4.14.4.2 of PNL-5600).

Finally, PNL has recommended that newly installed tubing and fittings be in-spected for leakage following engine operation after the engine is shutcown, and that the inspector look for wet fittings or other signs of leakage. PNL

. has noted that inspection of the tubes during engine operation may be hazard-ous to cperating personnel due to the high pressure of the fuel in the line.

This recommendation is not considered by the NRC staff to be an engine reli-ability or nuclear plant safety issue, and therefore licensees may implement

. this reccamendation at their discretion. However, the staff urges licensees

- to give due consideration to this recommendation since it reflects the con-siderable and distinguished experience of diesel engine expert consultants under contract to PNL.

2.1.3.18 Jacket Water Pump PNL has endorsed the findings of the Owners Group and their consultant, Stone and Webster Engineering Corporation (SWEC) as discussed in Section 4.15.4.3 of PNL-5600. This represents an endorsement of recommended design changes for the DSR-48 engines and of the jacket water pump periodic maintenance items recommended by the Owners Group and which are contained in the generic DR/QR Appendix II maintenance program, Revision 2. However, the staff notes that the Appendix II maintenance program, Revision 2, does not fully address addi-tions to the pump assembly recommended by SWEC for the DSRV-20 engine pumps at San Onofre 1 and which are identified in Section 4.15.3.3.3 of PNL-5500. The I- licensee for San Onofre 1 will b'e required to confirm that the items have been fully implemented and/or have been incorporated as part of the plant maintenance procedures as appropriate.

2.1.3.19 Piston Skirts - Type AE PNL has concluded in[Section 4.16.3.3 that the type AE piston skirts are ade-quate for service at their rated load and overload conditions. This finding updates and supercedes earlier FNL findings of an interim nature that the AE piston are adequate for loads ranging to 185 psi bmep. Accordingly, the staff concludes that loading restrictions on AE piston skirts which were imposed for a few plants (e.g. , Catawba (Jnit 1, Grand Gulf) are no longer necessary. The staff will consider any licensee proposals to delete this restriction assuming there are no other components subject to load restrictions.

PNL has endorsed the Owners Group recommended quality revalidation inspections in the plant DR/QR reports. As reccamended by PNL, however, the staff will 2-20

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[ . ..

require that all AE piston skirts complete these quality revalidation inspec-tions prior to initial plant operation. For AE piston skirts at operating plants which did not receive these preservice inspections, the staff will re-quire that these pistons be inspected at the first 10 year overhaul.

2.1.3.20 Piston Skirts - Modified Type AF Like the D'SRV crankshafts, PNL and the staff have concluded that modified type AF piston skirts are adequate for engine loads ranging to 4500 kW ( 5%).

Accordingly, the discussion in Section 2.1.3.7 of this SER concerning the load .

limitation for the DSRV-20 crankshaft applies also to the Type AF piston skirts installed at San Onofre Unit 1. The load limitations discussed in Sec-tion 2.1.3.12 will remain in place for the Type AF piston skirts even after the crankshafts have been modified to eliminate the c.ause of previously observed cracks in the crankshaft.

As noted in Table 2.1, the modified type AF piston skirts are among these components which PNL has concluded warrant special emphasis from a maintenance /

f surveillance standpoint. Accordingly, the periodic inspections recommended by PNL in Section 5.16.4.3 of PNL-5600 will be incorporated as license conditions (see Appendix A of this SER, " Sample License Conditions"). Consistent with

, PNL's recommendation, the license condition need only be in force until a

. total of 750 hours0.00868 days <br />0.208 hours <br />0.00124 weeks <br />2.85375e-4 months <br /> have been accumulated on the pistons and a subsequent inspection of all of the pistons is successfully performed.

2.1.3.21 Pisten Skirts - Type AH and AN The staff concurs with PNL's findings in Section 4.16.5.2 of PNL-5600 concern-ing the necessary actions to qualify Type AH piston skirts for nuclear service.

The staff concludes that AH pistons skirts should not be placed into nuclear service without NRC approval.

The staff concurs with PNL's finding in Section 4.16.6.3 of PNL-5600 that Type AN piston skirts should not be used in nuclear service.

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2.1.3.22 Push Rods I- The NRC staff concurs with PNL's findings in Section 4.17.4.3 of PNL-5600.

