ML19329E335
| ML19329E335 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 11/24/1976 |
| From: | Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEC-76-01, IEC-76-1, NUDOCS 8006120645 | |
| Download: ML19329E335 (2) | |
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Generas offices: 212 w.st Michigan Avenue Jackson, Machigan 4Q201 November 24, 1976 Mr James G Keppler, Regional Director Nuclear Regulatory Commission Region 1TI 799 Roosevelt Rd
. Glen Ellyn, IL 60137 MIDIAND PROJECT DOCKET IREERS 5 32 50-330 CIRCUIAR 76-01 FILE: 0505.2 SERIAL: 2974 Your letter,of July 29, 1976 transmitted Circular 76-01 which discusses crane hoist control for information and action.
With regard to the action items identified in IE Circular No 76-01, Numbers la), lb), and 2 do not apply to the cask handling cranc for the Midland Plant as no modifications to the crane controls are planned based on infor=ation in the circular. With regard to action item 1c) we offer the following informa-tion as to the ability of the crane to prevent overtravel situations resulting from arcing across brake contactors.
The crane is designed with a 550 lb. ft D.C. magnet type brake on each of the hoist drives. 'lhe power for these brakes is taken directly from the leads supplying power to the hoist motor. 'lhe brake contactor located in the rec-tifier panel is rated at 40 amps and the brake coil current is 3.48 amps.
'Ibe brake circuitry is designed so that when the motor primary circuit is excited, the control contactor coil and the transformer primary are ener-gized.
'Ihe control contactor then closes which applies the transformer secondary output to the rectifier. When the current across the brake coil has built up to the proper level, the current sensitive relay detects this and switches the transformer tc a lower tap so that lower voltage holding current will keep the brske in the open position.
In addition to this holding brake on the hoist drives, a small auxiliary self-excited alternator is mounted on the eddy current brake shaft; this provides dynamic or controlled lowering., It performs its braking function independently of external power or any mechanical holding equip =ent and thus prevents the load from dropping or gaining excessive speed in case of power or mechanical brake failure.
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o Based on the above information, which included a review of electrical diagrams it is our opinion that the brake power contactors and crane hoist controls are adequate.
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o sm/ar/m CC: Director, Division of Reactor Inspection Programs Office of Inspection and Enforcement U S Nuclear Regulatory Commission Washington, DC 20555 i
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