Fissile elements monitoring system with coincidence counting for waste package characterisation

The former reprocessing plant Karlsruhe (WAK, Wiederaufarbeitungsanlage Karlsruhe) is since several years in the phase of decommissioning. The radioactive waste to be handled during decommissioning contains fissile material in addition to beta and gamma radioactivity. This material must be analysed and quantified before conditioning and transportation to interim and/or final storage. The drums with raw waste are transported from WAK to the waste treatment facility of the research center Karlsruhe for treatment, product control and analysis. A high gamma radiation field must be considered when performing the measurements. For the waste characterisation a sensitivity of 10 mg/Pu-eff is required for 200 or 400 l drums filled with raw waste, containing up to 100 g Pu. The expected gamma flux can be as high as 1 Sv/h at the drum surface. New measuring components were developed for the operation in such a high gamma field. The drum measuring device is an advanced application of the monitor system FEMOS which was developed in cooperation with FZK and RWE Nukem GmbH. FEMOS is a specially developed monitor to detect fissile materials for waste characterisation and it is also suitable to identify the main neutron emitters.