Small modular reactors (SMRs) are a proposed class of nuclear fission reactors, smaller than conventional nuclear reactors, which can be built in one location (such as a factory), then shipped, commissioned, and operated at a separate site. The term SMR refers to the size, capacity and modular construction only, not to the reactor type and the nuclear process which is applied. Designs range from scaled down versions of existing designs to generation IV designs. Both thermal-neutron reactors and fast-neutron reactors have been proposed, along with molten salt and gas cooled reactor models. SMRs are typically anticipated to have an electrical power output of less than 300 MWe (electric) or less than 1000 MWth (thermal). Many SMR proposals rely on a manufacturing-centric model, requiring many deployments to secure economies of unit production large enough to achieve economic viability. Some SMR designs, typically those using Generation IV technologies, aim to secure additional economic advantage through improvements in electrical generating efficiency from much higher temperature steam generation. Ideally, modular reactors will reduce on-site construction, increase containment efficiency, and are claimed to enhance safety. The greater safety should come via the use of passive safety features that operate without human intervention, a concept already implemented in some conventional nuclear reactor types. SMRs should also reduce staffing versus conventional nuclear reactors, and are claimed to have the ability to bypass financial and safety barriers that inhibit the construction of conventional reactors. As of 2023, there are more than eighty modular reactor designs and yet unfinished demonstration projects, and the first SMR units are in operation in Russia and China. The floating nuclear power plant Akademik Lomonosov (operating in Pevek in Russia's Far East) is, as of October 2022, the first operating prototype in the world. The first unit of China’s pebble-bed modular high-temperature gas-cooled reactor HTR-PM was connected to the grid in 2021. SMRs differ in terms of staffing, security and deployment time. US government studies to evaluate SMR-associated risks have slowed licensing. One concern with SMRs is preventing nuclear proliferation. Background Economic factors of scale mean that nuclear reactors tend to be large, to such an extent that size itself becomes a limiting factor. The 1986 Chernobyl disaster and the 2011 Fukushima nuclear disaster caused a major set-back for the nuclear industry, with worldwide suspension of development, cutting down of funding, and closure of reactor plants. In response, a new strategy was introduced aiming