Silicon Carbide TRIPLEX Materials for CANDU Fuel Cladding and Pressure Tubes

Abstract

Ceramic Tubular Products (CTP) has been developing and testing advanced Silicon Carbide three-layered tubular components for use as fuel cladding in water cooled reactors, and as channel boxes in Boiling Water Reactors (6” x 6” by 14 foot long components). Tests have been run under simulated LOCA conditions, including steam corrosion at temperatures up to 1600 oC, thermal shock resistance after quenching in water from 1000 oC, and mechanical shock conditions representative of handling and transportation loads. Results have been positive, demonstrating three orders of magnitude increase in accident resistance as compared to traditional Zirconium based materials. This paper reports the results of testing and manufacturing development, and evaluates application to CANDU®’s including: (1) As fuel cladding to replace zircaloy in existing CANDU® reactors. Initially this could involve replacing only the central 7 zircaloy fuel pins with SiC clad fuel pins to achieve a major improvement in accident behavior, (2) Coupling the use of SiC TRIPLEX cladding with Thorium fuel in advanced fuel cycles. This would enable longer irradiation times and conversion to fissile U233 than is possible with zircaloy clad (3) As a replacement for current ZrNb pressure tubes that enable pressure tube lifetimes of 60 years, and (4) As fuel cladding material for Gen IV reactors such as SCWRs, where steel cladding has parasitic neutron absorption properties that are prohibitive.