PNL concludes that the forged head and friction-welded push rod designs are acceptable for nuclear service, and that the ball end design is not acceptable.

The generic DR/QR Appendix II maintenance program, Revision 2, incorporates PNL's recommendations for preservice and periodic inservice inspection of push rods. In view of the' fact that each push rod of the friction-welded design will be liquid penetrant inspected prior to service, PNL's suggestion concern-ing radiograph inspections is considered by the staff to be an optional item to be implemented at the utility's discretion.

Finally, the generic DR/QR Appendix II maintenance program, Revision 2, does not include provision for a destructive examination of friction-welded push rods on random samples from each future manufacturing lot. This was an initial recommendation of the Owners Group and was endorsed by PNL. However, again because each push rod will be initially inspected by liquid penetrant, the 2-21

o '. .

staff concludes that the subject destr'uctive examination should be at the utility's option.

2.1.3.23 Rocker Arm Capscrews The NRC staff concurs with PNL's findings in Section 4.18.4.3 of PNL-5600 re-garding the acceptability of the rocker arm capscrews for nuclear service assuming they are properly torqued. The staff notes that the generic DR/QR Appendix II maintenance program, Revision 2, addresses the need for verifying proper torquing.

2.1.3.24 Turbochargers

, 'As discussed in Section 4.19.4.3 of PNL-5600, PNL has endorsed the Owners Group recommendations for installation and implementation of the drip and full-flow prelubrication system, quality revalidation inspections, and periodic mainte-nance and surveillance actions. In addition, PNL has identified some addi-tional recommendations in Section 4.19.4.3 of PNL-5600 which relate to peri-odic maintenance and surveillance. Except as noted below, the staff finds that these recommendations are generally included either in the plant-specific DR/QR reports or in Revision 2 of the generic Appendix II of the DR/QR reports deal-

, ing with the maintenance / surveillance program.

PNL recommended that turbine inlet temperature be directly monitored with appro-priate instrumentation to ensure that it does not exceed the 1200 F maximum spe-cified by the turbocharger manufacturer. This would require installation of ,

additional instrumentation for most engines. However, the Owners Group has proposed in Revision 2 of the generic DR/QR Appendix II maintenance program to monitor cylinder exhaust temperatures with existing instrumentation. Data pro-vided by TDI indicates that limiting the maximum cylinder exhaust temperature to 1050 F ensures that the turbine inlet temperature will not exceed the manu-facturer's specified limit. Thus, the staff finds the proposed alternative 4

action to be acceptable.

~

PNL recommended that full. flow lubrication be implemented during engine coast-3 down. Although the Owners Group has indicated such capability exists, it was not actually included among the list of Owners Group recommendations. The NRC L staff finds that periodic bearing inspections and float measurements called '

for by the generic DR/QR Appendix II maintenance program; Revision 2, ensures that degradation rates for the turbocharger thrust bearings will be adequately monitored. The staff finds, therefore, that full flow lubrication during coast-down should be implemented at the licensee's option.

PNL recommended that the spectrochemical and ferrographic oil analyses recom-

! mended by the Owners' Group consultant, Failure Analysis Associates (FaAA), be performed quarterly to provide early evidence of bearing degradation. The staff concurs with this recommendation; however, it is not clear that it has been incorporated into the generic DR/QR Appendix II maintenance program, Re-vision 2. The staff will require that each utility verify that this recom-mendation has been incorporated into the respective plant specific program.

In view of previous problems with nozzle ring components and inlet guide vanes, PNL recommended inspection of these items at each refueling outage. Recog-nizing that many of the problems with nozzle ring components have occurred 2-22

---

,r.._-- --- ,,, .,,y ,, , m___ , . ,, - - , - - - - _ , ,

,,_,,-y.,_-- -.- ,

y- , - --, --,. _ -

\ .

very early in the life of these components, the Owners Group has proposed in the Appendix II, Revision 2, M/S plan that each turbocharger be inspected after approximately 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of preoperational testing or, alternatively, at the first refueling. Subsequently turbocharger nozzle ring components would be inspected at each nuclear unit on a one turbocharger per refueling outage basis, and all would be inspected at each turbocharger overhaul which is performed at 5 year intervals. Notwithstanding PNL's concern regarding the potential for broken nozzle ring components (particularly the vanes) to cause damage to the turbine, the staff notes that none of the nozzle ring problems to date has caused a turbocharger or engine failure. The staff concludes that the fre-quency of inspection proposed by the Owners Group is acceptable. However, the staff will require that plant-specific programs specify that any turbocharger in which nozzle ring anomalies are found be reinspected at the next refueling outage. - -

