Contribution to Fission Product Transport in Soil in Connection with the Underground Arrangement of Nuclear Reactors; Explanation of Planned Experiments

[Automatically extracted and translated] The present work describes the fission product release path in a hypothetical accident (loss of coolant and failure of the containment integrity) in an underground reactor facility, without making any statement about the relevance of such an incident. By choosing suitable backfill materials, the backfilling of the containment can be optimized with regard to its fission product retention properties, thus preventing radioactive contamination of the environment. In addition to describing the radioactive source and the theoretical description of the spread of radioactive substances in the backfill and the subsequent natural soil, the safety containment of the entire Kr-85 activity of an HTR 1160 after a loss of coolant accident with failure of the containment integrity is calculated based on a simplified calculation model. Furthermore, an attempt is made to systematize the release paths from the source to the sink (human) and to identify the transmission chain using transmission coefficients. Another part of the work describes the experimental setup under construction to determine the diffusion and adsorption coefficients of the relevant backfill materials in order to have sufficient realistic input data for future fission product spread calculations in the backfill and the soil.