SAMOSAFER

Severe Accident Modeling and Safety Assessment for Fluid-fuel Energy Reactors

Horizon 2020

Start: 2019

End: 2023

Within the SAMOSAFER project, the challenge is to develop new assessment and simulation tools for this Gen-IV reactor with respect to these innovative safety features.

World-wide research is being done on various classes of Molten Salt Reactors (MSR) each having its own characteristics. One major classification is the neutron spectrum: thermal, epithermal or fast. The latter class of reactors can be subdivided into the ones using a chloride fuel salt or a fluoride fuel salt. Chlorides can contain a larger fraction of actinides and will therefore result in a harder neutron spectrum, making these better candidates for breeding with the uranium-plutonium fuel cycle, or for plutonium / minor actinide burning, while the fluoride salts perform better for breeding with the thorium fuel cycle. Above mentioned reactor class has a single salt mixture acting both as a fuel and as a coolant. The Molten Salt Fast Reactor (MSFR) is the only Generation-IV reactor concept with a liquid salt to carry the fuel and to transport the heat. This special feature enables the MSFR to use innovative safety features.

SAMOSAFER project

The SAMOSAFER project is a European HORIZON 2020 project started in 2019 and selected on call for projects NFRP-2018 Nuclear Fission, Fusion and Radiation Protection Research. It is coordinated by the Delft University of Technology in the Netherlands with European partners such as the SUBATECH laboratory under the triple supervision of the Institut Mines-Télécom through its school, IMT Atlantique, the University of Nantes and the CNRS with the National Institute of Nuclear Physics and Particle Physics (IN2P3) as the main institute. The project will last 4 years and the EU funding is about 3.5 Millions of euros. SAMOSAFER aims to develop and demonstrate new safety barriers for more controlled behaviour of Molten Salt Reactors (MSR) in severe accidents, based on new simulation models and tools validated with experiments. The grand objective is to ensure that the MSR can comply with all expected regulations in 30 years’ time.

Method

In the chosen approach, the strength of each barrier between the fuel salt in the core and the environment will be demonstrated and where possible, suggestions will be made for improvements. The Primary Fuel Circuit (PFC) contains the reactor core (including the blanket, primary pumps, and heat exchangers) for power production, the Emergency Drain System (EDS) for safe storage of the fuel salt in accidental conditions, and the Fuel salt Treatment Unit (FTU) to continuously extract fission products from the fuel salt and to keep the Redox potential of the salt in the right range to reduce corrosion, see Fig 1. The radionuclide inventory from the ‘inside’ (fuel salt) to the ‘outside’ will be followed in all possible scenarios with the aim to prevent and mitigate severe accidents. In the safety analyses, the whole reactor system including the reactor core, FTU and EDS will be taken into account.

Expected results

Milestone over the 48th month project for Subatech

MS3.1: (Month 06) Initial distribution of FPs and the reprocessing scheme

Delivrable

D3.1: (Month 48) Distribution of fission products in the representative MSFR system

School's role

Part of the work is to develop and validate models for tracing the source term and its chemical form and

mobility during nominal and accidental conditions. IMT Atlantique, one of the supervision‘s SUBATECH laboratory is task leader on this topic: tools capable of coupling fuel depletion with material exchanges between the locations will be applied to evaluate the source term distribution.