Experimental Quantification of the Effect of Neutron Irradiation Induced Microstructural Changes on the Hardening of Model Alloys and Steels

The nuclear reactor core is contained in a steel vessel, which is not replaceable during the lifetime of the reactor. It is therefore of crucial importance to make sure that the material properties under irradiation remain adequate to fulfil the expected structural duties. In order to actually predict the behaviour of the material, models are needed based on the microstructural variations observed by state-of-the-art experimental examination. To identify the physical phenomena leading to the microstructural changes, several model alloys and steels are neutron irradiated and subsequently examined. Four different techniques are used by different European laboratories on the same material, to detect, identify and quantify different irradiation-induced defects. In this work, the attention is focused on the use of the positron annihilation spectroscope and the quantification of its results. The results of the four techniques are also compiled together in a complementary way for the full understanding of the microstructural changes during irradiation. Based on this knowledge, an attempt is made to predict the hardening mechanisms in the investigated materials under irradiation.