TECHNOLOGICAL IMPACT OF MICROSTRUCTURAL EVOLUTION DURING IRRADIATION

Neutron irradiation produces a wide range of effects that must be take n into account in both the design and operation of reactors. Direct me asurements of the mechanical properties and dimensional changes of mat erials from operating reactors are important in assessing the potentia l life of components, but without an understanding of the underlying p rocesses undue conservatism is inevitable. Microstructural analysis ha s proved an invaluable aid to this understanding and the construction of models of material behaviour. The paper emphasises the need to carr y out microstructural studies on real materials as well as model alloy s, because of the complexity of the internal structures and the import ant role of impurities and minor alloying elements. The embrittlement of reactor pressure vessel steels, void swelling of fast reactor compo nents, irradiation sensitisation of stainless steels and the growth of zirconium alloys are taken as examples of how microstructural analysi s has played a vital role in nuclear technology.