FRACTURING OF BORIDES UNDER NEUTRON-IRRADIATION

The neutron irradiation of high-temperature borides results in high in ternal stresses. This leads to considerable swelling and micro- and ma crofracturing. The results of direct investigations of the boride degr adation process under neutron irradiation over a wide range of tempera tures and fluences have been summarized. A change in the mechanism of radiation damage of borides within the temperature interval of 400 to 530 degrees C is discussed. The macrocracking with formation of annula r and radial cracks is observed below this temperature range. The accu mulation of microfractures and the process of gas-induced swelling tak e place at irradiation temperatures above 530 degrees C. The results o btained were conformed by resistance measurement data. The effect of h igh internal stresses is compared with that of external pressure.