Thermal Cycling of Uranium Dioxide - Tungsten Cermet Fuel Specimens

Gripshover, P.J.; Peterson, J. H.

doi:10.2172/972751

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“…The base constituents within CERMET fuels used for high temperature space operations are usually tungsten (W) and uranium dioxide (UO 2 ). There have been many development efforts to fabricate and test W-UO 2 fuel forms at the General Electric (GE) High Temperature Gas Reactor Program Summary Report, 1973a; High Temperature Gas Reactor Program Summary Report, 1973b, Argonne National Laboratory (ANL) Rocket Program Terminal Report, 1966 and National Aeronautics and Space Administration (NASA) Johnson et al, 1965;Marlow and Kaznoff, 1970;Lobsinger et al, 1966;Gedwill et al, 1965;Gripshover and Peterson, 1969;Takkunen, 1967;Sikora and Millunzi, 1968;Lamartine and Hoppe, 1965 as well as basic attempts at characterizing the neutronic effects of tungsten and rhenium additions to critical geometries (Webb and Charit, 2011). The traditional formula for fabricating W-UO 2 elements involves coating spherical UO 2 particles with tungsten to a predetermined tungsten volume fraction (MacInnis and Schulze, 1965;Angelo and Buden, 1985).…”

Section: Introductionmentioning

confidence: 99%

Neutronic effects of rhenium, gadolinia and uranium dioxide addition to a tungsten based fast spectrum space reactor

Webb

Charit

2015

Annals of Nuclear Energy

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a b s t r a c tThe neutronic effects of rhenium (Re), gadolinia (Gd 2 O 3 ) and uranium dioxide (UO 2 ) addition to a W-60 vol.% UO 2 fast spectrum fuel form were investigated relative to a prismatic reactor type using the MCNP5 Monte Carlo code with the ENDF/B-VII.1 cross-section database. The effects of rhenium addition to the cladding tubes and sleeves were studied over the range of 2-25 at.% as well as the corresponding effects on the reactor mass and control drum reactivity swing and neutron energy spectrum. The effects of rhenium addition to the tungsten matrix over the range of 1-5 at.% was also investigated. Lastly, the UO 2 concentration was varied from 55 to 60 vol.% UO 2 and the UO 2 was mixed with Gd 2 O 3 at concentrations ranging from 2 to 10 mol.%. Each configuration was investigated for its effects on the control drum shut down margin both in a dry state and in a submerged state where the reactor was surrounded and flooded with fresh water. The high thermal spectrum absorption cross-section of tungsten, rhenium and gadolinium proved excellent in maintaining the reactor in a subcritical state when submerged in fresh water. However, increases in the concentration of rhenium and gadolinia to the matrix, cladding and fuel kernels were also accompanied by an increase in reactor mass. The control swing within the drums was not influenced by the material compositions; however, the increase in reactor size with varying UO 2 and Gd 2 O 3 concentrations did prevent a large fraction of the neutron population from reaching the control drums. The decrease in neutron population with access to the reflector region containing the control drums caused a loss of reactivity swing in the drums by up to 2.8% Dk/k ($4.36).

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Section: Introductionmentioning

confidence: 99%