The Nikkei reports that Mitsubishi Heavy Industries (MHI)is moving ahead with its plans to develop and commercialize nuclear microreactors—reactors small enough to be delivered on trucks—by the end of the next decade. At 3 meters tall and 4 meters wide, the microreactors will weigh less than 40 tons. The reactor and power generating equipment will fit inside a standard 40' cargo container.

From an MHI presentation at a 2021 IAEA technical meeting.

The microreactors will have a maximum electrical output of 500kW. Multiple microreactor units could be combined to provide larger total power output. Mitsubishi plans to commercialize the technology in the 2030s at the soonest, once it receives approval from Japan and other governments.

Based on an all-solid-state core concept, the microreactor uses a highly thermal conductive graphite-based material that removes heat from core without liquid coolant.The nuclear reactor core and all other equipment will be contained in capsule containers that are tightly sealed.

MHI is planning mock-up tests from 2023 to 2025 to verify the cooling function—i.e., the passive core cooling by natural heat transfer without power source, water source, and operator action. The tests will not use nuclear fuels.

After those tests, prototype testing is planned to be performed from 2026 to 2030 to verify various features of the microreactor such as long-term operation, start-up/shutdown, and safety system functions, including passive shutdown and containment.

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.

Each microreactor is projected to cost tens of millions of dollars.