United States Nuclear Regulatory Commission - Protecting People and the Environment

Proposed Staff Actions to Improve and Maintain Diesel Generator Reliability (Generic Letter No. 84-15)

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                           WASHINGTON, D.C. 20555

                                July 2, 1984 

TO ALL LICENSEES OF OPERATING REACTORS, APPLICANTS FOR AN OPERATING LICENSE,
AND HOLDERS OF CONSTRUCTION PERMITS 

Gentlemen: 

SUBJECT:  PROPOSED STAFF ACTIONS TO IMPROVE AND MAINTAIN DIESEL GENERATOR 
          RELIABILITY (Generic Letter 84-15)  

As part of the proposed technical evaluation of Unresolved Safety Issue 
(US-I) A-44, Station Blackout, the staff is considering new requirements 
that would reduce the risk of core damage from station blackout events. The 
reliability of diesel generators has been identified as being one of the 
main factors affecting the risk from station blackout. Thus, attaining and 
maintaining high reliability of diesel generators is a necessary input to 
the resolution of USI A-44. 

Plants licensed since 1978 have been required to meet the reliability goals 
of Regulatory Guide 1.108 for their diesel generators. However, the staff 
has determined that many operating plants do not have reliability goals in 
place for their diesel generators. Considering the critical role diesel 
generators play in mitigating various transients and postulated events 
following a loss of offsite power, the staff has determined that there is an
important need to assure that the reliability of diesel generators at 
operating plants is maintained at an acceptable level. The staff has 
determined that the risk from station blackout is such that early actions to
improve diesel generator reliability would have a significant safety 
benefit. Toward this objective, we hove developed the following approach to 
assess and enhance, where necessary, the reliability of diesel generators at 
all operating plants. 

The items covered by this letter fall into the following three areas: 

1.   Reduction in Number of Cold Fast Start Surveillance Tests for Diesel 
     Generators 

     This item is directed towards reducing the number of cold fast start 
     surveillance tests for diesel generators which the staff has determined
     results in premature diesel engine degradation. The details relating to
     this subject are provided in Enclosure 1. Licensees are requested to 
     describe their current programs to avoid cold fast start surveillance 
     testing or their intended actions to reduce cold fast start 
     surveillance testing for diesel generators. 

2.   Diesel Generator Reliability Data 

     This item requests licensees to furnish the current reliability of each
     diesel generator at their plant(s), based on surveillance test data. 
     Licensees are requested to provide the information requested in 
     Enclosure 2. 

8407020206 
.
                                    - 2 - 

3.   Diesel Generator Reliability 

     Licensees are requested to describe their program, if any, for 
     attaining and maintaining a reliability goal for their diesel 
     generators. An example of a performance Technical Specification to 
     support a desired diesel generator reliability goal has been provided 
     by the staff in Enclosure 3. Licensees are requested to comment on, and 
     compare their existing programs or any proposed program with, the 
     example performance specification. 

Accordingly, pursuant to 10 CFR 50.54(f), operating reactor licensees are 
requested to furnish, under oath or affirmation, no later than 90 days from 
the date of this letter, the information requested in Items 1 through 3 
above. Applicants for operating licenses and holders of construction permits
are not required to respond. 

Licensees may request an extension of time for submittals of the required 
Information, Such a request must set forth a proposed schedule and 
justification for the delay. Such a request shall be directed to the 
Director, Division of Licensing, NRR. Any such request must be submitted no 
later than 45 days from the date of this letter. 

This request for information has been approved by the Office of Management 
and Budget under Clearance Number 3150-0011, which expires April 30, 1985. 

                              Sincerely, 


                              Darrell G. Eisenhut, Director 
                              Division of Licensing 

Enclosures:
1. Reduction in Number of Cold
    Fast Starts for Diesel
    Generators
2. Diesel Generator Reliability
    Data
3. Diesel Generator Reliability
.
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