SPECIAL REPORT | ACCIDENT TOLERANT FUEL
The complexities of developing ATF
Accident Tolerant Fuels are seen to offer both safety and economic benefits. Although some designs under consideration are evolutionary rather than revolutionary, it’s clear that progress is positive
By Judith Perera
THERE IS A GROWING INTEREST worldwide in the development and deployment of accident tolerant fuels (ATFs). Accident tolerant fuels are included in a wider generic group of Advanced Technology Fuels. ATFs are seen to offer both safety and economic benefits for nuclear power reactors with many designs under consideration.
They can be defined as fuels: ● That have potential to enhance the safety in case of a severe accident in a reactor core for a longer time than the current UO2
-zirconium alloy fuel system
● That can maintain or improve fuel performance during normal operation and operational transients
● That are compatible with all aspects of the nuclear fuel cycle (transport, storage, and possible use within a closed fuel cycle)
ATFs mostly involve new cladding and fuel pellet designs that increase the performance and severe accident response times of nuclear fuel. They take advantage of new materials that reduce hydrogen build-up, improve fission production retention, and are structurally more resistant to radiation, corrosion, and higher temperatures. In addition, they are expected to last longer than current fuel designs
and may extend the time between refuellings from 1.5 to 2 years for pressurised water reactors. This would reduce the amount of fuel assemblies needed, leading to less waste production and a reduction in fuel costs. Those technologies that are mature enough to start fuel
qualification and achieve near-term deployment – within the coming decade in the existing fleet of light water reactors (LWRs) and in the LWR-based small modular reactor (SMR) designs – are termed “evolutionary accident tolerant fuels (eATFs)”. There are numerous designs and concepts that could be termed as eATFs, based on features such as enhanced cladding, modified uranium oxide fuel (including dopants), and increased enrichment. A great deal of research and development has been
undertaken to support the introduction of eATFs into commercial nuclear power reactors, with the first eATFs entering service in 2021 as part of a number of test programmes. These tests support the economic and safety cases for reactor core operations and provide preliminary information to anticipate potential impacts on the back end of the fuel cycle when compared with traditional power reactor fuels. This includes during storage, transportation, reprocessing and recycling, and disposal.
Above: The basic assembly design of uranium oxide fuel pellets clad with zirconium alloy tubing has remained the fuel of choice for the vast majority of commercial nuclear power plants
36 | January 2024 |
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