On the irradiation behaviour of fuel pins in power reactors

Fuel pins in power reactors are subject to numerous adverse conditions during their lifetime within the reactor. Besides thermal effects and corrosion the alteration of the original fuel pin is brought about mainly by material conversion due to fission and by radiation damage in metallic components. All these alterations are influencing the operational conditions of the pins, some of them even determining their lifetime. For fast breeder fuel pins it is mainly the internal corrosion produced by fission products and oxygen which is thought to shorten the lifetime whereas lightwater fuel pins are threatened by fuel restructuring. One type of radiation damage, void formation in stainless steels, was discovered only a few years ago. The consequences of that effect cannot yet be fully realilzed since irradition experiments have not reached the high neutron dose expected in the fast reactor. - All irradition induced alterations of the fuel pins, however, can be reduced by choosing appropriate reactor operation conditions so that they do not impede normal power production. (orig.)