ML20246Q278
| ML20246Q278 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 08/31/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246Q231 | List: |
| References | |
| NUDOCS 8909120001 | |
| Download: ML20246Q278 (4) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT N0.119TO FACILITY-OPERATING LICENSE NO.-DPR-72 FLORIDA POWER CORPORATION, ET AL.
CRYSTAL RIVER UNIT NO. 3 NUCLEAR GENERATING PLANT DOCKET NO. 50-302 INTRODUCTION By letter dated December 23, 1988, as supplemented dated July 12, 1989, Florida i
Power Corporation (FPC or the licensee) requested an amendment to the Technical Specifications (TS) appended to Facility Operating (CR-3).
License No. DPR-72 for the Crystal River Unit No. 3 Nuclear Generating Plant The proposed amendment would add 15 Sections 3.9.13, 4.9.13.1, 4 9.13.2, and 4.9.13.3, along with their associated bases, to increase the allowable percentage of enrichment of fuel to be stored in the dry fuel storage racks and storage pool A to 4.5%
Uranium-235. This enriched fuel may be irradiated in excess of 33 GWD/MT but not to exceed 60 MWD /MT.
The current allowable percentage of enrichment is 4.0% for fuel in the dry storage racks and 3.5% for fuel in storage pool A.
In addition, the proposed amendment would revise Sections 5.3.1 and 5.6.1 of the TS, which refer to the maximum percentage enrichment of the fuel.
Ey letter dated July 12, 1989, the licensee provided their environmental assessment in support of the proposed license amendment. This information did not change the action noticed or the proposed determination by the staff that the proposed amendment did not involve significant hazards considerations.
In addition, the NRC staff made minor changes to the licensee's proposed changes to TS 5.6.1.
These changes provide clarity and were discussed with and agreed to by members of the licensee's staff.
EVALUATION Dry Fuel Storage Racks i
The purpose of limiting the allowable enrichment of assenblies in the dry fuel storage racks is to prevent inadvertent criticality. To assure criticality safety of the new fuel storage vault, it is necessary to meet the following criteria as defined in NUREG-0800:
1.
When fully loaded with fuel of the highest anticipated reactivity and floooed with clean unborated water, the maximum reactivity, including uncertainties, shall not exceed a keff of 0.95.
2.
With fuel of the highest anticipated reactivity in place and assuming the optimum hypothetical low density moderation (i.e., fog or foam), the maximum reactivity shall not exceed a keff of 0.98.
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, The new fuel storage vault consists of a 6x11 array of storage cells with center-to-center spacing of 21.125 inches. Since this spacing is identical to that in storage pool B, the calculations performed for keff as function of enrichment for storage pool B are applicable to the case of the fuel storage vault flooded with clean unborated water. These calculations, performed using the CASMO-2E calculational model, arrived at an infinite multiplication factor of 0.9393. Taking uncertainties into account, it was determined that the maximum infinite multiplication factor is 0.9436. This is less than the limiting keff value of 0.95 and is therefore acceptable.
For the hypothetical condition of low density moderation, criticality analyses were performed with the AMPX-KENO computer package using the 123-group GAM-THERMOS cross-section library and the NITAWL routine for U-238 resonance shielding.
Preliminary calculations indicated that with all of the fuel vault locations filled, the reactivity would not provide an adequate shutdown margin at optimum moderation. Through trial and error it was detemined that if every fourth row were left empty, the shutdown margin would be acceptable.
Rows 4 and 8 t;ere subsequently blocked to prevent fuel from being stored in them. The analysis of the new fuel storage configuration showed that optimum moderation occurred at a water density of.075 grams /cc and yielded a keff of 0.9412. Taking uncertainties into account, a maximum value for keff of 0.9524 was determined.
This value is acceptable since it does not exceed the staff's criterion of a maximum value of 0.g8.
Since the staff's criteria for the storage of 4.5% U-235 enriched fuel are met, the storage of this fuel in dry storage racks is acceptable.
Storace Pool A The purpose of limiting the combination of ellowable fuel enrichment and burnup of assemblies stored in pool A is to assure a sufficient safety margin to prevent inadvertent criticality.
