MIMOSA (MultI-recycling strategies of LWR SNF focusing on MOlten SAlt technology) is a EURATOM Research and Innovation Action that will run from June 2022 to May 2026 with a budget of 5.75M EUR.

It was funded under the call HORIZON-EURATOM-2021-NRT-01 within the topic ‘Multi-recycling of spent nuclear fuel from light water reactors (LWR)’.

The project has been labelled by the Sustainable Nuclear Energy Technology Platform (SNETP).


In a time of heightened environmental concerns and resource scarcity, the closure of the fuel cycle – which reduces the radioactive waste disposal footprint and the need for natural resources – reinforces a sustainable nuclear energy strategy. This involves reprocessing of spent nuclear fuels and the extraction of elements that can be (re)used.

While the EU has the highest share of spent nuclear fuel reprocessing worldwide, most of the spent uranium oxide fuels are declared waste. Multi-recycling in light-water reactors (LWRs) is a tangible solution, but it presents some limitations related to the degradation of the plutonium (Pu) isotopic composition and the generation of minor actinides (MAs).

Cl MSR : a promising technology to achieve closure of the fuel cycle

Significant improvement in converting Pu isotopes and MA into fission products with shorter half-lives can be achieved with the introduction of advanced fast reactor systems, among which the molten salt reactor using Chloride salt (Cl MSRs) is a particularly promising option. In this type of reactor, the fuel is dissolved in the salt circulating through the core, with such liquid form of fuel eliminating the major technological bottleneck of refabrication of solid fuels with high content of transuranics.


The MIMOSA project will devise and demonstrate an risk-cost optimised integrated multi-recycling strategy of plutonium and uranium combining multi-recycling options in LWRs with recycling Pu and other transuranics today considered as waste in Cl MSRs using existing European infrastructures such as the Orano reprocessing plant in La Hague (France).

MIMOSA overall concept
MIMOSA overall concept

Today, the maturity of Cl MSRs is low. For this reason, MIMOSA will also seek to demonstrate several key aspects of technical feasibility and performance:

Development of synthesis routes of the chloride fuel salt for use at the industrial scale

Selection and qualification of optimised fuel salt composition with respect to thermo-physical properties

Qualification of innovative materials, new corrosion monitoring and mitigation methods, control of accidental situation

Pyro-chemical processes to recycle Pu and MAs

New methods for fission product management: removal, disposal, extraction and purification when valuable

Qualification of codes coupling neutronics and thermo-hydraulics


MIMOSA will raise the TRL of several Cl MSR-related technologies, processes and materials from 1 or 2 to 3 or 4.

This will pave the way for Cl MSR deployment in Europe, which could be a game changer in nuclear energy through closure of the fuel cycle and a significant reduction in the high-level waste storage footprint.

Furthermore, the project will contribute to the development of materials and technologies that can be useful to other high temperature, high corrosion applications such as the chemical industry or energy storage.

Project news


The MIMOSA consortium, led by nuclear fuel cycle service provider Orano, brings together twelve partners from four European countries with complementary and state-of-the art expertise.