Model of ambient dose equivalent for radium contamination: Dependence on the geometry of the source

Industrial activities involving radium sources, such as watchmaking, were still common up until the 1960s. They produced contaminations in building materials and the soil in a large variety of geometries. The potential remediation of such places requires instruments that are properly calibrated as well as adequate procedures. We have developed a model that estimates the rate of ambient dose equivalent H˙^∗(10) at 10 cm and 1 m from a source of ²²⁶Ra and its progeny in both the soil or the building materials. Our model, described here, uses Monte Carlo (GEANT4) computed yield functions of H˙^∗(10) per unit activity induced by point-like sources in different contaminated materials. Fit functions of the yield curve of H˙^∗(10) are provided for outdoor contamination. The model can be used for any geometrical activity distribution and we present an example showing the dependency of H˙^∗(10) on the diameter and the depth profile of the sources, for both outdoor and indoor contamination.