A feasibility study of using CeO₂as a surrogate material during the investigation of UO₂thermal conductivity enhancement

Abstract

A possible substitution of UO 2 for research purposes is the cerium dioxide (CeO 2 ) owing to its chemical and physical properties. Neutronic properties are different and fission is absent in the case of CeO 2 ; however, similarities were studied recently to have a possibility to compare the neutronic influence of secondary additives into the matrix. This paper deals with increasing the thermal conductivity of UO 2 nuclear fuel on surrogate material (CeO 2 ); the main focus of the research is given on the sintering behaviour of CeO 2 . The incorporation of highly thermally conductive material (SiC) is the investigated concept of thermal conductivity enhancement. Conventional sintering and spark plasma sintering (SPS) were applied to compare the behaviour of CeO 2 and UO 2 reported in the literature. High temperature thermal conductivity measurements did not confirm the positive influence of SiC additive inside the CeO 2 matrix mainly due to grain boundary disruptions. Similar behaviour was also previously reported for UO 2 pellets with SiC.

Sintering trials of analogues of americium oxides for radioisotope power systems

“…The relative densities achieved were 72.2 % to 91.3 % when non-milled powder was used, and 81.4 % to 95.4 % when milled powder was used. Data for particle size and morphology of the powder (in particular whether the powder is lath-shaped) were not reported by Roleček et al [24]. Cold-press-and-sinter of Nd2O3 has been reported [25] using powder with an average grain size of 4 µm, achieving a relative density of 86-89 % but with cracking attributed to a hygroscopic reaction.…”

“…Wang [19] demonstrated the cold-press-and-sinter of CeO2 at a larger powder size of 5 µm; however, this was ball-milled before sintering. Roleček et al [24] reported a comparison of cold-press-and-sintered milled and non-milled powder. The relative densities achieved were 72.2 % to 91.3 % when non-milled powder was used, and 81.4 % to 95.4 % when milled powder was used.…”

“…Roleček et al [24] reported a comparative study on the SPS and cold-press-and-sinter of CeO2. SPS allowed a much reduced processing time (5 min cf 1 hour) and pressure (50 MPa cf 300 MPa); however, there was XRD evidence of reduction to Ce2O3.…”

First-principles investigations on the anisotropic elasticity and thermodynamic properties of U3Si2–Al

“…[1][2][3][4] Traditional UO 2 fuel has the advantages of high melting point, outstanding radiation performance and exceptional compatibility with cladding materials, but it has the disadvantage of low thermal conductivity. 2,5 In the context of the Fukushima nuclear accident, the research on the accident-tolerant fuel system (ATF) has attracted the interests of many researchers. 6,7 Replacing UO 2 with new nuclear material is one of the focuses for the ATF development and ensures that the new fuel has high thermal conductivity and other advantageous properties.…”

Estudo da formação de fases cristalinas por difração de raios X no sistema UO₂-Er₂O₃

“…visto que o óxido de cério é estruturalmente similar ao óxido de urânio: ambos são isoestruturais, i.e. possuem mesma estrutura fluorita, e com parâmetros de rede [62,70] tais que a CeO 2 a U O 2 = 5,40972 5,47127 ≈ 0,9888, sendo o CeO 2 frequentemente utilizado como substituto do UO 2 para fins de simulação de propriedades de pastilhas combustíveis [71,72,73,74] . Utilizando no refinamento Rietveld uma estrutura, denominada aqui de ρ, derivada de uma fase romboédrica observada para o sistema U-La-O, [75,68,76] Incidentalmente, utilizando a função do parâmetro de rede médio para o Figura 6.17 -Algumas regiões em detalhes do refinamento do padrão de difração da pastilha com 9,8 wt% de Er 2 O 3 , com os picos mais intensos de cada uma das fases α, β e ρ indicado.…”