ML20117E326
| ML20117E326 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 07/24/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20115A155 | List: |
| References | |
| FOIA-84-665 NUDOCS 8505100402 | |
| Download: ML20117E326 (8) | |
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SAFETY EVALUATION REPORT GRAND GULF NUCLEAR STATION UNIT 1 RELIABILITY OF DIESEL GENERATORS MANUFACTURED BY TRANSA!4 ERICA DELAVAL, INC.
TDI PROJECT GROUP DIVISION OF LICENSING
1.0 INTRODUCTION
In support of its request for a full power license for Grand Gulf Nuclear Station (GGNS) Unit 1 and in response to an NRC Order dated May 22, 1984, Mississippi Power and Light Company (the licensee) submitted by letter dated July 5,1984, a description of the June 1984 disassembly ar.d inspection of the Division I diesel generator; the post-inspection engine test program; and prcposed enhancements to the licensee's maintenance and surveillance program.
As required by the NRC Order, the licensee submittal also addresses the similarity of the "as-manufactured quality" of the Division I and II diesel generators as part of the licensee's justification for not inspecting the Division II engine.
2.0 BACKGROUND
Concerns regarding the reliability of large bore, rnedium speed diesel generators of the type supplied by TDI at GGNS Unit I and at fifteen (15) other 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 have since beccme evident at Shoreham, Grand Gulf Unit I and at other nuclear and non-nuclear facilities employing TDI diesel generators.
These deficiencies stem from inadequacies in design, manufacture and QA/QC by TDI.
In response to these problems, thirteen U.S. nuclear utility owners, including the licensee, formed a TDI Diesel Generator Owners Group to address operational and regulatory issues relative to diesel generator sets used for standby emergency power. The Owners Group program, which was initiated in October 1983, embodies three major efforts.
1.
Resolution of 16 known generic problem areas (Phase I program) intended by the Owners Group to serve as an interim basis for the licensing of plants.
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Design review of important engine components and quality revalidation of 2.
important attributes for selected engine components (Phase II program).
3.
Identification of any needed additional engine testing or inspections, based on findings stemming from the Phase I and II programs.
8505100402 8411t3 PDR FDIA PDR DELL 84-665
Pending completion of the Owners Grcup program, the licensee submitted a number of reports concerning its actions to ensure the reliability of the TDI diesels at GGNS Unit 1.
Based on its review of these reports and the status of the Owners Group program, the staff stated in its Safety Evaluation Report issued in support of the May 22, 1984 Order that additional information was.needed regarding the present condition of critical engine components to support operation of GGNS Unit 1 at power levels in excess of 5% of full power for the interim period pending completion of the Owners Group program and NRC staff review of recommendations stemming from this program as they apply to GGNS Unit 1.
In addition to the engine inspections and subsequent post-inspection engine tests reouired by the Order, the staff's SER stated it would be necessary to review the licensee's proposed engine maintenance and surveil-lance program and any needed license conditions prior to issuance of a full pcwer license.
3.0 EVALUATION to this SER is a Technical Evaluation Report (TER) entitled
" Review and Evaluation of Transamerica Delaval Inc. Diesel Engine Reliebility and Operability - Grand Gulf Nuclear Station, Unit 1."
This TER was prepared by Pacific Northwest Laboratory (PNL) which is under contract to the NRC to perform technical evaluations of the TDI Owners Group's generic program, in addition to plant-specific evaluations relating to the reliability of TDI diesels. PNL has retained the services of several expert diesel consultants as part of its review staff.
In addition to the July 5,1984 submittal, PNL and its consultants also
. reviewed the licensee submittals dated February 20, April 17, and May 6, 1984, and performed an onsite inspection of key engine components in June 1984, while the Division I engine was disassembled.
PNL and its consultants also considered the status of the generic Owners Group program relative to the actions taken by the licensee to establish the reliability of the diesels.
The staff has reviewed the enclosed TER, and adopts the TER as part of this Safety Evaluation by reference.
3.1 Division I Enoine The June 84 inspection of key engine compenents, including those identified by the Owners Group as known potential problem areas, indicates that these components are acceptable for nuclear service for the interim period extending to the first refueling of GGNS Unit 1.
