Development of quantitative detection method for mass spectrometry coupled to an infrared laser spectroscope (Picarro) to monitor in nitrogen matrix a complex gas mixture of H2 , He, CO, N2 , Ne, O2 , Ar, CO2 , H2 S, CH4 , C2 H4 , C2 H6 , C3 H6 , C3 H8 , i-C4 H10 , n-C4 H10 , and C5 H12.

RATIONALE: The deep geological repository is considered the international reference for radioactive waste management. All gas exchanges must be understood in the context of the feasibility of such a repository. The technological challenge is to continuously monitor a wide range of gaseous molecules at low concentrations in confined spaces. METHODS: A gas monitoring station, composed of two complementary analyzers, was developed: an electron impact quadrupole mass spectrometer (HPR-20 R&D Hiden Analytical) and an infrared laser spectroscope (Picarro). The spectrometer was calibrated using simple mixtures (i.e., C2 H6 in N2 ) and multiple mixtures (i.e., H2 , He, CO2 , CH4 , and O2 in N2 ) at different concentrations to correct interferences. A matrix calculation is proposed to calculate the relative concentrations. RESULTS: The method developed allows the measurement of gaseous species: light hydrocarbons, noble gases, sulfides, greenhouse gases, oxygen, hydrogen, and nitrogen in the same mixture. For each gas, the SDs and the limits of detection and quantification were calculated. The method was validated by comparing the concentrations of the measured gas species with the reference values of two standard gas cylinders. CONCLUSIONS: Calibration of a complex gas mixture remains a challenge because fragmentation of molecules, especially hydrocarbons, reduces the sensitivity of the method. The method developed is suitable for continuous gas monitoring in a confined environment and can be implemented to perform experiments in underground structures: galleries, microtunnels (cells), and boreholes.

Diffusion of water in industrial cement and concrete.

We propose a deuterium diffusion tracer approach to measure diffusion coefficient in the case of very short NMR relaxation times, too short for NMR pulsed field gradient sequences (T1 or T2 below 1 ms). We also treat the case of porous media containing metallic fibers (such as reinforced concrete) strongly disturbing the magnetic field, and the case of inhomogeneous porous media containing large non porous granulates. For the latter, we propose a hollow geometry maximizing the investigated volume and minimizing the experimental time. The method is a 3D diffusion technique in which samples are immersed in deuterium and the water content inside the sample is monitored as a function of time. Water diffusing outside the sample with very long relaxation times can be subtracted either from T2 relaxation time distribution or not polarizing these components using a short repeat delay. Using analytical formulations describing the concentration of a tracer diffusing out of a cylinder or a hollow cylinder, we can calculate the corresponding pore diffusion coefficient.