ML20046C824
| ML20046C824 | |
| Person / Time | |
|---|---|
| Issue date: | 06/24/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045E001 | List: |
| References | |
| NUDOCS 9308120239 | |
| Download: ML20046C824 (4) | |
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ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO TOPICAL REPORT BAW-10184P "GDTAC0 - URANIA GADOLINIA FUEL PIN THERMAL ANALYSIS CODE" B&W NUCLEAR TECHNOLOGIES 1
INTRODUCTION By letter of April 30,1992 (Ref.1), B&W Nuclear Technologies (B&W) submitted Topical Report BAW-10184P, "GDTACO - Urania Gadolinia Fuel Pin Thermal Analysis Code" (Ref. 2) for U.S. Nuclear Regulatory Commission (NRC) review.
The topical report documents modifications to a currently approved B&W Fuel Company (BWFC) computer code, TAC 03 (Ref. 3), that incorporate the physical material properties of gadolinium oxide (gadolinia), for calculating the thermal performance of urania-gadolinia fuel pins. The code retains the thermal-mechanical model from the currently approved code.
The NRC has reviewed similar codes in which gadolinia material was modeled as a burnable absorber and has accepted them for referencing in licensing applications.
B&W wil' use the GDTACO code, with the new gadolinia material property database, to perform calculations for the reload designs of pressurized water reactors (PWRs), that is, to calculate fuel melting, fuel rod internal gas pressure, cladding strain, cladding creep collapse code initialization, and loss-of-coolant accident (LOCA) 3nalyses initialization. The creep collapse initialization calculations will include predictions of rod internal gas pressure and cladding temperatures. The LOCA initialization calculations will include predictions of the local volumetric average fuel temperature as a function of linear heat rate and burnup, fuel rod internal gas pressure, gas composition, and fuel rod dimensions and characteristics. These values will 9308120239 930624 PDR TOPRP Et1VBW C
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2 EVALUATION OF THE TOPICAL REPORT 1
The NRC staff was supported in this review by a technical assistance contract with Pacific Northwest Laboratory (PNL).
The staff has adopted the findings recommended in the PNL technical evaluation report (TER) (Enclosure 2), as modified by this safety evaluation.
GDTACO includes models for pellet-to-cladding gap conductance, fuel densification and swelling, cladding creep and deformation, gap closure, and fission gas release calculations for individual fuel pins using urania-gadolinia fuel pellets as an integral burnable absorber.
GDTAC0 uses the same methodology (TAC 03) as that the NRC has reviewed and accepted (Ref. 4) for urania-only fuel pin thermal performance analysis.
B&W participated in a program sponsored by the U.S. Department of Energy to develop and demonstrate an advanced fuel assembly design incorporating urania-gadolinia.
Five demonstration lead test assemblies, designated as Mark-GdB with 15x15 fuel lattice designs, were irradiated in the Duke Power Company i
Oconee Unit I core for one to four cycles of operation, with one fuel assembly achieving a burnup of 58,300 megawatt-days per metric ton of initial uranium j
(mwd /MTU). Data from both nondestructive poolside and hot-cell facility fuel examinations were used by BWFC to develop and benchmark the accuracy of the analysis models in GDTACO.
B&W performed comparisons.for both 4 and 8 weight percent (wt%) gadolinia concentratiors, with burnups ranging from 2,160 to 49,780 mwd /MTU, showing good agreement between the measured and calculated fuel densities presented.
In Topical Report BAW-10184P, B&W also compares the GDTACO calculational models with published measurements for thermal diffusivity, specific heat, and fuel melting point data for urania-gadolinia material of up to 12 wt% concentration. These comparisons are used to
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validate B&W's use of GDTACO to analyze reload cores for PWR units with both BWFC Mark-B (15x15) and Mark-BW (Westinghouse 17x17) fuel lattice designs.
B&W will use these methods to calculate the thermal-mechanical characteristics of individual fuel rods containing urania-gadolinia fuel pellets for PWR reload cores. These calculations will assist B&W in designing and licensing these reload cores for its utility fuel customers, including analyzing fuel bundle design and core loading patterns, and supplying data for safety analyses.
3
SUMMARY
AND CONCLUSIONS i
The staff has reviewed Topical Report BAW-10184P and finds it acceptable for PWR reload licensing applications of urania-gadolinia fuel, as discussed in I
the enclosed TER.
This acceptance applies to gadolinia concentrations up to 8 wt% nominal (8.3 wt% maximum pellet) for BWFC Mark-B and Mark-BW fuel types.
j B&W has committed to analyze both the urania-only and urania-gadolinia rods on a cycle-specific basis for each reload licensing application.
The staff concludes that the GDTAC0 methodology, as validated by B&W, can be i
applied to steady-state PWR calculations for the reload applications discussed herein.
B&W has demonstrated that this methodology is sufficiently accurate for use in PWR licensing applications, including performing thermal-mechanical reload analysis and producing data for safety analyses initialization.
The approved GDTACO code may be used only for the range of fuel design j
l configurations and core design parameters that were verified in the topical report. Any fuel or core designs with significant differences that might be introduced must be further validated by B&W or the licensee.
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REFERENCES 1.
Letter from J. H. Taylor (B&W Nuclear Technologies) to Document Control Desk (NRC),
" Submittal of Topical Report BAW-10184P, GDTACO - Urania Gadolinia Fuel Pin Thermal Analysis Code, May 1992," JHT/92-90, April 30, 1992.
2.
BAW-10184P, "GDTACO - Urania Gadolinia Fuel Pin Thermal Analysis Code,"
B&W Fuel Company, Lynchburg, Virginia, May 1992.
3.
BAW-10162P-A, " TAC 03 - Fuel Pin Thermal Analysis Computer Code," B&W Fuel Company, Lynchburg, Virginia, October 1989.
4.
Letter from A. C. Thadani (NRC) to J. H. Taylor (Babcock & Wilcox),
" Babcock & Wilcox Topical Report BAW-10162P, ' TAC 03 - Fuel Pin Thermal Analysis Computer Code,'" August 14, 1989.
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