SANS INVESTIGATIONS OF THE IRRADIATION-CAUSED STRUCTURAL DAMAGES IN VVER 440-TYPE REACTOR PRESSURE-VESSEL STEELS

Small-angle neutron scattering (SANS) experiments were performed at KW S2 facility of the KFA Julich for investigating the defect structures, which are produced by neutron irradiation in Russian Cr-Mo-V alloyed reactor pressure vessel steel. Irradiation and post-irradiation anneal ing considerably change both SANS intensity and its course in the Guin ier plot, which was analysed by the Glatter method. As a rule, bimodal size distribution functions were found with a first maximum at a radi us of 1-2 nm and a second maximum at 6-8 nm. Irradiation increases the first maximum, annealing reduces it.