ML17054D076
| ML17054D076 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/31/1976 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML17054D077 | List: |
| References | |
| IEB-76-07, IEB-76-7, NUDOCS 7909050197 | |
| Download: ML17054D076 (6) | |
Text
NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 76-07 DATE:
July 28, 1976 Page 1 of 2 CRANE HOIST CONTROL CIRCUIT MODIFICATIONS DESCRIPTION OF CIRCUMSTANCES:
Xn response to NRC concerns about the potential for, and consequences of, dropping a spent fuel shipping cask or other heavy load, Commonwealth Edison modified the hoist control system for the fuel cask handling cranes at their Dresden Units 2 and 3 and Quad cities Units 1 and 2 to provide additional hoist redundancy and slow speed hoist capability.
The original design utilized a General Electric "magspeed" hoist control system.
Xn this system which includes two electro-mechanical brakes in
- series, spring force holds the brakes engaged while DC solenoids, ener-gized when the hoist motor is energized, disengage the brakes.
The modification which added the slow speed hoist capability included installing additional contactors in the brake solenoid power circuit to energize the solenoids when the low speed hoist motor was energized.
The original hoist control system design utilized a single Size 2 DC contactor (two contacts in series) in the solenoid circuit.
The design modification added a circuit in parallel with the original DC contactor, with utilized four AC rated Size 1 single contacts in a series-parallel array to distribute current carrying and interrupting burden.
Xnitial experience with the modified, hoist control system at Dresden showed that the circuit interrupting capacity of the series-parallel array was marginal.
On several occasions when the low speed motor was stopped in the lowering mode, the solenoid circuit contacts arced re-sulting in power being supplied to the solenoids long, enough so that the load dropped some distance before the brakes engaged.
Over travel of as much as 15 inches was reported, but no damage to hoist or load was found.
The crane manufacturer's representatives.
have advised the NRC that the proposed corrective action is to install a single Size 2 DC contactor (two contacts in series) with arc suppressors, the same as originally
'rovided in the General-Electric design, in place of the added four AC rated contacts.
The original contactor in the normal speed control circuit has shown satisfactory service since initial operation of the plant in 1969.
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IE Bulletin No 76-07 DATE:
July 28, 1976 Page 2 of 2 ACTION TO BE TAKEN BY LICENSEE:
1.
Determine and report to this office within 20 day's the following information:
(a)
Have you made, or do you plan to make modifications to the hoist control for your installed cranes similax to the described modifications?
(b)
If such modifications have been made, or are planned, identify changes required in brake po~er and contxol circuitry?
2.
(c)
What steps have been taken or are planned, to pro-vide assurance that brake power contactors are adequate for the service?
If modifications are planned, provide the schedule for completion and a brief description of your plans for design review and functional testing.
d to the Director of this Office, with a Your response should be submitte o
s Office of to the Dixector, Division of Reactor Inspection Programs,
$. Nuclear Regulatory Commission, Nashing-Inspection and Enforcement, U. S.
uc ear e
ton p D ~
C ~ 20555
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e r r'e orts concexning possible generic Approval of NRC requirements for r'epo m the U. S. General as been obtained under 44 U. S.
C.
3152 from tie al B-180255 (R0072) expires 7/31/77)
Acc'ounting Office.
(GAO Approval B-1
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UNITED STATES NUCLEAR REGULATORY COMMISSION REGION I 631 PAIIK AVLNUC KING OF PAUSSIA, PENNSYLVANIA 19400 Niagara Mohawk Power Corporation Attention:
Mr. R'. R. Schneider Vice President Electric Operations 300 Erie Boulevard Hest
- Syracuse, New York 13202 July 21, 1976 Docket No. 50-220 Gentlemen:
Enclosed is XE Bulletin No. 76-06 which requires action by you with regard to your power reactor facility(ies) with an operating license.
Should you have questions regarding this Bulletin or the acti'ons re-quired of you, please contact this office.
Sincerely, 0- James P. O'Reilly Director Enclosure XE Bulletin No. 76-06 cc:
T. E. Lempges, General Superintendent, Nuclear Generation T. J. Perkins, Station Superintendent C. L. Stuart, Operations Supervisor E. B. Thomas, Jr., Esquire A. Z. Roisman, Counsel for Citizens Committee for Protection of the Fnvironment bcc.
E Mail 6 Files Central Files Publ c o
blic Document Room (PDR) nt Room (LPDR)
Techn cai 1 Information Center REG:I Reading Room State of New York
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