This finding is subject to (1) operating restrictions as identified in Section 3.4 of this SER, and (2) completion of licensee actions pertaining to confirmatory issues as identified in Section $.5 of this SER.
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. 3 Post-inspection testing, as required by the May 22, 1984 Order, was satisfactorily completed. The licensees letter dated July 2,1984, provided, the licensees clarifications / interpretations of the required testing.
Although the fast start tests of the engine in accordance with the Order were performed subsequent to a manual prelubing of the turbocharger thrust bearings and thus did not simulate the worst challenge to the bearings, PNL does not recommend additional testing to simulate this challenge. The NRC staff concurs with this PNL finding and concludes that the tests performed by the licensee meets the intent of the NRC Order.
3.2 Division II Engine In the Order dated May 22, 1984, the NRC staff stated that the need for Division II engine inspection would be contingent upon:
1.
Results of the inspection of the ' Division I engine 2.
The licensee's ability to demonstrate, through a review of the manufacturers OA records, that the two engines are of similar "as manufactured" quality.
The Division I engine inspection revealed only one component, the turbocharger, where failed elements, bolts and a vane, might be expected to occur in the Division II engine. The other components showed no rejectable indications or incipient problems that suggested adverse conditions might be present in the Division II engine.
Accordingly, PNL concluded that the turbochargers from the Division II engine should be inspected and any corrective actions taken and findings documented.
' No other Division II inspections were recommended on the basis of the Division I results.
In its submittal dated July 20, 1984, the licensee reported that the Division II turbochargers have been inspected for the type of damage found in the Division I turbochargers. The scope of the inspection included the stationary nozzle ring, vanes, bolts, and rotating turbine blades.
The Division 11 turbochargers showed no signs of rotating disk damage, although one vane was found to be missing from each stationary nozzle ring (a similar condition was observed in the Division I turbochargers - see discussion in enclosed TER). The stationary nozzle ring bolts were found to be intact with no evidence of stress corrosion cracking. The licensee elected to replace the nozzle ring assembly and bolts although the old parts were judged to be acceptable. Turbine rotor float measurements were also performed and indicated no significant thrust bearing wear. Based upon its review of the licensee's July 20, 1984 submittal, the NRC staff cgncludes that the licensee has satisfactorily addressed PNL's concern with respect to the Division 11 turbocharger.
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On the basis of the review conducted by the licensee on the manufacturer's QA records and the upgrades accomplished for both engines, PNL concludes that the Division I and II engine components are of comparable "as-manufactured" quality.
On the basis of their operating history, PNL concludes that the
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. 3 engines have been assembled and maintained comparably. Moreover, PNL has noted that the Division II engine has seen less service than the Division I engine.
In addition, based upon the status of its review of the Owners Group proposed generic resolution of the connecting rod issue, PNL has concluded that visual inspections of the connecting rods and a preload check of the connecting rod bolts should be performed on the Division II engine prior to plant operation above Si power. The license has ccamitted to per-forming this insrection in its submittal dated July 20, 1984. Based on these factors and the absence of significant adverse findings from the recent inspection of Divisicn I engine, the staff has concluded that no further inspections of the Division II engine beyond those identified above are necessary at this time.
3.3 Augmented Maintenance and Surveillance Procram PNL concluded in the enclosed TER that n.odifications to the Augmented Maintenance / Surveillance Program proposed by the licensee in their July 5, 1984 submittal are needed to provide adequate assurance of engine reliability /
operability. These modifications are discussed in detail in Section 6 of the enclosed TER.
By letters dated July 20, and July 23, 1984, the licensee committed to a revised Augmented Maintenance and Surveillance Program. The NRC staff has reviewed these letters and concludes that the MP&L program incorporates all of the modifications recomended by PNL. Therefore, the staff finds the Augnented Maintenance and Surveillance Program, as identified in the licensee's July 20, and July 23, 1984 letters, to be acceptable.
3.4 Operating Restrictions PNL recommendations and conclusions regarding TDI diesel engine reliability at GGNS Unit I are predicated on the following assumptions:
1.
