The need for improved temperature control during reactor irradiation

Abstract

The irradiation conditions of materials irradiated in fission reactors are nearly always insufficiently described in the literature. A carful inspection of temperature-reactor power histories reveals a deficiency in the conventional control of irradiation temperatures. In particular, a short transient irradiation at a lower temperature commonly occurs during the startup of the reactor. A large difference in the final defect structure is expected to be caused by this transient irradiation from the mechanism of the defect structure development. An electron irradiation with a similar transient irradiation leads to a remarkably different defect microstructure. The defect structures introduced by a fission neutron irradiation with this transient was compared with those produced by a fusion neutron irradiation with perfect temperatrue control without transient. The difference in structures was found to be much greater than what is normally expected between fission and fusion neutron irradiations. An essential improvement in the control of reactor irradiations is proposed.