Fabrication of U-Pu-Zr Metallic Fuel Elements for the Irradiation Test at Experimental Fast Test Reactor Joyo

Abstract

The Central Research Institute of Electric Power Industry and Japan Atomic Energy Agency have fabricated the first sodium-bonded metallic fuel elements in Japan as a collaborative research for the irradiation test at the experimental fast test reactor Joyo. The U-20 wt.%Pu-10 wt.%Zr fuel slugs of 200 mm length and approximately 5 mm diameter were fabricated in a small-scale injection casting furnace using U metal, U-Pu alloy and Zr metal. The fuel slugs met the specifications determined on the basis of the specifications of the Experimental Breeder Reactor II driver fuels in the United States and the results of preliminary casting tests. Each fuel slug was loaded into a ferritic-martensitic stainless steel (PNC-FMS) cladding tube with a few pieces of sodium rods as thermal bonds, the U-10 wt.%Zr thermal insulator and the PNC-FMS reflector in a helium gas atmosphere glove box. After top-end plug welding to the cladding tube and the heat treatment of the welding area, each fuel element was subjected to sodium bonding to fill the annular gap between the fuel slug and the cladding with the melted sodium. After inspection, six metallic fuel elements were manufactured successfully and transferred to the Joyo site.