Shielding Factors and External Dose Evaluation

The kerma in typical European houses in urban and suburban environments due to the gamma radiation from the contamination of different deposition areas such as lawns, trees, windows, walls, roofs, paved areas, light-shafts and internal surfaces has been calculated by extensive Monte Carlo simulations. The indoor kerma has been determined for different contamination patterns, one week and one year after a deposition of radionuclides. It turned out that shielding factors, defined as the ratio of the indoor exposure to the exposure over lawns, are relatively independent of time but are different for dry and wet deposition. The importance of the deposition areas 'trees' and 'internal surfaces' is stressed. For outdoor exposures the doses to children are enhanced by up to 80% compared with adults.