Present status of hydrogen isotope separation by CECE process at the NIFS

Kinetics and reactive stripping modelling of hydrogen isotopic exchange of deuterated waters

“…The effect of total pressure was investigated by the CEPE model while a negligible deactivation by pore condensation of water was assumed. Increasing the total pressure, as suggested by Sugiyama et al [4], would maintain high H2OL levels in the liquid phase at high temperatures. This is confirmed by Fig.4 (a), which validates that reducing the pressure leads to increased proportion of H2OV and a reduced concentration of deuterium in the hydrogen gas.…”

“…Figures 3 (c) and (d) confirm that HD and H2OV, as intermediate component in the reaction mechanism (Eqs. [4][5][6], present the highest compositions of HD at low conversions of D2OV while HDOV production increased constantly at high conversions. This result clearly anticipates the potential merit of using a gas/liquid counter-current flow of D2OL and H2 in an LPCE column, in which D2OV is maximized along the column, and thus would maintain a high production of HD and low conversion to condensable components (H2OV and HDOV) as illustrated in the following section on the reactive stripping process by the equilibrium and non-equilibrium controlled models.…”

“…Therefore, the model of Roland et al [26] is still valid but reduced to three reactions (i.e. reactions [4][5][6] where reactions 4 and 6 were assumed to be under kinetic control and reaction 5 under a quasi-equilibrium state [26]. H2 + D2OV <mml:math><mml:mo>&DoubleLeftRightArrow;</mml:mo></mml:math>D2 + H2OV (4) H2 + D2 <mml:math><mml:mo>&DoubleLeftRightArrow;</mml:mo></mml:math>2HD (5) HD+ H2OV <mml:math><mml:mo>&DoubleLeftRightArrow;</mml:mo></mml:math>H2 + HDOV (6) The sum of these reactions (the reverse reaction of Eq.…”

“…The simplest solution to preventing tritium contamination of downstream facilities is to deploy detritiation systems on the heat transfer fluid loops between the facilities and the utility systems but the management of these detritiation systems remains one of the main technological challenges for future industrial development [3]. The recovery of tritium in the forms of DTOL, HTOL or T2OL is an important process, not only because it allows for the reduction of concentration of the radiation hazard of intermediate level wastes, but also because tritium is a precious element for fusion reactions, and tritium recovery can help offset the high costs of disposal and storage [4]. Various technologies have been developed for water detritiation, including combined electrolysis and chemical exchange (CECE), liquid hydrogen distillation, cryogenic adsorption, palladium membrane diffusion, thermal diffusion, laser separation and electrochemical isotope separation [5][6][7].…”

“…Reaction (2) expresses the liquid/vapour distillation exchange of mixture including water and heavy water isotopologues. This reaction is also known to be promoted at mild temperatures, since the associated enthalpy of evaporation of heavy water is higher than that of water, and is known to be kinetically accelerated by packing structures of a hydrophilic nature [4,14,15]. The hazards associated with handling tritium have promoted the development of extensive works aimed at modelling the overall process of the isotopic exchange for tritium detritiation.…”