The Appendix II, Revision 2, M/S program also specifies that the nozzle ring inspections may be discontinued after nozzle rings of an appropriate redesign have been installed. The staff interprets this provision as applying to the I inspection of one turbocharger per refueling outage item and not to the turbo-charger inspections to be performed at 5 yect intervals. The staff will re-quire that this point be clarified in plant-specific programs. On this basis,

, the staff finds the proposed provision "to delete" to be acceptable.

!~ As noted in Table 2.1, the turbochargers are among those components which PNL has concluded warrant special emphasis from a maintenance /surveill'ance stand-point. Accordingly, the major maintenance / surveillance recommendations of the Owners Group and PNL will be incorporated as licensa conditions (see Appendix A,

" Sample License Conditions").

2.2 Technical Resolution of Phase II Phase II of the Owners Group Program proceeded beyond known problem areas to systematically consider all components (approximately 150 to 170 component types per engines) important to the operbility and reliability of the engines.

Phase II was intended primarily to ensure that significant new problem areas do not develop in the future due to deficiencies in design or quality of manu-facture. The Owners Group performed the Phase II design reviews and, as was the case for Phase I, reccmmended needed ccmponent 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 ccmprehensive engine maintenance and surveillance program to be implemented oy the individual owners.

I These Phase II efforts were documented by the Owners Group in Design Review /

Quality Revalidation'(DRQR) reports. In general, a DRQR report was issued for one nuclear unit at each statit,n, but not for the second nuclear unit at a two-unit station. The staff does expect, however,that a Unit 1 DRQR program will be fully implemented for the Unit 2 engines at the same station.

. Design reviews performed by the Owners Group for engine components at one plant were generally applicable to similar components at other plants. Similarly, Owners Group recommended quality revalidation inspectio" for engine components at one plant were generally applicable to similar engine components at other 2-23 I

y . , . . . . . . . . . . . . _ _ . . . _ . _ . . . . . . . .

~

plants, although the actual inspections were generally performed by the indi-vidual owners. The DRQR reports for the Shoreham DSR-48 engines and the Comanche Peak DSRV-16-4 engines generally constituted the lead engine reviews.

These reports were extensively referenced in DRQR reports prepared for other (follow-epgine) plants.

The staff's contractor, PNL, performed a detailed audit review of the DRQR reports for the Shoreham DSR-48 engines and for the Comanche Peak DSRV-16-4 engines. These PNL reviews are documented in PNL reports numbered PNL-5336 and PNL-5444, respectively. PNL found that the DRQR efforts fully met the intent of the Owners Group Program Plan which was to establish ".... reasonable assurance of the ability of the TDI engines to provide reliable backup power supplies for nuclear power plant service." '

PNL found that the Owners' Group had adequately addressed the design and/or quality aspects of all the components included in the audit-type reviews for both plants. From the PNL review of the adequacy of the Owners' Group mainte-nance recommendations for the audited components, PNL concluded that the main-tenance plan as proposed was acceptable. During their review of the Owners' Group M/S recommendations for the audited components, the PNL consultants did

• identify additional areas which, in their engineering judgement, woulo repre-sent improvements for a total of 7 components out of the 150 reviewed for both

; plants (see Section 4.0 of PNL-5336 and Section 4.0 of PNL-5444). Failure to accomplish these additional items would not seriously affect engin.e operability;

' however, PNL feels that, on the basis of good engineering practice, the engine owners should incorporate these recommendations into their M/S pl,ans as they apply to the DSR-48, DSRV-16-4, and DSRV-20-4 engines. Based on the above, the staff concludes that these items should not be required by the NRC, and that their implementation should be at the discretion of the individual utilities.

