Influence of the migration of radioactive contaminants in soil, resident occupancy, and variability in contamination on isodose lines for typical Northern European houses

Abstract

In the remedial phase following an accidental radioactive release, it is important that soil decontamination measures are carried out on the areas that contribute most to the radiation dose. In this study, the newly developed concept of isodose lines was applied to the area around typical Swedish dwellings to identify these areas. The influence of the most common building materials in Sweden, wood and brick, and the importance of the positions of doors and windows on the isodose lines were demonstrated for specific positions inside the houses, as well as for the entire house, assuming the residents exhibit typical resident occupancy. Decontamination of the areas within certain isodose lines was shown to result in a greater dose reduction than decontaminating the same area of soil within a certain distance of the house. Furthermore, the impact of vertical migration of the radioactive contaminants in the soil on the isodose lines was studied, showing that the area enclosed by isodose lines decreases over time as the contaminants migrate deeper into the soil. The resulting isodose lines and their change over time are dominated by the downward movement of the contamination in the upper layer of soil. The impact of the variability in contamination on the final isodose lines and their dependence on building materials are demonstrated.

Monte-Carlo simulations of external dose contributions from the surrounding ground areas of residential homes in a typical Northern European suburban area after a radioactive fallout scenario

“…According to previous findings (e.g. by Hinrichsen et al 19 ), the contaminated areas that contribute most to the dose at a certain position move closer to the observation point, as the ground contamination migrates into the ground as the contributions from more remote areas become less www.nature.com/scientificreports/ significant due to the attenuation of the gamma flux by the ground in the line of sight between the source area and the observation point. Therefore, the external dose contribution from the neighbouring surfaces in this study can be assumed to be an upper limit and, in reality, the dose contribution from contaminated areas of one's own property may be higher.…”

“…The external dose contribution to a specific room inside the house is highly dependent on the position of the windows in a brick house, whereas for a wooden house the distance to the source region is also of importance, as this building material provides less shielding. These principles can be also applied to other positions inside the house and have been already found in one of our previous studies 19 , in which dose contributions have been studied in higher resolution for a smaller area. Furthermore, this study shows the importance of considering the occupancy of the various rooms in the house (e.g.…”

“…Therefore, the external dose contribution from the neighbouring surfaces in this study can be assumed to be an upper limit and, in reality, the dose contribution from contaminated areas of one's own property may be higher. Moreover, in reality the contamination would not be homogeneous as assumed in this study, but the impact of variability in contamination with its dependence on building material in regard to dose contribution of certain contaminated areas has already been studied and discussed in one of our previous publications 19 .…”

“…Among other processes, the code accounts for photon creation and loss through relevant mechanisms such as bremsstrahlung, fluorescence, Compton scattering, photon capture, pair production and p-annihilation. The complex 3-dimensional models of typical Northern European one-storey houses as described previously 19 , were defined through a combinatorial geometric technique, based on construction drawings and descriptions of an actual wooden and a brick house made available by the Urban Planning Department of the Municipality of Hässleholm in Sweden (Stadsbyggnadskontoret, Hässleholms kommun) ( Fig. 5).…”

Guest Edited Collection: Radioisotopes and radiochemistry in health science

“…Surveys into the distribution and detection of naturally occurring radioactivity are an important part of the Collection as well, as they demonstrate how radioisotope science helps assess radiation doses from natural radioactivity; the "isodose" concept to Swedish residential buildings was applied to optimize topsoil removal concepts 33 .…”