Papers by Supitcha Chanyotha
Several industrial processes are known to enrich naturally occurring radioactive materials (NORM)... more Several industrial processes are known to enrich naturally occurring radioactive materials (NORM). To assess such processes with respect to their radiological relevance, characteristic parameters describing this enrichment will lead to interesting information useful to UNSCEAR. In case of mineral treatment plants, the high temperatures used in smelting and refining processes lead to high concentrations of 238 U and 232 Th. Also due to thermal power combustion, concentration of U and Th in the fly ash increases manifold. NORM samples were collected from a Thailand mineral treatment plant and Philippine coalfired thermal power plants for investigation. Some studies are initiated from a high background radiation area near Gopalpur of Orissa state in India. These NORM samples were analysed by gamma-ray spectrometry as well as inductively coupled plasma mass spectrometry. The radioactivity in case of Orissa soil samples is found to be mainly contributed from thorium. This study attempts to evaluate levels of thorium activity in NORM samples.
Journal of Radioanalytical and Nuclear Chemistry, 2014
This paper reports on the distribution of three natural radionuclides 238 U, 232 Th and 40 K in m... more This paper reports on the distribution of three natural radionuclides 238 U, 232 Th and 40 K in marine sediments along the Gulf of Thailand to establish baseline data for future environmental monitoring. Sediments were collected from five potential sites selected for nuclear and thermal power plants commission as well as heavy industry development. Concentration of uranium and thorium were determined using inductively coupled plasma mass spectrometry (ICP-MS) as well as activity of 238 U series ( 226 Ra), 232 Th series ( 228 Ac) and 40 K by c-spectroscopy. The radiation hazard parameters were calculated based on United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Variation in concentration of natural radionuclides at different sampling areas could be attributed to organic matter content and sediment particle size. The radiological health hazards to the people living nearby sampling areas and the people who handle the marine sediments are within limits recommended by UNSCEAR.
Radiation Protection Dosimetry, 2015
ABSTRACT The aim of this study was to provide the baseline data information on natural radioactiv... more ABSTRACT The aim of this study was to provide the baseline data information on natural radioactivities in vegetables and fruits produced and consumed locally in the areas of potential nuclear power plant sites in Thailand. Four provinces (Prajuab-Kirikhan, Chumphon, Surat-Thani and Nakhon-Si-thammarat) were selected for collection of native vegetables and fruits samples, together with their corresponding soils. The activities of (226)Ra, (228)Ra, (40)K and (210)Po were determined in all these samples. The obtained results for (226)Ra, (228)Ra, (40)K and (210)Po for all vegetable and fruit samples were in the range of 1-34, 1-108, 32-4392 and 0.2-47 Bq kg(-1), respectively, which were much lower than those obtained for their corresponding soils. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected].
Journal of Physics: Conference Series, 2015
ABSTRACT This study designed a simple, custom-made system to estimate the diffusive radon flux fr... more ABSTRACT This study designed a simple, custom-made system to estimate the diffusive radon flux from solid materials (e.g., sediments, soils, building materials). Determination of the radon flux is based on the measurement of the radon activity in the air over time inside a closed loop system. For sediments, the system consists of wet sediment and water inside a gas-tight flask connected in a closed loop to a drying system and a radon analyzer (Durridge RAD7). The flux is determined based on an initial slope method in which the slope of radon activities vs. time plot during the first 12 h is evaluated. The slope is then multiplied by the total air volume and divided by the exposed sediment area to obtain the radon flux. The minimal thickness or mass of wet sediment should be about 4 cm or (equivalent to approximately 150 g of wet sediment) to obtain a reliable radon diffusive flux in this study.
Radiation Protection Dosimetry, 2015
ABSTRACT The aim of this article is to provide information on the systematic approach that has be... more ABSTRACT The aim of this article is to provide information on the systematic approach that has been developed for the measurement of natural radiation exposure and the characterisation of naturally occurring radioactive materials (NORM) in terms of occurrence and distribution in various industrial processes, including the produced waste from the mineral industries in Thailand. The approach can be adapted for various types of study areas. The importance of collaboration among research institutions is discussed. Some developments include 25 documents; the redesign of the field equipment, such as the gamma survey meter, for convenient access to conduct measurement in various study areas; the method to collect and analyse radon gas from a natural gas pipeline and the manganese dioxide fibre to adsorb radium on-site for laboratory analysis. The NORM project in Thailand has been carried out for more than 10 y to support the development of NORM regulation in Thailand. In the previous studies as well as current, international standards for action levels have been adopted for safety purpose. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected].
