United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9605070306

                                                  Illinois Power Company
                                                  Clinton Power Station
                                                  P. O. Box 678
                                                  Tel 217 935-5623
                                                  Fax 217 935-4632

                                                  Wilfred Connell
                                                  Vice President
  POWER                                                U-602579
                                                  May 2, 1996

Docket No.  50-461                                10CFR21.21

Document Control Desk
Nuclear Regulatory Commission
Washington, D.C.  20555

Subject:  10CFR21 Final Report 21-96-001: Ideal Generators Installed with
          Emergency Diesel Generators Have Generator Rotor Mass Greater
          Than Originally Calculated

Dear Sir:

     On January 15, 1996, Illinois Power (IP) identified a condition
involving the Divisions 1 and 2 Emergency Diesel Generators (EDGs) as
potentially reportable under the provisions of 10CFR21.  Specifically,
Condition Report (CR) 1-96-01-029 was initiated to identify that Ideal
Electric, the manufacturer of the generator portion of the EDGs, had
discovered that the mass of the generator rotors had been incorrectly
calculated.  The revised calculation shows a larger rotor mass and
rotational inertia.  IP purchased the EDG units from Stewart & Stevenson.
The generators are Ideal model numbers SA6-50 and SA6-44, and Ideal
drawings B-MED-221 and B-MED-217.

     On March 13, 1996, IP submitted an interim report (IP letter U-
602564) to inform the NRC that the reportability evaluation for the
condition was not complete.  In that report, IP noted that an evaluation
of the impact of the condition on the seismic qualification of the diesel
generator units was complete and concluded that the larger rotor mass has
no adverse impact on the units.  The interim report further noted that IP
had not completed an evaluation of the impact of the larger rotor mass on
the frequency and torsional analysis of the units.  Prior to the interim
report, a preliminary review of the impact of this issue on generator
frequency and torsional vibration had been performed and additional
evaluation was to follow.  The preliminary review had found the condition

     IP has completed an evaluation of the impact of this condition on
the frequency and torsional analysis of the units and concludes that the
larger rotor mass does not have an adverse impact on the ability of the
Divisions 1 and 2 EDGs to perform their intended design function.
Therefore, on the basis that this condition could not create a
substantial safety hazard, it is not reportable under the provisions of

                                                            Page 2

     Additional information regarding this issue may be obtained by
contacting S. P. Hong, Plant Engineering, at (217) 935-8881, extension

                                             Sincerely yours,

                                             Wilf Connell
                                             Vice President
cc:  NRC Clinton Licensing Project Manager
     NRC Resident Office, V-690
     Regional Administrator, Region III, USNRC
     Illinois Department of Nuclear Safety
     INPO Records Center
     Ideal Electric
     Stewart & Stevenson


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