The Scenario Team at the Subatech laboratory contributes to the CNRS/IN2P3's "Energy" research theme through innovative academic work on nuclear energy transition scenarios. Our goal is to advance knowledge to inform strategic decisions for the future of nuclear energy, through an interdisciplinary approach that combines reactor physics, fuel cycle modeling, and energy economics.

We are at the center of a dynamic collaborative network, both nationally (with IJCLab, LPSC, and several CEA institutes) and internationally, actively contributing to discussions about the future of nuclear power in the context of the energy transition.

Our research is structured around three main areas:

Nuclear reactor simulation
Dynamic modeling of the nuclear fuel cycle
Nuclear economics and long-term electricity mix modeling

Our work relies on the CLASS code (Core Library for Advanced Scenario Simulation), a dynamic simulation tool for the nuclear fuel cycle developed by CNRS/IN2P3 in collaboration with IRSN. CLASS models the evolution of nuclear fleets by tracking isotopic inventories over time at each facility in the cycle. It is designed to evaluate long-term fuel cycle strategies and technology deployment options.

Three key physics-based modules have been developed in CLASS:

Fuel Loading Model (FLM): Builds fresh fuel using available stockpiles and reactor parameters.
Cross Section Predictor (CSP): Provides average cross sections required for irradiation simulations.
Bateman Solver (SB): Solves isotopic evolution equations during reactor irradiation.

The FLM and CSP rely on fast neutron physics predictors trained on a comprehensive database of several thousand reactor simulations. These simulations are generated using transport codes such as MCNP or Serpent, via the SMURE computational chain developed and maintained by LPSC. The resulting data feed neural networks specifically trained to embed these predictions into CLASS.

CLASS also includes a recently developed economic evaluation module, enabling system-level cost assessments of different nuclear fuel cycle strategies. This allows for refined economic analysis, accounting for both upstream and downstream phases of the fuel cycle.

The code supports a wide range of reactor and fuel types, including:

PWR: UOx / MOx / MOXEUS / MOx-Am / URE / MOX-MR
SFR: ESFR-type fast reactors
Water-cooled SMRs (in development)

This modeling capability enables the exploration of diverse trajectories for the French nuclear fleet, particularly looking ahead to 2050 and 2100. It incorporates key challenges such as uranium and plutonium recycling, and economic and technical constraints.

Starting from a detailed reconstruction of the historical French fleet, our scenario studies project the evolution of fuel flows, evaluate technological options, and assess the economic impacts of alternative strategies. Altogether, our research contributes to informed decision-making regarding the role of nuclear energy in a future low-carbon electricity mix.