Surface Alloying of Boron into Zirconium-Alloy Fuel Cladding Material

摘要

High neutron cross-section elements such as boron are presently added as IFBAs (Integral Fuel Burnable Absorbers) to the UO_2 fuel pellets to counteract initial reactivity in nuclear reactors. This addition has to be made in separate nuclear-regulated facility and adds 20 to 30% to the manufacturing cost of the fuel. Other manufacturing issues that impact cost and performance are maintaining the correct levels of dosing, the reduction in fuel melting point due to IFBA additions, parasitic neutron absorption at fuel's end-of-life, and build-up of pressure due to the formation of transmutation gases. These drawbacks can be overcome if the IFBA element is alloyed into the outer surface of the cladding tube, rather than as additions to the fuel pellets as is presently done. With this objective, this research is aimed at investigating the feasibility of alloying boron into the zirconium alloy fuel clad material using an intense ion beam process developed at Sandia National Laboratories. The thermal stability of the alloyed layer was tested in pressurized steam autoclaves at Westinghouse.