کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
7963432 1514145 2018 23 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Experimental thermochemistry of neptunium oxides: Np2O5 and NpO2
موضوعات مرتبط
مهندسی و علوم پایه مهندسی انرژی انرژی هسته ای و مهندسی
پیش نمایش صفحه اول مقاله
Experimental thermochemistry of neptunium oxides: Np2O5 and NpO2
چکیده انگلیسی
Neptunium (Np) compounds are important in the nuclear fuel cycle because of the buildup and long half-life (2.14 Ma) of Np-237 in nuclear waste, especially during long-term disposal in a geological repository. Neptunium in environmental conditions exists mainly in two oxidation states (+5 and + 4) and can substitute for uranium and/or rare earths in solid phases. Yet thermochemical data for solid neptunium compounds are scarce, despite being critical for evaluating the environmental transport of this radioactive and toxic element. Although high temperature oxide melt solution calorimetry has proven very useful in obtaining thermodynamic data for the formation of uranium and thorium oxide materials, it has not yet been applied to transuranium compounds. Continuing a program at Notre Dame to study the thermodynamics of transuranium compounds, we report the first determination of the enthalpies of drop solution of well-characterized neptunium oxides (Np2O5 and NpO2) using oxide melt solution calorimetry in molten sodium molybdate solvent at 973 K. The enthalpy of the decomposition reaction, Np2O5(cr) = 2NpO2(cr) + 1/2O2(g) at 298 K, is determined to be 7.70 ± 5.86 kJ/mol, and this direct measurement is consistent with existing thermodynamic data. The calorimetric methodology is straightforward and produces reliable data using milligram quantities of radioactive materials, and can be applied to many other transuranium compounds.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Nuclear Materials - Volume 501, 1 April 2018, Pages 398-403
نویسندگان
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