ML20043G734
| ML20043G734 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 06/11/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043G730 | List: |
| References | |
| NUDOCS 9006210071 | |
| Download: ML20043G734 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS,16 AND 6 TO FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 HOUSTON LIGHTING & POWER COMPANY C1TY PUBLIC SERVICE BOARD OF SAN ANTONIO I
CENTRAL POWER AND LIGHT COMPANY CITY OF AUSTIN. TEXAS DOCKET NOS. 50-498 AND 50-499 SOUTH TEXAS PROJECT, UNITS 1 AND 2
- 1. 0 INTRODUCTION By application dated March 1, 1990 (ST-HL AE-3387), Houston Lighting & Power Company, et al.
(the licensee) requested changes to the Technical Specifica-tions (Appendix A to Facility Operating License Nos. NPF-76 and NPF-80) for the South Texas Project, Units 1 and 2.
The proposed changes would change Technical Specification (TS 5.3.1) to increase the maximum fuel enrichment to 4.5 weight percent Uranium 235.
The current value for enrichment is 3.5 weight percent.
The proposed change consisted of allowing Westinghouse 17x17 standard extra length (STD/XL), optimized (OFA), and VANTAGE $ (V5) fuel with a maximum enrichment of 4.5 weight percent (w/o) U-235 to be stored in the fresh fuel storage racks at South Texas Units 1 and 2.
The staff has previously approved storage of 4.5 w/o Westinghouse 17x17 fuel in the high dontity spent fuel storage rackt..
The licensee did not propose any change to the presently approved core average burnup of 23,740 megawatt days / metric ton.
2.0 EVALUATION The fresh fuel storage racks consist of cells on a 21-inch centor-to-center spacing.
Under normal conditions, fresh fuel is stored in these cells in a dry (air) condition.
However, the staff requires the dry sto* age racks to be designed so that the effective multiplication factor (k-eff' for the racks fully flooded with pure water is no greater than 0.95.
TN staf f also requires the dry storage racks to be analyzed for extreme, low-dr.isity water or other hydrogenous material as may occur for fog, mist, and fire-fighting foam.
For this latter case, the extreme, low-density water or other hydrogenous material must result in a maximum k-ef f no greater tiian 0.98.
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9006210071 900611 PDR ADOCK 05000498 P
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2-The calculation of k-ef f makes use of the KENO IV three-dimensional Monte Carlo theory computer code with neutron cross sections generated by the AMPX system of codes.
These codes were benchmarked against a series of critical experiments which included characteristics similar to the South Texas fresh fuel racks.
These comparisons resulted in a model bias of +0.0083 and a 95/95 probability / confidence uncertainty of 0.0018 in the model bias.
The worst case model of the fresh fuel storage racks is bared on the minimum thickness of the sheet metal of the rack as well as a fuel enrichment of 4.55 w/o U-235 to account for manufacturing variations.
Both of these assumptions are conservative.
For the full density moderation analysis, the fuel array is assumed to be infinite in lateral and axial extent.
This is conservative as it precludes any neutron leakage from the array.
The maximum worst case k-off is calculated to be 0.9252, meeting the NRC acceptance criterion of no greater than 0.95.
For the low density optimum moderation analysis, the fuel array is finite in all directions and the concrete walls and floor are modelled.
This is conserva-tive for low water density conditions since the presence of concrete reflects neutrons back into the fuel array more efficiently than they would be with just low density water.
The maximum worst case k-eff is calculated to be 0.9361, thereby meeting the NRC acceptance criterion of no greater than 0.98.
In addition, the staff concludes that these and other appropriate uncertainties have been considered and have been determined at least at a 95% probability 95% confidence level and are acceptable.
The fresh fuel racks are maintained in a dry environment under normal conditions.
The worst case accident scenarios are the introduction of full density and low density moderator, the results of which have been shown to be acceptable.
3.0 SUMARY Based on the review described above, the staff finds the criticality aspects of storage of Westinghouse 17x17 fuel with maximum enrichment of 4.5 w/o U-235 in the South Texas Units 1 and 2 fresh fuel storage racks meet the requirements I
of General Design Criterion d for the prevention of criticality in fuel storage and handling.
The aff has previously approved the South Texas high density spent fuel racks fer Atorage of Westinghouse fuel with enrichments up to 4.5 w/o U-235. Therefore, the maximum enrichment limit of reload fuel given in Technical Specifice' ion 5.3.1 can be increased to 4.5 w/o U-235.
4.0 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 Reaister on June 8, 1990 (55 FR 23492).
Accordingly, based upon the environmental assessment, the Commission has determined that issuance of these amendments will not have a significant effect on the quality of the human environment.
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5.'0 CONCLUSION I
Based upon its evaluation of the proposed changes to the South Texas Project, Units 1 and 2, Technical Specifications, the staff has concluded that:
(1) p
,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 the amendments will not be inimical to the common defense and security or to the health and safety of the public.
The staff, therefore, concludes that the proposed changes are acceptable.
t Date:
June 11. 1990 Principal Contributor:
L. Kopp t
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