Low-Temperature Uranium Fission Fragment Irradiations Of Alpha-Iron

We present here a study of 5 K irradiation damage in iron: a high purity iron ribbon and various dilute Fe- 235 U alloys (0.01 to 0.5 at.% uranium) are introduced in the liquid helium irradiation loop of the Garching reactor. The sample holder is set in a zone of intense thermal neutron flux: the alloys are consequently submitted to uranium fission fragments irradiations. Electrical resistivity increase measurements allow us to follow the damage processes and to explain why they differ from those occurring during neutron or light ion irradiations.