Preliminary design of hybrid small modular boiling water reactor with external superheater

Abstract

Nuclear power plants (NPPs) are known to be used as providers of base-load power. As the share of the intermittent renewables in the energy mix increases, the maneuvering (load-following) of NPPs is becoming more important. Previous studies have found that combining Light Water Reactors (LWRs) with external superheater would improve their cycle thermal efficiencies and maneuvering capabilities. Implementation of this concept in a small modular boiling water reactor (SMBWR) might offer additional benefits, such as vessel size reduction and further boost of cycle thermal efficiency at higher operating pressure. This paper presents a preliminary design of hybrid SMBWR, focusing on the effect of system pressure on reactor capability to operate with natural recirculation of coolant and on steam cycle thermodynamic performance. It is demonstrated that hybrid SMBWR has natural circulation system operating at higher pressure than the conventional system by increasing its chimney height. The study of the effect of system pressure on power cycle thermodynamic performance was done by considering both fossil fuel heat and renewable heat as the potential heat source for the external superheater. The cycle thermal efficiency of hybrid SMBWR with fossil heat option varies between 40 to 42% depending on the system operating pressure while the values for renewable heat option are between 38 to 40%.