Kajian radiologi alam sekitar Semenanjung Malaysia dan anggaran implikasi radiologi menggunakan kod simulasi Monte Carlo

Setiap manusia terdedah kepada pelbagai jenis dedahan sinaran mengion dari sumber-sumber semulajadi dan buatan manusia. Penganggaran dos berkesan tahunan yang diterima oleh orang awam akibat dedahan sinaran mengion adalah sesuatu yang diperuntukkan bagi penilaian komprehensif risiko orang awam terhadap kesan-kesan stokastik sinaran, dan bagi memenuhi syarat piawai sistem perlindungan radiologi orang awam yang digariskan oleh suruhanjaya ICRP dan agensi IAEA. Kajian ini telah dilakukan bagi menganggarkan dos berkesan tahunan dan risiko stokastik yang diterima orang awam di Semenanjung Malaysia akibat dedahan sinaran mengion dari sumber keradioaktifan alam sekitar dan antropogenik di Semenanjung Malaysia. Kajian ini telah menggunakan kaedah pengukuran in-situ berdasarkan instrumen spektrometer gama, pengesanan sintilasi dan kaedah numerik iaitu simulasi bagi penganggaran kerma dalam udara dan dos organ berdasarkan teknik Monte Carlo MCNP5. Kajian ini mendapati purata dos berkesan tahunan yang diterima oleh orang awam di Semenanjung Malaysia adalah 2.8 mSv (0.01 – 10 mSv). Nilai ini adalah setanding dengan nilai-nilai yang dianggarkan di Amerika Syarikat, 2.9 mSv; United Kingdom, 2.3 mSv; Jerman, 2.1 mSv; dan nilai purata global 2.4 mSv yang dianggarkan oleh jawatankuasa UNSCEAR. Sumber dedahan sinaran yang paling dominan (0.87 mSv) adalah pancaran sinaran γ dari siri radionuklid 238U, 232Th, dan 40K dalam kediaman, dan diikuti oleh dedahan sinaran dalaman akibat penyedutan gas 222Rn, 220Rn dan progeninya (0.86 mSv), dan akibat penelanan siri 238U, 232Th, 40K dan 137Cs dalam diet pemakanan (0.59 mSv). Sumbangan dedahan sinaran kosmik pula adalah 0.28 mSv berdasarkan hipsograf beraltitud 0 – 50 m dan peratusan demografi 83% populasi menetap di wilayah persisiran pantai. Sumbangan dedahan sinaran paling rendah (0.18 mSv) adalah sumber sinaran γ daratan dari siri 238U, 232Th, 40K dan 137Cs dalam sistem litologi di Semenanjung Malaysia. Dos dedahan sinaran γ daratan yang rendah yang diterima oleh orang awam adalah disebabkan oleh faktor demografi populasi yang majoritinya menetap di wilayah pesisiran pantai iaitu di luar zon igneus plutonik dan volkanik, selain dos setara organ yang rendah akibat pancaran foton γ dari sumber antropogenik 137Cs (< 0.1 nSv j⁻1). Sumbangan dos setara organ yang rendah dari 137Cs ini adalah disebabkan oleh impak kecil luruhan nuklear dari ujian senjata nuklear global dan kemalangan nuklear di Chernobyl dan Fukushima dengan keluasan kontaminasi 137Cs ~ 312 Bq m⁻2. Kajian ini mendapati anggaran risiko kesan stokastik akibat dedahan 2.8 mSv setahun adalah terlalu kecil iaitu kurang daripada 6 kes per 10,000 orang. Nilai purata dos berkesan 2.8 mSv setahun yang diterima oleh orang awam di Semenanjung Malaysia ini diklasifikasikan sebagai dos aras rendah dan normal bagi sumber sinaran mengion. Bagi kes dedahan dos normal, aras rujukan 1–20 mSv setahun dan pengkelasan situasi “dedahan sedia ada” dari ICRP adalah terpakai dan relevan bagi tujuan perlindungan radiologi orang awam di Semenanjung Malaysia

