Basic Research on the Minerals Related to High-Level Radioactive Wastes.

每当为下一次有效使用而对使用过的核燃料进行再加工时，不可避免地会留下高放射性废物。这些废物必须在很长一段时间内远离人和动物的安全。因此，寻找最佳的处置方式是原子能利用的一个紧迫课题。本课题主要研究与放射性废物有关的矿物的微观结构，因为放射性废物经过较长的地质时期后可能会观察到这种结构。为了研究放射性废物的微观结构，我们对放射性矿物或被认为是类似物的稀土矿物进行了研究，以显示放射性废物的未来特征。从而阐明各种原子在转移、浓缩、取代过程中的行为。…的主要内容(1)微区X射线衍射仪的发展：常规微区X射线衍射仪只能获得50微米的粉末衍射图，更小的区域很难获得结晶学信息。通过对专门设计的X射线衍射仪的控制，结合开发的软件系统，用单晶衍射法获得了10微米范围内的晶体信息。通过这项技术，将有可能识别小矿物和分析矿物之间的定向关系。(2)利用X射线衍射仪、扫描显微镜、光子活化分析等手段，对巴西碱性碳酸盐岩杂岩中的多种稀土矿物的矿物组合、结构、风化、元素含量等进行了研究。这些结果将可用于预测放射性废物周围岩石的变化。(3)与海外科学家进行国际合作，讨论处置放射性废物的地质环境。托科纳米为封堵岩石裂缝提供了可能有用的材料。较少

High-level radioactive wastes unavoidably remain whenever the used nuclear fuels are reprocessed for the next effective use. These wastes must be kept away from human being and animals in safety for a very long period. Thus, the search of the best way of their disposal is an emergency subject for the use of atomic energy. Most of researches on this problem are performed from technological point of view, however, basic researches of wasted substances are not strongly promoted.In this project, microtextures of minerals which are related to radioactive wastes are mainly investigated because such textures might be observed for the radioactive wastes after a geologically long period. In order to study microtextures, we investigated radioactive minerals or rare-earth minerals which are thought as analogues to show a future's feature for the radioactive wastes. As a result, behaviors of the process of transfer, concentration, substitution of various atoms will be clarified.Main contents which … More we contributed to these subjects are; (1) Developments of Microarea X-ray Diffractometer : Conventional microarea X-ray diffractometer is only available to take powder diffraction pattern of such a small area as 50mum, and it is difficult to get a crystallographic information from smaller area than that. We could get a crystallographic information from 10mum area by single crystal diffraction technique by making a control of a specially designed X-ray gonioneter combined with a developed soft-ware system. By this technique, it will become possible to identify small minerals and to analyze orientation relationship among minerals. (2) Many of rare-earth minerals which are obtained from alkali-carbonatite complexes of Brazil are studied on mineral assemblage, textures, weathering, element concentration etc. by means of X-ray diffraction, scanning microscopy, photon activation analysis and so on. These results will be available to expect the change of rocks around radioactive wastes. (3) International collaboration with overseas scientists in order to discuss geological environments for disposal of radioactive wastes. Tokonami contributed to potentially useful materials for sealing cracks of rocks. Less