Radioprotection, 2009
The paper presents a simple technique for determination of the Equilibrium Equivalent Thoron Conc... more The paper presents a simple technique for determination of the Equilibrium Equivalent Thoron Concentration (EETC). A solid-state nuclear alpha track detector (SSNATD) named CR-39 manufactured by BARYOTRAK is used as the detector. This technique can be utilized anywhere, provided that air sampling is carried out with a DC driving pump. Although the measurement of Thoron concentrations is useful enough for screening high Thoron exposure, it is still necessary to determine Thoron progeny concentrations in order to complete dose assessment. After applying this technique for determining the EETC in some selected areas in southern Thailand, it has been found that the obtained EETC values are consistent with the values presented in the report compiled by UNSCEAR in 2000.
Journal of Radioanalytical and Nuclear Chemistry, 2015
Natural radioactivity in surface soil samples collected at potential sites from southern part of ... more Natural radioactivity in surface soil samples collected at potential sites from southern part of Thailand to set up nuclear power plants has been investigated. 238 U and 232 Th were determined by inductively coupled plasma mass spectrometry whereas gamma-ray spectroscopy was used for 40 K determination. The activity concentrations for 238 U, 232 Th and 40 K varied in range from 4 to 122, 6 to 170 and 5 to 1,422 Bq kg -1 , respectively. The large variation of radionuclide concentrations showed heterogeneous distribution that could be attributed to geological origin. The radiation hazard parameters were estimated from activity concentration of 238 U, 232 Th and 40 K in accordance with the UNSCEAR 2000. Data obtained indicated that soils in the study areas did not pose any significant radiological health hazard to the local population.
Journal of Hydrology, 2014
ABSTRACT We conducted surveys of several canals in Bangkok, Thailand using continuous measurement... more ABSTRACT We conducted surveys of several canals in Bangkok, Thailand using continuous measurements of naturally occurring 222Rn (“radon”) and 220Rn (“thoron”). Shallow groundwater seeping into these canals is an important pathway for contamination of surface waters. Radon, with a half-life (3.82 days) shorter than the suspected flushing time of the canals, is widely distributed throughout the waterway. It can thus be used to estimate discharge via a mass balance approach but cannot specify precisely where the discharge is occurring. Thoron, on the other hand, with its rapid decay (56 s half-life) will only occur very close to points of entry. Thus, if one detects thoron in the environment, there must be a source nearby – a good ‘prospecting’ tool. We found thoron spikes in Klong Bangkok Noi during a survey in August 2009. We repeated the same survey route in June 2013 and found essentially the same pattern of high thoron peaks (indicating points of discharge) adjacent to several temples along the canal. The connection to temples is thought to be a consequence of these structures being built on relatively higher ground and having sandy substrates.
Environmental Earth Sciences, 2014
Distribution of rare earth elements (REEs), thorium and uranium in 54 marine sediments collected ... more Distribution of rare earth elements (REEs), thorium and uranium in 54 marine sediments collected from five selected areas along the Gulf of Thailand is discussed in this paper. These areas have been selected as potential sites to set up thermal and nuclear power plants. Concentration of elements was determined using inductively coupled plasma mass spectrometry (ICP-MS). Absolute concentrations of REEs, Th and U show a sample-to-sample variation and may be due to different geological characteristic of area as well as grain size effect. Total REE concentrations (not including Y) range between 9.4 and 206 lg/g. The chondrite-normalized REE patterns of all samples are similar to Post-Archean Australian Shale (PAAS) and average Upper Continental Crust, with LREEs' enrichment relative to HREEs (La N / Yb N = 6.5-29), fairly flat HREEs' patterns (Gd N / Yb N = 1.0-3.8) and ubiquitous negative Eu anomaly (Eu/ Eu* = 0.3-0.7). Th concentrations (0.9-28 lg/g) are relatively higher than those of uranium (0.4-4.0 lg/g). Th/U ratios (1.5-9.9) are higher than the average upper crust. These results are consistent with terrigenous sediments that formed from the weathering and erosion of felsic rocks.
