INDOOR MEASUREMENTS OF RN-220 AND RN-222 AND THEIR DECAY PRODUCTS IN A MEDITERRANEAN CLIMATE AREA

A research program on characteristics of radon exposure in dwellings i n Rome was executed. The results of measurements of Rn-220 gas concent ration, besides Rn-222 and their decay product concentrations, are rep orted. These measurements were carried out in the sitting-room of six dwellings, for 2-d periods in spring 1995, under normal living conditi ons. The Rn-220 concentration was measured at about 1 cm from the wall , using the method of delayed coincidences between Rn-220 and Po-216 d ecays. The average value in the dwellings ranged from 5 Bq/m(3) to abo ut 1100 Bq/m(3). The average Rn-222 and Rn-220 equivalent equilibrium concentrations, measured in the middle of the room, were within 8-43 B q/m(3) and 0.5-9.5 Bq/m(3), respectively. The average potential alpha energy concentration ratio between Rn-220 and Rn-222 was within 0.9-4. 6. The average equilibrium factor of Rn-222 ranged from 0.42 to 0.55. The estimate of effective doses is also discussed. These results confi rm the significant presence of Rn-220 (thoron) and its decay products and the role of certain natural building materials used in some Italia n Regions, not only as gamma and Rn-222 sources, but also as Rn-220 so urces. Copyright (C) 1996 Elsevier Science Ltd.