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Apr 19 – 22, 2022
Vienna, Austria
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Study on actinide conversion capabilities of Molten Salt Reactors (MSR)

Apr 20, 2022, 12:04 PM
Vienna, Austria

Vienna, Austria

ORAL Track 6. Modelling, Simulations, and Digitilization 6.1 Neutronics


Laura Mesthiviers (LPSC/IN2P3/CNRS)


To date, French nuclear power plants mainly use uranium extracted from the mines and enriched. The used fuel is reprocessed to extract useful materials, such as plutonium, which is recycled once in dedicated PWRs of the park. Once used, the quality of the plutonium decreases and it becomes more difficult to recycle this plutonium in thermal spectrum reactors.

A molten salt reactor (MSR) is a liquid fuel reactor, which flexibility allows different fuel types to be used. This concept is inherently safe thanks to its negative feedback coefficients due to the liquid fuel travelling in the entire fuel circuit, from the core to the heat exchangers. Its versatility is such that this reactor can operate in burning or breeding modes. If operated with a fast neutron spectrum, the fission over capture ratio will be improved for all heavy nuclei, allowing to fission significantly most of the actinides. This reactor concept is therefore theoretically adapted to convert actinides such as plutonium.

New studies have started in a CNRS/Orano collaboration to evaluate the efficiency and options of MSR to convert actinides. Indeed, the concept of MSR, called MSFR, the most studied up to now in France and European projects is a fast thorium-cycle breeder reactor, hence a lack of knowledge on the converter concept.

In this article, we will show some preliminary results of these conducted studies. Neutronic studies use a Monte-Carlo approach to calculate the burn-up, feedback coefficients and irradiation damages, whereas reactor optimisations are carried out with a thermohydraulic and neutronic correlation-based algorithm. The molten solvent considered in the calculations -- NaCl-MgCl$_{2}$ -- to incorporate plutonium has shown a neutronic impact according to the proportions of the two constituents. A large amount of magnesium tends to epithermalise the spectrum, which is deleterious when considering non-fissile actinides. An observed increase of the irradiation damages on large core volumes will be explained and the impact of reflectors to mitigate this effect through the mean neutron energy will be presented. Finally the paper will show that the calculated feedback coefficients are very good ($\approx$-15 pcm/K), which assure a good inherent safety. The ongoing studies thus demonstrate the promising potential of fast neutron chloride MSR for such applications.

Country/Int. organization France
Affiliation/Organization LPSC/IN2P3/CNRS, Grenoble INP, UGA
Speaker's email address
Speaker's title Ms

Primary authors

Laura Mesthiviers (LPSC/IN2P3/CNRS) Daniel Heuer (LPSC/IN2P3/CNRS, Grenoble INP, UGA) Elsa Merle (LPSC-IN2P3-CNRS / Universite Grenoble Alpes)


Presentation materials

Peer reviewing