Site selection for nuclear power plant in Mersing Johor

Nuclear power is considered as energy source option for future power generation in the National New Energy Policy 2010. The first nuclear power plant (NPP) construction is expected to start at 2017, and officially operated in 2025. This paper aims to propose possible candidate site areas for NPP in Mersing District, Johor. The evaluation uses the Atomic Energy Licensing Board (AELB) guideline documents as main reference, supported by regulation documents from International Atomic Energy Agency (IAEA). 4 safety parameters are used in the assessment – geological characteristic, air dispersion (meteorological) analysis, population data and safety characteristics. This study ranked 4 proposed areas possible candidate site area for NPP in Mersing district

The naturally occurring radioactivity of 'scalar energy' pendants and concomitant radiation risk

Forming part of a study of radiological risk arising from use of radioactive consumer products, investigation is made of pendants containing naturally occurring radioactive material. Based on use of gamma-ray spectrometry and Monte Carlo (MC) simulations, the study investigates commercially available 'scalar energy pendants'. The doses from these have been simulated using MIRD5 mathematical phantoms, evaluation being made of dose conversion factors (DCFs) and organ dose. Metallic pendants code MP15 were found to contain the greatest activity, at 7043 ± 471 Bq from 232Th, while glass pendants code GP11 were presented the greatest 238U and 40K activity, at 1001 ± 172 and 687 ± 130 Bq respectively. MP15 pendants offered the greatest percentage concentrations of Th, Ce, U and Zr, with means of 25.6 ± 0.06, 5.6 ± 0.005, 1.03 ± 0.04 and 28.5 ± 0.08 respectively, giving rise to an effective dose of 2.8 mSv for a nominal wearing period of 2000 h. Accordingly, these products can give rise to annual doses in excess of the public limit of 1 mSv

Kajian fizik kesihatan negeri Selangor, Wilayah Persekutuan Kuala Lumpur dan Putrajaya

Terrestrial gamma radiation is one of the main constituents of background radiation and the irradiation is due to the terrestrial radioactivity. Health physics study were carried out to obtain the baseline data of radioactivity and terrestrial gama radiation (TGR) level in State of Selangor, Federal Territories of Kuala Lumpur and Putrajaya. The study provide a methodology of sampling for TGR dose rate survey and a statistical regression model for predicting the TGR dose rate based on linear relationship between total dose rate with geological background, Dg and soil types, Ds. The TGR dose rate survey, Dm has been conducted using scintillation detector Ludlum 19 micro R meter NaI (Tl). Based on airborne survey map, geological background map and soil survey map, the sampling method was used to determine survey point Dm. For quality control of the sensitive TGR dose rates, Dm at environmental level, a statistical interpolation of gradient between calculated dose rate, Dc and Dm have been carried out to obtain the correction factor, Cf using radioactivity data of ? - rays emitters 238U, 232Th and 40K in soil samples. The analysis of radioactivity concentration of radionuclides 238U, 232Th and 40K in soil samples were carried out using coaxial hyper-purity germanium (HPGe) gamma spectrometer. Based on baseline information of TGR dose rate data from previous research (1995 - 2013), 9884 data were analysed using Shapiro - Wilk, Kolgomorov - Smirnov and Levene statistical test for the normality distribution test. For verification of relationships of geological background and soil types on TGR dose rate, statistical hypothesis analysis of Welch’s ANOVA and Tamhane T2 were carried out. Based on baseline information, statistical regression model was built to predict TGR dose rates, Dp. The study has found that the average value of TGR, Dm dose rate was (182 ± 81) nGy h-1 which is three times higher than global average value and two times higher than average value for Malaysia with measurements range within 17.4 nGy h-1 - 500.0 nGy h-1. The derived equation for statistical regression model for predicting the TGR dose rate was given as Dp = [0.664 Dg + 0.414 Ds - 12.134]. The p value of ANOVA regression model analysis was p < 0.001 with F - ratio (f(2, 983) = 2341.053) and Pearson’s correlation value R is 0.903. At significant level of 0.05, null hypothesis was rejected and it is concluded that the dose rates of Dg and Ds influenced Dp value and there is a strong correlation between geological background and soil types. For statistical verification of the model validity, Dm and Dp data were analysed using ANOVA test and the F - ratio obtained (0.004) is smaller than F - critical (4.08) and H0: µx = µ0 were accepted at (fcal f1, 40, 0.05 = 4.08). Based on obtained regression model and the TGR dose rate survey, the baseline data are presented as an isodose map

Radon activity concentration measurements in water sources from Perak state Malaysia

