ML20002D998
| ML20002D998 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/07/1971 |
| From: | Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P, Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101260022 | |
| Download: ML20002D998 (2) | |
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June 7, 1971 Dr. Peter A. Morris, Director Re:
Docket 950435 Division of Reactor Licensing DPR-6 (ZEK)
United States Atomic Energy Commission Washington, DC 20545
Dear Dr. Morris:
Att:
Mr. D. J. Skovholt On May 26, 1971, during routine exercising of the Big Rock Point control rod drives, it was noted the drive C-3 would not withdraw after being inserted one notch from its normally fully withdrawn position. Pre-scribed plant procedures for malfunctioning control rod drive were fol-loved.
It became evident that the drive would freely insert but could not be withdrawn, apparently due to a foreign object lodged in the control rod drive housing extension or possibly control rod drive hydraulic system problems. Experimentation with the drive was stopped with the drive at notch 15, and the drive insert and withdrawal hydraulie water was valved and tagged out of service.
Physics calculatior_s were cade concerning peak heat fluxes and rod worths for both the current power level, 163 W, and 244 Wt with t
rod C-3 at notch 15 The results were as follows:
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163 Wt f
Peak Heat Flux 277,100 B1.u/Ft U
TIN Y
Rod Worth (C-3)
.1376%
Maximum Rod Worth (E-2) 57%
MCHFR 3 26o1 tU g 10M g.,
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2hk Wt 1 (
Peak Heat Flux 409,100 Btu /Ft jy MCHFR 2.1362 to e'
cn 24h Wt represents the 122% overpower condition. At the begin-ning of this cycle (March 1971), the picoammeters were set at 100% reactor power corresponding to 200 Wt in order to limit heat flux and fuel clad-ding temperatures because of the Cu-Fe crudding.
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Dr. Petsr A. Morris.
2 June 7, 1971 The peak heat flux at 163 MWt with C-3 at notch 15 case is only a slight increase over the peak heat flux for this core with a normal rod patte rn.
The reactor shutdown margin was verified at the start of this cycle with two rods fully withdrawn and an adjacent rod at notch 6.
- Thus, for any shutdown, the shutdown margin requirements are easily met with C-3 fully withdrawn.
4 Based on the above data, it was decided to continue operations at 163 MWt with C-3 in an abnormal position until the currently scheduled bhrch 1972 refueling outage. Subsequent work with the drive has resulted in the drive bein6 withdrawn to notch 17 Based on this work, it appears the problem is not hydraulic in nature but symptomatic of problems with very small foreign objects in drives.
If a scram occurs, C-3 vill be scrammed as the scram water is i
not isolated. If this occurs and the control rod cannot be withdrawn, it is planned to continue plant operation at 163 MWt with C-3 fully inserted.
e In this condition, the' peak heat flux would be 292,200 Btu /ft,
the maximum rod worth for C-3 is 13375%, and the MCHFR is 3 0907 These l
values are still well within plant license requirements.
As was stated above, Big Rock Point has been operated at 163 LVt since refueling in March 1971.
It was previously planned to continue operation at this power level during the remainder of this run. Since the.out-of-position rod has not significantly increased peak heat fluxes, it is concluded that this incident will not hinder plant operation. The AEC Compliance Officer in Chicago was notified on May 26, 1971, and this letter confirms the information given to him over the telephone. A com-plete evaluation of the cause of the drive malfunction will be made during the refueling shutdown. We will keep Compliance informed of our findings.
Yours very truly, w
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BBS/ map Bobert L. Haueter Electric Production CC:
BHGreer Superintendent - Nuclear Div of Comp USAEC v
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vm Consumers Power Ceegany DATE OF DOCUMENT:
DaTE RECevtO ho.:
Jackase, lyichigan 49201 June 7. 1971 Jwne 10, 1971
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