Fuel for a Supercritical Water Pressurized Heavy Water Reactor

Abstract

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. Therefore, single crystal sapphire is being considered as a sheath/clad material for uranium oxide fuel in a supercritical water PHWR1.

This paper identifies sixteen damage mechanisms as being credible for the refit sapphire fuel. They are binned into three groups: thermal integrity, structural integrity, and compatibility with interfacing components. Even though some material properties of sapphire currently have uncertainties, we expect that a sufficiently robust detailed design of the sapphire fuel can be crafted for the refit reactor.