Keywords: external exposure, natural radioactivity, household kits, low radiation, radionuclides, contaminated ground, annual effective dose
External exposure due to natural radioactivity in some household kits
Specific activities (Bq/kg and ppm) of naturally occurring radionuclides were measured for about 57 samples from some household kits. The maximum specific activity values were 76.12, 118.37 and 3340.6 Bq/kg for U-238, Th-232 and K-40, respectively. The external exposure rate (μR/h) and dose rate (nG/h) were calculated. The maximum mean annual effective dose due to U-238 from Chinese ceramic dishes was 59.24 μSv/y, while the maximum mean annual effective doses due to Th-232 and K-40 were 126.31 and 63.81 μSv/y, respectively. The maximum total mean annual effective dose was 248.19 μSv/y for Portuguese dishes. The surface area concentration (Bq/m²) was calculated to estimate the annual equivalent dose to all organs and the effective dose due to contaminated ground. To estimate the annual effective dose, a value of 0.7 Sv/Gy was used for the conversion coefficient from the absorbed dose in air to the effective dose received by workers. The mean annual effective dose to workers due to U-238, Th-232 and K-40 is given using two methods: the first one is according to the International Atomic Energy Agency (IAEA) (2003) recommendations and the second one is a Monte Carlo technique for the dose calculations, which ranged from 0.0036 to 0.248 mSv/y for the first method and 0.0039 to 0.214 mSv/y for the second method. The total annual dose from U, Th and K for each organ shows that the lowest dose was received by the oesophagus, while the skin received the highest dose.