Reactivity, Isotopic, and Thermal Steady-State Analysis of Homogeneous Thoria-Urania Fuel

Journal Article · Fri Feb 15 04:00:00 EST 2002 · Nuclear Technology

OSTI ID:20826729

Loewen, Eric P; Weaver, Kevan D; Hohorst, Judith K ^[1]

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1. Idaho National Engineering and Environmental Laboratory (United States)

Recent investigations into the performance and economics of mixed thoria-urania fuel cycles demonstrate potential advantages at high burnup. Initial neutronic and fuel behavior calculations for several ThO{sub 2}-UO{sub 2} mixtures being considered for use in commercial nuclear power plants are described.The Monte Carlo N-Particle -Origen2 Coupled Utility Program (MOCUP) was used to analyze the reactivity characteristics and isotopic concentrations of unit fuel pins/cells and lattice/assembly models as a function of burnup and reactivity. Neutronic results for a three-batch 6-yr cycle for each of three proposed ThO{sub 2}-UO{sub 2} mixtures with the UO{sub 2} enriched to 19.5% {sup 235}U are presented. Neutronic results show that fuels fabricated from ThO{sub 2}-UO{sub 2} mixtures can reach an average discharge burnup of up to 70 MWd/kgHM, which will increase the time between refueling and decrease the production of weapons-grade plutonium by a factor of 3 as compared to all-urania fuel.A version of FRAPCON-3, modified to handle pure thoria and ThO{sub 2}-UO{sub 2} mixtures, was used for the fuel performance and behavior calculations. The new version called FRAPCON-3Th includes the updated material property models for thermal conductivity, specific heat capacity, emissivity, thermal expansion, modulus of elasticity, and melting temperature to predict fuel behavior for pure ThO{sub 2} or ThO{sub 2}/UO{sub 2} mixed fuel. For a concentration of 75% ThO{sub 2}/25% UO{sub 2}, initial fuel performance parameters (peak centerline temperature, gap conductance, thermal expansion, etc.) predicted operating conditions are better than those of current UO{sub 2} fuel. A ThO{sub 2}-ThO{sub 2}/UO{sub 2} thermal conductivity model is still in the development stage. For all fuel calculations, an interim model that interpolates between the Belle and Berman predicted thermal conductivity using a correction factor for radiant heat transport and the MATPRO-predicted thermal conductivity for UO{sub 2} was applied.

• OSTI ID: 20826729
• Journal Information: Nuclear Technology, Journal Name: Nuclear Technology Journal Issue: 2 Vol. 137; ISSN 0029-5450; ISSN NUTYBB
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
BURNUP
ECONOMICS
EMISSIVITY
FUEL CYCLE
FUEL PINS
MELTING POINTS
MIXED OXIDE FUELS
MONTE CARLO METHOD
NUCLEAR POWER PLANTS
PERFORMANCE
PLUTONIUM
REACTIVITY
SPECIFIC HEAT
STEADY-STATE CONDITIONS
THERMAL CONDUCTIVITY
THERMAL EXPANSION
THORIUM OXIDES
URANIUM 235
URANIUM DIOXIDE