Values for initial enrichment and burnup are selected to maintain a keff less than or equal to 0.95. The spent fuel racks in storage pool A at CR-3 are currently licensed to store new fuel of 3.5% enrichnent. The licensee presented an analysis to determine the minimum l
discharge burnup required for fuel of higher initial enrichment to be safely l
stored in the pool A storage racks.
Calculations for initial enrichments ranging from 3.5% to 4.5% were performed and a curve defining the acceptable burnup domain war generated.
In performing the criticality safety calculations, the CASMO-2E and 123-group AMPX-KENO methods were used. The CASMO-2E proved to be slightly more conservative and yielded a maximum keff of 0.9474 for fuel of 4.5% initial enrichment and i
I burned to a minimum of 7.0 Hwd/kg-U.
In addition, calculations show that, in the long-term, after decay of xenon, reactivity decreases as Plutonium-241 decay s.
CASMO-2E burnup calculations were confimed by the B&W NULIF code and EPRI-CELL code methods of analysis. Agreement between the three methods was good, and CASMO-2E gave the more conservative value for the infinite multipli-cation factor. The uncertainty applied was 5% of the total burnup reactivity
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Several other criticality,afety analyses of spent fuel storage racks have used 5% of the total reactivity change as the uncertainty in burnup calculations and it is believed to be a conservative estimate.
The effect of axial burnup was also assessed.
Initially, fuel will accumulate a higher than average burnup in the central, more reactive region.
As burnup progresses, the axial distribution tends to flatte For the relatively low fuel burnup considered, the axial power distribution will have retained much of its original cosine shape; therefore, calculations submitted by the licensee are conservative.
The difference in the amount of decay heat generated by the 4.5% enriched fuel, as opposed to that generated by 3.5% enriched fuel, is not significant and is well within the heat removal capabilities of the storage pool cooling system.
Since the storage of fuel of initial concentration of 4.5% enrichment and burr.ed to 7.0 Mwd /kg-U will not result in a keff of greater than 0.95 in storage pool A, and since the decay heat generated by this fuel is within the heat removal capability of the storage pul cooling system, storage of this fuel in storage pool A is acceptable.
Effect on Design Basis Accidents The licensee analyzed the effects of the increased enrichment and irradiation of the fuel on a fuel handling accident.
In performing this analysis it was determined that 1-131 fuel gap activity in the pak fuel rod with 60 GWD/MT could be as high as 12%, a value 2% higher than that assunied in Regulatory Guide 1.25 (Assumptions Used for Evaluating the Consequences of a fuel Handling Accident in the Fuel Handling and Storage Facility for Boiling and Pressurized Water Reactors). All other fuel rod gap release activities would be lower than those assumed in the Regulatory Guide. The limiting results of the licensee's analysis of the postulated fuel handling accident are presented below.
Design Edended Dose Type Basis Fuel Burnup Thyroid Exclusion Boundary (REM) 40.6 48.7 These results show that the thyroid doses that would be received at the exclusion area boundary are well within the 300 rem limit of 10 CFR Part 100. They also show that the increases in dose that would result fmm the increased enrichment and irradiation of the fuel are only a small fractWt of the. limits of 10 CFR Part 100.
The staff agrees that the proposed increases in fuel enrichment and irradiation will not result in doses exceeding the limits of 10 CFR Part 100.
Furthermore, the staff concludes that, although the isotopic mix in expended feel may change due to increased burnup, any such change will be small in comparison to the limits of 10 CFR Part 100. Therefore, the staff finds that the proposed changes will have no significant radiological impact.
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c. ENVIRONMENTAL CONSIDERATION Fursuant to 10 CFR 51.21, 51.32, and 51.35, an environmental assessment and finding of no significant impact have been prepared and published in the Fedaral Register (54 FR 35954) on August 30, 1989. Accordingly, based upon the environmental assessment, the Commission has determined that the issuance of this amendment will not have a significant effect on the quality of the human environment.
CONCLUSION We have 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, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendnent will not be inimical to the common defense and security or to the health and safety of the public.
Dated: August 31, 1989 Principal Contributor:
G. Wunder
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