Dose rates and seasonal variations of 238U, 232Th, 226Ra 40K and 137Cs radionuclides in soils along Thrace, Turkey

Concentrations of ²³⁸U, ²³²Th, ²²⁶Ra, ⁴⁰K and ¹³⁷Cs are measured in collected soil samples from various locations in the Thrace region of Turkey. The activity concentrations range from 12.82 to 101.75 Bq kg^?1 d.w. (dry weight) for ²³⁸U, from 5.16 to 73.34 Bq kg^?1 d.w. for ²³²Th, from 185.54 to 5399 Bq kg^?1 d.w. for ⁴⁰K and from 11.42 to 90.73 Bq kg^?1 d.w. for ²²⁶Ra. In addition to naturally occurring radionuclides, ¹³⁷Cs activity concentration is determined between 3.05 and 46.78 Bq kg^?1 d.w. for soil samples. Determination of the radiological hazard is achieved through calculations of the external terrestrial gamma dose rate in air (nGy h^?1) and annual effective dose rate (mSv year^?1) and the results are compared with the similar works in different countries.     

Distribution of 238U, 226Ra, 232Th and 40K in soil samples around Tarapur,India

The radioactivity concentrations of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples around Tarapur vary from 11.5 ± 2.6 to 50.3 ± 6.6, 14.9 ± 0.6 to 40.5 ± 1.2, 18.1 ± 0.4 to 75.0 ± 1.5 and 130.1 ± 1.6 to 295.1 ± 2.6 Bq/Kg respectively. The measured activity concentrations for ²³⁸U and ²²⁶Ra were compared and found in good agreement with the Indian as well as world average. The average ²³²Th and ⁴⁰K concentrations in Tarapur were lower than the Indian average value.     

Measuring activity of 235, 238U, 232Th and 40K in geological materials using neutron activation analysis

The radioactivity of the ^{235, 238}U and ²³²Th isotope decay chains for geological samples can usually be assumed to be in equilibrium due to their age. Similarly, one can assume that the isotopic mass proportions are equal to natural isotopic abundance. Current methods used to ascertain activity in these decay chains involve alpha particle spectrometry, ICP-MS or passive gamma-ray spectrometry, all of which can be laborious and time consuming. In this research, we have used thermal and epithermal neutron activation analysis (NAA) of small sample sizes of various geological materials in order to ascertain these activities. By using NAA, we aim to obviate cumbersome sample preparation, the need for large samples and extended counting time. In addition to the decay chains of uranium and thorium, ⁴⁰K was also determined using epithermal neutron activation analysis to determine total potassium content and then subtracting out its isotopic contribution.     

Prediction of the activity concentrations of 232Th, 238U and 40K in geological materials using radial basis function neural network

In this paper, three individual models and one generalized radial basis function neural network (RBFNN) model were developed for the prediction of the activity concentrations of primordial radionuclides, namely, ²³²Th, ²³⁸U and ⁴⁰K. To achieve this, gamma spectrometry measurements of 126 different geological materials were used in the development of the RBFNN models. The results indicated that individual and generalized RBFNN models are quite efficient in predicting the activity concentrations of ²³²Th, ²³⁸U and ⁴⁰K of geological materials.

     

Depth-wise distribution of 238U, 232Th and 40K in sand samples of high background radiation areas (Tamilnadu coast), India

Journal of Radioanalytical and Nuclear Chemistry - To understand the depth wise distribution of the primordial radionuclides, especially in high background radiation areas, their radioactivity...     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K, <Superscript>232</Superscript>Th and <Superscript>238</Superscript>U in coastal marine sediments of Margarita Island,Venezuela

This work presents the results of ¹³⁷Cs, ⁴⁰K, ²³²Th and ²³⁸U concentration (Bq kg⁻¹) values in coastal marine sediments collected from 38 sites along the coastline of the island of Margarita, Venezuela. The purpose was to determine baseline values for these radionuclides in surface marine sediments and to detect if there were any anomalously high concentration values. Only three of the 38 sediments analyzed had measurable values above the detection limit of 0.9 Bq kg⁻¹ for ¹³⁷Cs and the highest only being 1.4 Bq kg⁻¹. While, the concentration (Bq kg⁻¹) ranges for the primordial radionuclides, ⁴⁰K, ²³²Th and ²³⁸U were as follows: 12.2–211.7, <1.5–9.8 and <4.4–20.7, respectively. These concentration ranges for the primordial radionuclides can be considered as baseline values for surface marine sediments for areas that are considered not polluted by man or contaminated by nature. Finally, the concentration range of ¹³⁷Cs can also be employed as baseline values, which only seem to have been the result of the atmospheric testing of nuclear weapons in the past.     

