การประเมินปริมาณสารกัมมันตรังสีธรรมชาติและแก๊สเรดอนในวัสดุก่อสร้างและในอาคารเรียนบริเวณตอนล่างของจังหวัดยะลา

Abstract

The objectives of this research was to investigate the amount of natural radioactive substances, including 226Ra, 232Th and 40K in 41 samples in building materials using the gamma spectrometry analysis system with a highly pure geranium detector (HPGe), to assess the relevant radioactive hazard index and to study the amount of radon gas in the school building in lower part of Yala Province because the lower part of Yala province has geological conditions that consist of sedimentary rocks, metamorphic rocks, and granite igneous rocks scattered in various areas. There are also construction industries where most of these building materials are granite, limestone and often contain naturally occurring radionuclides 226Ra, 232Th and 40K, which are the source of radon emissions which result in health problems and increase the chances of lung cancer of residents in the area in the long run. It was found that the mean radioactive contents of 226Ra, 232Th and 40K in rock, soil, sand samples in the lower part of Yala Province were higher than the world average for soil (UNSCEAR, 2000) and the world average for building materials (UNSCEAR, 1993). In the rock samples, the highest concentrations of 226Ra and 40K were found at Ban Padeng School, Than To District. As for 232Th, it had the highest value in Betong School (Weerarat Prasarn), Betong District. Soil samples showed that the radioactive content of 226Ra, 232Th was the highest at Ban Wang Mai School, Betong District. 40K was highest in Ban Thai Pattana School, Than To District, and for sand samples, 226Ra, 232Th was highest in Ban Sri Nakhon School, Than To District, while 40K was highest in Bang Lang School, Bannang Sata District. For the five radiation hazard indices, including the radium equivalent (Raeq), external hazardous index (Hex), internal hazardous index (Hin) and the amount of gamma radiation absorbed (D) and annual radiation dose (E), it was found that all 5 radiation hazard index values of the stone samples were lower than the specified standards. For the soil and sand samples, the radium equivalent radioactivity, the external hazardous index, the internal hazardous index, and the absorbed gamma radiation dose rate were higher than the standard set. Only the annual radiation dose was below the established standard. In terms of radon concentrations within school buildings in the lower part of Yala Province, the mean values were 9.12±3.42 Bq/m3, with the highest values at Ban Sai Kaew School, Bannang Sata District and lowest at Ban Tanohputeh School, Bannang Sata District. All schools were below the threshold set by the US EPA for indoor radon levels of 148 Bq/m3. In the study area, the geology was granite but the concentration of radon gas was not very high because most of the school buildings have windows and doors open, which could the concentration of radon inside the building.