Study of swelling of irradiated Zr-B alloys

Studied are the effects of irradiation by the 4.8x1021 n/cm2 fluence at 375 deg C and of the following annealing up to 1200 deg C on the Zr-1.3%B alloy swelling. It is shown that an accumulation of the B10(n,α)Li7 reaction products takes place in zirconium diboride precipitates (ZrB2) and in a narrow region of zir.conium matrix surrounding these precipitates. A specimen volume increase reaches 0.5% and is explained by forming small gas bubbles and by increasing the volume of elementary cells of ZrB2 and the matrix. Increase in Zr-1.3%B alloy volume begins at 900 deg C and reaches 28% at 1200 deg C. Evolution of helium forom ZrB2 precipitates is observed over the whole temperature range studied. Swelling takes place with activation energy of 1.95 eV and is explained by a gas bubbles formation and by increasing their sizes