High temperature heat capacity of (U,Am)O2
| Autor: | Epifano, E., Benes, O., Valu, OS., Zappey, J., Lebreton, F., Martin, P., Gueneau, C., Konings, R. |
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| Přispěvatelé: | CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), amplexor, amplexor |
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | NuFuel 2017 NuFuel 2017, Sep 2017, Lecco, Italy NuFuel 2017, Sep 2017, Lecco, Italy. 2017 |
| Popis: | International audience; Minor actinides (MAs), i.e. Np, Am and Cm, are produced in the nuclear fuel during in-pile operation. After plutonium extraction, these elements are the main responsible for the long-term radiotoxicity of the remaining high level waste. In order to achieve a nuclear fuel cycle with low environmental impact, it is essential to partition and transmute MAs into stable or short-lived nuclei. A thorough knowledge of the thermodynamic properties of advanced nuclear fuels to which minor actinides have been incorporated is essential for the safe use of future Generation IV reactors. In this work, the enthalpy increments with temperature of (U, Am)O2 compounds- which are promising transmutation targets- were measured in the 470-1750 K range by drop calorimetry for Am/(Am+U) ratios equal to 0.32, 0.39, 0.49, 0.58 and 0.68. Then, the heat capacity functions of these five investigated compositions were obtained by derivation of the enthalpy data. The results of this work are compared to the heat capacity and enthalpy functions reported in the literature for the U0.9Am0.1O2±x, U0.8Am0.2O2±x mixed oxides [3], UO2 [1] and AmO2 [2]. For the latter, the experimental data are limited to 1080 K and the enthalpy function was extrapolated above this temperature, even if stoichiometric AmO2 is not stable at high temperature and starts to be reduced (AmO2-x). An excess contribution to the enthalpy increment is found for T>1100 K in the compositions with Am/(Am+U)≥0.4. A possible explanation for this anomalous increase of the enthalpy function could be the formation of oxygen vacancies at high temperature. Therefore, in order to better understand the occurring phenomena, the experimental data were compared to thermodynamic computations based on the CALPHAD method |
| Databáze: | OpenAIRE |
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