Behavior of Radon and Its Daughters in a Basement: Model-Experiment Comparison

On the basis of Jacobiʹs model (1972), we have developed the PRADDO model, which describes the behavior of radon and its daughters in a system of one or more chambers. In this article we compare theory and practice in the case of a one-chamber system. The principal equations of the classical room model, describing one single enclosure, are given and the assumptions made in modeling are discussed. Field measurements in the basement of a four-story house in Brittany are described. Radon and its daughters, the ambient aerosol, and ventilation were measured in order to characterize the system accurately and to define the modelʹs input parameters. The measurement protocol used allowed definition of the extent to which the assumptions of the model were respected in the real system. Results of the theory--experiment comparison show satisfactory agreement between calculation and measurement of the radon daughters activities, the potential alpha energy concentration and the equilibrium factor; the model reproduced well the time-dependent variations in these parameters. The model tended to underestimate the activities of the attached and total fractions of radon daughters, the calculation-measurement deviations remaining less than 50%. The levels of the unattached fraction in the basement were too low to allow any conclusion to be drawn regarding their modeling