An experimental apparatus for in-situ neutron diffraction studies of hydrogen ingress, dissolution and precipitation at controlled temperature and applied tensile stresses

This manuscript presents the design and utilisation of a unique environmental chamber allowing specimens to be heated and cooled, under tensile load and controlled atmosphere, while in a neutron beam, offering a unique opportunity for in-situ neutron diffraction experiments. The chamber was built to gain insight into the impact of parameters such as tensile stress, temperature and exposed atmosphere on the hydrogen solubility of materials and on the mechanisms relating to delayed hydride cracking, hydrogen embrittlement and hydrogen ingress. The investigation presented in this work shows the chamber's performance up to 450°C and 275 MPa applied tensile stress. The effect of tensile stresses and temperature on hydrogen solubility in Zr-2.5Nb is presented for samples nominally charged to hydrogen concentration equivalents of 200 and 500 wppm (mg/kg). Due to kinetic factors, no significant effect of tensile stress on the hydrogen solubility of our samples was found for temperatures up to 300°C and at tensile stresses up to 275 MPa.