Activity determination of the Am-241 sources from radioactive lightning rods

The authorization for manufacture commerce and installation of radioactive lightning rods, in Brazil, was lifted in 1989 by the National Nuclear Energy Commission ‐ CNEN (Resolution n o 4/89). Since this date, these devices have been replaced and have been sent to th e Institutes subordinated to the CNEN, amongst them the Nuclear and Energy Research Institute ‐ IPEN-CNEN/SP. Radioactive Waste Management Laboratory ‐ RWML of the IPEN - CNEN/SP had received, approximately, 16,000 units up to the end of 2008. The radioactive lightning rod is constituted in its maj ority, for a central metallic rod, where two or thr ee metallic plates are mounted. In these plates, on average, si x Am-241 sources are fixed. The process used for th e radioactive lightning rods treatment is the dismant ling of the device and the withdrawal of the source s from the metallic plates. The activity values of the lightni ng rods sources, supplied by the manufacturers, var y from two to three orders of magnitude and therefore it is ne cessary to characterize these sources. This paper d escribes the methodology used to measure the actual activity of each Am-241 sources extracted from the radioactive lightning rods. The first step was to sample tens o f Am-241 sources and carry out the activity measure ments for further use in the system calibration. The equipmen t used in this first stage was a gamma spectrometer , previously calibrated with an Am-241 standard sourc e, in agreement with the same arrangement and same geometry in the measures of the sources. Results sh ow that there are sources with similar activity val ues of those supplied by the manufacturers, but there are also s ources with no activity ‐ or also activity very low compared with the expected value ‐, as well as sources conte nd other radionuclides.