Reliability of Standby Diesel Generator (DG) Units (Generic Letter 77-07)

                                                               GL 77-07

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

                                                  December 15, 1977

ALL POWER REACTOR LICENSEES


The demonstrated reliability of standby diesel generator (DG) units in
operating nuclear power plants has been less than anticipated.  The NRC has
concluded that a systematic review and analysis of operating problems
associated with diesel generator units is necessary to establish what
practical measures may be taken to enhance the reliability of these units.
The NRC, with the assistance of the University of Dayton, has initiated such a
study.  It is our intent that this study will provide practical results that
will prove useful to each nuclear utility, therefore, each operating reactor
licensee is requested to respond to the enclosed questionnaire.

An analysis will be performed on the information received and the results of
this analysis, along with recommendations that may lead to improved
reliability, will be transmitted to licensees and applicants for their use.
We believe that this information will assist in identifying as well as
avoiding or minimizing operating experiences encountered by others.  We view
this effort as one of mutual interest.

We ask that a single completed copy of the enclosed questionnaire be returned
to the Director of Nuclear Reactor Regulation, U.S. Nuclear Regulatory
Commission, Washington, D.C. 20555, by January 20, 1978.  Please include on a
separate sheet the name, address and phone number of the person(s) at the
reactor site responsible for completing the questionnaire and responsible for
responding to any follow-up communications concerning the questionnaire or for
arranging a reactor site visit.

The responses to the majority of the questions can be answered with just a few
words or by checking the appropriate space.  In responding to those questions
which do not apply to a particular installation and/or situation, please
indicate "N/A" for "not applicable".  If the question does apply to a
particular installation or situation but the answer is not known, please
indicate "UN" for "unknown".  For those entries on the questionnaire where the
requested information is not known by January 20, 1978, please provide it in
follow-up correspondence when it becomes available.



7912130830
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Further, the detailed information obtained in this study will be subject to
disclosure pursuant to the Freedom on Information Act Regulations as
implemented by 10 CFR Part 9 - Public Records.

In the event that any information requested as a part of this study, is
considered by you (or your contractor) to be proprietary, it is necessary that
you make a written application to withhold such information from public
disclosure.  Any such application must be accompanied by an affidavit executed
by the owner of the information, which identifies the document or part sought
to be withheld, and which contains a statement of reasons which address with
specificity the items which will be considered by the Commission as listed in
subparagraph (b)(4) of Section 2.790 of NRC's "Rules and Practice", Part 2,
Title 10, Code of Federal Regulations.  The information sought to be withheld
shall be incorporated as far as possible into a separate part of the
affidavit.

In the event any portion of the questionnaire needs clarification, please
contact F. Clemenson at (301)492-8077.

This request for generic information was approved by GAO under a blanket
clearance number B-180225 (R0072); this clearance expires July 31, 1980.

                                  Sincerely,


                                  Karl R. Goller, Assistant Director
                                    for Operating Reactors
                                  Division of Operating Reactors

Enclosure:
Questionnaire