In the subsequent chapters, we will see more detailed accounts of how energetic radiation plays a significant role in modifying the microstructure of the materials involved. Radiation damage under the fast neutron flux involves atomic displace­ments (i. e., displacement damage) leading to the creation of a host of defects in the material. The effects of radiation can be diverse, including radiation hardening, radiation embrittlement, void swelling, irradiation creep, and so forth, with all hav­ing significant effects on the performance of the reactor components. Another interesting effect of radiation is the radiolytic decomposition of coolant (e. g., water molecule is radiolyzed into more active radicals) that may definitely affect the corro­sion behavior of the reactor components. Fission fragments also cause damage, but they are mostly limited to the fuel. So, for selecting materials for a nuclear reactor, we must know the concomitant radiation effects on these materials. That is why millions of dollars are spent to wage materials irradiation campaigns in test reactors followed by careful postirradiation examination to ascertain fitness-for-ser- vice quality of the materials to be used in nuclear reactors.

1.9.3