ML17333A799
| ML17333A799 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 02/27/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17333A798 | List: |
| References | |
| NUDOCS 9703050497 | |
| Download: ML17333A799 (5) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
213 TO FACILITY OPERATING LICENSE NO.
DPR-58 AND AMENDMENT N0.198 TO FACILITY OPERATING LICENSE NO.
DPR-74 INDIANA MICHIGAN POWER COMPANY DONALD C.
COOK NUCLEAR PLANT UNIT NOS.
1 AND 2 DOCKET NOS.
50-315 AND 50-316
1.0 INTRODUCTION
By letter dated February 26,
- 1996, the Indiana Michigan Power Company (the licensee) requested amendments to the Technical Specifications (TS) appended to Facility Operating License Nos.
DPR-58 and DPR-74 for the Donald C.
Cook Nuclear Plant, Unit Nos.
1 and 2.
The proposed amendments would change the TS to allow an increased limit for the nominal enrichment of new (unirradiated)
Westinghouse fabricated fuel stored in the new fuel storage racks.
The proposed changes would allow for the storage of fuel with an enrichment not to exceed a nominal 4.95 weight percent (w/o) U-235, subject to certain integral fuel burnable absorber (IFBA) requirements, in the new fuel storage racks.
Plant operation using the higher enriched fuel will be demonstrated to be acceptable by a cycle specific reload safety evaluation performed prior to each fuel loading.
- 2. 0 EVALUATION The analysis of the reactivity effects of fuel storage in the new fuel storage racks was performed with the two-dimensional multi-group transport theory computer
- code, PHOENIX-P, using a 42 energy group neutron cross section library.
PHOENIX-P is widely used for the analysis of fuel rack reactivity and has been benchmarked against results from numerous critical experiments.
These experiments simulate the Cook new fuel storage rack as realistically as possible with respect to parameters important to reactivity such as enrichment and assembly spacing.
Based on this, the staff concludes that the analysis methods used are acceptable and capable of predicting the reactivity of the Cook new fuel storage rack with a high degree of confidence.
Fresh fuel is normally stored dry in the new fuel racks.
However, to meet the criterion stated in Section
- 9. 1. 1 of the NRC Standard Review Plan (SRP), k,ff must not exceed 0.95 with the racks fully loaded with fuel of the highest anticipated reactivity and flooded with unborated water.
Furthermore, k,ff must be no greater than 0.98 under low density (optimum moderation) conditions.
The maximum calculated reactivity must include a margin for uncertainties in reactivity calculations and in manufacturing tolerances such 9703050497 970227 PDR ADOCK 050003i5 P
that tne true k, will not exceed these limits at a 95X probability, 95X confidence (95/N) level.
These uncertainties are described in Section 9.7 of, the D.C. Cook UFSAR.
Previous calculations approved by the NRC have shown that fuel assemblies with enrichments up to 4..55 w/o U-235 can be safely stored in the Cook new fuel racks.
In order to store fresh fuel with initial enrichment greater than 4.55 w/o U-235, the concept of reactivity equivalencing was used.
In this technique, which has been previously approved by the NRC, credit is taken for the reactivity decrease due to the IFBA material coated on the outside of the UO< pellet.
Based on these calculations, 32 IFBA rods are required to maintain the k,<< criteria for fuel initially enriched to a nominal 4.95 w/o U-235.
Due to the normal manufacturing enrichment variability of 10.05 w/o U-235, a nominal enrichment of 4.95 w/o U-235 can result in a maximum enrichment of 5.0 w/o U-235.
These IFBA requirements were based on the standard IFBA patterns used by Westinghouse.
However, since the reactivity worth of individual IFBA rods can change depending on position within the assembly due to local variations in thermal flux, additional calculations were performed to evaluate this effect and a conservative reactivity margin was included to account for this effect.
This assures that the IFBA requirement remains valid at intermediate enrichments where standard IFBA patterns may not be available.
In addition, the IFBA requirements also include a conservatism of approximately IOX on the total number of IFBA rods at 4.95 w/o U-235 to account for calculational uncertainties.
The staff finds that sufficient conservatism has been incorporated into the IFBA determina'tion to adequately account for manufacturing and calculational uncertainties.
As an alternative method for determining the acceptability of fuel storage in the new fuel racks, a reference k calculation was performed using PHOENIX-P.
The calculation used a 4.55 w/o U-235 enriched fuel assembly with no burnable absorbers in the Cook reactor geometry at a temperature of 68'F.
The resulting k
was 1.4857 and included a IX reactivity bias to account for calculational uncertainties.
Thus, fuel assemblies which are to be stored in the Cook new fuel racks must either meet the initial enrichment versus IFBA requirements previously described, or have a reference k less than or equal to 1.4857, to ensure that the final k,<< of the Cook new fuel racks will be no greater than 0.95 (if fully flooded) and 0.98 (under optimum moderation).
The following Technical Specification changes have been proposed as a result of the requested enrichment increase.
The staff finds these changes as well as the proposed additional administrative changes acceptable.
(I)
TS 5.6.2 has been revised to incorporate the information presently in TS 5.6.2. 1 and 5.6.2.2 into a format similar to the format used in the improved standard TS (NUREG-1431, Rev I).
All current TS requirements are still retained.
Table 5.6-1 is added to clarify the individual enrichment limits for the various fuel types used at Cook.
The revised TS also includes the requirement for k,, to be no greater than 0.95 if fully flooded with unborated water, which is consistent with NRC requirements.
(2)
TS Table 5.6-1 has been revised to include a footnote for the Westinghouse fuel types to allow a maximum nominal enrichment of 4.95 w/o
U-235 provided sufficient IFBAs are present such that k is no greater than 1.4857.
3.0
SUMMARY
Based on the review described
- above, the staff finds the proposed increase in the allowable U-235 enrichment of fuel to be stored in the new fuel storage facilities of the D.C.
Cook plants to be acceptable.
The proposed change meets the requi.rements of General Design Criterion 62 for the prevention of criticality in fuel storage and handling.
Although the Cook TS have been modified to specify the increased enrichment fuel as acceptable for storage in the new fuel racks, evaluations of reload core designs will continue to be performed on a cycle by cycle basis as part of the reload safety evaluation process.
Each reload design is evaluated to confirm that the cycle core design adheres to the limits that exist in the accident analyses and TS to ensure that reactor, operation is acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32 and 51.35, an environmental assessment and finding of no significant impact was published in the Federal
~Re ister on February 12, 1997 (62 FR 6565).
Accordingly, based upon the environmental assessment, the Commission has determined that issuance of the amendments will not have a significant effect on the quality of the human environment.
6.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed
- manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
Larry Kopp, NRR Date:
February 27, 1997
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