On 11 March 2011, Japan was hit by an 9.0 magnitude earthquake and tsunami that caused a major nuclear accident at the Fukushima Daiichi Nuclear Power Plant. It was the most catastrophic nuclear accident since Chernobyl, and the only one to be classified as Level 7 on the International Nuclear Event Scale. One of the causes of the disaster was that the reactor’s primary fuel cladding lacked adequate protection and thus was catastrophically damaged during the earthquake. To prevent similar accidents from happening in Europe, the EU-funded PLASTICERA project is developing a new nanoceramic coating. The solution has the potential to drastically reduce the chances of an accident in a conventional light-water nuclear reactor (LWR). According to PLASTICERA project coordinator Fabio Di Fonzo, nuclear energy is one of the key scalable technologies we have for fighting climate change. “But before we can leverage this technology, we need to create safer and more sustainable ways of producing nuclear energy,” he says. “PLASTICERA represents a big step towards achieving this goal.” Di Fonzo, a technologist and group leader from the Nanomaterials for Energy and Environment Laboratory at the Istituto Italiano di Tecnologia’s Center for Nano Science and Technology, supervised the work of Erkka Frankberg, a rising star of material science research and Marie Skłodowska-Curie fellow. The research was undertaken with the support of the Marie Skłodowska-Curie Actions.
From concept to reality
PLASTICERA is a concept still on paper. It uses amorphous oxide thin films to protect the primary fuel cladding from being damaged during a nuclear accident. “The idea is that the oxide thin film can provide a unique combination of a strong oxygen diffusion barrier with the capability of accommodating the plastic strain originating from the fuel bar’s thermal expansion,” explains Frankberg. This functional coating should then significantly delay the onset of uncontrollable degradation of the primary fuel cladding. “This would allow for timely emergency cooling and a drastic reduction in the production of explosive hydrogen gas within the reactor. The production of such gas is the major threat for any nuclear power plant using water as coolant and zirconium as fuel cladding,” adds Di Fonzo. With the support of EU funding, Di Fonzo and Frankberg aimed to make this concept a reality. Using a range of disruptive material manufacturing technologies, they began producing such ceramic materials as amorphous oxides – a prerequisite for low temperature plasticity. They then tested these materials’ mechanical and corrosion properties in an LWR simulation resembling both normal and emergency operating conditions.
The quest continues
According to Di Fonzo, the researchers may have found the Holy Grail of material science: a ductile amorphous ceramic, also known as a ductile glass. “Although we have not yet found a final solution to the issues related to LWR, we did demonstrate the possibility of fabricating nanoceramic materials with unprecedented mechanical properties like plasticity,” he remarks. “Of particular importance is our demonstration that alumina glasses are ductile in tension – a first in ceramics.” However, because alumina dissolves in LWR conditions, the quest for PLASTICERA continues. “We are currently working on other nano and amorphous ceramics offering the same mechanical properties as alumina but that can withstand harsh LWR conditions,” concludes Frankberg.
PLASTICERA, nuclear energy, nuclear accident, Fukushima Daiichi disaster, Chernobyl, fuel cladding, nanoceramic coating, light-water nuclear reactor