Groundwater and Subsurface Environments, 2011
Proceedings of SPE Asia Pacific Health, Safety, and Security Environment Conference and Exhibition, 2007
Engineering Journal, 2011
The aim of this study was to evaluate the level of terrestrial radioactivity on Phuket Island, wh... more The aim of this study was to evaluate the level of terrestrial radioactivity on Phuket Island, which used to be the richest tin province in Thailand. We measured 124 survey points of terrestrial gamma dose rate at one meter above the surface of local soil along roads in the surroundings of Phuket Island. Another 31 survey points were examined inside an old ore-dressing plant. The terrestrial gamma dose rate of the Island (excluding the abandoned area of the old dressing plant) ranges from 20 to 900 nGy h -1 while the geometric mean Island value was 190 nGy h -1 . Soil samples were also collected from specific areas indicating high gamma dose rates to analyze for activity concentrations of 226 Ra, 232 Th and 40 K. Based on these soil activities, the calculated terrestrial gamma dose rate indicating range between 25 and 520 nGy h -1 . The corresponding annual effective doses ranged between 0.03 and 0.6 mSv y -1 . The results of the terrestrial gamma dose rate obtained from direct measurement in the old tin dressing plant ranged from 110-17170 nGy h -1 with a mean value of 1410 nGy h -1 . The terrestrial gamma dose rate calculated from soil samples in the dressing plant ranged from 590 to 206080 nGy h -1 which corresponded to annual effective dose of 0.7-250 mSv y -1 . The dose rate in the almost whole area of Phuket Island is equivalent to the typical background level whereas the dose rate in the old tin dressing plant was 16 times higher than the background level.
Science of The Total Environment, 2009
Radon-222 is very concentrated in groundwater relative to surface waters and thus serves as an ef... more Radon-222 is very concentrated in groundwater relative to surface waters and thus serves as an effective groundwater discharge tracer. We observed spikes in radon data from an earlier (2004) survey of the Chao Phraya River that appeared to correspond to locations where major canals ("klongs") enter the river. We returned in 2006 and conducted more detailed surveys along some of the main klongs on the western (Thonburi) side of the Chao Phraya to evaluate this possibility.
Radiation Protection Dosimetry, 2010
This study aims to introduce thoron ( 220 Rn), a naturally occurring isotope, as a new groundwate... more This study aims to introduce thoron ( 220 Rn), a naturally occurring isotope, as a new groundwater tracer for detecting groundwater seepage into Bangkok canals. Previous studies by the group using radioactive radon ( 222 Rn) and conductivity as groundwater tracers suggested that there is shallow groundwater seeping into the man-made canals ('klongs') around Bangkok. Furthermore, the groundwater was shown to be an important pathway of nutrient contamination to the surface waters. Thoron is a member of the natural 232 Th decay chain, has exactly the same chemical properties as radon, but has a much shorter half-life (56 s) than radon (3.84 d). By using its advantage of rapid decay, if one detects thoron in the environment, there must be a source nearby. Thus, thoron is potentially an excellent prospecting tool. In the case of measurements in natural waters, sources of thoron should indicate the point of groundwater discharges more precisely than radon. During the surveys in the canals of Bangkok, thoron was successfully measured and its distribution was more variable than that of radon, suggesting that seepage into the canals is not uniform.
Radiation Protection Dosimetry, 2010
There is a well-known discrepancy between dosimetrically derived dose conversion factor (DCF) and... more There is a well-known discrepancy between dosimetrically derived dose conversion factor (DCF) and epidemiologically derived DCF for radon. As the latter DCFs, International Commission on Radiological Protection (ICRP) recommends a value of ∼6.4 nSv (Bq h m 23 ) 21 and 7.9 nSv (Bq h m 23 ) 21 for radon decay products (RnDP) in dwellings and workplaces, respectively. On the other hand, the dosimetric calculations based on the ICRP-66 respiratory tract model derived a DCF of 13 nSv (Bq h m 23 ) 21 and 17 nSv (Bq h m 23 ) 21 for RnDP in dwellings and workplaces, respectively, and 83 nSv (Bq h m 23 ) 21 for thoron decay products (TnDP) in dwellings. In addition, the DCFs derived from both approaches and UNSCEAR were applied to comparative dosimetry for two thoron-enhanced areas (cave dwellings in China and dwellings at a spa town in Japan), where the equilibrium equivalent concentration of radon and equilibrium equivalent concentration of thoron have been measured. In the case of the spa town dwellings, the dose from TnDP was larger than the dose from RnDP.
