Investigation of the radiation risk due to environmental contamination by 241Am from lightning rods disposed at uncontrolled garbage dumps

Abstract

Radioactive lightning rods were manufactured in Brazil until 1989, when the licenses for using radioactive sources in these products were lifted by the national nuclear authority. Since then, these rods have been replaced by the Franklin type and collected as radioactive waste. However, only 20% of the estimated total number of installed rods has been delivered to the Brazilian Nuclear Commission. This situation causes concern, since there is the possibility of the rods to be disposed as domestic waste. In Brazil, 64% of the municipal solid waste is disposed at garbage dumps without sufficient control. In addition, (241)Am, the radionuclide most commonly employed, is classified as a high-toxicity element, when incorporated. In the present study, (241)Am migration experiments were performed by means of a lysimeter system, in order to evaluate the risk of contamination caused by radioactive lightning rods disposed as common solid waste. (241)Am sources removed from lightning rods were placed inside lysimeters filled with organic waste that was collected at the restaurant of the Instituto de Pesquisas Energéticas e Nucleares. The generated leachate was periodically analyzed, and characteristics such as pH, redox potential, solid content and the concentration of the radioactive material were determined. The equivalent dose for members of the public was calculated considering ingestion of contaminated drinking water as the major path of exposure. Estimated doses were about 20-times below the effective dose limit of 1 mSv year(-1) for members of the public as recommended by the International Commission on Radiological Protection. This suggests the radiation risk caused by lightning rods disposed at uncontrolled garbage dumps to be low. It should be noted, however, that the number of investigated lightning rods was quite small. The results of this study might therefore not be entirely representative and should be interpreted with care. They provide, however, a very first basis for characterizing the transfer of (241)Am from lightning rods to the human food chain.

Influence of americium-241 on the microbial population and biodegradation of organic waste

“…As reported previously (Marumo et al 2008), the release of 241 Am was not constant, the initial amount of americium being relatively large, followed by a more constant longterm release. Figure 1 shows the average values obtained from the three lysimeters.…”

“…However, only 20% of the estimated total number of installed rods was delivered to the Brazilian Nuclear Energy Commission. An assessment of the risk of contamination by 241 Am used in lightning rods discarded as domestic waste was recently published (Marumo et al 2008). In that study, the radionuclide was placed in a lysimeter filled with organic waste from a restaurant.…”

“…In that study, the radionuclide was placed in a lysimeter filled with organic waste from a restaurant. The leachate was periodically analyzed to determine environmental parameters such as pH, redox potential, solid content and concentration of radioactive material (Marumo et al 2008). As the disposal of food waste mixed with general waste in open garbage dumps is still common in some parts of Brazil, this kind of waste was used in the present study.…”

Microbial bioremediation processes for radioactive waste

“…Microorganisms can play a pivotal role in changing 241 Am(III) solubility and efficient biosorption by E.coli, a marine bacterium, Rhizopus arrhizus, and Candida utilis [51][52][53][54]. In particular, Marumo et al reported the new radionuclides-tolerant bacterial strains such as Flavobacterium spp., Pseudomonas gladioli, Chryseobacterium indologenes and Ochrobactrum anthropi, which have an influence on the microbial community responsible for the degradation processes of organic waste [55,56].…”