Radon activity concentration in water samples from Perak state Malaysia and their possible health risk was assessed. The Samples were from lakes, hot springs, and rivers. The RAD7 Detector was used for in-situ measurement of radon concentration. The radon activity concentration ranged from 0.04 ± 0.08 — 3.98 ± 0.39 Bq l – 1, with mean of 0.69 Bq l – 1 and standard deviation of 0.92 Bq l – 1. The activity concentration ranged from 0.08 ± 0.12 — 0.45 ± 0.27, 0.04 ± 0.08 — 0.62 ± 0.32, 0.33 ± 0.23 — 3.98 ± 0.39 Bq l – 1, with a mean of 0.24 ± 0.19, 0.30 ± 0.21, 1.26 ± 0.34 Bq l – 1 for lakes, hot springs, and rivers respectively. The result was below the UNSCEAR, USEPA and WHO action levels of 11.1 Bq l– 1and100 Bq l – 1respectively. The 222Rn contribution from water to indoor air was found to be below the recommended action level. The annual effective dose for inhalation and ingestion ranged from 0.000102 — 0.009954 mSv y – 1 and 0.000102 — 0.010112 mSv y – 1, with mean annual effective dose of 0.001733 and 0.001759 mSv y – 1 respectively. The effective doses for both inhalation and ingestion were below the world average of 0.002 mSv y – 1. The 222Rn activity concentration in the study could be termed normal and without threat to human health

Radiological assessment subjected to outdoor radon and thoron concentrations and terrestrial gamma radiation measurements in Perak Malaysia

The concentrations of radon, thoron and terrestrial gamma radiation were measured to evaluate the outdoor effective dose. The outdoor radon activity concentration ranged from 5.79 to 5110 ± 46.36 Bq m-3, with a mean of 320.03 Bq m-3 which is higher than the EPA level of 14.8 Bq m-3. The range of the thoron activity concentration outdoor was from 0.00 to 4226.7 ± 58.5 Bq m-3, with a mean of 226.1 Bq m-3 which was above the UNSCEAR recommended level of 10 Bq m-3. The terrestrial gamma radiation dose rates range was from 98.31 to 3769.71 nGy h-1 with a mean of 446.27 nGy h-1. The effective dose contribution from radon exposures in the study was estimated to be 3.2 ± 0.5 mSv y-1 is about 84% total annual effective dose received by the population in those areas. The estimated thoron and gamma dose contributions (15%, and 1% respectively) were not significant. The outdoor doses for thoron and gamma were lower than the ICRP (2007) value of 1 mSv. The total annual outdoor effective dose with an occupancy factor of 1825 h (5 h day-1) was estimated to be within the range of 0.30–551.41 ± 0.65 mSv, with a mean of 3.75 mSv which is a little higher than the world average of 2.4 mSv

Terrestrial gamma dose rate in Pahang state Malaysia

Environmental terrestrial gamma radiations (TGR) were measured in Pahang state Malaysia between January and April 2013. The TGR dose rates ranged from 26 to 750 nGy h-1. The measurements were done based on geology and soil types of the area. The mean TGR dose rate was found to be 176 ± 5 nGy h-1. Few areas of relatively enhanced activity were located in Raub, Temerloh, Bentong and Rompin districts. These areas have external gamma dose rates of between 500 and 750 nGy h-1. An Isodose map of the state was produced using ArcGIS9 software version 9.3. To evaluate the radiological hazard due to terrestrial gamma dose, the annual effective dose equivalent and the mean population weighted dose rate were calculated and found to be 0.22 mSv year-1 and 168 nGy h-1 respectively

