Design and development of hydrogen isotope sensor in liquid PbLi

Indian LLCB – TBM uses liquid Lead-Lithium (Pb-Li) as tritium breeder, neutron multiplier and coolant. Tritium bred in liquid PbLi stream has to be recovered by tritium extraction system. Therefore, a reliable sensor with quick response time for measurement of hydrogen isotope is essential.A hydrogen isotope sensor in liquid Pb-Li, based on permeation of hydrogen isotopes through metal (sensor material) is designed. The capsule shaped sensor, made of iron membrane coated with Pd from inside (downstream side), allow hydrogen isotope to permeate through it. The design work mainly includes the selection of proper material, its thickness and surface conditions, which is to be supported by numerical calculations for optimization of maximum permeation flux, fast response and fabricability. The numerical calculation utilizes a physical model having recombination of two hydrogen isotope atoms at the surface and atomic diffusion through the bulk. In this work, design calculations based on numerical simulation and fabrication procedure of the hydrogen isotope sensor are presented.