Load following by cogeneration: options for small modular reactors, Gen IV reactor and traditional large plants

Nuclear Power Plants (NPPs) has been historically deployed to cover the base-load of the electric power demand. Nowadays this scenario is changing and some NPPs are requested to perform daily load cycling operation (i.e. load following) between 50% and 100% of their rated power. The traditional methods to perform the load following are by inserting negative or positive reactivity into the core, moving the control rods. This strategy reduces the produced thermal power and in turn the electric power output with respect to the base-load strategy. From a technical standpoint this strategy submits the primary circuit to thermodynamic transients, which causes thermomechanical stresses on some components. From an economic standpoint this operation is very inefficient since, in NPPs, costs are mainly fixed and sunk, and there is a negligible cost saving (if any) in reducing the power of the reactor. A more efficient alternative might be doing the “Load Following by Cogeneration”, i.e. performing the Load Following by diverting the excess of power to an Auxiliary Plant. This paper assesses the technical feasibility of the coupling between a NPP and hypothetical cogenerate plants producing: diesel-like fuels from plastic pyrolysis, or desalinated water, or pellets from waste wood, or hydrogen from water splitting.