ANALYSIS OF TRITIUM BEHAVIOR AND RECOVERY FROM A WATER-COOLED PB17LI BLANKET

The question of the tritium recovery in water-cooled Pb17Li blankets h as been under investigation for several years at JRC Ispra. The method which has been more extensively analysed is that of slowly circulatin g the breeder out from the blanket units and of extracting the tritium from it outside the plasma vacuum vessel by helium gas purging or vac uum degassing in a suited process apparatus. A computerized model of t he tritium behaviour in the blanket units and in the extraction system was developed. It includes four submodels: (1) tritium permeation pro cess from the breeder to the cooling water as a function of the local operative conditions (tritium concentration in Pb17Li, breeder tempera ture and flow rate); (2) tritium mass balance in each breeding unit; ( 3) tritium desorption from the breeder material to the gas phase of th e extraction system; (4) tritium extraction efficiency as a function o f the design parameters of the recovery apparatus. In the present pape r, on the basis of this model, a parametric study of the tritium perme ation rate in the cooling water and of the tritium inventory in the bl anket is carried out. Results are reported and discussed in terms of d imensionless groups which describe the relative effects of the overall resistance on tritium transfer to the cooling water (with and without permeation barriers), circulating Pb17Li flow rate and extraction eff iciency of the tritium recovery unit. The parametric study is extended to the recovery unit in the case of tritium extraction by helium purg e or vacuum degassing in a droplet spray unit.