ML20085F715
| ML20085F715 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 08/28/1974 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085F712 | List: |
| References | |
| AO-74-11, NUDOCS 8308230150 | |
| Download: ML20085F715 (3) | |
Text
i n
d,3 b(m N ConSum8f5 Ng/ji POW 8r Company
. B Ggnerat Offices-212 West M,chegan Avenue. Jackson, Mech.gan 49201 o Area Code S17 7H8 OSSO August 28, 1974 Directorate of Licensing Re: Docket 50-255 US Atomic Energy Commission License No DPR-20 Washington, DC 205h5 Palisades Plant A0-Th-ll (Additional Info)
Gentlemen:
By letter dated June 20, 1974, we provided a preliminary report of an abnormal occurrence (No 74-11) at the Palisades Plant on June 9, 1974. This abnormal occurrence involved Control Breaker 72-203 on the 1D bus.
The investigation disclosed several other problems which have been corrected and are included as part of A0-74-ll.
We now consider this investigation to be complete, and the attached report is submitted.
Yours very truly, Ralph B. Sevell (Signed)
DAB /mel Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC W
co
&Nr 9
L
$W
~
SEPo 4,M C Sa.ga.t tr 11 gSfdNS g
+
N B309230150 750919
- 7[.g6 >/p.f PDRADOCK05000g f9N byraddO k
O O
ABNORMAL OCCURRENCE REPORT Palisades Plant 1.
Report Number:
A0-Th-11, Docket 50-255 2.
a.
Report Dates: June 19, 197h and August 28, 1974 b.
Occurrence Date: June 9, 1974 3
Facility: Palisades Plant 4.
Identification of Occurrence: Loss of d-c control power to bus 1D feeder breaker - Breaker 72-203.
5 Condition of Occurrence: Plant in cold shutdown condition.
6.
Description of Occurrence: On June 9, 1974, at approximately 1615
{
hours, the operator reported to the Shift Supervisor that the indicating lights for the circuit breakers on Bus 1D vere out.
The local lights at 1D bus were also out, and d-c Control Power Breaker 72-203 (100 amp) was tripped and attempts to reset failed.
With the assistance of an electrician, the breaker was reset; how-ever, no reason for the breaker trip could be determined at that time. Additional testing and visual inspection could detennine no problem with the loading circuits. However, on at least one occa-sion, the breaker tripped while the circuit was being loaded (that incident could not be repeated).
7 Designation of Apparent Cause of Occurrence: Component failure.
The most probable cause was a marginal reset latch in the breaker.
3 Test on manual resetting of the breaker indicated that special I
breaker handle motion was required to assure consistent latching of the breaker. The investigation also revealed that the breaker l
had been operated earlier in the day; and it was concluded that when the breaker was reset, it probably did not close properly.
In addition to the marginal reset latch on the breaker, several other problems were found during the investigation. These were as follows:
a.
The d-c undervoltage alarm for Bus 1D was not connected (scheme A1006).
b.
The power feed to Bus 1D undervoltage and load shed (Scheme A1006) was not properly wired. The scheme was wired to Breaker 72-202 instead of Breaker 72-203 (per Bechtel draw-ings).
The investigation also detennined that the incoming breaker's d-c control did not have an undervoltage alarm. This additional alarm system is considered desirable and a facility change to add alarms to both the 1C and 1D buses is being processed.
/N CS U
2 8.
Analysis of Occurrence: The loss of d-c control power to the Bus ID feeder breaker results in the breakers not being able to trip in case of equipment malfunction. With no alarm resulting from loss of control power, the operator would not be aware of the situation.
9 Corrective Action:
a.
Replaced Breaker 72-203 with a new one.
b.
Corrected power to Scheme A1006 so that it is fed from 72-203 c.
Completed wiring undervoltage alarm for 72-203 and verified operability.
d.
Verified that the proper schemes are fed from the proper d-c breaker on 1D bus.
e.
Verified the proper breaker feeds on 1C bus and the undervoltage alarm function.
f.
Verified the proper breaker feeds on lE bus and the control power light function.
10.
Failure Data:
a.
There are no records of a previous failure or malfunction of this type on this equipment.
b.
Equipment Identification: Westinghouse Circuit Breaker, Model No FB21550ML, Type FB, 600 VAC - 250 VDC, 100 amp continuous current rating, Style No h99hD95G08.
l
_