There is an unprecedented need to expand thetoolbox of solutions to boost the scalability of clean powerand energy systems. Amidst this challenge, nuclear energy isincreasingly recognized as an important player in the pathtoward deep decarbonization of the global energy mix. Thispaper presents a technology review of small modular reactor(SMR) concepts currently under development and deployment.Both conventional and next-generation reactor technologies areevaluated with a focus on potential power system integrationbenefits, added system values, and provision of system-bearingservices. Nevertheless, there are currently some uncertainties inthe techno-economic competitiveness of SMRs, whether they canleverage economics of mass production over their inherent lack ofeconomics of scale. To address this challenge, our paper providessome basic cost analysis of SMRs, taking into account theirexpected learning curves to evaluate the cost of future deploymentsand give insights into their economic competitiveness andpotential role as a disruptive solution in the energy transition.