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Report No.

Basic Research on Radiation Effects of Ceramics (5)

Maruyama, Tadashi*

Ion irradiation ezperiment was carried out to elucidate microstructural change of neutron-irradiated B4C. The materials used in this investigation were boron carbides made of carbothermi-reduction method. The specimens were irradiated with helium ions having 15 MeV and 100 to 200 keV, to the fluences of 1$$times$$10$$^{13}$$ to 2$$times$$10$$^{8}$$/cm$$^{2}$$ at temperatures from room temperature to 1000$$^{circ}$$C. After ion irradiation, the microstructure of specimens was analyzed by transmission electron microscopy (TEM). The difference in maicrostructures disappeared among different B$$_{4}$$C pellets after ion irradiations. The ion-irradiation by 15 MeV helium ions produced a radiation-induced amorphization in the matrix. A radiation-enhanced precipitation of micro-crystals which consists of Fe-rich composition was observed in the materials irradiated below 800$$^{circ}$$C. High temperature helium ion irradiation created a number of He bubbles which is associated with strain fields. When irradiation temperature was increased to 1000$$^{circ}$$C, extended planer bubbles were formed on the (001) plane of B$$_{4}$$C, Extremely higher helium irradiation lead to initiation of itragranular clarks. We have also carried out studies of method for measurement of isotopic content was accurately measured when recovery of boron from irradiated B$$_{4}$$C was higher than 60%. Since ICP-MS is rather cheap and easy to measure isotopic content of materials, we studied the feasibility of using ICP-MS for measurement of 10 B in B$$_{4}$$C.



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