One of the big problem for engineering a nuclear reactor is the negative impact of neutron bombardment on the steel used to construct the reactor core. Over time, the steel become brittle and less capable of fulfilling its primary function of safely containing the nuclear fuel and the nuclear reaction. When the neutrons hit the crystalline lattice of the steel, the result is dislocation of atoms in the lattice, voids and cracks in the metal and swelling which increases the volume of the metal but decreases the density.
New reactor design are aimed at producing more energy more economically. One way that they will do this is to operate at higher temperatures and greater levels of radiation that current nuclear power reactors. In many power reactors, water is used as a coolant. Water is less corrosive to the materials used to make the reactor core that other possible coolant liquids. However, there are limits to the temperatures at which water is an effective coolant. New reactors will exceed those temperature limits for water cooling. Other coolants such as liquid metals like sodium and lead can function at higher temperatures but they are much more corrosive to the materials in the reactor core.
One solution to the problem of the use of corrosive coolants is to coat the components of the reactor core with some material that is more resistant to corrosion. Of course, whatever substance is used to as a coating must be able to withstand embrittlement caused by the radiation. Researchers at the Istituto Italiano di Tecnologia (IIT) in Milan, Italy have developed a promising coating material for nuclear reactor parts.
The new material from the IIT is an aluminium oxide nanoceramic. (A nanoceramic is "a type of nanoparticle that is composed of ceramics, which are generally classified as inorganic, heat-resistant, nonmetallic solids made of both metallic and nonmetallic compounds. The material offers unique properties." Wikipedia)
This new nanoceramic material is able to withstand embrittlement from radiation and heat which makes it ideal for use in new reactor designs. Instead of becoming harder and cracking from radiation like other materials, the new nanoceramic actually becomes tougher. A technical article about the new material was just published in the September 22, 2016 issue of the Nature journal, Scientific Reports.
The IIT team has been working with nanoceramics for several years, exposing them to radiation and varying the composition to see how their mechanical properties change. Another team at the University of Wisconsin - Madison has been using an electron microscope to analyze the structure of samples from the IIT lab to reveal the effects of the radiation on the material at the atomic level.
This new material is a major breakthrough in coating technology because no other materials tested actually benefits from radiation bombardment. If this nanoceramic material can be brought out of the lab and commercialized, it will make a significant contribution to the safety of new reactor designs.
