This paper deals with the tensile behavior of CW316Ti and CW15-15Ti Phénix fuel pin cladding. The tension tests were conducted on defueled tubes irradiated up to 115 dpa³ in the 400–640°C temperature range. Test temperature corresponds essentially to irradiation temperature. The results emphasize that, although irradiation induces a reduction of ductility, the failure always occurs with significant plastic deformation, even for the most highly irradiated cladding.

At irradiation temperatures below 560°C, the embrittlement of both steels is correlated to the swelling and thus to the occurrence of irradiation-induced voids; in this case, the failure is transgranular. In the high irradiation temperature range, a marked difference is observed between the two steels when the tests are conducted at the irradiation temperature, since the rupture is essentially intergranular on CW316Ti and transgranular on CW15-15Ti. The tensile properties of the CW15-15Ti cladding are better than those of CW316Ti because it swells less and is less prone to creep-like embrittlement.