Fuel for a supercritical water pressurized heavy water reactor

Fuels for current water-cooled power reactors are primarily sheathed/clad in Zircaloy-4. While Zircaloy-4 has proven to be highly successful, it loses strength rapidly at temperatures above those of current reactor cooling systems. This makes Zircaloy-4 an unsuitable material for fuel sheath/cladding in a supercritical water-cooled reactor that operates at considerably higher coolant temperatures. While stainless steel can be used — and has been tested — at higher temperatures than Zircaloy-4, it absorbs significantly more neutrons. This makes it a poor choice for PHWRs that are designed for high neutron economy. This paper examines the use of single-crystal sapphire as a sheath/clad material for uranium oxide fuel in a supercritical water PHWR. Single-crystal sapphire is a non-metallic material that has good strength at high temperatures. It also exhibits high resistance to oxidation/corrosion. These qualities make it an appealing material for applications in supercritical water reactors. In this paper, the focus is on the potential failure modes of sapphire-clad oxide fuel in a supercritical water reactor – with the objective of identifying the feasibility and strategy for the above application. (author)