Operational beryllium handling experience at JET

摘要

Beryllium is favoured for plasma facing components in fusion reactors such as International Thermonuclear Experimental Reactor (ITER). As a toxic material the safety aspects of beryllium handling need careful consideration. Beryllium has been used on a large scale since 1988 in Joint European Torus (JET), as tiles and evaporators, with > 3000 kg in the torus at one time. Tile degradation and the evaporated deposit produce dust particles that can mobilise to create potentially harmful exposures. Eighteen separate manual vessel interventions have been conducted since beryllium was introduced. Although few solid tiles are used for current first wall configurations, considerable operational experience has been gained over the last 14 years working in beryllium contaminated atmospheres, and handling contaminated materials. A stringent regime for worker protection was developed for JET operations, and has maintained extremely low exposures. In the period 1988-2001, > 81,000 personal exposure assessments were carried out. Allowing for the respiratory protection worn, 99.98% of exposures are below the regulatory exposure limit of 2 μg/ m~3. To date no identifiable beryllium health effect has emerged in any of the 1200 beryllium workers that have been engaged on JET in this period. The exposure limit is likely to be reduced from 2 to 0.2 μg/m~3 in coming years. Future fusion devices will encounter even more challenging conditions involving the control of beryllium.