RESUMO
The present work was aimed at measuring indoor radon activity concentrations in dwellings in Mvangan locality, South Cameroon, in order to assess the extent of measures that may be necessary for controlling public indoor radon exposure in this area. Measurements were carried out using passive solid-state nuclear track detectors (RADONAVA Inc., RadTrak2, Sweden) following ISO 11665-4 standard. Radon concentration ranged between 36 ± 20 and 150 ± 30 Bq m-3 with arithmetic and geometric means values of 64 ± 25 and 60 ± 1 Bq m-3, respectively. These mean values were greater than worldwide values presented by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are, respectively, 40 and 30 Bq m-3. 96% of dwellings that have radon concentrations below the World Health Organization (WHO) reference level of 100 Bq m-3, whereas 4% of dwellings have radon concentrations higher than this level but lower than 300 Bq m-3, the International Commission on Radiological Protection (ICRP) reference level. Annual effective doses due to indoor radon ranged between 0.7 and 2.8 mSv y-1 with an arithmetic mean value of 1.2 ± 0.5 mSv y-1. These values were below the lower limit of the ICRP-recommended action level interval 3-10 mSv y-1. It has been observed that annual effective dose received by residents in cement bricks dwellings were not significantly different (P-value = 0.565) than those received by residents in mud dwellings in Mvangan locality. The mean number of persons expected to be diagnosed with or die from cancer (solid cancers and leukemia) were 162 ± 48 (61 ± 25 for males and 101 ± 41 for females) and 82 ± 24 (33 ± 13 for males and 49 ± 20 for females), respectively. The results obtained in this study prove that the populations of Mvangan locality are exposed to a relatively low potential risk of cancer incidence and mortality.
Assuntos
Neoplasias , Radônio , Humanos , Camarões , SuéciaRESUMO
The optimum encapsulation of 241Am/Be disused sealed radioactive sources (DSRS) based on PHITS Monte Carlo simulations for their long-term storage in Cameroon was performed. The country capacity for the management of disused neutron sources was also evaluated and showed that a Am1 P60 capsule is sufficient for the total available inventoried 241Am/Be DSRSs. The effective dose rate was computed in the enclosures of the DSRS container, which will be temporarily stored in the centralized radioactive waste facility. The obtained results were in agreement with the ALARA principle for the exposure rate optimization and the obtained exposure dose rates were found to be 1.830 µSv/h (horizontal calculation) and 0.137 µSv/h (vertical computation) which values are lower than the 2.5 µSv/h acceptable limit for the public area. The dose profile for 241Am/Be source obtained, the neutron flux, and gamma generated from neutron absorption showed agreement with the research hypothesis. The Monte Carlo assessment achieved in the present research will be useful for dismantling and preparing the waste package for long-term storage.
