Overview of Radiation Accidents at Industrial Accelerator Facilities

Industrial irradiators have been used for decades for various reasons. In the last decade sterilisation of products, e.g. medical products or food, became an important part of many industries. The required dose rates in order to make an efficient sterilisation might be up to hundred thousand of Gy/s. Due to such extremely intense radiation fields, defence in depth shall be implemented in the design of irradiation facilities and strong safety culture shall be in place. The facilities are based either on a use of radioactive materials, i.e. Co-60 or Cs-137, or accelerators. In the last decade irradiators with radioactive sources became obsolete in order to avoid security issues as well as handling a disused source. The use of sources in industrial sterilisation facilities is related to numerous safety features assuring safe operation of facilities as sources are linked to high risks to human health in case of an accident. In the available open literature, the accidents related to industrial irradiators using radioactive sources are well described including detailed analyses of accidents with fatalities, e.g. in Kjeller 1982 and in Nasvizg in 1991. Much less information is available when industrial accelerator facilities are involved in accidents although the first accident related to industrial sterilisation happened in 1965 in USA where accelerator was involved resulting in amputation of worker's leg and arm. The literature reveals only five reported cases i.e. demonstrating that accident with health consequences are very rare. But except in one case all exposures of workers required extensive medical treatment, e.g. amputation of limbs. The present very first analysis based on a short description of reported cases, identification of initial events and contribution factors as well as lessons learned could help the regulatory bodies, designers, suppliers, installers, operators, maintenance companies and others involved in radiation safety of industrial accelerators to identify design flaws as well as human errors leading to such dreadful accidents. The analysis demonstrates that three of five cases were related to so-called "dark current" showing that there was a clear lack of understanding technical characteristics of accelerators and the risks associated with such facilities.