Fiber optics remote monitoring of gas concentrations by Spontaneous Raman Scattering - Application to the H2-risk management in nuclear containment during a severe nuclear accident

International audience; During a severe nuclear accident leading up to core melting, reaction of core constituents with coolant water and Molten Corium-Concrete Interaction (MCCI) both release large amounts of hydrogen (H2) gas in the containment atmosphere. Depending on local partial pressures of H2, air and water vapor, deflagration and detonation may occur with potential deleterious impact over equipments and structures.The MITHYGENE Project designed, assembled and tested proprietary free-space Raman gas cells, fiber-coupled to an acquisition unit placed far away from the radiological perimeter. We first describe the calibration procedure performed in climatic chamber and in flame-propagation tubes. Then, we show the results obtained during thermo-hydraulic tests in the MISTRA facility, representative of a PWR containment at 1/10 scale designed for studying turbulent convective gas flows with condensation. Complementary experiments (temperature, hygrometry, radiation, shock/vibrations) will be described during the conference, providing an assessment of the Raman prototype for H2-risk management during severe accidents.