Evaluation of weapons grade MOX fuel performance in light water reactors using Comethe computer code
- Texas A and M University, Dept. of Nuclear Eng., Zachry Engineering Center, College Station, TX 77843 (United States)
Both the Russian Federation and the United States are pursuing mixed uranium-plutonium oxide (MOX) fuel in light water reactors (LWRs) for the disposition of excess plutonium from disassembled nuclear weapons. These reactors (PWR, BWR, and VVER-1000) were designed to use uranium oxide fuel. However, behavior of MOX under typical power reactor conditions is different from that of the conventionally used uranium oxide fuel. The present study is focused on assessing the difference in thermo-mechanical behavior of the weapons-grade MOX fuel as compared to the conventionally used uranium oxide fuel. Behavior of the fuel is being analyzed using the COMETHE (Computer code for the mechanical and thermal behavior of fuel rods, version 4D, release 23). COMETHE computer code was developed by Belgonucleaire of Brussels, Belgium, and is licensed to Texas A and M University. COMETHE has a capability to address both UO{sub 2} and MOX. This code has been developed on the basis of extensive irradiation programs over a number of years, which serve to characterize the fundamental processes in the performance of nuclear fuel. Computer simulation of the in-pile irradiation of the fuel pins using COMETHE was accomplished by incorporating the fuel pin design data and irradiation conditions into a COMETHE input file. Once executed, COMETHE generated a set of output files that contain the fuel performance characteristics calculated for the specified time steps throughout the life of the reactor core. The present study led to the development of six COMETHE input files to simulate MOX and UO{sub 2} cases for each of the three reactor types (PWR, BWR, VVER). Fuel pin designs currently utilized in the considered reactors were used for development of the COMETHE input files for both UO{sub 2} and MOX cases, i.e., it was assumed that no fuel pin, reactor design, or operation conditions changes will be adopted during transition of these reactors from UO{sub 2} to MOX. The fuel performance criteria addressed in this study included: (1) thermal behavior, (2) fuel pin dimensional changes, (3) pellet-clad mechanical interaction, and (4) efficiency of plutonium consumption. COMETHE predicted that MOX fuel pins would have a higher fuel centerline temperature than UO{sub 2} fuel pins for the same irradiation conditions. The fission gas generation rate was found to be approximately equal for both fuels, however the fraction of the fission gas released into the free volume of the fuel pin was higher for the MOX, resulting also in the higher fuel pin inner pressure. The axial elongation did not differ between MOX and UO{sub 2}, but the radial growth due to fission induced swelling was predicted to be higher for the uranium oxide fuel. As a consequence of higher radial growth, the value of the clad hoop strain was significantly higher for the UO{sub 2} cases. COMETHE predicted that approximately one-half of the Pu-239 (major component of the weapons Pu) would be consumed for the considered burnups of 50 GWd/tox. Despite predicted differences in thermo-mechanical behavior of MOX and UO{sub 2} fuels, preliminary estimate indicates that during normal reactor operation these deviations remain within the limits foreseen by the fuel pin design.
- Research Organization:
- American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 23142293
- Resource Relation:
- Conference: Global'99: International Conference on Future Nuclear Systems - Nuclear Technology - Bridging the Millennia, Las Vegas, NV (United States), 29 Aug - 3 Sep 1999; Other Information: Country of input: France; 1 ref.; available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (US)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
BWR TYPE REACTORS
COMPUTERIZED SIMULATION
FISSION
FISSION PRODUCT RELEASE
FISSION PRODUCTS
FUEL PINS
FUEL RODS
IRRADIATION
MIXED OXIDE FUELS
NUCLEAR WEAPONS
PLUTONIUM
PLUTONIUM 239
PLUTONIUM OXIDES
REACTOR CORES
REACTOR DESIGN
REACTOR OPERATION
URANIUM
URANIUM DIOXIDE
WWER TYPE REACTORS