ML19345A440
| ML19345A440 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 07/28/1976 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8011210531 | |
| Download: ML19345A440 (1) | |
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i fJUCLEAR REGULATO" COMMitSION h
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n July 28, 1976 E
Yankee Atomic Electric Company Docket No. 50-29 Attention:
Mr. Robert H. Croce k
Licensing Engineer 20 Turnpike Road f.
irestborcugh, Massachusetts OUB1 f*-
Gentlecen:
i Tha enclosed Eulletin, 76-07 is forwarded to you for information and i
c e tic:2. A similar document entitled Circular 76-01, is being trans-r.itted to each holder of a Construction Permit.
Therefore, if you have l
a nuclear power plant in the construction stage, you will also receive a I
copy of Circular 76-01 which will require separate response.
You will J
note that the significant difference between the two documents is the
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time allowed for response.
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Inspection and Enforcement Bulletins have been and will continue to be a
lir_ited to subjects considered to be of significance and which require prompt responc.e.
In the future Bulletins vill be supplcmented by fg Cir~:ulars as a cormunication medium where the subject matter is of i
lesser significance. immediacy, or for uhich a longer response time or I?
na response may be acceptable.
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James P. O'Reilly 3
- Director
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Enclosure:
s IE Eulletin 76-07
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H. Autio, Plant Superintendent g
Donald G. Allen, President 1
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e IE yall & Files Centr:1 Files Public Dacument Room (PDR) i r
Local Public Dacurent Room (LPDR) j
' uclear Safety Infornation Center (MSIC)
Iechnical Information Center (TIC)
}y REC:I Reading Room Cormonrealth of Massachusetts p
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NUCLEAR REGULATORY COMMISSION E
OFFICE OF INSPECTION AND ENFORCEMENT
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WASHINGTON, D.C. 20555 IE Bulletin No. 76-07 DATE:
July 28, 1976 Page 1 of 2 E
CRANE HOIST CONTROL - CIRCUIT MODIFICATIONS LESCRIPTION OF CIRCUMSTANCES:
f In response to NRC concerns about the potential for, and consequences 5
of, dropping a spent fuel shipping cask or other heavy load, Commonwealth
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Edison modified the hoist control system for the fuel cask handling crancs at their Dresden Units 2 and 3 and Quad cities Units 1 and 2 to y
provide additional hoist redundancy and slow speed hoist capability.
The original design utilized a General Electric "magspeed" hoist control
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system.
In this system which includes two electro-mechanical brakes in i
series, spring force holds the brakes engaged while DC solenoids, ener-gized when the heist motor is energized', disengage the brakes.
i The modification which added the slow speed hoist capability included i
installing additional contactors in the brake solenoid power circuit to energize the solenoids when the low speed hoist motor was energized.
l The original hoist control system design utilized a single Size 2 DC 2
i contactor (two contacts in series) in the solenoid circuit.
The design i
codification 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 carry!ng and interrupting burden.
Initial experience with the modified hoist control system at Dresden showed that the circuit interrupting capacity of the series-parallel i
array was marginal.
On several occasions when the low speed motor was stopped in the lowering mode, the solenoid circuit contactc 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 cuch as 15 inches was reported, but no damage to hoist or load was found.
I The crane manufacturer's representatives.have advised the NRC that the i'
proposed corrective action is to install a single Size 2 DC contactor i
(two contacts in series) with arc suppressers, the same as originally j
provided in the Cencral Electric design, in place of the added four AC l
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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DATE: July 28, 1976
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Page 2 of 2
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il ACTION TO BE TATEN BY LICENSEE:
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to this office within 20 days the M
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Determine and report C!
following information:
hk llave you made, or do you plan to makn modific~ations
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(a)
Y.j to the hoist control for your installed cranes g
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'[4 similar to the described modifications?
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(b)
If such modifications have been made, or are planned, identify changes required in brake power and control circuitry?
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(c)
What steps have been taken or are planned, to pro-
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vide assurance that brake power contactors are i
adequate for the service?
,q1d If modifications are planned, provide the schedule for sij 2.
completion and a brief description of your plans for h!
M design review and functional testing.
Your respense should be submitted to the Director of this Of fice, with a 4
copy to the Director, Division of Reactor Inspection Programs, Office cf
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Inspection and Enforcement, U. S. Nuclear Regulatory Commission, Washing-
.l ton, D. C. 20555.
J Approval of SRC requirements for reports concerning possible generic problems has been obtained under 44 U. S. C. 3152 from the U. S. General (GAO Approval B-180255 (R0072), expires 7/31/77).
J Accounting Office.
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