The main objectives of this study were to evaluate the geochemical characteristics, reservoir temperatures (related to the natural ambient gamma radiation levels), and natural background radiation levels of the geothermal spring attractions in Central and Western Thailand. The hydrochemical properties of the geothermal waters revealed that K + -Na + bicarbonate dominates the geochemistry of these hot spring waters. Due to their chemical characteristics, the geothermal waters reflect the homogeneity of the geological formations, which indicates that limestone originated and mixed with shallow groundwater/freshwater. On the other hand, no significant correlations were found between the reservoir temperatures and naturally occurring background radiation levels. The natural background radiation levels were investigated at the main pool and 10 m from the main pool. In addition, the annual effective dose equivalent (AEDE) and excess lifetime cancer risk (ELCR) would be considered in the areas with low natural background radiation levels. The highest averages for the AEDEs and the ELCRs were discovered in the Ratchaburi Hot Spring (RB1), at approximately 0.48 and 1.90 mSv/year, respectively. Although the ELCR is slightly higher than the annual average effective dose (1.45 mSv/year) due to the natural background radiation, a preventive strategy should be considered to protect the effects on visitors' health.
Aircrew members are occupationally exposed to higher levels of galactic cosmic radiation than the general population in most parts of the world. The International Commission on Radiological Protection (ICRP) is concerned by the exposure of aircrews to cosmic radiation. The cosmic radiation intensity in the Earth atmosphere depends on many factors, e.g., the solar activity, altitude, and geomagnetic vertical cutoff rigidity on Earth. This study aimed to calculate the occupational radiation dose for aircraft crews during the solar minimum and maximum on fl ights from Suvarnabhumi Airport (BKK), Thailand, to 11 destinations worldwide. Based on the Monte Carlo simulation code of CARI-7 and JISCARD GUI, the cosmic radiation doses on fl ights was calculated. The maximum dose of a roundtrip fl ight (Bangkok–Helsinki) during the solar minimum condition was approximately 97.4 μSv (CARI-7) and 84.7 μSv (JISCARD GUI). The maximum radiation dose corresponded to 110 and 20 roundtrips for general aircraft crew and pregnant crew, respectively. This fi nding indicates that the polar-latitude region of Helsinki fl ights at low vertical cutoff rigidity ranges is of concern in terms of high-exposure cosmic radiation. The uncertainty associated with the result of the two codes was less than 30%. Therefore, the results were in reasonable agreement, and the codes could be used to calculate the exposure of aircraft crew to cosmic radiation.
Neutron monitors are recognized as a key tool for studying the time variations of galactic cosmic rays, especially with regard to solar effects. Cosmic-ray detectors inside the atmosphere do not record cosmic ray particles directly. The so-called primary cosmic rays interact with nuclei in the atmosphere to produce secondary daughter products. Neutron monitors record predominantly the secondary neutrons from these atmospheric showers. The Princess Sirindhorn Neutron Monitor (PSNM) is the first neutron monitor station in Chiang Mai, Northern Thailand, which installed at a high vertical cutoff rigidity of 16.8 GV. It provides unique data on the energy dependence of solar synodic variations, cosmic ray anisotropy, Forbush decreases, and solar modulation. In this work we performed Monte Carlo simulations of the atmospheric structure effects on secondary neutron counts above The Princess Sirindhorn Neutron Monitor by using the FLUKA program. These atmospheric processes are well understood, and the response of neutron monitors to these secondary particles is simulated. This work also provides the techniques for further analysis and a better understanding of those effects.
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