ML20085D461

Ro:On 720620,three Control Rods Dropped Into Core.Caused by Failure of Multiplexing Thyristor of Moveable Gripper Coil Circuit.Thyristor Replaced

ML20085D461
Person / Time
Site:	Robinson
Issue date:	06/30/1972
From:	Utley E CAROLINA POWER & LIGHT CO.
To:	Block E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085D189	List: ML20085D461
References
NUDOCS 8307250692
Download: ML20085D461 (1)

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Carolina Power & Light Company 50-M/

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.1 Raidgb, North Carolina 27602 Junt 30, 197J '

Mr. Edward i. Bloch, Director Diroctn a! of Licensing C. S. Atomic Energy Commission l Washington,'D. C. 30545 H. B. ROBINSON UNIT NO 2 LICENSE DPR-23 CONTROL ROD DROP INC ENT

Dear Mr. Bloch:

' It is reported that on June 20, 1972, while operating at approx-imately 987. reactor power, three control rods (Bank D-Group 2) dropped into the core. Following the rod group drop. the turbim runback operated as expected, load wao removed and the reactor placed in hot shutdown until repairs could be completed.

[ The cause et tb. malfunction was determined to be the failure of a multiplexing thyrist or of the neveable gripper coil circuit located in power cabinet 2BD. The failed thyristor was replaced and the reactor returned to power on June 20, 1972 Yours very t ruly ,

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t. . E. Utley ft'

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bulk Power Supply NBU:jb cc- Mr. N..B. Bessae Mr. I',. J.-Futr Mr. C. D. Barhau b5 f i

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