The radioactivity of thorium incandescent gas lantern mantles

The use of thorium in providing the intense white luminescence emitted from gas mantles, has a history of some 130 years, the initial application pre-dating by several decades large-scale urban electric lighting. Accordingly, the thoriated gas mantle has proved itself to be of enormous utility, remaining popular in more rural areas well into the 20th century, continuing to enjoy use in campsites and street night markets lanterns until today. The discovery of thorium in 1828 preceded the discovery of radioactivity, with subsequent little appreciation initially of any potential harm from exposure to radioactivity. Study has been made herein of small quantities of five different types of the thoriated gas mantle, all purchased online devoid of any control measures. Several approaches were used concerning the232Th activity and dose consequence. First, the activity of232Th was estimated using an HPGe detector, with sample M5 providing the greatest activity at 1.25 × 104 Bq, exceeding the exemption limit for thorium in a mantle. Compared to sample M5, samples M1 to M4 were low in radioactivity, from 5.1 ± 1.31 to 16.33 ± 1.92 Bq. Moreover, the thorium content in M5 constituted 50% of the mantle mass, somewhat greater than previous literature values. The dose equivalent rate on the surface of a single M5 mantle was found to be 0.68 µSv/h, while at the surface of a pack of six the level was 1.9 µSv/h. Monte Carlo simulation codes have been used to obtain organ equivalent and effective dose rates, the greatest close contact (10 cm) exposure to an unlit mantle being to the thymus, at 0.68 µSv/h and 0.62 µSv/h for a male and female phantom respectively. Accordingly, with packages of thoriated gas mantles potentially giving rise to non-negligible equivalent doses, greater incorporation of controls on the sale of such items in national radiation protection legislation would seem worthy of consideration

Naturally occurring radioactive materials in bracelets and necklaces: radiological risk evaluation

A particular category of jewelry is one involving bracelets and necklaces that are deliberately made to contain naturally occurring radioactive material (NORM)—purveyors making unsubstan-tiated claims for health benefits from the release of negative ions. Conversely, within the bounds of the linear no-threshold model, long-term use presents a radiological risk to wearers. Evaluation is conducted herein of the radiological risk arising from wearing these products and gamma-ray spectrometry is used to determine the radioactivity levels and annual effective dose of 15 commer-cially available bracelets (samples B1 to B15) and five necklaces (samples N16 to N20). Various use scenarios are considered; a Geant4 Monte Carlo (Geant4 MC) simulation is also performed to validate the experimental results. The dose conversion coefficient for external radiation and skin equivalent doses were also evaluated. Among the necklaces, sample N16 showed the greatest levels of radioactivity, at 246 ± 35, 1682 ± 118, and 221 ± 40 Bq, for238 U,232 Th, and40 K, respectively. For the bracelets, for238 U and232 Th, sample B15 displayed the greatest level of radioactivity, at 146 ± 21 and 980 ± 71 Bq, respectively. N16 offered the greatest percentage concentrations of U and Th, with means of 0.073 ± 0.0002% and 1.51 ± 0.0015%, respectively, giving rise to an estimated annual effective dose exposure of 1.22 mSv, substantially in excess of the ICRP recommended limit of 1 mSv/year

Radiation hazard assessment from NORM-added paint products in Malaysia

[Introduction] Across the globe, radioactive consumer products are widely marketed for daily use. [Objectives] The present study investigated commercially available ion paint, and the evaluations were using gamma (γ)-ray spectroscopy and Geant4 Monte Carlo (GMC) simulations. [Methods] An assessment of a radiological risk arising from using such products in the painting of living areas is conducted when Technologically Enhanced Naturally Occurring Radioactive Material (TENORM) was observed, with a daily inhalation exposure dose being of particular concern. Organ doses were simulated using adult mathematical Medical Internal Radiation Dose 5 (MIRD5)-type phantoms, incorporating dose conversion factors (DCFs). [Results] Results showed that a product sample code of IP04 contained the highest activity, i.e., 4449 ± 530, 31888 ± 2175, and 2963 ± 405 Bq kg, for U, Th, and K, respectively. Contrarily, NP18 recorded the lowest, i.e., 16 ± 2 and 30 ± 5, Bq kg of U and Th, respectively. The IP04 paint offered the most significant concentrations, with mean percentages of 0.026, 0.81, and 0.06 for U, Th, and Pb, respectively. Its use in a designated Room 1 had resulted in an annual effective dose of 1.53 mSv y, assuming an exposure for a period of 8 h day. [Conclusion] In brief, using these ion paints could result in amounts that exceed the annual public dose limit of 1 mSv.This work was supported by the Ministry of Science, Technology and Innovation (MOSTI) of Malaysia through Kumpulan Wang Amanah (KWA) Majlis Sains dan Penyelidikan Kebangsaan (MSPK) (R.J130000.7317.4B658 and R.J130000.7317.4B659). The authors gratefully acknowledge the Ministry of Higher Education Malaysia and Universiti Teknologi Malaysia through Industry-International Incentive Grant (No. 03 M18)