ML20112F118
| ML20112F118 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/27/1984 |
| From: | Dixon O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| SPR-84-017, SPR-84-17, NUDOCS 8501150394 | |
| Download: ML20112F118 (3) | |
Text
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t SOUTH CAROLINA ELECTRIC & GAS COMPANY POST OFFIC. 764 COLUMelA. south CAmouNA 29218 Scip.'.T.C
~35 JfJ! 7 Pl: \\6 December 27, 1984 uvet... o...rio~.
o Mr. James P. O'Reilly Regional Administrator U.S. Nuclear' Regulatory Commission Suite 2900 101 Marietta Street, NW Atlanta, GA 30323
SUBJECT:
Virgil C. Sumiier Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Special Report (SPR 84-017)
Dear Sir:
Attached is a Special Report for the Virgil C. Summer Nuclear Station.
This Report is required by Nuclear Regulatory Guide 1.108, " Periodic Testing of Diesel Generator Units Used as Onsite Power Systems at Nuclear-Power Plants."
Should there be any questions, please call us at your convenience.
e y trgly yours,
\\
)
W. Dixon, Jr.
RJB:0WD/ led Attachment K.
E. Nodland oc:-
V. C. Summer Jr.
R. A. Stough T. C. Nichols, Jr./0. W. Dixon, E. H. Crews, Jr.
G.
Percival E.-C.
Roberts C. W. Hehl W. A. Williams, Jr.
J. B. Knotts, Jr.
D. A. Nauman I&E Washington Group Managers Document Management Branch
- 0. S. Bradham INPO Records Center C.
A.
Price ANI Library l_
_D. A. Lavigne NPCF J. F. Heilman File C. L. Ligon (NSRC)
OFFICAL COPY
$$$11SoSEoEo$$9s ifI f3D S
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_y Mr. James-P. O'Reilly SPR 84-017 Page_Two December-27, 1984 EVENT DESCRIPTION During surveillance testing with the Plant in Mode 5, Diesel Generator.XEG-0001B (DGB) failed on two (2) separate occasions.
There were no adverse consequences to the events.
CAUSE OF FAILURE The first failure occurred on November 27, 1984 and was caused by a low oil level in the mechanical governor.
After forty minutes of run_ time, the unit experienced large load swings and was manually. tripped.
The second failure occurred on-November 30, 1984
-and was caused by two.(2) grounds on the 125 VDC. control power
. The ground faults on the control power circuitry were circuitry.
such that the unit could not detect the undervoltage condition.
. The. grounds were located on the positive DC. bus side of the Emergency Start Pushbutton (located on the main control board) and the;. positive DC bus itself:in containaent penetration XRP-0030-ES.
~
This condition provided' two _ current paths through the Emergency Safeguard System _(ESS)_ relay; circuitry: (1) the normal control.
circuit path, and (2) through the ground connection to the positive DC bus.
On initiation of the undervoltage test, the undervoltage contacts opened which should have de-energized the ESS relay and.
caused.the. diesel-te start.
However, due to~the current path.
.provided by the. ground, the ESS relay remained energized.
Under the. pretest conditions, the parallel current. contribution to'the 64 ampereifuselin_ the control circuitry was minimal.
When the
~
undervoltage_ contacts opened,:the normal control circuit was opened and only the ground circuit remained.
This caused an increase in the' circuit' amperage which exceeded the'6 ampere rating of the control. circuit fuse.. Af ter approximately _ twenty-five -(25) seconds the fuse blew, opening the ground circuit:which de-energized the
- ESS; relay _and' completed the diesel start circuit..
The diesel started'and the; test:was completed _without further-incident.
ke'groundontheEme'rgency'StartPushbuttonresultedfromthe
~
- rotation of_.the_pushbutton assembly which. allowed <a connectionJto-
.becomefgrounded.to.the metal' enclosure.',The ground at XRP-0030-ES-.
-wasidue--toitwo (2) pins shorted together.,
s t
e G
Mr. James P.
O'Reilly SPR 84-017 Page Three December 27, 1984 ACTION TAKEN Following the failure on November 27, oil was added to the mechanical governor, the unit retested and declared operable at 2040 hours0.0236 days <br />0.567 hours <br />0.00337 weeks <br />7.7622e-4 months <br /> on November 28.
The ground faults on the 125 VDC control power circuitry were located and cleared following the failure on November 30.
To correct the fault associated with the containment penetration, the circuit was relocated to two (2) spare connectors.
The Licensee corrected the ground associated with the Emergency Start Pushbutton and inspected the pushbutton associated with the other unit to verify that a similar condition did not exist.
In. addition, lock rings and heat shrink insulation have been installed on the switches to preclude recurrence.
SURVEILLANCE STATUS The failure on November 27 was an invalid start failure.
The run time was less than one-(1) hour, and during emergency operation isochronous speed control is utilized.
'The event on November 30 is considered an invalid start in accordance with Regulatory Guide 1.108, " Periodic Testing of Diesel Generator Units'Used as Onsite Power Systems at Nuclear Power Plants."
As-previously noted, the' failure of the unit to start was due to a: double fault (two grounds).
The ground on the Emergency Start Pushbutton alone would not have prohibited a successful start; the malfunction in the circuitry. not ' associated with the diesel caused the failure.
South Carolina Electric and Gas Company, in a letter from O. W. Dixon, Jr. to H. R. Denton dated December 14, 1984, has requested NRR Staff concurrence on this-interpretation of the Regulatory Guide.
The. only valid. failure of "B" Diesel Generator at the Virgil C.
-Summer Nuclear' Station-occurred on December 18, 1982.
Therefore, in accordance with the testing frequency outlined in Table ~4.8-1 of theiTechnical Specifications, SCE&G will continue testing the diesel = generators atL east once every thirty-one (31) days.
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