Very High Temperature Reactor
The Very-high-temperature reactor (VHTR) is a development of the high-temperature gas-cooled reactors (HTGR), which has been worked on in UK, Germany and the US. It is a graphite-moderated, helium-cooled reactor, which can supply nuclear heat with very high core-outlet temperatures of 1000°C which is useful for hydrogen production or heat for processing in the petrochemical industry.
The VHTR has an intermediate heat exchanger to extract the process heat, meaning it produces both high quality heat as well as electricity.
There are two main ways the fuel can but arranged in the core; either a prismatic block such as operating in Japan, or a pebble-bed core as is the case in China. For the prismatic block reactor, the particles are formed into fuel compacts embedded in the graphite block while the pebble-bed reactor; the particles are instead formed into graphite-coated pebbles.
The VHTR system is the nearest-term hydrogen production system, estimated to be deployable by 2020. It offers the potential for the cogeneration of electricity and hydrogen, alongside process heat applications.
At core-outlet temperatures of 1000°C, VHTR can generate electricity with 50% efficiency and enable nuclear heat application to processes such as steel, aluminum oxide, and aluminum production.
VHTR also has the potential to achieve a high burn-up of fuel, low operation and maintenance costs, modular construction, and many desirable safety characteristics.