Thermodynamic analysis on the Np–Zr–H system

The thermodynamic data base of the Np–Zr–H ternary system was developed based on the description of its binary constituents, coupling with the calculated enthalpies of formation obtained using the Miedema model and the Griessen–Driessen model. The provisional isothermal sections of the Np–Zr–H phase diagram were calculated using the data base. It was found that the Np–Zr–H ternary system at 972 K includes the liquid phase in the region of low hydrogen to metal ratio. It is pointed out that the composition of the Np–Zr–H hydride should be selected to avoid the hydride fuel melting in designing of a nuclear reactor fuel element.