생활주변 건축자재로부터 대기로 방출되는 라돈-222 농도측정

Abstract

We are exposed to a radioactive dose of 2.4 mSv annually. Among these, some 1.3 mSv is from Radon and its progeny, and 79% of this radon exposure dose is by our Radon inhalation indoors. This study provides some information of key factors affecting indoor radon concentration through measurement of radon and its daughter nuclide produced from Uranium and Thorium decay contained in building materials around us. Using RTM1688-2, Silicon Surface-Barrier Detector that can measure both Radon and Thorium at the same tome, Radon concentration was measured for 10 kinds of construction materials in the experimental container. Building materials were put in the airtight acrylic container with a volume of 216ℓand sealed; radon concentration was measured for 10 hours at 60-minute interval starting from the 91 st hour when Rn-222 concentration reached 50% of Ra-226. Radiometric quantity of 0.64 Bq/m3Kg ~ 121.7 Bq/m3Kg was obtained per unit mass: Tile(clay+limestone) 0.64 Bq/m3Kg < Kaolin Brick 0.7 Bq/m3Kg < Tile(gypsum) 0.82 Bq/m3Kg < Red Brick 1.1 Bq/m3Kg < Loess Tile(loess+charcoal) 6.75 Bq/m3Kg < Gypsum Board 11.04 Bq/m3Kg < Ecocarat 12.22 Bq/m3Kg < Cement Brick 23.71Bq/m3Kg < Cement Block 28.07 Bq/m3Kg < Texture(cement) 121.7 Bq/m3Kg Calculation based on the amount of materials required in 3.3m2 in building showed 24.6Bq/m3 ~ 13065.2Bq/m3 range: Tile(gypsum) 24.6Bq/m3 < Tile(clay+ limestone) 38.4Bq/m3 < Gypsum Board 208.8Bq/m3 < Loess Tile(loess+charcoal) 221.3Bq/m3 < Kaolin Brick 225.0Bq/m3 < Ecocarat 382.9Bq/m3 < Red Brick 441.7Bq/m3 < Texture(cement) 2811.6Bq/m3 < Cement Brick 10875.0Bq/m3 < Cement Block 13065.2Bq/m3 Among the samples, high radon emission building materials such as Texture(cement), Ecocarat, Cement Brick, Loess Tile, Cement Block and Gypsum Board were analyzed utilizing Bi214(609.3KeV) peak, Tl208(583 keV) peak, and K40(1460.8 keV) peak with HPGe. Hazard indices were calculated with the measured radioactivity levels of Ra226, Th232 and K40. Hazard index of all materials was in the range of 0.07 ~ 0.51 which did not exceed the national recommendation of 1: Texture( Cement) 0.51, Cement Brick 0.39, Cement Block 0.39, Ecocarat 0.31, Loess Tile 0.27, Gypsum Board 0.07. In this study to evaluate the exterior exposure dose on sample materials, the hazard level was evaluated to be within recommendation value, but it still indicates a precautionary principle in selecting and applying building materials to reduce the radon exposure. Also, Ecocarat appeared to be worth of further study for its peculiarity based on comparison between radon emission rate and amount of nucleid, which seemed to have a close relation with thickness, surface treatment, porosity and density of construction materials. Effects of radon was evaluated and some methods were suggested in this study to reduce personal exposure dose. Positive publicization and control of the authority is invited to use building material with low radon emission.