Uncertainty Analyses of Reconstructed Inhabitant Doses from 60Co-Contaminated Rebar Buildings

Abstract

The first 60Co-contaminated rebar building was discovered in Taipei city in 1992. As of 31 January 1997, 178 buildings with 1537 dwellings were found to contain 60Co-contaminated rebars. Almost all contaminated reinforced concrete buildings were constructed between 1982 and 1984. Thousands of inhabitants had been exposed to ionising radiation of various degrees. Preliminary assessments by the Atomic Energy Council showed that the accumulated maximal doses ranged from a few mSv to several Sv. More reliable individual doses for 24 highly contaminated dwellings were later reconstructed by us for epidemiologic and medical purposes. This reconstruction was made by a large scale deployment of thermoluminescence dosemeters in the contaminated dwelling and by a consideration of the variation in residential daily activities for individual family members. In the present work, the reconstructed dose uncertainty is estimated by analysing the non-uniform exposure rates of the dwelling using isodose contour plots and by assigning different occupancy factors to different areas in each contaminated room. The non-uniform exposure rate and the occupancy factor are the main factors causing the dose reconstruction uncertainty. The total dose uncertainty is within a factor of two for all inhabitants living in the 24 contaminated dwellings studied.