General description

COSI is a calculation code that simulates nuclear reactor fleets and the associated fuel cycle facilities over several decades. This tool is developed by the SPRC (Reactor Physics and fuel Cycle Service) at the IRESNE Institute of the CEA/Cadarache.

COSI is used for scenario studies analyzing the consequences of the choices made over reactor fleet dimensions and nature, fuel types, and the different fuel cycle facility features (plants, interim storage, geological storage, etc.).

COSI processes all the fuel cycle isotopic material flows (natural U, depleted U, reprocessed U, Pu, minor actinides, fission products, etc.). COSI6 is coupled with the code CESAR, jointly developed by CEA and ORANO, for all the evolution calculations of materials, in or out of neutron flux.

The COSI simulation contains:

• The different fuel cycle facilities (mines, enrichment and fabrication plants, power plants, reprocessing plants);
• The main storing and stocks (nuclear materials, fresh and burnup fuels, waste);
• Many physical models including fresh fuel equivalence, depletion and cooling.

The fuel cycle can be closed by reprocessing plants feeding the front-end plants (enrichment, fabrication) with reprocessed nuclear materials.

The simulation is driven by the dynamics of reactors and reprocessing, which interact with:

• The front-end (materials demand);
• The back-end (spent fuel cycle and waste management).

At any date of interest, the post-processing features evaluate:

• The materials balance in the different fuel cycle facilities (mass, isotopic composition);
• Fleet power and energy produced;
• Radiotoxicity and activity;
• Non-nuclear materials use.