ML20084D102
| ML20084D102 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/08/1971 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084D105 | List: |
| References | |
| 11474, NUDOCS 8304080470 | |
| Download: ML20084D102 (2) | |
Text
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s y; e Commomveahh Edison Company 72 WCGT ADAMS STREET
- C H 1 C A G O.
ILLINOIS Address Repff re:
POST offlCE BOX 747
- C H I C A G O, ILLINOIS 40490 Dresden Nuclear Power Station W
R. R. #1 f
g Morris, Illinois 60450 8
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Dr. Peter A. Morris, Director
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Division of Reactor Licensing U.S. Atoraic Energy Comission Washington, D.C.
20545 SuluECT: LICINSE DPR-19, DRESDEN NUCLEAR PO.ER STATION UNIT 2, SECTION b.6. B.2 0F Tl!E TECIC!ICAL SPECIFICATIONS
Dear Dr. Morris:
This is to report a ccadition relating to a loss of electrical power to the Low Pressure Coolant Injection (LPCI) System, which rendered it incapabic of performing its intended safety fuaction as required by Sect ion 3.5. A of the Technical Spceifications.
Tue condition occurred during a startup progran test (Startup Test Procedurc 33) in which a planned generator trip and reactor scram was performed in coajunction with a simulated loss of all offsite power.
Tne power loss to the LPCI System was temporcry and affected only the electrical supply to the systems' injection valves.
It did not prevent the normal readiness of the LPCI injection pumps had they been required for injectica of coolant to the reactor nor the operability of the injection valves from the manual operating mode.
~ Description A sinulated loss of power test was performed on February 26, 1971 One of the purposes was to demonstrate the correct performance of the station electrical supply system during the loss of the main generator and all offsite power.
Following the planned generator trip, the electrical feed froc emergency Bus 29 to Motor Contnd Centers (MCC's) 29-7/28-7 tripped on Bus 29 undervoltage.
The automatic transfer of c1cetrical feed from the sister Bus 28 to MCC 29-7/28-7 did not occur.
The control room operator was unable to reclose the feed from Bus 29 to MCC 29-7/28'-7.
An equip-rent operator was dicpatched^to resht the undervoltage trip lockout at
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Bna 29.
After the undervoltage trip was reset, power was manually re-stored to MCC 29-7 and 28-7 frc:a Bun 29 l
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BIS 8304080470 710308 PDR ADOCK 05000237
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Dr. Peter A. Morris Page 2 March 8, 1971
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The electrical feed to the LPCI Systern Injection Valves
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[2-1501-21 A,n and 2-1501-22 A,B) from MCC 29-7/23-7 was interrupted
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/for approximately 20 ninutes follouing the initial trip.
During thid C-20 minute period, the core spray ryste:a remained operabic and the LPCI Syster was not called upon to opercte.
Investigative Acticu E.wrination of the 1CC 29-7/28-7 supply breakers from Buses 29 and 23 revealed the following:
1.
Tac supply breakers from Bus 29 had opened.
2.
The supply breaker from Bus 28 closed, but the breaker at l
l'CC 20-7 did not close due to a blown 10 ampere fuse in the breaker control circuit.
The breaker position had been veri-fled prior to the test and the fuse apparently blew when the breaker received a closing signal from the power transfer lo3 c.
i In additica, a wiring error was discovered in the power supply transfer circuit th.t caused the 1:CC 29-7/28-7 power supply
.o transfer alnoct it=cJ iately, rather than on a time delay.
Corrective Action Le pc.ier supply control circuit was repaired and operaticaally to LeJ uith :.atis factory results.
During this testing the breaker at liCC 28-1 was cycled re paLedly without blouing the control power fuse.
t Because we have been. unable to duplicate the blown fuse, we believe it.aust have been defective.
Sincerely yours, L,).
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K. Iloyt
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Superintendent ilKil:ihac l
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