On load-following operations of small modular reactors

Load-following capability is one of the distinguishing features between Small Modular Reactors (SMRs) and traditional large-scale reactors in existing nuclear power plants. An SMR needs to possess load-following capability to integrate with non-dispatchable energy resources, e.g., renewable ones, to form an off-grid hybrid energy system. This paper provides a comprehensive review of different aspects of load-following operations of nuclear reactors by systemically examining early studies and some practical operating experience on existing nuclear reactors in various applications. These applications include electricity generation, marine vessel and spacecraft propulsion, and heat generation for industry applications. Considering different advanced reactor design concepts proposed for SMRs, the paper has concentrated on six representative reactor types and highlighted their unique features and feasibilities for load-following operations. Since an SMR can be considered as a combination of the reactor and the balance-of-the-plant, its power output can be regulated at the reactor power output or from the balance-of-the-plant. Different techniques to implement load-following operations have been described regarding different reactor designs and compositions of the balance-of-the-plant. Several special issues deserve special attention when performing load-following operations. These issues are rarely encountered in existing nuclear power plants for base-load operation, for example, imbalance in core power distribution, flow-induced vibration, excessive production, higher risk of fission products leaking, and flowaccelerated corrosion. The paper has provided necessary coverage of these less obvious consequences associated with load-following operations.