ML20108F352
| ML20108F352 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/14/1984 |
| From: | Dixon O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8412200194 | |
| Download: ML20108F352 (3) | |
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-S' SOUTH CAROLINA ELECTRIC & gas COMPANY POST OFFICE M4 CowuelA. South CANoWNA 2921s O.' W. DixoN, JR._
uue7.1R oE.l" iou.
December 14,.1984
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Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S.: Nuclear Regulatory Commission
_ Washington, D.C. 20555 Subjects - Virgil C. Summer' Nuclear Station Docket No.l 50/395 Operating License No. NPF-12 Diesel-Generator Testing
Dear Mr. Denton:
On November 30,.1984, in accordance with Technical Specification Surveillance Requirement 4.8.1.1.1, the "B" Emergency Diesel Generator was
- being started for testing purposes by a simulated undervoltage (UV) s ignal.
- However, 'upon actuation of the test signal, the diesel did not start within
' the required ten -(10)~ seconds. Therefore the test was determined to be a failure.
South Carolina Electric and Gas Company (SCE&G) has concluded that under the provisions of Regulatory Guide 1.108, " Periodic Testing of Diesel-Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants," Revision 1, August 1977, Section C.2.e(2), the unsuccessful start of the-diesel was attributed to the malfunction of equipment that is not a part of the defined diesel generator unit design and is therefere not a valid-test failure..The cause of tlue start failure of the diesel is described below to support this. conclusion.
The situation which caused the start failure was a ground on both the
-positive DC bus side of the Emergency Start Pushbutton (located on the main
' control board) and the positive DC bus itself at' penetration KRP0030-PS, plug 5, pins 57 and 65 (see Attachment I).
In this condition two (2) current paths were available to keep the Emergency Safeguards System (ESS)
' relay energized:
(1) the normal control circuit path, and (2) the path through the ground connection to the positive DC bus.
On initiation of the LUV test, the UV contacts opened which should have deenergized the ESS relay
~
causing the diesel to. start. However, the current path through fuse
,FU-AH284 and the ground loop back to the positive DC bus still existed.
Under ' the pre-test conditions the parallel current contribution to FU-AH284-was'ainimal, but when the UV contacts opened the only path lef t to keep the ESS relay energized 'was through the ground loop. This additional current exceeded the 6 amp rating of the fuse, thus opening' the circuit and allowing the ESS to relay drop out.. When this occurred the diesel started aad the test was corpleted without 'further incident..
8412200194 841214 ?
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~ Mr. Harold-D. Denton
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Diesel Generator Testing December 14, 1984 Page #2 The iground at the main control board resulted from the pushbutton rotating in its assembly and grounding on the metal enclosing the pushbutton. The
. ground at KRP-0030-ES occurred when the circuit, which is not a portion of the diesel generator unit design, was energized af ter performing a modificiation to the plant during the present refueling outage. This ground, in conjunction with the pushbutton ground on the control board, prevented the successful start of the diesel generator. The pushbutton ground alone would not have prohibited a successful start, and therefore, the malfunction in the circuitry not associated with the diesel design caused the failure.
Since the unsuccessful start of the "B" diesel generator on November 30, 1984 is not considered by SCE&G to be a valid test failure, the only valid diesel test failure at the Virgil C. Summer Nuclear. Station occurred on December 18, 1982. SCE&G requests the Nuclear Regulatory Commission Staff's concurrence on this position to support continued testing of the diesel generators on a staggered test basis of at least once every thirty-one (31) days as outlined in Table 4-8.1 of the Technical Specifications.
If you have any questions, please contact this of fice.
I Very truly your,
L O. W. Dixon, Jr.
AMM/OWD/gj At tachment:
I -
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V. C. Summer C. A. Price T. C. Nichols, Jr./O. W. Dixon, Jr.
C. L. Ligon (NSRC)
E. H. Crews, Jr.
K. E. Nodland
'E. C. Roberts R. A. St ough W. A. Williasm, Jr.
G. Percival D. A. Nauman C. W. Hehl J. P. O'Reilly J. B. Knotts, Jr.
Group Managers NPCF O. S. Bradham File
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