ML19256B403
| ML19256B403 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/02/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 7906130137 | |
| Download: ML19256B403 (1) | |
Text
CENTRAL FILES Sa nscg UNITE D STATES
'o NUCLEAR REGULATORY COMMISSION POR:HQ IgR P
[ 'A I
REGION iv o
(.j 611 RYAN PL AZA DRIVE, SUITE 1000 o'$
ARLINGTON,1E XAS 76011 ij$ ((
t'N
/
May 2, 1979 Docket No. 50-298
?!ebraska Public Power District ATTft:
J. M. Pilant, Director Licensing & Quality Assurance Post Office Box 499 Columbus, Nebraska 68601 Centlemen:
The enclosed IE Circular No. 79-07, is forwarded to you for inforTnation.
fio written response is required.
Should you have any questions related to your understanding of this matter, please contact this office.
Sincerely,
.'?h f.,/ ledh
.x j
s i
KarlV.Sehf,rit
)
Director
Enclosures:
1.
IE Circular No. 79-07 2.
List of IE Circulars Issued in the Last Twleve Months cc:
L. C. Lessor, Superintendent Cooper Nuclear Station Post Office Box 98 Brownville, Nebraska 68321 s.m-1 K) 790613019[
M
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 IE Circular f.o. 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 tenninal panel cover was removed, licensee 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 tenninated 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 licensee contacted the vendor regarding the second fuse and was infonned 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 located in the position followup circuit.
in a loss of the nulling signal to the maximum speed position.
DUPLICATE DOCUMENT The licensee examined the circui Entire document previously actuator and discovered that it entered into system under:
indicated on the vendor's drawin ANO No. of pages: