The Estimation of potential Consequences from the Sabotage of Nuclear Material Transports

A terrorist sabotage attack with explosives or explosively formed projectiles (EFP) against transport and storage casks could cause fragmentation of the (brittle) radioactive inventory and the formation and release of aerosol-borne radioactivity. For assessing the radiological consequences the characterization of the damage pattern of the cask and the source term, i.e. the release fraction defined as the fraction of the inventory released as (respirable) aerosols, needs to be determined. In order to quantify the release fraction and to observe the basic release mechanisms, a series of small scale experiments simulating sabotage attacks with explosives and EFPs was performed. In case of the experiments using explosives, various amounts of it were placed on steel panels, which were simulating the wall of the cask. In the “EFP-experiments” pre-manufactured flyer plates of 24 mm caliber were shot against asmall-scale mock-up of a transport cask equipped with stainless-steel wall segments of variable thickness. Chemically doped quadratic ceramic plates, cylindrical concrete-targets and mock-ups of fuel elements filled with non-radioactive ceramic pellets were used as surrogates for brittle radioactive inventory inside of the casks. During the experiments the mass of two aerosol size fractions < 5 μm and < 10 μm, was measured by aerosol diagnostics. Temperature and pressure were recorded as additional input for numerical analysis and to model a potential outflow of gases out of casks. First results show, that release fractions determined during the experiments with explosives are in between 0.2 % and 2 % of the inventory surrogate comparedto below 1 % in case of the experiments with EFPs. A dependence of the release fraction and the amount of explosives used, as well as on the thickness of the steel panel penetrated by the projectile was quantified, leading to specified correlations be-tween input energy and release fraction. The results of the small scale experiments are supposed to serve as input data for the development of a predictive model to assess the aerosol release from explosive or EFP impact on casks during transport. In our contribution we will present the results and first analysis of the different experiments.