Modeling and Simulation of Thermophysical Properties of Minor Actinides-Containing Oxide Fuels
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1043-T09-06
Modeling and Simulation of Thermophysical Properties of Minor Actinides-Containing Oxide Fuels Masahito Katayama1, Jun Adachi1, Ken Kurosaki1, Masayoshi Uno1, Shuhei Miwa2, Masahiko Osaka2, Kenya Tanaka2, and Shinsuke Yamanaka1 1 Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, 565-0871, Japan 2 Japan Atomic Energy Agency, Narita-cho 4002, Oarai-machi, Higashiibaraki-gun, Ibaraki, 3111393, Japan ABSTRACT The molecular dynamics (MD) calculation was performed for minor actinide (MA: Np and Am)-containing mixed oxide (MOX) fuels, U0.7-xPu0.3MAxO2, in the temperature range from 300 to around 2500 K to evaluate the thermal expansion, heat capacity, and thermal conductivity. The MD results showed that the calculated heat capacity and thermal conductivity were similar in all the composition ranges, indicating that MA scarcely affected the thermal properties of the MOX fuel in the perfect crystal system.
INTRODUCTION The minor actinide (MA) contained mixed oxide (MOX) fuels, (U,Pu,MA)O2, are candidates for advanced fuels for fast breeder reactors and/or transmutation reactors [1,2]. Although the physical properties of (U,Pu,MA)O2 are quite important to understand the fuel performance and integrity, the data have been scarcely reported due to the difficulties associated with the high radiation fields and scarcities of the MA resources. The thermal conductivity of (U,Pu,MA)O2 have been reported by Morimoto et. al. [3,4], but the other thermal properties such as the thermal expansion and heat capacity of (U,Pu,MA)O2 have not been reported. In our previous works, the thermal properties of the oxide fuels such as UO2, PuO2 and MOX [5-7] have been evaluated by the molecular dynamics (MD) simulation. From these studies, it was found that the MD simulation is very effective to evaluate the physical properties of the oxide fuels. Therefore, in the present study, the MD calculation was performed on the Npcontaining MOX fuels (U0.7-xNpxPu0.3O2 (x = 0, 0.05, 0.1, 0.12, 0.15)) and the Am-containing MOX fuels (U0.7-xPu0.3AmxO2(x = 0, 0.016, 0.03, 0.05, 0.1, 0.15)) to evaluate the thermal expansion, heat capacity, and thermal conductivity.
CALCULATION PROCEDURE The MD calculations for (U,Pu,MA)O2 were performed for a system of 768 ions (256 cations and 512 anions) initially arranged in the CaF2 type crystal structure. The calculation was performed using an MD program based on MXDORTO [8] in the temperature range from 300 to around 2500 K. The temperature and pressure of the system were independently controlled through a simple velocity scaling method and/or a combination of methods proposed by Andersen [9] and Nose [10].
As the potential function and the ionic model, we employed Morse type potential with the Busing-Ida term (Eq. 1) and the partial ionic model [11,12]. U ij (rij ) =
zi z j e 2 rij
+ f 0 (bi + b j ) exp(
{
a i + a j − rij bi + b j
)−
ci c j rij 6
},
(1) where f0 equals 4.186, zi and zj are the effective part
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