Waste drum characterization by gamma tomographic assay with the SRWGA system

The SEA Radioactive Waste Gamma Analyser (SRWGA), here described, is the gamma assay system of the ENEA Laboratory for Waste Characterisation, which started the operation in 1996 as a simple gamma scanner and was under a continuous improvement process to became a multi-techniques system as it is now. The SRWGA is designed for the assay of radioactive waste drums containing gamma emitting nuclides. It accommodates drums up to 1500 kg and 220, 400 and 500 litres capacity. The system operates with a high resolution HPGe coaxial detector, 40% relative efficiency, liquid nitrogen cooled, shielded by means of a lead cylinder (10 cm thick) with a rectangular collimation window (2.5 X 10 X 20 cm). Three load cells are installed under the turntable for measuring the drum mass and one transmission mixed source is provided ( 114mIn plus 110mAg, 100 and 10 mCi respectively). Recently SRWGA has been endowed with the possibility of new mechanical movimentations such to offer tomographic capabilities (transmission and emission). Tomographic reconstructions are obtained by means of a backprojection filtered by convolution methods (for transmission tomography) and Best Likelyhood Maximisation (for emission tomography). This work presents the first experimental results