Thorium Energy Conference 2015 (ThEC15) October 12-15, 2015, Mumbai, India MOLTEN SALT REACTOR RELATED RESEARCH IN SWITZERLAND Jiri Krepel * , Boris Hombourger, Carlo Fiorina, Sergii Nichenko, Jarmo Kalilainen, Arnoldo Badillo, Konstantin Mikityuk, Terttaliisa Lind, Peter Burgherr, Marco Streit, Urs Berner, Dmitrii Kulik, Bojan Niceno, Andreas Pautz, Horst-Michael Prasser, Martin A. Zimmermann Department of Nuclear Energy and Safety, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland * Email of corresponding author: jiri.krepel@psi.ch ABSTRACT Switzerland represented by the Paul Scherrer Institute (PSI) is a member of the Generation IV International Forum (GIF). In the past, the research at PSI focused mainly on HTR, SFR, and GFR. Currently, a research program was established also for Molten Salt Reactors (MSR). The main long-term aim of this program is the safety of MSR. However, the safety cannot be evaluated before competence and knowledge in several research areas is acquired. At the initial stage, the program focuses on several dedicated studies, which are divided into four working packages: • WP1: MSR core design and fuel cycle. • WP2: MSR fuel behavior at nominal and accidental conditions. • WP3: MSR thermal-hydraulics and decay heat removal system. • WP4: MSR safety, fuel stream, and relevant limits. Keywords: Molten Salt Reactor, Nuclear Safety, Fuel cycle, Thermochemistry INTRODUCTION The Molten Salt Reactor (MSR) has potential for high resources utilization, low waste production, and risk reduction with strongly reduced potential for severe accidents. It may fulfill the “low waste, low risk” requirement of the broad public towards a better acceptance of nuclear energy generation in the future. Furthermore, since MSR operates at low pressure and since both the safety approach and the fuel cycle may be potentially simplified, it might in the long term become more economical than current or planned nuclear reactors. Safety is the key point and main interest of the MSR research at the Nuclear Energy and Safety (NES) department of PSI. However, it cannot be evaluated without knowing the system design, fuel chemistry, salt thermal-hydraulics features, safety and fuel cycle approach, and the relevant material and chemical limits. Accordingly, sufficient knowledge should be acquired in the other individual fields before the safety can be evaluated. The MSR research at NES may be divided into four working packages (WP): • WP1: MSR core design and fuel cycle. • WP2: MSR fuel behavior at nominal and accidental conditions. • WP3: MSR thermal-hydraulics and decay heat removal system. • WP4: MSR safety, fuel stream, and relevant limits. WP1 evaluates several fuel-cycle design options for MSR using predominantly the in-house EQL0D fuel cycle procedure coupled with Monte Carlo code SERPENT. For the WP2 a vital tool is the open- source code GEMS (Gibbs Energy Minimization Software for Thermodynamics Modelling). WP3 should focus on MSR thermal-hydraulics and issues related to volumetrically heated liquids. WP1: core design & fuel cycle WP2: fuel behavior (nominal & accidental) WP4: safety, limits, & fuel stream WP3: thermal- hydraulics & DHR Fig. 1: Illustration of WPs interdependency.