Objective In order to achieve the strategic goal of "carbon peaking and carbon neutrality" and accelerate the development of microreactor nuclear systems (referred to as microreactors), it is necessary to comprehensively analyze various conceptual designs and technology basis up to date.

Method The progress of micro reactor projects such as Holos Quad, Xe Mobile, Pele, and Aalo-1 was highlighted by comprehensively investigating the R&D of microreactors in the United States and other major countries. According to the classification of gas-cooled microreactors, liquid metal cooled microreactors and heatpipe microreactors, one representative conceptual design was selected, and the main design characteristics and technical parameters of Holos-Quad, MARVEL and eVinci microreactors were summarized.

Result Among them, the Holos-Quad microreactor adopts the technical route of "TRISO fuel, helium coolant, and helium Brayton cycle", with a typical power generation of 10 MWe. The MARVEL microreactor adopts the technical route of "uranium-hydrozirconium fuel, sodium-potassium alloy coolant, and Stirling cycle", with a typical power generation of 20 kWe. The eVinci microreactor adopts a technical route of "TRISO fuel, sodium heat pip, and air Brayton cycle", with a typical power generation of 5 MWe. At present, the maturity of microreactor technology has not reached the conditions for commercial application, and there are obvious technical challenges in nuclear fuel, core cooling and reactivity control.

Conclusion As an important direction of advanced nuclear technologies, the microreactor with the characteristics of simple and compact, flexible and diverse, as well as high inherent safety, has good application prospects in remote areas, polar regions, off-grid islands and other isolated grid occasions.