Advances in technology, design and deployment of microreactors- a review

A group of small nuclear reactors that are less than 20 MWe are often referred to as microreactors. This review provides recent advances in the nuclear reactor fuel and core design technology leading to compact microreactor designs, design features, types of microreactors currently considered in the industry and studied by researcher, regulatory design criteria, and deployment potentials for these new microreactors. This review indicates that there are a wide variety of microreactor designs being developed, some of which use coolant other than water such as liquid metal (e.g., sodium), helium gas or molten salt in order to achieve their operational objectives. Some of these designs utilize passive heat pipes in order to transfer heat from the reactor cores. Others make use of helium gas due to its compatibility at high temperature and inert nature. Currently there are no operating reactors which utilize either of these technologies for power generation. To aid the technology commercialization the nuclear regulatory bodies like US NRC are developing new design criteria and the licensing process to assess the microreactors for design certification, construction, and operation. The review indicates that there are potential design criteria challenges for the microreactors. For example, helium reactors need to show that the heat can be dispersed efficiently and passively, and the heat pipe reactors need to demonstrate that the coolant in their heat pipes will not escape the primary boundary. The US NRC has developed design criteria for microreactors are highlighted in the review.