ML19347E210
| ML19347E210 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 04/13/1981 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML19347E211 | List: |
| References | |
| NUDOCS 8104240257 | |
| Download: ML19347E210 (2) | |
Text
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O') On3 First N tional Pitza Chicigo Illinois Commonwealth Edison
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') Address Reply to: Post Office Box 767 Chicago, Illinois 60690 j
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April 13, 198
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'q bES% 3198 W 4 I-Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation 8'h @ms*gm ' /
U.S. Nuclear Regulatory Commission s
Washington, D. C. 20555
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Subject:
Zion Station Units 1 and 2 Proposed Change to Facility Operating License Nos. DPR-39 and DPR-48 NRC Docket Nos. 50-295 and 50-304
Dear Mr. Denton:
Pursuant to 10 CFR 53.90, Commonwealth Edison Company hereby requests a change to Operating License Nos. DPR-39 and DPR-48, Appendix A, Technical Specifications.
The purpose of this amendment is to revise the Zion Station Technical Specifications by removing the rod bow penalty from the equation used to calculate the radial peaking factor limit, F H.
The proposed changes to the Zion Station Technical Speci cations are enclosed in Attachment A to this letter and the basis for this change is discussed below.
N A rod bow penalty had been included in the F gg equation to ensure an adequate DNBR margin.
This penalty was based on equations given in the NRC's " Interim Safety Evaluation Report on Effects of Fuel Rod Bowing on Thermal Margin Calculations for Light Water Reactors" (Revision 1), dated February 15, 1977.
The equations defined a relationship between fuel region average burnup and reductions in F AH, taking generic thermal margins into N
account.
These thermal margins consisted of
- 1) Design pitch reduction,
- 2) Conservatively chosen thermal diffusion coefficient (TDC) used in design,
- 3) Design limit DNBR value (1.30) greater than the actual DNBR value (1.24) for 95% of the data at a 95%
confidence level, and 4) Densification power spike factor used in design.
On April 5, 1979, the NRC completed an evaluation of the Westinghouse report - "Effect on CHF of a Partially Bowed Heated Rod in a Cold Wall Thimble Cell Geometry".
The NRC staff concluded that the relation for bow penalty as a function of gap closure given in the report "is an acceptable bow penalty for use on Westinghouse fuel designs".
In light of this NRC conclusion, the existing rod bow penalty on FNAH can be eliminated for feel with region average burnups less than 33,000 MWD /MTV.
Ho rod bow penalty for 8104240257
D 6 fuel with region average burnups greater than 33,000 MWD /MTU is required due to the peaking factor burndown effect.
The higher burnup fuel is not capable of achieving the limiting peaking factor due to the decrease in fissionable isotopes and the buildup of the fission product inventory.
Confirmation of the burndown effect is performed during the reload design review process where the expected i
Fag for fuel with burnup greater than 33,000 MWD /MTU is verified not to exceed the limiting peaking factor.
The proposed changes of Attachment A delete references to the rod bow penalty and eliminate the curve used to calculate the FNay rod bow penalty.
These changet have been reviewed and approved by Commonwealth Edison On-Site and Off-Site Review with the conclusion that the plant can be operated safely.
Removal of the rod bow penalty will also alleviate a separate potential calculational problem associated with the F H limit at part power for Zion Unit 2 end of cycle operation.
Specifically, Commonwealth Ediscn has determined that the limit could be exceeded at approximately 25% of rated power during the Summer 1981 coastdown of the unit.
Since the coastdown is expected to commence in mid-July 1981, Commonwealth Edison requests approval by July 1, 1981.
Pursuant to 10 CFR 170, Commonwealth Edison has determined that this proposed amendment is a combined Class III and Class I Amendment.
As such, Commonwealth Edison has enclosed a fee remittance in the amount of $4,400.00 for the proposed amendment.
Commonwealth Edison has concluded that the proposed amendment change does not involve a significant hazards consideration and that the acceptability for this issue has been clearly identified by an NRC position.
Please address any questions that you may have concerning this matter to this office.
Three (3) signed originals and thirty-seven (37) copies of this letter are provided for your use.
Very truly yours,
[/k,VN. -
T. R. Tramm Nuclear Licensing Administrator Pressurized Water Reactors cc:
Zion Resident Inspector j
Attachment SUBSCRIBED and SWORN to before me
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1981 d, v off (m,a* /'e
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Notary Public
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