Regular Article

Exploring the safety and performance of molten salt reactors for their deployment in the European Union: the MIMOSA and ENDURANCE projects

¹ Orano 125 Avenue de Paris 92320 Châtillon France
² Politecnico di Milano Via La Masa 34 20156 Milano Italy
³ Delft University of Technology, Radiation Science and Technology department Mekelweg 15 2629 JB Delft The Netherlands
⁴ NRG Westerduinweg 3 1755 LE Petten The Netherlands
⁵ Research Centre Řež 130, Řež 250 68 Husinec Czech Republic
⁶ Thorizon Amsterdam 1012 SN The Netherlands
⁷ IJCLab, CNRS/IN2P3, Université Paris-Saclay 91405 Orsay France
⁸ European Commission, Joint Research Centre Karlsruhe Germany
⁹ Orano 11 Rue d’Idalie 1050 Ixelles Belgium
¹⁰ Nuclear 21 Groenstraat 35 Waasmunster 9250 Belgium
¹¹ Politecnico di Torino Corso Duca degli Abruzzi, 24 10129 Torino Italy
¹² LPSC, IN2P3/CNRS, Grenoble INP – UGA, Univ. Grenoble Alpes 53 Avenue des Martyrs 38000 Grenoble France
¹³ Subatech, IN2P3/CNRS, IMT-Atlantique, Nantes Université 4 Rue Alfred Kastler – La Chantrerie 44000 Nantes France
¹⁴ Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES/SAG, Cadarache Centre 13108 St. Paul lez Durance Cedex France
¹⁵ Framatome 1, Place Jean Millier Courbevoie 92400 France
¹⁶ Paul Scherrer Institute (PSI) Forschungsstrasse 111 5232 Villigen Switzerland
¹⁷ ARTTIC 39 Rue des Mathurins Paris 75008 France

^* e-mail: isabelle.morlaes@orano.group
^** e-mail: stefano.lorenzi@polimi.it

Received: 22 November 2024
Received in final form: 12 March 2025
Accepted: 7 May 2025
Published online: 30 June 2025

Abstract

Molten Salt Reactors (MSR) are Generation IV nuclear systems in which the fuel is dissolved in a molten salt circulating through the primary system. There is growing interest in this advanced technology in Europe, but also in the US, China, South Korea, Japan and Russia, due to their inherently high safety level, flexibility, reliability, load-following capabilities, and potential for multi-recycling of materials contained in light-water reactors’ spent nuclear fuels. These advantages could position MSRs as ideal complements to other decarbonized energy sources in a future sustainable energy mix. In this respect, it is probably one of the most promising advanced technologies and, at the same time, the least mature and studied one. Two ongoing EURATOM-funded projects, MIMOSA and ENDURANCE projects are exploring molten salt reactors’ safety and performance features, as well as fuel cycle aspects, in order to assess and demonstrate their potential for future deployment in Europe. The MIMOSA and ENDURANCE projects have the common objective of improving the maturity of MSR technology. The MIMOSA project develops and analyses multi-recycling strategies for the European Union based on the use of MSR and demonstrates several key aspects of their technical feasibility and performance by both calculations and experimental investigations. The ENDURANCE project supports the safe operation and the development of Critical Technology Elements by connecting design developers and industry with universities and research centres while ensuring alignment with regulatory requirements. Whereas ENDURANCE is in its starting phase, MIMOSA has already delivered important results.