PARATI--a dynamic model for radiological assessments in urban areas. Part III: Parameter uncertainty analysis

The uncertainties in the exposure predictions after contamination of an urban area due to the variabilities in environmental transfer parameters and in dose conversion factors have been estimated. This was done using the "Latin Hypercube" sampling scheme and the computer codes PRISM and PARATI. For the scenario 'urban contamination by 137Cs' and the population groups considered, the main sources contributing to the uncertainty in the resulting exposures are the limited knowledge of the initial deposition and retention, the weathering processes, the actual urban environments, and the characteristics and habits of the population. The effect of the parameter uncertainties on the variability of the dose is almost constant over time.

PARATI--A dynamic model for radiological assessments in urban areas. Part II. Specifications of individuals and populations, their radiation exposures and variabilities

After a large-scale contamination of an urban area with gamma-ray emitting radionuclides (e.g. caesium isotopes) decision makers will need guidance as to its potential radiological consequences and to optimum means of mitigation. To provide such information, a dynamic radioecological model PARATI has been developed and used to simulate the contamination of realistic urban environments in a computer model and to estimate the various radiation fields in such environments. In this study, the computer-simulated realistic behaviour and movements of individuals and populations in such radiation fields are described, and the resulting radiation exposures and their variabilities are estimated. For the scenarios considered, the doses of individuals in the same contaminated environment may vary by more than one order of magnitude. Studies on population habits and on the behaviour of radionuclides on important urban surfaces even a long time after the contamination might reduce the uncertainty considerably.

PARATI--a dynamic model for radiological assessments in urban areas. Part I. Modelling of urban areas, their contamination and radiation fields

The structure and mathematical model of PARATI, a detailed computer programme developed for the assessment of the radiological consequences of an accidental contamination of urban areas, is described with respect to the scenarios used for the estimation of exposure fields in a village or town, the models for the initial and secondary contamination with the radionuclide 137Cs, the concepts for calculating the resulting radiation exposures and the changes with time of the contamination and radiation fields. Kerma rates at various locations in tropical urban areas are given, and the contribution of different contaminated surfaces to these rates after dry or wet deposition are discussed.