The role of dislocations and inclusions in the formation of gas bubbles in the irradiated fissile material

It has already been shown that the process of formation of gas bubbles in the irradiated fissile material depends on the concentration of trapping site (dislocations and inclusions etc.), the irradiation temperature and the neutron flux. In the present paper, the interaction of vacancies, interstitials, gas atoms produced in the fissile material by irradiation with dislocations or inclusions are investigated in detail and the process of nucleation of gas bubbles is discussed. In Chap. I, the general consideration is given and in Chap. II, the calculation is carried out in the case of uranium based upon the general considerations described. The major conclusions are as follow: (1) In the case of irradiation at T ≲ -50℃, no nucleus of gas bubble is formed. (2) In the case of irradiation at -50℃ < T ≲ 500℃, the nuclei of gas bubble are formed at the neighborhood of dislocation and the average spacing of nuclei is about 10^-5cm. (3) In the case of irradiation at 500℃ < T ≲ 670℃, the nuclei of gas bubble are formed near inclusions or grain boundaries. (author)