Ceramic Coatings for Clad (The C^3 Project): Advanced Accident-Tolerant Ceramic Coatings for Zr-alloy Cladding

Enhancing the safety of nuclear fuel is an important component in the continued use, and expansion, of nuclear power. One area where safety can be enhanced is enhancing the cladding around the nuclear fuel. Such a coating will enhance further the long term stability of the fuel under normal reactor operation, whilst at the same provide an extra level of insurance should an incident similar to that in Fukushima happen. These new coatings will provide a barrier between the Zircalloy cladding and air/water, which will help to prevent the formation of hydrogen gas from steam formed when there is a loss of coolant accident (LOCA), i.e. the process that happened at Fukushima Daichi, in March 2011.

Using the combined expertise/knowledge from within the UK and US a collaborative research team has been put together to develop such coatings. Two options will be addressed one based on using oxide, such as zirconia, whilst a second will be based on ternary carbide/nitride based materials, such as MAX phases. M(n+1)AX(n) phases have previously been shown to not only recover rapidly from radiation damage, but also excellent thermal/corrosion properties making them ideal for this application.

For the development of new coatings to be used in the current, and future, nuclear reactor fleet, new coatings must be prepared, and examined for stability, under a range of reactor conditions. The experimental programme will address issues such as the preparation of the coating, stability of bonding between coating and fuel, the effects of radiation damage on the interface, and how the enhanced coating increases stability of the fuel to both high temperatures/pressures experienced within a fission core. These experiments will also be used to validate simulations of corrosion, providing a means by which simulations can be reliably used.

One final assessment of the coatings once tested, is how they behave under conditions that model a LOCA event.

The results from this work will be used in developing technologies for existing and future reactor technologies.

This project will impact in many areas primarily technology development, for example new coating technologies which can be applied to those materials where there is a requirement for a lower temperature of fabrication than would currently be ideal. The development of new coatings for use within fission reactors will be the prime driver of this work, such coatings can increase both the lifetime and stability of current fuel assemblies, while at the same time provide a means by which fuel for future, e.g. GenIII and GenIV designs, can be enhanced while still in the development stage. The results form this work can be directly used in developing future designs, and extending the life of the current fleet of fission reactors.

A secondary, although equally important, impact is the development of new collaborations between the US and UK in nuclear materials development. In recent history both have been expanding but, there are still opportunities available by which enhancements in both knowledge and materials developments can still be increased, this is one of those opportunities. Utilising the skills within the UK, and combining them with contrasting skills and capabilities in the US enhances further the quality of outcomes for this work.From a UK stand point, enhancement in our nuclear R&D capabilities will go some way to overcome the gap highlighted by the House of Lords report into nuclear science and engineering. At the same time exposure to US laboratories, and industrial partners will highlight the expertise available in this country, and go some way to ensure the UK is considered a valuable partner in nuclear research worldwide. Since nuclear research has now reached the point where international consortia are considered routine, highlighting the UK as a place to collaborate with can only enhance our future impact in this area.