Bubble nucleation in advanced ODS ferritic steels for fusion applications

Abstract

Oxide dispersion strengthened (ODS) ferritic steels have been suggested as an advanced ferritic steel for service as the structure of a fusion power plant operating at high temperatures (up to 800°C) as well as low swelling fast reactor fuel cladding. Powder metallurgical methods are used to fabricate such steels, which contain a fine dispersoid of nanometric scale strengthening particles. In this paper, the author investigates the possibility that the ODS particles not only strengthen the steel, but also act as centres for the nucleation of bubbles containing transmutation helium atoms, generated over the 5–10 year lifetime in the replaceable first wall blanket by 14 MeV fusion neutrons. Calculations suggest that the lifetime swelling of such materials will be of the order of 2% in a fusion power plant, and the helium atoms are prevented from reaching grain boundaries where embrittlement might otherwise occur.