Evolution of beryllium pebbles (HIDOBE) in long term, high flux irradiation in the high flux reactor

Abstract

In the HIDOBE ( HIgh DOse irradiation of BEryllium) experiment, various grades of constrained and unconstrained beryllium pebbles, beryllium pellets and titanium-beryllide samples are irradiated in the high flux reactor (HFR) in Petten at four different temperatures (between 425 °C and 750 °C). The irradiation has been performed in a high flux position in order to obtain a DEMO relevant dpa–helium ratio. High dose irradiation testing is important because the beryllium irradiation behaviour, in particular its swelling and creep, has impact on, e.g. structural integrity of the breeder blanket and the tritium inventory and it is considered a critical issue for the HCPB concept for performance, safety and waste management. The first of two HIDOBE experiments, HIDOBE-01, has reached its irradiation target of 3000 appm He production after two years of irradiation and has been dismantled. The sample specimens have been retrieved and Post Irradiation Examination (PIE) has started on a selection of materials. This work presents the first observations of the material and preliminary results of material evolution (e.g., swelling, porosity/density changes, etc.) due to irradiation effects on different beryllium grades.