ML20084D852
| ML20084D852 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/16/1970 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084D850 | List: |
| References | |
| NUDOCS 8304120481 | |
| Download: ML20084D852 (2) | |
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- CHICAGO. BLLINOIS Address R. ply nas rost orrict sox 747
- cn ic A c o, li t l N O l$ 40690 Dresden Nuclear Power Station
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October 16, 1970 ikgW'nlQJ, 00 m5 %C3
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Dr. Peter A. Morric jQ/
Division of Reactor Licensitig
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SUBJECT:
LICENSE DPR-19 DRESDEN NUCLEAR PO!JER STATTON UNIT 2, SECTION 6.6.C.1 OF Tile TECilNICAL SPECIFICATIONS.
Dear Dr. Morris:
Thic in to report a condition relating to the operation of the station in which the Unit 3125 V DC battery was found to be discharged and the 125 V DC hattery chcrger inoperable while the plant was at 600 MWo.
The battery and battery charger were required to be operable by Section 3.93 of the Tcchnical Specifications.
Problem and Initial Action On the 12 MN - S /d! shift of September 15, 1970, the Unit 3 125 V DC battery charger tripped several times.
Investigation revealed that the charger was producing maximum amperage and subsequently tripping on thermal overload.
Further investigation revealed what appeared to be a cyclic ground on the Unit 3 125 V DC system.
Efforts to locate the cause of the trouble were unsuccessful and by 8:00 a.m. September 15, 1970, it was determined that the battery was discharged and that the battery charger would no longer produce proper voltage.
The Unit 3 125 V DC battery and battery charger were declared inoperabic at this time.
Continued reactor operation was allowed by Section 3.9.B.3 of the Technical Specifications.
The Unit 2 reserve 125 V DC bus was transferred to be supplied from the Unit 2 battery and the 2/3 125 V DC battery charger was placed' on the Unit 3 battery to begin recharging it.
8304120481 701068 I ' e t- -
PDR ADOCK 05000237
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Y; Dr. Peter A. 1Mrrir 0:teber 16, 1970 Inventigation and Corrective Action A thorough investigation revealed a Unit 3 construction wiring error that connected 115 V AC to the 125 V DC at a limit switch.
This was corrected imm2diately.
It is believed that the AC signal caused the battery discharge by three methods:
Blocking the battery charge output.
a.
b.
Tici:n the bettery positive (+) and negative (-) buscs together through the AC systems transformer.
Creating a higher than normal driving voltage for normal DC c.
loads.
Troubic shooting of the battery charger revealed a b1cwn control circuit board.
Tnis vac replaced and the Unit 3 125 V DC battery charger tested satinfactorily on September 17, 1970.
Tne Unit 3 125 V DC battery reached fully charged status on Septem-ber 19, 1970. At this time the Unit 3125 V DC battery and battery charger was declared operable and the battery system returned to noutal lineup.
Tnis incident has been reviewed by the Station Review Board and it was concluded that the initial action and corrective actions were proper.
Very truly yours, g
II. K. Iloyt Superintendent ill31:dmc x
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