At 3m tall and 4m wide, the microreactors will weigh less than 40 tonnes. The reactor and power generating equipment will fit inside a container truck, enabling it to be delivered to remote or disaster-hit areas.

They are small enough to be buried underground, mitigating the risk of an accident. The technology could also be used in space exploration.

The microreactors will have a maximum output of 500kw, or one-twentieth of the capacity of typical nuclear reactors that produce more than 1 gigawatt.

Mitsubishi plans to commercialise the technology in the 2030s at the soonest, once it receives approval from Japan and other governments.

The microreactors will have to be made safer than conventional reactors, since they will operate closer to populated areas. The nuclear reactor core, the coolants and all other equipment will be contained in capsule containers that are tightly sealed.

Highly enriched uranium will be used as fuel and will not require replacement during its entire duration of operations of approximately 25 years. Once the fuel is spent, the entire microreactor can be recovered.

Since the reactors will require minimal maintenance, they can be installed underground to reduce risk from natural disasters and terrorism.

Mitsubishi Heavy will also cut the risk of a disaster resulting from a coolant failure. Instead of liquid coolants, the microreactors will adopt solid-state graphite material that is highly thermal conductive.

The graphite surrounds the core and transfers heat to the power generating system during normal operations. If an accident does occur, excess heat from the core is eliminated by natural ambient cooling.

Each microreactor will cost tens of millions of dollars, far less than the US$6 billion or so it would take to build a 1.2 gigawatt nuclear plant.

The cost to produce 1 kilowatt-hour will exceed that of a conventional reactor, but will be in line with the cost it now takes to provide power to isolated islands. The microreactors will enable remote areas to access an economical source of power that is not reliant on carbon.

Nuclear power is receiving another look amid the global decarbonisation push. The European Union this year unfurled a plan to designate nuclear power and natural gas as low-carbon energy alternatives.