Due to the Great East Japan Earthquake in 2011, the Fukushima Nuclear Power Plant suffered an accident in which it was impossible to cool the reactor due to the damage of a 10m high tsunami. Like the Chernobyl nuclear accident in 1986, it has been recorded as a major accident up to level 7 of the international nuclear accident class. To prevent such an accident, it is said that a small reactor that can be safely operated with only natural cooling even in a power loss state is being developed.
NuScale Power is developing a small reactor. Instead of building one large reactor, the company’s approach could cut the construction schedule in half by constructing 12 modular reactors and connecting them later. It also has a passive cooling design that does not rely on pumps and generators that are subject to emergency failure, allowing the reactor to be installed in an underground containment vessel to maintain a safe state in the event of an operator absence or power loss.
Small reactors have the advantage of not always running like large reactors. It can be shut down in a relatively short time, and each reactor can operate for up to two years, so it is like a battery that can be charged for two years.
In the United States, nuclear reactor construction requires certification by the Nuclear Regulatory Commission, but the company passed the first stage evaluation in April last year and plans to build and operate the first power plant in 2026. However, the scientists’ association (ucsusa.org), a non-profit for scientists, is concerned that Newscale Power believes its reactors are safe and do not need to meet the same criteria as large reactors. It also argues that there is a potential for problems with passive cooling designs. Related information can be found here .