ORC technology used in a Heat Removal System for Advanced Nuclear Power Plants

This work concerns the design of a specific passive system for an advanced pressurized water reactor (PWR). The system studied is based firstly on passive safety condensers, which are increasingly used in the design of advanced nuclear power plants. These condensers are typically immersed in large water tanks that serve as a heat sink. They are located at a sufficient height to ensure a natural twophase circulation mode. Such a heat removal system can be used for a relatively long period depending on the size of the tank. The present research is based on using a fraction of the energy stored in this volume of boiling water as a heat source for an organic Rankine cycle via an immersed heat exchanger. The electrical energy produced will power various critical components, complementing existing systems. Three unusual issues challenge the use of an ORC in this context: the nature of the hot source (boiling pool water), the low temperature of the hot source (100°C), and the requirement for system reliability and robustness. Apart from these three challenges, the usual constraints associated with ORC systems still exist: maximizing energy performance, using an environmentally friendly fluid and minimizing space requirements. An experimental test bench with a boiling water pool and an ORC with submerged evaporator was built to address the main questions. The first set of results shows the nominal operation of the coupling between the boiling water pool and the ORC when Novec649TM is used as working fluid. The reliability of the system is then studied through the investigation of the immersed evaporator and the implementation of a theoretical model. The theoretical model of the system will be used to scale the system.