Development and Testing of an Irradiation Rig for ATF Cladding Materials: Lessons Learned from Irradiation of SiC/SiC Tubes and Small-Scale FeCrAl Specimens

Abstract

Accident Tolerant Fuel (ATF) claddings are widely developing after Fukushima accident in 2011 to achieve the accident-tolerant properties and improve or replace the current zirconium alloys. New ATF concepts, including SiC-based composites, Ni-Ti alloys, aluminum-containing alloys such as FeCrAl, Mo-based refractory materials, and other promising candidates, are still under development. The JV group conducts programs on ATF structural materials, including the development of new methods and the modification of existing procedures for irradiated claddings. This contribution deals with two prospective ATF materials, SiC/SiC composite and FeCrAl B136Y3, irradiated in newly designed irradiation rig placed inside the LVR-15 reactor fuel for two reactor cycles. Irradiated samples reached the target neutron fluence of about 1,55 × 20 n/cm2 for E > 1 MeV. Different types of samples were irradiated to verify the irradiation rig function. Another objective of the program was to handle and test irradiated ATF claddings in hot cells and to characterize the effects of neutron irradiation on material properties at low damage level around 0.2 dpa and elevated temperature of about 312°C for SiC/SiC and 330°C for FeCrAl. Mechanical testing and microstructural analyses of the SiC/SiC tube revealed the effects of neutron irradiation on material properties. TEM analysis of FeCrAl irradiated in 3 mm discs identified radiation-induced dislocation loops. Thermo-physical property measurements of non-irradiated samples were also performed and discussed.