Uncertainty, variability and sensitivity analysis applied to the RAGENA model of radon generation, entry and accumulation indoors

The application of a radon model is useful to understand the processes that drive the radon gas behaviour from its sources to its accumulation indoors. Since in a given inhabited house the detailed knowledge of the values of all the parameters that affect indoor radon levels is not available, the response of the model has to be explored in a reference site in which all the parameters are supposed to be known. We call this site the reference configuration. In this paper we report on the procedure followed to carry out uncertainty, sensitivity and variability analysis of the model response for a reference configuration that corresponds to a single family multi-zone house. We have obtained from the uncertainty analysis that, assuming a normal distribution of all the input parameters with a 10% relative standard deviation ŽR.S.D.., the model outputs present a R.S.D. in the range 17 22%. The sensitivity analysis reflects, in general, a good behaviour of the model, in the sense that its response describes a realistic behaviour of the system. The variability analysis has shown that the model is applicable to a wide range of situations, and that the most relevant parameters for the reference configuration are: the soil gas-permeability Žobtained from the mean soil grain diameter.; the ventilation rate of the rooms; the air-exchange rate between the basement and room 2; the soil-indoor pressure difference; the open area; and the concrete radium content.