Since the Fukushima disaster, efforts are made worldwide to improve the accident performance of nuclear fuel. The development of the so called accident tolerant fuel (ATF) comprises both, new fuels and new cladding materials.
Main goal of the fuel development are the increase of thermal conductivity to reduce the thermal capacity of the fuel after termination of the nuclear chain reaction. Examples are developments of UN and U3Si2 fuel.
The goal of the cladding developments are materials releasing less heat and hydrogen if they react with hot steam in the case of an accident. They can be divided into three groups:
- Coated zirconium alloys for instance chromium coatings
- New metallic materials for instance FeCrAl
Even the investigations were initiated to found materials with better severe accident performance than the classical zirconium alloys used, most studies were performed under operational or design basis accident conditions. The research at KIT is focused on the high and very high temperature behavior of promising cladding materials. Experiments on laboratory scale as well at fuel rod simulator bundle scale were and will be performed.
In the presentation, an overview about the work done at KIT on this field will be given. The thermal limits of promising candidate materials for ATF claddings chromium coated Zircaloy, FeCrAl and SiC will be discussed.