It is estimated that until 1978 about 200000 lightning conductor rods with -a emitting sources attached to their end were installed worldwide. The sources were supposed to increase the lighting collection efficiency of these rods through the ionization of the surrounding air. Nevertheless, this improvement has never been established conclusively. Such devices are, in most cases, not accessible by the pub- lic; therefore, the dose to the population is considered insignificant. However, the possibility of radioactive material leakage, due to the source attachment failure, and the subsequent contamination of the surroundings that could lead to possible health risk of the public cannot be excluded. In this work, the case of 241Am contamination due to a lightning rod conductor failure is investigated. This contamination was accidentally detected on the surface soil around a laboratory building in the National Technical University of Athens Campus, during a routine in-situ gamma-ray measurement campaign that took place in 2003. A detailed survey revealed that this 241Am contamination was due to the leakage from two lightning rods on the building roof. Consequently the rods were removed from the building and the contamination pattern on the roof and on the surface soil around the building was examined in detail. From the results obtained so far it may be concluded that there exists well localized contamination on the roof and also around the building. It was established that the pathway through which contamination reached the ground was the rainwater drainage system of the building. The gamma ray dose rate due to 241Am contamination found on the roof and on the surface soil is low compared to that due to its natural radioactivity and does not seem to pose any health risk to the people working in the building or to the public.
Surface soil radioactivity is being studied at NED-NTUA since almost thirty years. The last few years this research has expanded to the study of soil particle size fractionation of radionuclides. The purpose of the present work was to study the tendency of many radionuclides to accumulate in the smaller particle size fractions. To this end, soil samples were collected from an area in the NTUA Campus where 241Am contamination, due to a failed 241Am-tipped lightning rod, had been previously detected. The samples were separated into size fractions using a sieving machine and analyzed by gamma spectrometry to determine 210Pb, 241Am, 234Th, 228Ra, 228Th, 226Ra, 7Be, 137Cs and 40K. The activity concentrations of these nuclides were found to significantly differ among the size fractions examined.
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