The emergency service requirements the licensee currently forsees for GGNS Unit I will not exceed tne engine load corresponding to a break mean effective pressure (BMEP) of 185 psig. The need for this assumption is based on PNL ccncerns regarding the acceptability of crankshaft stresses at higher BMEP loadings.
2.
All future engine testing (except the torsiograph test and the test to i
obtain preturbine exhaust temperature data as described in the next Section) including surveillance testing required by the plant Technical Specifications will be limited to within : Si of the nominal engine load where the upper limit of this load range corresponds to a BMEP of 185 pst. ;
9 3.
In the absence of the Owners Group completing all elements of their program plan, PNL's conclusions are plant-specific, applying enly to G3NS Unit I and are applicable only during its first reactor refueling cycle.
It is understood by PNL that at the first refueling, the licensee will implement all applicable recomendations of the Owners Group.
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e.
With regard to item I above, the licensee reported by letter dated July 20, 1984, (AECM-84/0376) that 185 psig BMEP corresponds to a generator load of 5740KW, about 82% of full rated load. This exceeds the maximum ESF loads, 52% and 68% of full rated load for the Division I and II engines, respectively, required to shutdown the plant and maintain it in a safe condition for loss of offsite power and LOCA. Thus, there exists sufficient engine capacity at 185 psig BMEP to assure that the fuel design limits and design conditions of the reactor coolaat system boundary are not exceeded, and that the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents as required by GDC-17.
Tte licensee also states in a letter dated July 20,1984,(AECM08/0373) that a precautionary note will be added to the GGNS Off-Normal Event Procedure for loss of Offsite Power to ensure that loads will not be added unnecessarily to the engines in excess of 185 psig BMEP (5740 KW).
In addition, future training with respect to this procedure will explain both the basis for the note and the aspects to be taken into consideration in its application. The staff agrees in principle with these precautions; hou.ever, the staff is adding a condition to the license (See Appendix A
" License Conditions") to require that these actions be conpleted prior to plant operation above Si power, whichever is later.
The NRC will verif.y that these actions have been completed.
With regard to item 2 above, the licensee has submitted proposed Technical Specification changes incorporating this item. Specifically, the proposed changes would require that the monthly and 18 month surveillance tests be performed at a minimum of 5450 KW (70% of rated load), but not to exceed 5740 KW (82% of rated load, 185 psig BMEP). The lower limit is greater than the auto-connected loads required for the loss of offsite power and post-LOCA conditions as described above. Therefore, the staff finds these changes to be acceptable.
With regard to item 3, the full power license is being conditioned to require NRC review and approval of licensee actions pertaining to a final resolution of the TDI diesel generator issues at GGNS Unit 1 (See Appendix A).
3.5 Additional License Conditions By letter dated July 17, 1984, the staff identified additional information requested by the staff. The specific information requested was identified under item D in the July 17, 1984 letter and includes those informational items (referred to as " additional MP&L submittals") identified in Section 6 of the enclosed TER.
ByletterdatedJuly 20, 1984, AECM-84/0373, the license provided satisfactory
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responses to all but 3 items. These items for which satisfactory responses were not received include the following:
- 1) cranksh' aft torsiograph data at 0%, 25% 50%, 75%, and 100% of engine nameplate loading were not submitted. Thisinformationisneeded(1) w
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to confirm adequate crankshaft torsional responses over the spectrum of engine loads to be seen in service, and (2) to provide relevant data to assist the staff and PNL in conpleting its generic evaluation of the 2dequacy of the DSRV-16-4 crrn.J.aTL design.
- 2) Preturbine exhaust temperature data at 0%, 25%, 50%, 75%, and 100% of engine nameplate loading was not submitted. This data was requested as a result of a review of cylinder exhaust temperature data obtained from the engine operating logs when the PNL diesel engine expert consultants visited the site on June 4 and 5, 1984. This information is needed to confirm that the even hotter turbine inlet temperatures do not exceed the manufacturers recomendations.
