Researchers at Russia’s AA Bochvar Research Institute of Inorganic Materials (VNIINM – part of TVEL) together with specialists from the Research Institute of Atomic Reactors (NIIAR – part to Rosatom) have completed initial tests of samples of products made from silicon carbide in NIIAR’s BOR-60 research reactor.

Shell samples with various reinforcement methods (biaxial frame, triaxial frame, nanovoloclane) were exposed. The main goal of the study is to obtain the first experimental data in Russia on changes in the key physical and geometric parameters of silicon carbide products after reactor exposure.

Earlier, scientists at VNIINM received samples of experimental cladding for fuel rods made from composite material based on silicon carbide (carbon silicon). Development is being carried out as part of the Tolerant Fuel Creation Programme or accident tolerant fuel (ATF). New data are needed to develop and justify the industrial technology for the serial production of silicon carbide cladding for light water reactors.

The specificity of silicon carbide-based materials is that they have high mechanical strength, wear resistance and thermal conductivity, as well as corrosion and radiation resistance. At the same time, they are brittle and with low-plasticity. Silicon carbide fibre, developed at VNIINM, evenly redistributes the load on the reinforced high-strength braided fibre frame, thereby making cladding more durable. According to Rosatom scientists, silicon carbide is potentially one of the most promising options for ATF cladding, but it is also the most technologically complex (silicon carbide fibre fuel rods cannot be manufactured using technology that has been used on metals for decades).

In theory, silicon carbide cladding will not only minimise risks, but completely eliminate the vapour-zirconium reaction at nuclear power plants,” explained Fyodor Makarov, Chief expert of the Materials Science & Technology Department of Composite, Magnetic & Special Materials at VNIINM. [Currently most fuel rods use zirconium as cladding]. “Thus, with the introduction of silicon carbide fuel rods, there will be no need for some safety systems, which will make it cheaper to build nuclear power units. Also, their use can increase the efficiency of modern reactors by increasing fuel burnout and the duration of the fuel campaign."

Image courtesy of Rosatom