Density-functional study of U–Mo and U–Zr alloys

Abstract

Density-functional theory previously used to describe phase equilibria in U-Zr alloys [A.Landa, P. Söderlind, P.E.A. Turchi, J. Alloys Comp. 478 (2009) [103][104][105][106][107][108][109][110] is extended to investigate the ground-state properties of U-Mo solid solutions. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components, and how the specific behavior of the density of states in the vicinity of the Fermi level promotes the stabilization of the U 2 Mo compound. Our calculations prove that, due to the existence of a single -phase over the typical fuel operation temperatures, -U-Mo alloys should indeed have much lower constituent redistribution than -U-Zr alloys for which binodal decomposition causes a high degree of constituent redistribution.

Density-functional study of bcc U–Mo, Np–Mo, Pu–Mo, and Am–Mo alloys

“…Together with our ab initio results obtained previously for U-Mo, U-Am, Pu-U, Pu-Np, and Pu-Am alloys [2,9,11,19,49] these new results will be used to build a thermodynamic database for U-TRU-Mo alloys that are considered to be very promising fuels for fast breeder reactors [4,[50][51][52][53][54][55][56]. …”

“…We found that a significantly larger absolute value of the charge transfer from U atoms in the case of the -U-Mo alloys than in the case of the -U-Zr alloys causes the ponderable negative Madelung energy contribution to the heat of formation of the -UMo alloys in comparison with one for the -U-Zr alloys [2]. This difference in the absolute value of the charge transfer from U atoms results in much higher constituent redistribution in -U-Zr than in -U-Mo fuels where a single -phase field exists and can be retained (quenched) as a metastable phase up to room temperature.…”

“…In our previous papers [1,2] we performed detailed ab initio studies of the fundamental thermodynamic properties of the body-centered-cubic (bcc) or -phase of the U-Zr and U-Mo systems that are candidates as metallic nuclear fuels for fast breeder reactors. We found that a significantly larger absolute value of the charge transfer from U atoms in the case of the -U-Mo alloys than in the case of the -U-Zr alloys causes the ponderable negative Madelung energy contribution to the heat of formation of the -UMo alloys in comparison with one for the -U-Zr alloys [2].…”

“…As was mentioned above, we undertook an ab initio study of the fundamental thermodynamic properties of -U-Mo alloys [2] while thermodynamic properties of U-TRU-Mo alloys have not been modeled yet. Thus, in the present study we report results of ab initio calculations for bcc-based ( ) X-Mo (X = Np, Pu, Am) alloys.…”

Ab Initio Study of Advanced Metallic Nuclear Fuels for Fast Breeder Reactors

“…We later expanded our study to the ternary U-Pu-Zr system [16] as well as to the bcc alloys that plutonium forms with MA [17]. In our recent paper [18] we presented results of ab initio calculations of the heat of formation of the -U-Mo solid solutions. In this study we summarize results published in Ref.…”