Car-borne survey and dose assessment from external radiation exposure in Bangka Island.

With a history of more than 200 years of tin mining, Bangka Island has brought along a byproduct of heavy minerals containing radionuclide elements. There are some concerns about this byproduct material contributing to natural radiation in the environment. In this study, a car-borne survey was conducted to accurately assess natural background radiation in Bangka Island. Indoor and outdoor ambient dose rates in 146 houses were also measured to assess the radiation dose from external exposure received by the public. Soil samples were collected and measured using a gamma spectroscopy system to evaluate the contributions of specific radionuclides to external terrestrial exposure. From 3790 measurement points during the car-borne survey, the highest ambient dose equivalent rate was 596 nSv h-1 measured in Muntok area, with a mean value of 101 nSv h-1 and a median value of 95 nSv h-1. The ambient dose equivalent rate distribution map showed a relatively higher value in the northern coastal area of the island, where the Pemali tin deposit is located. The annual effective dose received from external radiation in the 146 houses in Bangka Island ranged from 0.44 to 1.30 mSv year-1, with a median value of 0.66 mSv year-1. The soil contained a relatively high amount of thorium (232Th), which contributed 69% to external radiation exposure in Bangka Island.

A unique high natural background radiation area - Dose assessment and perspectives.

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h-1 and 1109 nGy h-1. Indoor radon concentrations ranged from 124 Bq m-3 to 1015 Bq m-3. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m-3 recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

RADON CONCENTRATIONS IN DWELLING OF SOUTH KALIMANTAN, INDONESIA.

Determination radon concentrations in dwelling in South of Kalimantan Province by using a passive method had been conducted. South Kalimantan is a province in Indonesia and also known as a coal mining area which has the potential for internal exposure of Naturally Occurring Radioactive Materials (NORM) to the human. The research area divided into several sections called grid. Each grid represents a 60 km × 60 km area that installed passive radon monitoring 10 population. Passive radon monitors installed in the dwelling with exposures time approximately 3-4 months and then radon monitors were collected and brought to the laboratory for processing and then read the track to calculate the radon concentrations. The data concentrations of radon in the dwelling and GPS location as an input to the make a map of radon concentration by using MapInfo Software v.10.5. The results of the analysis of the concentration of radon in the dwelling of South Kalimantan in the ranged 3.1 ± 0.2 Bq m-3 up to 94.0 ± 6.7 Bq m-3. The result was lower than the reference level radon set by UNSCEAR was 300 Bq m-3. These data are useful in the development plans and regional development, as well as the basis for health policy analysis due to radon in Indonesia. Furthermore, these data will be the contribution of Indonesia in the international world through UNSCEAR, IAEA and WHO. The data obtained as an input in making a map of the concentration of radon in houses of Kalimantan Selatan as part of the map of the concentration of radon in Indonesia.

National comparison of activity measurements of ¹³¹I, 6°Co, and ¹³³Ba in Indonesia.

National comparisons of radioactivity measurements of (131)I and (60)Co (in 2010) and of (133)Ba (in 2011) were carried out within the framework of the National Radiation Metrology Laboratory Program of Indonesia, coordinated by PTKMR-BATAN. Eleven laboratories took part in the comparison, and all measurements were made using gamma spectrometry, on point sources with an activity between 2000Bq and 6000Bq. Several laboratories reported values which were more than 10% different from the reference value for (131)I and (133)Ba. Possible reasons for these differences are discussed. This program will be continued with other radionuclides to maintain and control quality assurance for the local laboratories.

Quantification of the dependency of radon emanation power on soil temperature.

A study on the quantification of the dependency of the radon emanation power on soil temperature has been made using the accumulation method. The emanation from dry soil was studied at temperatures between -20 degrees C and 45 degrees C. A formula to calculate the radon emanation power as a function of the temperatures has been developed. The formula would contribute to the modeling of radon transport in soils and building materials.