Radiation Protection Dosimetry, 2012
The naturally occurring radioactive materials (NORMs) distributed in products, by-products and wa... more The naturally occurring radioactive materials (NORMs) distributed in products, by-products and waste produced from Thai mineral industries were investigated. Samples were analysed for radioactivity concentrations of two principal NORM isotopes: 226 Ra and 228 Ra. The enrichment of NORM was found to occur during the treatment process of some minerals. The highest activity of 226 Ra (7310 7 Bq kg 21 ) was in the scale from tantalum processing. The radium concentration in the discarded byproduct material from metal ore dressing was also enriched by 3-10 times. Phosphogypsum, a waste produced from the production of phosphate fertilisers, contained 700 times the level of 226 Ra concentration found in phosphate ore. Hence, these residues were also sources of exposure to workers and the public, which needed to be controlled.
Journal of Radioanalytical and Nuclear Chemistry, 2013
A new portable type cascade impactor has been developed to determine the activity size distributi... more A new portable type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a natural environment more efficiently. The modified impactor consists of 4 stages with a back up filter stage for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 lm at a flow rate of 4 L min -1 . Five CR-39 chips were used as alpha detectors for each stage. In order to separate a particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. The thickness of each film is adjusted to allow a particles emitted from radon and thoron progeny to reach the CR-39 detectors. The technique has been successfully tested in field studies, particularly inside a mineral treatment industry in Thailand to estimate doses in the working environment. The dose calculations by lung dose evaluation program showed that activity median aerodynamic diameters played a significant role in determining the particle size distributions of the attached radon and thoron progeny. The dose conversion factor determined from short term measurements due to exposure from the inhalation of thoron and its progeny was found to be 4 times higher than comparable values for radon and its progeny. The effective dose for workers exposed to radon is about 4-6 times higher than thoron.
Journal of Radioanalytical and Nuclear Chemistry, 2014
ABSTRACT We present a laboratory system to evaluate radon flux and pore water radon via automated... more ABSTRACT We present a laboratory system to evaluate radon flux and pore water radon via automated sediment equilibration experiments. The setup includes a measured mass of sediment and water inside a gas-tight reaction flask connected in a closed loop to a radon-in-air analyzer. Diffusive fluxes are determined either from the near-linear slope of the activity versus time over the first several hours or by running the experiment longer to estimate the equilibrium concentration via a curve fitting approach. By combining the equilibrium activity with relevant physical parameters, one can also estimate the pore water concentrations.
Journal of Radioanalytical and Nuclear Chemistry, 2013
Tonle Sap Lake (Cambodia) is the largest freshwater lake in SE Asia, and is reported to have one ... more Tonle Sap Lake (Cambodia) is the largest freshwater lake in SE Asia, and is reported to have one of the highest freshwater fish productions anywhere. During the dry season (November-April) the lake drains through a tributary to the Mekong River. The flow in the connecting tributary completely reverses during the wet monsoon (May-October), adding huge volumes of water back to the lake, increasing its area about fourfold. We hypothesize that nutrients are at least partially delivered via groundwater discharge, especially during the draining portion of the annual flood cycle. We surveyed over 200 km in the northern section of the lake using a customized system that measures natural 222 Rn (radon), temperature, conductivity, GPS coordinates and water depth while underway. Results showed that there were portions of the lake with significant enrichments in radon, indicating likely groundwater inputs. These same areas were generally characterized by lower electrical conductivities. Samples collected from nearby wells also showed a general inverse relationship between radon and conductivity. Our data suggest that groundwater pathways are important, accounting for roughly 10-20 % of the freshwater flow of the Tonle Sap tributary (connection to the Mekong River), the largest single source of fresh water to the lake. Nutrient inputs from these inputs, because of higher concentrations in groundwater, will be correspondingly higher.
Applied Radiation and Isotopes, 2009
Field measurements were conducted to assess the effects of an air cleaner on radon mitigation in ... more Field measurements were conducted to assess the effects of an air cleaner on radon mitigation in a dwelling with a high radon concentration in Okinawa, Japan. The measurements included indoor radon concentration, individual radon progeny concentration, equilibrium equivalent concentration of radon (EECRn), unattached fraction, and size distribution of aerosol-attached radon progeny. These measurements were conducted in a 74 m 3 room with/without the use of an air cleaner. The results showed that the mean radon concentration during the measurement was quite high (301 Bq m À3 ). The operation of air cleaner decreased the radon progeny activity concentration, EECRn and equilibrium factor by 33%, 57% and 71%, respectively, whereas the unattached fraction increased by 174%. In addition, the activity concentration of attached radon progeny in the accumulation mode (50-2000 nm) was obviously deceased by 42%, when the air cleaner was operated. According to dosimetric calculations, the operation of air cleaner reduced the effective dose due to radon progeny by about 50%.
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Papers by Supitcha Chanyotha