Thermodynamic assessment of the neptunium–oxygen system: Mass spectrometric studies and thermodynamic modelling

A.L. Smith (1) , J.-Y. Colle , O. Beneš , R.J.M. Konings (1) , B. Sundman (2) , C. Guéneau (3, 4)

1 ITU - JRC Institute for Transuranium Elements [Karlsruhe]
2 KTH - Royal Institute of Technology [Stockholm]
3 SCP - Service de Chimie Physique
4 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

Knudsen effusion mass spectrometry measurements on neptunium dioxide are reported in this work, which have allowed to improve the understanding of its vapourization behaviour and solved discrepancies noticed in the literature: the enthalpy of formation of NpO2(g) has been re-assessed and the composition of neptunia at congruent vapourization has been determined at 2262 K. In addition, a thermodynamic model for the neptunium-oxygen system has been developed using the CALPHAD method.

Keywords: CALPHAD; Knudsen effusion mass spectrometry; Neptunium–oxygen system

Domains: Nuclear Theory [nucl-th]; Nuclear Experiment [nucl-ex]

A.L. Smith, J.-Y. Colle, O. Beneš, R.J.M. Konings, B. Sundman, et al.. Thermodynamic assessment of the neptunium–oxygen system: Mass spectrometric studies and thermodynamic modelling. unknown, 2016, 103, pp.257-275. ⟨10.1016/j.jct.2016.07.040⟩. ⟨cea-02381314⟩