Tomography applied to actinides detection by photofission

The development of nondestructive methods to inspect nuclear waste is important for nuclear waste management and nonproliferation purposes. Among methods using nuclear radiation as a probe, instrumental photon activation analysis (IPAA) seems to be a promising way. With IPAA, we can assay actinides masses in large volume nuclear packages. It consists of irradiating actinides with high energy photons and thus producing photofission reactions. Delayed neutrons counting, following photofission reactions, allow us to locate and assay the mass (activity) of actinides by tomography. For this purpose, we use a simulation tool named OPERA, to get information needed for tomography part, and SAPHIR facility, a linear accelerator setup for the experimental part. OPERA is able to track particles from electrons accelerated by linac to delayed neutrons counting. High energy photons of 15 MeV are produced with a tungsten bremsstrahlung target. The setup part consists of waste package surrounded by 7 detection units. First experimental results obtained on true waste package are given. They proved the good agreement between experimental part and simulation part and the possibility to get a good localisation of actinides and a detectability limit lesser than 1 g