ML19254A652
| ML19254A652 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 05/02/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| NUDOCS 7906130177 | |
| Download: ML19254A652 (1) | |
Text
rgs UNITED STATES p* *'%,,( g NUCLEAR REGULATORY COMMisslON f
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KING OF PRUS$1 A. PENNSYLV ANI A 19406 s, s y
May 2, 1979 Docket No. 50-271 Vermont Yankee Nuclear Power Corporation ATTN:
Mr. Robert H. Groce Licensing Engineer 20 Turnpike Road Westborough, Massachusetts 01581 Gentlemen:
The enclosed IE Circular No. 79-07 is forwarded to you for in-formation.
No written response is required.
Should you have any questions related to your understanding of this matter, please contact this office.
Sincerely, W
Boyce H. Grier
" Director
Enclosures:
1.
IE Circular No. 79-07 2.
List of IE Jirculars Issued in Last Twelve Months cc w/encls:
W. F. Conway, Plant Superintendent Ms. J. Abbey, Technical Secretary A. Z. Roisman, Natural Resources Defense Council 7906130 /77g
UNIN D STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 79-07 Date:
May 2, 1979 Page 1 of 3 UNEXPECTED SPEED INCREASE OF REACTOR RECIRCULATION MG SET RESULTED IN REACTOR POWER INCREASE Description of Circumstances:
On November 24, 1978, an unexpected rapid speed increase was experienced on the 'B' Reactor Recirculation MG set (RRMG) at the Cooper Nuclear Station.
Prior to the event, the RRMG set had been inadvertently tripped during the performance of routine maintenance.
Upon restart, the MG set would not respond to a speed increase signal.
Licensee personnel com-menced trouble shooting this problem in accordance with the instructions in the manufacturer's technical manual.
One step of these instructions suggested removing the fuse from the Bailey scoop tube actuator circuit (a blown fuse would de-energize the actuator and not permit the scoop tube to move).
When the terminal panel cover was removed, 1icensee personnel noted two fuses instead of one as shown on the vendor drawings.
When licensee personnel removed the second fuse to verify fuse integrity, a rapid speed increase of the MG set occurred.
This increase was terminated by replacement of the fuse or tripping of the MG set by the control room operator (both actions took place almost simultaneously).
The input signal to the scoop tube actuator is received from the speed controller via a function generator.
This signal is a scoop tube posi-tion demand signal.
As the actuator drives the scoop tube in or out of the fluid coupler, a position followup signal is generated to null the input signal and stop scoop tube motion at the required position.
The vendor's drawings of the scoop tube actuator circuit showed only one fuse in the circuit.
The liceasee contacted the vendor regarding the second tuse and was informed that this fuse had been added as a change in the initial circuit design to provide protection for certain elec-tronic components in this circuit.
This additional fuse is 1 the position followup circuit.
in a loss of the nulling signal to the maximum speed position.
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