Based on the audit reviews of the comprehensive Owners' Group Phase II reports for the two selected plants,'PNL concludes that no further detailed reviews of Phase II reports by the NRC staff or its contractors need be done. This con-t clusion is based on the favorable results of the two reviews and a cursory

examination of other Owners' Group Phase II reports. This latter examination

, confirmed the continued quality of the Owners' Group quality revalidation effort

> > and verified that a high degree of overlap exists between the Owners' Group Phase II design review conclusions pertaining to similar engine models, render-ing a detailed review unneces.sary and overly redundant.

The staff and its PNL consultants have concluded that implementation of the j Owners' Group recommendations in the Phase II reports will be effective in 1

improving and ensuring the design adequacy and quality of the. engine components l and, hence, the reliability and operability of the TDI engines at the various Owners' Group nuclear plants. The staff and PNL have therefore concluded that each individual owner should implement all Owners' Group recommendations stem-

.! ming from the plant specific Phase II evaluations.

4 2.3 Maintenance / Surveillance Procram i

The staff and its PNL consultants view the implementation of a comprehensive i maintenance and surveillance (M/S) plan to be a key element of the overall effort to establish and maintain TDI diesel engine reliability and operability.

l l 2-24

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Such a plan contributes to continued satisfactory engine performance and'facil-itates the timely identification of potential engine problems.

This section expands on earlier discussions in this SER of the M/S program for TDI engines in nuclear serivce to explain the background of the M/S program developed by the Owners Group, general findings regarding the M/S program reached by.PNL, subsequent revisions to the M/S program by the Owners Group, and, finally, the staff's conclusions pertaining to M/S programs for TDI j engines in nuclear service.

As a result of their generic Phase I and Phase II component reviews, the Owners Group developed an M/S plan applicable to each member utility's engines. This plan for each plant, which supplements the existing TDI Instruction Manual, was  !

developed by the Owners' Group from (I) their detailed review of each compo- )

nent's service hist Jry, (2) TDI Service Information Memos and correspondence i on specific components, and (3) the Owners' Group technical reviews done during the Phase II DR/QR reviews. The Owners' Group recommendations are docunented in Appendix II of the DRQR report for each plant.

In connection with its review of the Owners' Group Phase I program for the resolution of known problem areas, PNL performed detailed evaluations of the

. M/S requirements for Phase I components (

Reference:

PNL-5600). In addition, PNL evaluated the Owners' Group Appendix II maintenance and surveillance plans for representative engine models, namely, two DSR-48 engines (Shoreham and River Bend) and one DSRV-16-4 engine (Comanche Peak). (

References:

PNL-5336, 5485 and 5444). PNL also examined the Appendix II plans for other engines to determine overall content and coverage.

Based on its findings in each of the above referenced reports, PNL concluded in PNL-5718 that a satisfactory maintenance and surveillance program for nu-clear standby applications of TDI DSR-48 and DSRV-16-4 series engines should consist of the following elements:

(1) The recommendations concerning operation, testing, inspection, maintenance, adjustment, overhaul.and repair of the engine as incorporated in the TDI Instruction Manual, Service Information Memos (SIMS), and TDI correspond-j ence on specific maintenance / surveillance issues.

3 (2) The maintenance and surveillance recommendations developed by the Owners' Group in Appendix II of the DR/QR reports.

(3) PNL maintenance and surveillance recommendations stemming from its generic Phase I review (i.c. , PNL-5600).

(4) PNL recommendations pertaining to surveillance monitoring while the engine is in the standy condition and during operations. These recommendations were specifically identified in PNL-5304 which was incorporated as part of the staff's SSER for River Bend (

Reference:

NUREG-0989, Supplement No. 3,

" Safety Evaluation Report related to the Operation of River Bend Station,"

August 1985).

Subsequent to issuance of the above reports by PNL, the Owners Group issued Revision 2 of the Appendix II M/S program (transmitted by letter dated May 1, 1986 frca J. B. Georce, Chairman, TDI Owners Group, to H. R. Denton, Office 2-25

s -

of Nuclear Reactor Regulation, NRC). Revision 2 was issued following Owners Group consideration of a number of exceptions taken by individual utilities to initial versions of Appendix II. The Owners Group also considered the aforementioned PNL reports in developing Revision 2 of Appendix II. ' Revision 2 of Appendix II consists of a generic maintenance matrix applicable to all TDI engines and 12 site-specific sections that address particular items for each utility that are not covered by the generic document.

