Study of the thermomechanical and tritium release behaviour of Li 2ZrO 3 as tritium breeding ceramic for the European BIT blanket concept

Abstract

Among key issues identified for the BIT blanket concept developed in Europe is the physical integrity of the ceramic breeder pellets under operating conditions. The latter depends among other factors on the thermal, mechanical and elastic characteristics of the ceramic material. Relevant parameters such as thermal conductivity λ, mechanical strength (diametral compressive strength σ d), Young's modulus E and Poisson's ratio v have been determined. Their variation in the 75–85% TD range and the resulting variation of the expression (1−ν) λσ d/ E which is to be taken into account to predict whether or not pellets will fracture under given thermal stress conditions, were investigated. The above expression increases with increasing material density reflecting an improvement of the fracture resistance. In parallel, the tritium release behaviour of materials just described was investigated using out of pile tritium release annealing tests. Results show that in the density range explored and for grain size of 1 to 2 μm, no significant change in tritium release is observed. This study indicates that within certain limits an increase in Li 2ZrO 3 density can help fulfill the BIT concept requirements.