Airborne Release from Transport and Storage Casks Due to a Sabotage Attack with Explosives

A sabotage attack with explosives against transport and storage casks containing radioactive waste like spent fuel could generate a particulate radioactive matter from the inventory of the cask and with this subsequently an airborne release to the environment. The assessment of the radiological consequences requires the characterization of the damage pattern of the cask and, as a first step, the determination of the possible aerosol formation in the cask (respirable aerosols). In order to quantify the fraction rate realistically and to understand the influences of barriers in front of the target (like the wall of a cask) better, experiments with a real cask and a series of small-scale experiments were performed. Chemically doped cylindrical concrete-targets were used as surrogates for brittle radioactive inventory. The explosives with masses of 50 g and 200 g were put on steel panels (20 mm) simulating the wall of a cask in the small-scale experiments. The mass of two aerosol size factions < 5 µm and < 10 µm formed inside the cask was measured by proper size and time-resolved aerosol diagnostics, making use of the chemical tracer of the inventory. First results show that the release fractions are between 0.2 % and 2 % of the inventory surrogate for different experimental configurations. The distance between the steel panel and the target was varied from 2 mm to 33 mm to analyze its influence on the damage pattern and the correlation to the fraction rate of the inventory. Increasing this distance to 33 mm, a flyer-plate was formed leading to a higher fraction rate of the concrete target than if the target was closer to the steel panel. Furthermore, strain gauges were put on the back of the steel panels and on the inside of the real cask to receive extra information for attendant numerical analysis. The temperature and pressure were recorded as additional input for the development of a predictive model to assess the effects of explosives on various transport and storage casks. Further experiments are carried out with mock-ups of fuel elements filled with non-radioactive ceramic pellets.