Member

 The major research subjects of this group are explosion- and shock wave-related phenomena in dense systems such as solids and liquids. In addition to basic research aimed at investigating explosion phenomena by laser shock waves and fast time-resolved measurements, and studying the initiation mechanism of high explosives, the group is researching the explosion safety of energetic materials and developing new types of explosives storage magazines and technologies for reducing explosion effects by blasts, fragments and ground vibration. It is also doing research on the evaluation of shock response characteristics to underwater explosions of underwater structures related to nuclear installations. The group is also conducting large-scale field explosion experiments to meet administrative and international needs.

In regard to the safety technology of explosives, the group is collecting basic data about problems with the handling of explosives according to changes in social situations. To solve the problems found in the previous experimental results, and to attempt revision and enhancement of the safety standards of explosives using scientific rationality, the group is carrying out safety technology experiments (explosion effect reduction experiments) on explosives.

In case of explosion accidents, there is a risk that massive fragments will be generated from the blast walls used as fireworks storage magazines. The group is conducting large-scale field explosion experiments to create a new high-strength blast wall or reinforce and improve existing blast walls as a way of solving this problem. Assuming that there is not enough space between an explosives storage magazine and housing as a result of land development for housing in the neighborhood, it is also doing experiments to investigate the safety of a new type of explosives storage magazine called an underground magazine. The results of these experiments show that the safety distance for an underground magazine can be made shorter than that for an ordinary above ground type magazine. Data collection is scheduled to be continued.

With regard to an explosives storage magazine with a partition wall located between two storage rooms, the group also studied the relationship between the thickness of a partition wall and the ease of transmission of explosions, and collected highly reliable data that allows estimation of the partition wall thickness at which the explosion in a full-scale explosives storage magazine will not propagate to the next room.
It becomes possible to store double the amount of explosives if the detonation phenomenon of adjacent storage rooms can be prevented.

The group is collecting basic data on explosion effects to create a database and develop a system for assessing reaction mechanisms as part of research on the explosion safety evaluation technology of energetic substances concerning spent nuclear fuel re-processing.
As for the explosion effect data collection, underwater explosion experiments have been carried out using samples with different mixing ratios of hydrazine hydrate and hydrazine nitrate placed in a 20 mm inner diameter polyvinyl chloride tube container and detonated using 10 g of composition C4 explosive stuffed into the 20 mm inner diameter polyvinyl chloride tube.
With regard to the reaction mechanism assessment, the group is developing equipment for shock wave generation by pulsed laser irradiation, which is then subjected to time-resolved Raman spectroscopy to enable detailed investigation into the reaction mechanism at the molecular level of shock-compressed condensed matter. Time-resolved Raman spectroscopy of tetrachloromethane, an unreactive organic liquid, has been performed to study the microscopic response of molecules under shock compression, and consequently, effectiveness of the equipment and experimental methods has been confirmed.

The group has developed a container for their disposal, as part of an integrated system for the detection and disposal of explosives for antiterrorism purposes. Mitigation of the damage caused by a blast and the high velocity fragments ejected by the explosion was investigated as a starting point for its development. Mitigation of the blast caused by the explosion of high explosives, whose weight ranged from 100 g to 1 kg, using several types of buffer materials, was evaluated. The mitigation effect depended on the density of the buffer materials. Mitigation of the blast pressure using environmentally friendly, biodegradable, foamed buffers was also investigated.

As for mitigation of the damage caused by the high velocity fragments, the relation was investigated between the thickness of the buffer materials and the velocity and the size of the fragments. The group obtained an empirical equation by which a certain condition for stopping fragments can be determined with fragment sizes, speeds, and the thickness of the buffer materials set as variables where sand is employed as the buffer material.