Evidence of Irradiation Defection VVER Steels by Small Angle Scattering Experiments - Contribution to the Analysis of Irradiation Effects

Up to now there are only few investigations on the microstructural change of VVER-type reactor pressure vessel steels after neutron irradiation. Consequently, the understanding of the mechanism of neutron embrittlement is not physically but only empirically based. Apart from the modern methods of high resolution analytical electron microscopy the small angle scattering with neutrons and X-rays enables experiments to gain information on size, volume fraction and composition or structure of nanometer-scale precipitates as they are typical for irradiation-induced ones. First experiments with these techniques have shown the irradiation-induced microstructural changes significantly differ from the changes which were found in ASTM-type steels. For continuing such investigations a programme of joint Russian-German investigation is suggested.