Challenges for Disposal of Irradiated Beryllium

摘要

Beryllium is used as a neutron reflector in many research reactors around the world. Additionally, it is being considered as a plasma-facing material for the International Thermonuclear Experimental Reactor and for use as a neutron multiplier in tritium breeding blankets. Because of swelling associated with helium production under irradiation, it must be replaced at regular intervals in applications where dimensional tolerances must be maintained. Though dimensional tolerance will be less significant in fusion reactors, beryllium still will require disposal at the end of life or as cleanup of sputtered beryllium is necessary. Disposal or recycling of that beryllium is influenced by a number of factors, among which is its radioisotopic inventory. Tritium inventories have been known for years, but it has recently been discovered that activation of minor impurities including nitrogen, niobium, and uranium have the potential to change the waste classification for disposal. Recycling of beryllium with significant radioisotopic inventory has yet to be developed. Beryllium from different sources has widely differing uranium impurity levels, but nitrogen content and other impurities are determined more by processing methods. Other factors influencing radiological characteristics of irradiated beryllium are the neutron energy spectrum and the temperature at which it is irradiated. Research is needed to explore techniques for mitigating consequences of radioisotopic inventories in disposal or recycling of irradiated beryllium.