The staff.has reviewed Revision 2 of Appendix II and determined that a number -

of differinces exist between that document and M/S items endorsed and/or re-commended by PNL in the above-mentioned PNL reports. The staff has examined in detail those differences which exist for M/S items relating to Phase I com-ponents. The staff's findings in this regard have been documented in detail in Section 2.1.3 of this SER. The staff will require that plant M/S programs address these findings as appropriate.

Table 1 of Revision 2 of Appendix II basically incorporates PNL's recommenda-tions in Tables 6.2 and 6.3 of PNL-5304 concerning surveillance of key engine

.' parameters while the engine is either in a standby or operating mode. Although a few differences exist, these are considered to be relatively minor differences' by the staff (and are therefore acceptable) except as specifically noted in Section 2.1.3 of this SER.

The staff does not plan to perform a detailed review of Appendix II revisions affecting Phase II components. The staff believes, based upon the staff /PNL review of the Owners Group program, that the Owners Group has demonstrated a high level of commitment to identifying those actions which are necessary to ensure engine cperability/ reliability. In addition, the Owners Group has demonstrated strong leadership toward this goal as evidenced by the very com-1 prehensive nature of the requalification program that it has reccmmended to the individual utilities.

1 In summary, based on its review of the above-mentioned PNL technical evaluation reports and of the Appendix II, Revision 2 program proposed by the Owners Group, j the staff concludes that a plant M/S program incorporating the following elements i will constitute an acceptable program.

L (1) The recommendations concerning operation, testing, inspection, maintenance, adjustment, overhaul and repair of the engine as incorporated in the TDI Instruction Manual, Service Information Memes (SIMS), and TDI correspond-ence on specific maintenance / surveillance issues.

j (2) The maintenance and surveillance recommendations developed by the Owners

[ GroupinAppendijII, Revision 2,oftheDR/QRreports.

i (3) Additional items required by the staff as identified in Section 2.1.3 of this SER. .

The staff will require that the Owners for each plant commit to an acceptable maintenance and surveillance program as identified above prior to. issuing final plant specific SERs addressing the final resolution of the TDI engine issue.

i Typically, detailed steps of preventative maintenance and surveillance programs for important safety related systems such as diesel generators are not incor-porated as part of the plant license or the plant Tecnnical Specifications.

2-26 ene... - , , . - - - - - - , , - - , .? .-_.--.,-,-,,nn.,

V . .

i ..

Accordingly, changes to these programs are not normally subject to NRC review and approval. However, the staff believes that any future revisions to the M/S program (subsequent to issuance of final plant-specific SERs) should be subject to the provisions of 10 CFR 50.59 in view of the importance of the M/S program in ensuring the operability / reliability of the engines over the long term. Furthermore, in keeping with PNL's recommendation that certain components (see Table.2.1) warrant special emphasis in terms of maintenance / surveillance actions to ensure their adequate service, the staff will include key maintenance /

surveillance actions for these components as license conditions (see Appendix A,

" Sample License Conditions"). This ensures that any changes relative to the

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Owners Group and PNL recommended maintenance actions for these components will be subject to NRC approval. .

P 9

d t

e C.

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• ~

t 4 3 CONCLUSIONS The NRC sta'ff and its PNL consultants have completed their evaluation of the Owners Group program to validate and upgrade, as necessary, the design and manufacturing quality of the TDI diesel generators for nuclear standby service. .

The staff ~has concluded that implementation of the Owners Group and PNL recom-mendations concerning quality revalidation inspections, component modifications 1 and replacement, load restrictions, operating precautions, etc., will establish the adequacy of the TDI diesel generators for nuclear standby service as re-quired by General Design Criterion (GDC) 17. The staff further concludes that these actions will ensure that the design and manufacturing quality of the TDI engines is within the range normally assumed for diesel engines designed and manufactured in accordance with 10 CFR 50, Appendix B. Continued reliability /

operability of the TDI engines for the life of the facilities will'be assured '

,- by implementation of the maintenance / surveillance program discussed in Sec- ,

tion 2.3 of this SER.