3)
Information provided regarding the corrective actions taken in response to numerous fuel oil line leaks during the period of September to November 1983 has not convinced the NRC staff these actions are sufficient to prevent further occurrences of this kind. Apart from the najor leak which occurred on September 4,1983, causing a fire and for which the staff agrees the licensee has taken sufficient action (See attached TER), the other several occurrences involved minor danage to tubes from external causes, particularly from damage caused by maintenance operations. Clearly, periodic inspection of the fuel lines is a major element to preventing reoccurrences.
Although the torsiograph test is a requirement of the May 22, 1984 Order, it is the staff's understanding that the test has not yet been completed. Under the Order, the licensee must complete this test prior to operating the plant a%va % power.
The staff concludes that the above torsiograph and preturbine exhaust temperature data is primarily of a confirmatory nature and is therefore not likely to change the conclusions of this SER.
For this reason the staff concludes that plant operation in excess of 5% power should not be conditioned upon staff review and approval of this information. However, this data should be submitted to the NRC prior to plant operation above Si power as a condition of l
thelicense(SeeAppendixA).
Regarding the fuel oil lines, the staff concludes that the licensee should perform, as a condition of the license (See Appendix A), an inspection of all fuel lines in the Division I and II engines for external damage, and replace or repair all defective lines. These inspections may include inspections already completed provided they were performed subsequent to relevant engine reassembly operations associated with the inspection of the Division I diesel generator and of the Division II turbochargers in June and July 1984. The NRC will verify that these actions have been completed. The licensee should also submit a proposed periodic surveillance program for the fuel oil lines.
These actions shall be completed prior to plant operation above 5% power.
7-2 4.0 Conclusions The NRC staff concludes that the TDI diesel engines at GGNS Unit I will provide a reliable. standby source of onsite power in accordance with General Design Criterion 17. This finding is based upon the NRC staff /FNL review of (I) the current status of the TDI Owners Group Program in resolving the TDI diesel engine issue; (2) actions taken by the licensee to enhance and verify the reliability of the Division I and II engines, including those actions taken in response to the NRC order dated May 22, 1984; (3) the Augmented Engine Maintenance and Surveillance Frogram which the licensee concitted to by letters dated July 20 and 22, 1984; and (4) changes to the Technical Specifications to limit future testing of the engines to 185 BMEP.
In addition, this finding is subject to the license conditions identified in Appendix A, which assure that Grand Gulf Unit I will continue to meet GDC 17 beyond the first refueling outage.
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,'i Appendix A License Conditio'ns Pertaining to the Division I and II Diesel Generators at Grand Gulf Nuclear Station, Unit 1 1.
The licensee shall submit the following information prior to operation of GGNS Unit I at a power level exceeding 5% of full power.
a)
Torsiograph data for the Division I diesel generator at 0%, 25%,
50%, 75%, and 100% of full engine rated load, and associated stresses.
b)
Preturbine exhaust tenperature data for the Division I and II diesel generators at 0%, 25%, 50%, 75%, and 100% of full engine load. Maximum values for this data as recommended by the turbocharger manufacturer shall also be provided.
2.
The licensee shall complete the following actions prior to GGNS Unit 1 operation above 5% of full power.
a)
A precautionary note shall be added to the GGNS Off-Normal Event Procedure for Loss of Offsite Power to ensure that leads will not be added unnecessarily to the Division I and II engines in excess of 5740 KW. Operators shall be trained with regard to the basis for the note and the factors to be taken into consideration regarding its application.
b)
All fuel-oil lines (including injector lines) shall be visually inspected in the Division I and 11 diesel generator for external damage, and defective lines repaired or replaced. The inspections may include inspections already completed provided they were performed subsequent to relevant engine reassembly operations associated with the inspections of the Division I diesel generator and of the Division II turbochargers in June and July, 1984. The licenses shall also submit a proposed periodic surveillance program for the fuel-oil lines.
3.
Final evaluations and recommendations from the TDI Owners Group Program applicable to GGNS Unit 1, and the licensees actions in response to this program for the Division I and II diesel generators shall be submitted for NRC review and approval prior to plant restart from the first refueling cutage.
l b.