Irradiation swelling in self-ion irradiated niobium

Refractory metals and their alloys offer distinct advantages for applications in nuclear systems where high temperatures are required because they exhibit high elevated temperature strength, better corrosion resistance in liquid alkali metal coolants and better thermophysical properties than other structural materials. One of the important aspects of applications of these materials at high temperatures in irradiation environments is the neutron induced swelling. However, swelling data for these materials are limited and the current theoretical treatments of swelling are not directly applicable to refractory metal since they were developed for face centered cubic (fcc) rather than body centered cubic (bcc) materials. This paper presents initial results of an investigation of swelling mechanisms in a model bcc metal; niobium. The objective of this work is to achieve an understanding of the elevated temperature swelling in bcc metals. A theory-experiment coupling is used to achieve this goal. The neutron induced swelling is simulated by irradiation with self-ions with an accumulated dose corresponding to approx.1 x 1023 n/cm2 (50 displacements per atom, dpa) which exceeds the fluences expected in SP-100