Accordingly, the staff has concluded that a technical resolution is available

_ to address the so-called "TDI diesel generator issues" (namely the concerns which were raised regarding the reliability of the TDI diesel generators fol-lowing the crankshaft failure at Shoreham in August 1983). Technical resolu-tion will involve implementation of an acceptable Phase I program as identi-fied in Section 2.1 of this SER, an acceptable Phase II program as identified i in Section 2.2 of this SER, and implementation of an acceptable maintenance and surveillance program as identified in Section 2.3 of this SER. These i actions are supplemental to requirements which must normally be satisfied 3

(e.g. , Regulatory Guide 1.108) as a prerequisite for obtaining an operating L- license (

Reference:

NL' REG-0800, " Standard Review Plan").

4 Generic Phase I issues, problem areas of a plant-specific nature, and mainte-nance and surveillance programs must be fully addressed as a condition for

! issuance of an operating license. Where other issues remain to be closed out .

.' e; (e.g., Phase II issues) in accordance with this SER, a license condition should.be imposed requiring such closecut by the first refueling outage.

With regard to Phase I components, the NRC staff and PNL have concluded that several of these components merit special emphasis in the areas of load re-strictions and/or maintenance / surveillance. These components include the DSRV -

! connecting rods, DSR-48 crankshafts, DSRV-20-4 crankshafts, cylinder blocks, cylinder heads, type AF piston skirts and turbochargers. Engine load restric-tions must be addresded in the plant Technical Specifications, license condi-tions, engine operating procedures and operator training, as appropriate. The most critical periodic maintenance / surveillance actions for these components i will be incorporated as license conditions.

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APPENDIX A l

SAMPLE LICENSE CONDITION ,

1. General (applicable to all TDI engines)

Chan'ges to the maintenance and surveillance program for the TDI oiesel engines,asidentifiedin[ ]*, shall be subject to the provisions

~

of 10 CFR 50.59.

. The frequency of the major engine overhauls referred to in the license

~

conditions below shall be consistent with Section IV.I. " Overhaul Frequency" in Revision 2 of Appendix II of the Design Review / Quality Revalidation report which was transmitted by letter dated May 1, 1985, from J. George, Owners Group, to H. Denton, NRC.

I

2. Connectina Rods (applicable to TDI DSRV-16-4 and DSRV-20-4 engines only)

Connecting rod assemblies shall be subjected to the following inspections ^

at each major engine overhaul:

o The surfaces of the rack teeth should be inspected for signs of fretting. If fretting has occurred, it should be subject to an ,

engineering evaluation for appropriate corrective action. -

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o All connecti g-rod bolts should be lubricated in accordance with the engine manufacturer's instructions and torqued to the specifications of the manufacturer. The lengths of the two pairs of bolts above the crankpin should be measured u]?.rasonicly pre and p'ost-tensioning.

identify SER and section number which identifies the reference (baseline)

TDI engine maintenance and surveillance procram. -

A-1

( ,

o The lengths of the two paris of bolts above the crankpin should be measured ultrasonically prior to detensioning and disassembly of the bolts. If bolt tension is less than 93% of the value at installation, the cause should be determined, appropriate corrective a.,ction should be taken, and the interval between checks of bolt tension should be re-evaluated.

o All connecting-rod bolts should be visually inspected for thread damage (e.g., galling), and the two pairs of connecting rod bolts above the crankpin should be inspected by magnetic particle testing (MT) to verify the continued absence of cracking. All washers used with the bolts should be examined visually for signs of galling or cracking, and replaced if damaged.

. o. A visual inspection should be performed of all external surfaces of the link rod box to verify the absence of any signs of service induced distress.

1 o All of the bolt holes in the link rod box should be inspected for

. threaddamage(e.g., galling)orothersignsofabnormalities. In addition, the bolt holes subject to the highest stresses (i.e., the pair immediately above the crankpin) should be examined.with an appropriate nondestructive method to verify the continued absence of cracking. Any indications should be recorded for engineering evaluation and appropriate corrective action.

The following item applies only to DSVR engines with connecting rods

. employing 1-7/8 inch diameter bolts:

o The following actions should be performed if the engines are operated in excess of 5740 KW:

(Specific a,c'tions have not yet been developed)

3. Crankshafts (applicable to TDI DSR-48 engines at Rancho Seco)*

o During the first refueling outage, inspect the fillets and oil

• Appropriate license conditions have already been incorporated into the operating licensee for River Bend and into the forthcoming operating license for Shoreham (See section 2.1.3.9 of this SER).

