Recently the so-called “mini” or small and modular reactors have attracted a lot of attention. Since 2008, several small private companies have been created in the United States to support the design development, patenting, licensing and commercialisation of several new SMR concepts. The design concepts of such reactors were analysed in this study. The conclusions are as follows:

• The new small and modular (‘mini’) reactor concepts being developed in the United States fit well into the known technology lines for nuclear reactors. The new US small and modular reactors (NuScale, mPower, New Hyperion Power Module, and ARC-100) share many of their design attributes with other small reactor design concepts being developed in countries other than the United States. It is their repeated use of the three attributes, namely:

— multi-module plant option;

— option of flexible capacity addition/deletion; and

— underground location of the reactor modules;

that distinguishes most of the new US small and modular reactors from other small reactor concepts developed elsewhere in the world.

• The attributes of small and modular reactors, such as small upfront capital investments, short on-site construction time (with the accordingly reduced cost of financing), and flexibility in plant configuration and applications, could be attractive for private investors.