ML19269B844
| ML19269B844 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 01/10/1979 |
| From: | Reed C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7901170256 | |
| Download: ML19269B844 (2) | |
Text
-
~
r Commonwealth Edison One First National Plaza, Chicago, Ilknois Address Reply to: Post Office Box 767 c
Chicago. Illinois 60690 January 10, 1979 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Zion Station Units 1 and 2 Revised ECCS Evaluation NRC Docket Nos. 50-295 and 50-304
Dear Mr. Denton:
On January 9, 1979 Commonwealth Edison company was informed by Westinghouse Electric Corporation that a revised analysis of ECCS cooling performance for Zion Station Units 1 and 2 had been completed.
This revised analysis was done in accordance with the revised Westinghouse ECCS Evaluation Model approved by the NRC Staff in August 1978.
As discussed with the NRC Staff on January 9, 1979, the results of this analysis indicated that Zion Station F peaking factor decreased g
approximately 8% from the current interim value of 2.02.
The revised analysis indicated an FO peaking factor of 1.86 for an accumulator level range of 769 to 818 ft.3 The current interim F limit is 2.02 for an accumulator range of 851 to 866 ft.3,0 Based on this information, Commonwealth Edison reduced Zion Unit 1 to 90% of rated power while the F limit g
of 1.86 was programmed into the installed APDMS surveillance equipment.
The modified APDMS limit indicated that a reduction of only 5% power was required to accommodate the revised Fg limit.
Currently, the unit is operating at 93% power.
Zion Unit 2 was not affected by this information as the unit was in a coastdown mode of operation and well below the revised F
limit.
g With regard to the difference in accumulator levels, Westinghouse informed Commonwealth that the difference is more than covered by additional margin available in as-built fuel pellet temperatures which were not included in the revised k
\\
7 90117 0 4 9h
Commonwealth Edison NRC Docket Nos.
50-295/304
\\
4-Mr. Harold R. Denton: January 10, 1979 analysis.
Thus, an bmnediate change in accumulator levels was not deemed necessary at this time and that any change would be handled more appropriately in an orderly fashion.
In summary, based on the aforementioned revised ECCS analysis, Zion Station is currently operating with an FQ limit of 1.86.
To accommodate this limit, Zion Station is performing axial power distribution monitoring surveillance for power levels above 88.0% of rated power utilizing the appropriately adjusted normalized FQ envelope, K(Z), and the installed APDMS or the plant process computer whenever APDMS is unavailable.
In addition, Commonwealth Edison has informed Region III of the revised ECCS analysis and the actions taken.
At the present time, Commonwealth Edison anticipates that the complete re-analysis with appropriate Technical Specification change will be expedited and submitted to the NRC Staff for review within 2 to 3 weeks.
Please address any additional questions that you might have to this office.
Very truly yours,
[ b IL Cordell Reed
/
Assistant Vice-President