A new fission-fusion hybrid reactor will be assembled at Russia’s Kurchatov Institute by the end of 2018, Peter Khvostenko, scientific adviser of the Kurchatov complex on thermonuclear energy and plasma technologies, announced on 14 May. The physical start-up of the facility is scheduled for 2020.
The hybrid reactor combines the principles of thermonuclear and nuclear power – essentially a tokamak fusion reactor and a molten salt fission reactor. Neutrons produced in a small tokamak will be used be captured in a molten salt blanket located around tokamak. The facility will use thorium as a fuel, which is cheaper and more abundant than uranium. Moreover, unlike a fusion reactor, a hybrid will not require super high temperatures to generate energy.
Hybrid reactors reduce the impact of the nuclear fuel cycle on the environment. The concept combines conventional fission processes and fusion reactor principles, comprising a fusion reactor core in combination with a subcritical fission reactor. The results of the fusion reaction, which would normally be absorbed by the cooling system of the reactor, would feed into the fission section, and sustain the fission process. Thorium in a molten salt blanket will enable breeding or uranium-233.
Some of the expected advantages include:
- Utilisation of actinides and transmutation from long-lived radioactive waste;
- An increase in energy recovered from uranium by a large factor;
- The inherent safety of the system, which can be shut down rapidly; and
- High burnup of fissile materials leaving few by-products.
The hybrid fission-fusion reactor is seen as a near-term commercial application of fusion pending further research on pure fusion power systems.
The first Russian design of a hybrid reactor was developed in 1977 by Yevgeny Velikhov and Igor Golovin. The past few years have seen the design and upgrade of the original T-15 tokamak and other test beds and facilities at the Kurchatov Institute as physical prototypes for the Fusion Neutron Source (FNS) as well as development of the DEMO-FNS and design of a Pilot Hybrid Plant (PHP) for transmutation, tritium and fissile isotope breeding.
The institute began working on the DEMO-FNS in 2013. It will comprise a reactor in which neutrons produced during a thermonuclear reaction will be used to generate fissile materials from uranium-238, which can be used as fuel in a nuclear reactor. Demonstration of the DEMO-FNS project is planned for 2023, and the PHP will be built by 2050.
"The hybrid tokamak is now called the T-15MD, which is a large installation,” said Khvostenko. “At the end of the year we have to assemble it on the site of the old T-15 which we dismantled in order to build a new one on its foundation.” He added that in 2020 there would be a physical launch of a new facility, and scientists will work on the technologies that "are necessary for a thermonuclear neutron source precisely for a hybrid reactor”.
The experience gained should also feed into the International Experimental Thermonuclear Reactor (Iter) under construction in France. Russian scientific organisations are responsible for the manufacture of 25 systems for Iter. The Institute of Nuclear Physics (INP) of the Siberian Branch of the Russian Academy of Sciences will become the centre for integration of foreign participants in Iter. Components made in different countries will be assembled and tested at the INP site. The first plasma of Iter is planned for 2025.