Semi-empirical models of actinide alloying

Alloys of Np have been studied less than those of the neighboring elements, U and Pu; the higher actinides have received even less attention. Recent i nterest in Np-237, Am-241 and other actinide isotopes as significant, long- lived and highly radiotoxic nuclear waste components, and particularly the roles of metallic materials in new handling/separations and remediation tec hnologies, demands that this paucity of information concerning alloy behavi ors be addressed. An additional interest in these materials arises from the possibility of revealing fundamental properties and bonding interactions, which would further characterize the unique electronic structures (e.g., Sf electrons) of the actinide elements. The small empirical knowledge basis p resently available for understanding and modeling the alloying behavior of Np is summarized here, with emphasis on our recent results for the Np-Am, N p-Zr and Np-Fe phase diagrams. In view of the limited experimental data bas e for neptunium and the transplutonium metals, the value of semi-empirical intermetallic bonding models for predicting actinide alloy thermodynamics i s evaluated. (C) 1999 Elsevier Science B.V. All rights reserved.