Fabrication, properties, and tritium recovery from solid breeder materials

Abstract

The breeding blanket is a key component of the fusion reactor because it directly involves tritium breeding and energy extraction, both of which are critical to development of fusion power. The lithium ceramics continue to show promise as candidate breeder materials. This promise was recognized by the International Thermonuclear Experimental Reactor (ITER) design team in its selection of ceramics as the first option for the ITER breeder material. Blanket design studies have indicated properties in the candidate materials data base that need further investigation. Current studies are focusing on tritium release behavior at high burnup, changes in thermophysical properties with burnup, compatibility between the ceramic breeder and beryllium multiplier, and phase changes with burnup. Laboratory and in-reactor tests, some as part of an international collaboration for development of ceramic breeder materials, are underway. Current experimental research is addressing issues identified in ITER blanket design studies, for example, compatibility of the breeder with the beryllium multiplier, tritium release behavior at high burnup, effects of breeder burnup on th£rmophysical properties, and operation at lower temperatures (i.e., <623 K). At present, the design studies place a great emphasis on neutron irradiation effects, and the experimental effort reflects interest in multiple effects. However, complementary separate-effects laboratory experiments are still required to ensure correct interpretation of a material's irradiation behavior. This paper will focus on recent research concerning candidate materials properties, fabrication methodology, irradiation behavior, and tritium transport, as well as computer modeling of tritium transport and release. 2. Materials Preparation and Fabrication In this section the varied processes used to prepare the candidate ceramic breeder material are identified. The powder preparation, fabrication of shapes, and industrial scale production will be discussed. 2.1 Materials Preparation Preparation methods for the ceramic breeders fall into one of three classes, namely: a) solid state reactions, b) solution processes (aqueous or alcohol), and c}-so1-gel methods. Each method, when done properly, yields high purity materials. 2.1.1 Lithium aluminate HAIO2 The standard technique for the synthesis of UAIO2 is the solid state reaction: Li 2 C0 3 + AI2O3 = 2LiAl0 2 + C0 2 (1) This reaction, introduced by Hummel[6], is widely used at a temperature of about 700°C[7-9]. The time allowed for reaction ts between 3 hours[8] and 'This reaction can be performed at temperatures between 550° and 900°C[17,18]. Instead of the carbonate, it is possible to use Li"20[19] or

Fabrication of Li4SiO4 pebbles by wet method with modified powders synthesized via sol–gel process

“…Lithium orthosilicate (Li 4 SiO 4 ) has been recognized as promising tritium breeding material in nuclear fusion reactors due to its high content of Li, low neutron activation and good tritium release property [1][2][3][4][5][6][7]. Instead of pellets, the high density Li 4 SiO 4 pebbles with small size in the millimeter range are used to improve the mechanical stability and to reduce thermal stresses [8].…”

A comprehensive study on Li4Si1−xTixO4 ceramics for advanced tritium breeders

“…Compared with the undoped sample, the endothermic peak of Ti doped samples shifts to lower temperature, indicating Ti doping can reduce the reaction temperature and raise the reaction efficiency. This is due to the lattice distortion caused by the substitution of Ti 4+ for Si 4+ , which may reduce the activation energy [26]. No obvious weight changes are found above 800 ℃, suggesting the synthesis process is finished.…”

A Comprehensive Study on Li4si1-xtixo4 Ceramics for Advanced Tritium Breeders

“…the reaction temperature and raise the reaction efficiency. This is due to the lattice distortion caused by the substitution of Ti 4+ for Si 4+ , which may reduce the activation energy [25]. No obvious weight changes are found above 800 ℃, suggesting the synthesis process is finished.…”