2017 | AFC ACCOMPLISHMENTS 149 U-Pu-Zr system.The first revision (in 2016) contained information about the elements, binary alloys, and ternary alloys in the U-Np-Pu- Am-La-Ce-Pr-Nd-Zr system.This Handbook, the second revision, adds information about alloys whose nominal compositions include at least four elements. Each of the revisions includes information about phases and phase diagrams, heat capacities, thermal expansion, and thermal conductivities and diffusivities for the materials it covers.The Handbook has a strong bias in favor of experimental data when available, but supplements the experimental data by modeling results as needed.The Handbook contains numerous references to other modeling papers. The organization of the 2017 revision of the Handbook is significantly different from that of earlier versions, and presents all of the available information about each material or group of related materials together. This organization is intended to make it easier to compare materials with similar compositions (for example, to assess whether addition of minor actinides significantly changes the properties of U-Pu-Zr alloys, or to understand any changes caused by incorporation of rare-earth elements into these alloys). Because of its size, the 2017 revision has been split into two documents: Part 1 contains information about U-Zr, Pu-Zr, U-Pu, and U-Pu-Zr alloys with and without minor actinides (Np,Am, Cm), rare-earth elements (La, Ce, Pr, Nd, Gd) andY. Part 2 contains information about elements and other alloys in the U-Np- Pu-Am-La-Ce-Pr-Nd-Zr system. References considered for the 2017 revision of the Handbook were published from the late 1930s through 2017. Accomplishments: The majority of the research and writing for this revision of the Handbook was done by the Principal Investigator (PI), who is an Idaho National Laboratory (INL) employee. Some information was obtained from INL publications (including some that are not generally available).Authors of these publications are Douglas E. Burkes, James I. Cole, Randall S. Fielding, Steven M. Frank,Thomas Hartmann,Timothy A. Hyde, Dennis D. Keiser, Jr., J.Rory Kennedy,Andrew. Maddison, Robert D. Mariani, Scott C. Middlemas,Thomas P. O’Holleran, Cynthia A. Papesch, Bulent H. Sencer, and Leah N. Squires.Although some of these people are no longer employed at INL, all were INL employees when they performed the work used in the Handbook. Personnel from the INL Research Library provided invaluable help in finding obscure references, Dr. Pavel Medvedev assisted with Russian- language translation, and Dr. Steven Hayes and Dr. Steven Frank provided insight and valuable guidance. It is expected that the Metallic Fuels Handbook will be a multi-year project with new versions available periodically. Each version will update the data in the previous versions, as well as expand the scope of the Handbook.The original Handbook (in 2015) included information about elements and alloys in the Provides a single source of information about important properties of materials in the U-Np-Pu-Am-La-Ce-Pr-Nd-Zr system and a critical assessment of the information based on an extensive survey of widely scattered, often obscure, sources.