Properties of new-type liquid tritium breeders and advanced liquid blanket design

建立聚变燃料循环是实现D-T聚变堆系统的关键，在D-T聚变堆系统中，包层产生比D-T反应消耗的氚更多的氚。液体包层的研究和开发比固体包层的研究和开发滞后得多，但从经济效益的角度来看，液体包层有很大的发展潜力。在这项研究中，获得了液体增殖剂性能的基本数据，并利用这些数据对一些先进的包层概念进行了综述。特别补充了液态锂锡合金、氟化物熔盐的还原氧化控制和其他液态增殖材料的性能数据，以比较所有液态增殖候选材料的性能。利用数据讨论了新的液态包层概念，明确了其可行性和关键问题。完成了以下工作：(1)测量了锂锡液态合金的热性能、密度和相图等基本性质。利用安装在快中子源反应堆YYOI上的包层模拟系统，获得了该合金在高温中子辐照下的氚扩散系数和氚溶解度等氚释放特性。(2)以铍为还原剂，在氟化物熔盐(LiF-BEF_2)中进行了还原实验。研究了结构材料与还原氟化物熔盐的配伍性，证实了该方法的可行性。(3)进行了Er_2O_3绝缘陶瓷涂层的研制。(4)对本研究获得的数据进行了评价，并对其在先进包层设计中的应用进行了讨论。

Establishment of fusion fuel cycle is essential in order to realize D-T fusion reactor system, in which more amount of tritium should be produced in the blanket than that of tritium consumed for D-T reaction. The research and development for liquid blanket is more delayed than that of solid blanket, though the former one has a potential of charming concept from the point of economic efficiency. In this study, essential data for liquid breeder properties were obtained and some advanced blanket concepts are reviewed by using them. In particular, liquid lithium-tin alloy, the reduction-oxidation control of fluoride molten salt and the property data of other liquid breeders were supplemented in order to compare all the liquid breeder candidates. New liquid blanket concepts were discussed with the data, and the feasibility and the critical issues were clarified.The following tasks were accomplished;(1) Basic properties such as thermal properties, density and phase diagram of lithium-tin liquid alloy were measured. The tritium release properties such as tritium diffusivity and tritium solubility of the alloy were obtained under neutron irradiation at high temperature by using a blanket-simulated system installed in the fast neutron source reactor "YAYOI".(2) Reduction experiments for HF in fluoride molten salt (LiF-BeF_2) were demonstrated using beryllium as a reducing agent dipped in the salt. Compatibility of structural materials with the reduced fluoride molten salt was investigated and the feasibility of this method was confirmed.(3) Development of Er_2O_3 insulating ceramic coating was done.(4) Evaluation of the data obtained in this study and the discussion on the application to the advanced blanket design were carried out.