ML20211R067
| ML20211R067 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 07/24/1986 |
| From: | Agosti F DETROIT EDISON CO. |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| VP-86-0110, VP-86-110, NUDOCS 8607280089 | |
| Download: ML20211R067 (4) | |
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VP-86-0110 Office of Nuclear Reactor Regulation Ms. Elinor G. Adensam, Director Project Directorate No. 3 Division of BWR Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Ms. Adensam:
Reference:
1)
Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43 2)
Detroit Edison Letter to NRC, " Request for Exigent Amendment to the Fermi 2 Technical Specifications Governing ECCS Actuation Instrumentation Setpoints (Degraded Grid Relay Setpoints),
1 VP-86-0076, dated July 2, 1986 3)
Detroit Edison Letter to NRC, " Request for an Emergency Amendment to the Fermi 2 Technical Specifications Governing Emergency Core Cooling Actuation Instrumentation Setpoints", VP-86-0065, dated June 11, 1986 4)
NRC to Detroit Edison Letter, " DECO Request for an Emergency Amendment to the Fermi 2 Technical Specifications Regarding the Degraded Grid Voltage Setpoints", dated June 13, 1986 to F.
E.
Agosti from R. M. Bernero
Subject:
Response to NRC Request for Additional Information, Decraded Grid Voltage The following information is provided in response to verbal questions raised by your Mr. A. Marinos on July 22, 1986.
Question 1: Why did Reference 2 modify the time delay for the degraded grid voltage relay, while Reference 3 did not?
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k Ms. Elinor G. Adensam July 24, 1986 VP-86-0110 Page 2 DECO
Response
Analyses performed prior to the issuance of Refercnce 2 determined the limiting time delay condition to be the Division I voltage drop caused by starting two RHR pumps and two Core Spray pumps.
Further evaluation performed after receipt of Reference 4, to minimize the potential for inadvertent starts of the EDGs identified the limiting time delay to be the recovery time necessary for the Load Tap Changer (LTC) to increase the bus voltage above the reset point of the degraded grid relay.
Following the start of various pumps the Division I voltage recovers to an acceptable value but may be just below the degraded grid relay reset point.
The degraded grid relay resets at approximately 2% above the actuation setpoint.
Therefore, the LTC operation is required to take place for the voltage to recover above the degraded grid relay reset point and, thus, preclude unnecessary EDG actuation.
Question 2: Will the forty-four second time delay increase the probability of damage to Division I motors?
DECO
Response
The 44 second time delay consists of a 20 second LTC time delay, 20 seconds for LTC to operate, plus a 10% margin.
During the initial 19 seconds (present setting) of the delay, the motor start transient allows recovery of the bus voltage to above the 95%
trip setpoint.
The remainder of the 44 second time delay allows the LTC to compensate for the remaining 2% voltage restoration to allow the relay to reset at 97%.
During the 20 second difference in time settings, the bus voltage is actually above the minimum voltage at which all the motors are qualified to operate indefinitely (95%).
The probability of damage to equipment in Division I is not increased.
L I
i Ms. Elinor G. Adensam July 24, 1986 VP-86-0110
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If you have any further questions concerning this matter, please contact Mr. Frank Sondgeroth at (313) 586-5159.
Sincerely,
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cc:
Mr. M. D. Lynch Mr. W. G. Rogers i
USNRC Document Control Desk Washington, D.C..20555 i
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,,s Ms. Elinor G. Adensam July 24, 1986 VP-86-0110 Page 4 bcc:
F. E. Agosti C. Borr (WPSC, Inc.)
L. P. Bregni L. B. Collins J. E. Conen J. M. DuBay J. H. Flynn J. D. Leman R.
S. Lenart I
L. Martin i
S.
H. Noetzel G. R. Overbeck t
E. Preston
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T. Randazzo S. Savage F.
H. Sondgeroth B.
R. Sylvia l
G. M._Trahey A. E. Wegule J. M. Wisniewski R. L. Woolley Approval Control Secretary's Office (2412 WCB)
NRR Chron File
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