A-2

5 . _

holes of the three most heavily loaded crankpin journals (Nos. 5, 6, and 7) in each crankshaft with liquid penetrant. Indications found should also be evaluated with eddy current methods as appropriate.

o During the second and third refueling outages, inspect the fillets agd oil holes of.two of the three most heavily loaded crankpin journals in each crankshaft with liquid penetrant. Indications found should also be evaluated with eddy current methods as '

. appropriate.

o During each major engine overhaul, inspect the fillets and oil holes of the (1) the three most heavily loaded crankpin journals (Nos. 5, 6, and.7) and (2) the main journals located between crankpin journals 5, 6, and 7.

,- o The following actions shall be perfomed if the engines are operated inexcessofanindicatedloadof[3130kW]:*,**

a. For indicated engine loads in the range of [3130 kW) to [3200 1 kW] for a period less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> ***, no additional action shall be required.

b. For indicated engine loads in the range of [3130 kW) to [32fe0 kW] for a period equal to or exceeding 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> ***, a crankshaft inspection pursuant 'to Item d (below) shall be perfomad at the next refueling outage.

c. For indicated engine loads in the range of [3200 kW] to [3500 kW] for a period less the.n I hour ***, a crankshaft inspection pursuant to. item d (below) shall be performed for the affected

. engine at the next refueling outage.

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b .

• Momentary transients (not exceeding 5 seconds) that result from changing bus loads need not be considered as an overload.

• • The figures shown in brackets are for River Bend which has a qualified load capacity of 3130 kW. For Rancho Seco, different values may be appropriate depending on the value of the qualified load established for the Rancho Seco TDI engine crankshafts.

• • • If there are multiple overload events within a given load range since the previous crankshaft inspection, then the time criterion applies to the total accumulated time in that load range.

A-3

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. 1 e,

d. For indicated engine loads in the range of [3200 kW] to

. [3500 kW) for periods equal to or exceeding I hour *, and for engine loads exceeding [3500 kW] for any period of time, (i) the engine shall be removed from service as soon as safely possible, (ii) the engine shall be declared inoperable, and (iii) the crankshaft shall be inspected. The crankshaft inspection shall include crankpin journal numbers 5, 6, and 7 (the most heavily loaded) and the two main journals in between using liquid penetrant. Indications found should be evaluated with eddy

,- current testing as appropriate. ,

. o If cracks are found during inspections of crankshaft, this condition

~

shall be reported promptly to the NRC staff and the affected engine shall be considered inoperable. The engine shall not be restored to

" operable status" until the proposed disposition and/or corrective actions have been approved by the NRC staff.

4. Crankshafts (applicable only to DSRV-20-4 crankshafts at San Onofre 1) o 011 hole locations in the five most heavily loaded main journals (i.e., journals 3 through 12) for each crankshaft shall be inspe:ted i ; at each refueling outage with liquid penetrant. Indications found l <

shall be evaluated with eddy current testing as appropriate.

o During each major engine overhaul, the fillets of the most highly loaded main. journals (Nos. 4 through 12) should be inspected together with the oil holes, using liquid penetrant. Indications found shall be evaluated with eddy current testing as appropriate. In addition, these inspections should be perfomed for the oil holes and fillets in at least three of the crankpin journals at each major engine overhaul.

• If there are multiple everload events in a given load range since the previous crankshaft inspection, then the time criteria applies to the total accumulated time in that load range.

A-4

,o e o The folicwing actions shall be performed if the engines are operated in excess of 4500 KW (+5".):

(NOTE: Specific actions applicable to San Onofre 1 have not yet been developed. These actions should be specified in a manner similar to what was done for River Bend).

o If cracks are found during inspections of crankshafts, this condition shall be reported promptly to the NRC staff and the affected engine shall be considered inoperable. The engine shall not be restored to "cperable status" until the proposed disposition and/or corrective actions have been approved by the NRC staff.

