The potential presence and minimisation of plutonium within the irradiated beryllium in fusion power plants

Abstract

Beryllium is expected to be one of the materials used in DEMO-type fusion power plants as blanket neutron multiplier for solid breeders and also in ITER as protective layer of plasma facing components. Among the aspects to be considered when dealing with Be a relevant one is its impurities content. One of the impurity reported by manufacturers is uranium, and that could represent a main source of concern, because its irradiation under fusion neutrons will lead to the formation of actinides, such as plutonium. The paper presents a parametric assessment utilizing for beryllium material composition a range of possible U impurity content between 0 and 100 ppm wt. First Wall neutron wall load ranging from 0.5 to 2.2 MW/m 2 and neutron fluence from 0.5 to 10.5 MW year/m 2 are considered (for ITER and DEMO-type reactor, respectively) to estimate the Pu production. In all those analyses the irradiation scenarios considered are based on a deuterium–tritium plasma. The evaluation have been performed using the EASY-2007 activation code package, with the EAF2007 activation library. An estimate of the Pu production at the end of the ITER fusion machine preliminary operation with deuterium–deuterium plasma is also presented. A preliminary analysis of the regulatory constraints on the maximum Pu production and indications of possible way for its minimisation is presented and discussed in the paper.