Potential contribution of the energy conversion system to the core reactivity balance

• Energy Conversion System to compensate for reactivity loss due to fuel burn-up. • Determination of the contribution of an ECS to the reactor core control. • KGH steady-state method for evaluating the core power evolution. This study focuses on an Energy Conversion System (ECS) designed to fully compensate the reactivity swing during reactor operation. A methodology is proposed to assess the contribution of the ECS to the core reactivity and to propose a core with produced power uniquely driven by the control of the ECS. The aim is to control the core inlet and mean temperatures in order to take advantage of reactivity feedbacks in the core. PWR and SFR cores, connected to Rankine and Brayton cycles, are analysed. A static method is proposed to take into account the reactivity feedback effects on the core and the CYCLOP code (a software package developed by CEA) is used to model the Energy Conversion Cycles. The conclusion proposes a control of the ECS and the associated cycle efficiency to compensate the reactivity loss and to drive the reactor produced power.