5. Cylinder Blocks (applicable to all TDI engines)

1 o Cylinder blocks shr.11 be inspected for " ligament" cracks,

. " stud-to-stud" cra:ks and " stud-to end" cracks 7.s defined in a report

• by Failure Analysis Associates, Inc. (FaAA) entitled,

" Design Review of TDI R-4 and RV-4 Series Emergency Diesel Generator Cylinder Blocks" (FaAA report no. FaAA-84-9-11.1) and dated December 1984. (Note that the FaAA report specifies additional inspections to be perfomed for blocks with "known" or " assumed" ligament cracks). The inspection intervals (i.e., frequency) shall not exceed the intervals calculated using the cumulative damage index

. rnodel in the subject FeAA report. In addition, inspection method b shall be consistent with or equivalent to those identified in the subject FaAA report.

o In addition to inspections specified in the aforementioned FaAA report, blocks with "known" or " assumed ligament cracks" (as defined in the FaAA report) should be inspected at each refueling outage to determine whether or not cracks have initiated on the top surface exposed by the removal of two or more cylinder heads. This process should be repeated over several refueling outages until the

• This report was transmitted to H. Denton, NRC, from C. L. Ray, Jr., TDI Owners Group, by letter dated December 11, 1984.

A-5

o I entire block top has been inspected. Liquid-penetrent testing or a similarly sensitive nondestructive testing technique should be used to detect cracking, and eddy current should be used as appropriate to determine the depth of any cracks discovered.

o -If inspection reveals cracks in the cylinder blocks between stud holes of adjacent cylin.ders (" stud-to-stud" cracks) or " stud-to-end" cracks, this condition shall be reported promptly to the NRC staff and the affected engine shall be considered inoperable. The engine shall not be restored to " operable" statu.s until the proposed disposition and/or corrective actions have been approved by the NRC

. staff.

6. Cylinder Heads (applicable to all TDI engines)

The following air roll test shall be performed as soecified below, exceot when the plant is already in an Action Statement of Technical Specification 3/4.8.1, " Electric power Systems, A.C. Sources":

The engines shall be rolled over with the airstart system and with 'he t cylinder stopcocks open prior to each planned start, unless that start occurs within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of,a shutdown. The engines shall also be' rolled over with the airstart system and with the cylinder stopcocks open after

. 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, but no more than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> after engine shutdown and then rolled over 0~ once again approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after each shutdown. (In the event an engine is removed from service for any reason other than the rolling over procedure prior to expiration of the 8-hour or 24-hour periods noted above, that engine need not be rolled over while it is out of service.

The licensee sha}'1 air roll the engine over with the stopcocks open at the time it is returned to service.) The origin of any water detected in the cylinder must be determined and any cylinder head which leaks due to a crack shall be replaced. The above air roll test may be discontinued following the first refueling outage subject to the following conditions:

A-6

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5 . .

o. All cylinder heads are Group III heads (i.e., cast after September 1980.

o. Quality revalidation ins'pections, as identified in the Design Re. view / Quality Revalidation report, have been completed for all cylinder heads.

o. 5roup III heads continue to demonstrate leak free performance. This should be confirmed with TDI prior to deleting air roll tests.

7. Pist'on Skirts (applicable to modified type AF piston skirts only) o The stud boss attachments of the modified type AF piston skirts shall be inspected with liquid penetrant at each major engine overhaul. Indications found shculd also be inspected with eddy 1 current as appropriate. (This license condition may be deleted for individual piston skirts after they have completed 750 hours0.00868 days <br />0.208 hours <br />0.00124 weeks <br />2.85375e-4 months <br /> service atengineloadsequalling4500kW(5%)).

o The following actions shall be perfomed if the engines are operated in excess of 4500 kW (25%):

(Specific actions have not yet been developed).

8. Turbochanoers (applicable to Elliot Model 65G and 90G turbochargers for L all TDI engines)

Periodic inspections of the turbochargers shall include the fo11cwing:

o The turbocharger thrust bearings should be visually inspected for excessive wear after 40 non-prelubed starts since the previous visual inspection.

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• C Turbocharger rotor axial clearance should be measured at each I o

refueling outage to verify compliance with TDI/Elliott specifications. In addition, thrust bearing measurements should be coi. pared with measurements taken previously to determine a need for further inspection or corrective action. '

o Spectrographic and ferrographic engine oil analysis shall be .

performed quarterly to provide early evidence of bearing degradation. Particular attention should be paid to copper level and particulate size which could signify thrust bearing degradation.

o The nozzle ring components and inlet guide vanes should be visually

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. inspected at each refueling outage for missing parts or parts showing distress. If such are noted, the entire ring assembly should be replaced.

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