Enclosing NUREG/CR 0660, "Enhancement of on Site Emergency Diesel Generator Reliability" (Generic Letter 79-21)


                               UNITED STATES 
                          WASHINGTON, D.C. 20555 

                               June 4, 1979 



This letter is being sent to all licensees authorized to operated or 
construct a light water power reactor and to all applicants for a license to
operate or construct a light water power reactor. 

A review of the operating experience of the emergency diesel generators at 
light water reactors as reported in the Licensee Event ReportS (1969-1977) 
indicates that their reliability could be improved. 

The reliability of the diesel generator is strongly dependent on the 
interaction of the following factors: design, testing and operational 
requirements, operational history, inspections, maintenance, and the 
personnel qualifications of operators. To assist us in identifying any 
significant deficiencies the University of Dayton Research Institute, under 
our contract, prepared a report entitled "Enhancement of Onsite Emergency 
Diesel Generator Reliability" (NUREG/CR 0660) which identifies the major 
problems together with recommended corrective actions for improving 
reliability. We will review the report and evaluate each recommendation for 
its applicability to all licensees authorized to operate or construct light 
water power reactor by balancing the potential improvement in reliability 
versus the adverse impact of implementing the recommendation on the plants. 

As a respondent to the generic questionnaire jointly prepared by the 
University of Dayton and NRC, we are enclosing (NUREG 0660) a copy of the 
University of Dayton Research Institute report. It should be noted that our 
review and evaluation of the report has not been completed. Comments on this
report and other factors which may be considered major problems preventing 
improved onsite emergency diesel 

                                  - 2 -

generator reliability are encouraged and should be forwarded to Fred 
Clemenson, Plant Systems Branch, Division of Operating Reactors, U. S. 
Nuclear Regulatory Commission, Washington, D.C. 20555 

                                        D. Eisenhut, Deputy Director 
                                        Division of Operating Reactors 

Enhancement of Onsite Emergency Diesel Generator Reliability
NUREG/CR 0660 

cc w/o enclosure: Service List 

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