A study on the activity concentrations of 226Ra, 232Th, 40K, 137Cs and radiological risk assessments in soil samples from Seydisehir and Beysehir districts of Konya in Turkey

Journal of Radioanalytical and Nuclear Chemistry - The aim of this study is to investigate the activity concentrations of 226Ra, 232Th, 40K and 137Cs in soil samples from Seydisehir and Beysehir...     

Isomeric yield ratio of134I in photofission of232Th and238U

The isomeric yield ratios for¹³⁴I, for the photofission of²³²Th and²³⁸U with 25-MeV bremsstrahlung have been determined using radiochemical techniques and -spectrometry. Angular moment a of the corresponding fission fragments, J_rms, were calculated by the statistical procedure of Huizenga and Vandenbosch. We have discovered a significant proton odd-even effect on J_rms values, and demonstrated its dependence on the nuclear structure of fragments.     

Annual effective dose due to 222Rn and evaluation of 238U, 232Th and 40K contents in soil at the south-eastern coastal area of Bangladesh

Journal of Radioanalytical and Nuclear Chemistry - On-site 222Rn concentration at three different soil depths was measured at the south-eastern coastal area of Bangladesh to evaluate the annual...     

The dietary intake of238U,234U,230Th,232Th,228Th and226Ra from food and drinking water by inhabitants of the Walbrzych region

Intake with food and water of the natural radionuclides of the uranium and thorium series was determined for adult population of the south-western region in Poland, where in the 1950-ies an exploration of uranium ore was conducted. Concentration of the radionuclides was determined in food products and drinking water and their annual intake was estimated on the basis of the average annual consumption. The intake of²³⁸U,²³⁴U and²³⁰Th occurred mainly with water (33% to 68%), whereas the intake of²³²Th,²²⁸Th and²²⁶Ra was mainly with vegetables, potatoes, milk and flour. From the intake and dose coefficients the annual effective doses from the ingested radionuclides were calculated. The total dose was 5.6 Sv, of which 74% originated from²²⁶Ra.     

电感耦合等离子体质谱法测定水中铀钍元素的含量

建立了电感耦合等离子体质谱测定水中铀钍元素含量的方法。水样以硝酸酸化处理后直接用电感耦合等离子体质谱法测定,为了消除铀记忆效应对测定结果的干扰,测试溶液的质量浓度以不超过10μg/L为宜,样品测定间隙设置清洗时间为2 min。铀钍元素标准曲线线性相关系数分别为0.999 4,0.999 5;铀、钍的检出限分别为0.000 9,0.002 1μg/L;加标回收率分别为95.70%~112.33%,96.94%~109.98%;测定结果的相对标准偏差分别为0.61%~5.33%,1.16%~1.33%。     

Determination of40K and137Cs concentration in selected honey samples

Seventeen honey samples collected at different sites during 1992 have been measured using the method of -spectroscopy. Measurements were performed by a low background high purity germanium spectrometer of a relative efficiency of 14.5% and an energy resolution of 1.7 keV. Using natural -ray sources to determine efficiency, it has been shown that out of 17 samples of natural honey only two (of meadow type) have specific activity of¹³⁷Cs greater than 0.5 Bq kg^–1. The remaining samples have the same¹³⁷Cs concentrations as before May, 1986. Predominant activity in all samples comes from the⁴⁰K radionuclide, indicating natural honey.     

Fallout 137Cs in soils from North Western Libya

Fallout levels of ¹³⁷Cs in surface soil from North WesternLibya have been measured using gamma-ray spectrometry. The activity concentrationsof ¹³⁷Cs in soil ranged from 975 to 1720 mBq . kg ^—1 . The areal activity concentrations ranged from 1300 to 2250 mBq .m ^—2 , and were higly correlated with annual precipitation.The effective dose from external exposure to ¹³⁷Cs is found tobe 3 nSv . y ^—1 .     

Limitations of gamma-ray spectrometry in the quantification of 238U and 232Th in raw materials and by-products

The effect of interference and disequilibrium was evaluated in analyzing ²³⁸U and ²³²Th using gamma-ray spectrometry. The interference in ²³⁴Th as an indicator of ²³⁸U was considerably increased according to the activity level of ²³²Th compared with that of ²³⁸U. However, its correction was necessary to assume that the secular equilibrium in the thorium decay series must be secured in the material. In addition, the disequilibrium in the decay series can be easily shown in the chemical process for manufacturing materials. This makes the limitation in the indirect measurement of natural radionuclides using gamma-ray spectrometry, especially in chemically processed products.

     

Gamma-ray emission intensities of the232Th chain in secular equilibrium of235U and the progeny of238U

A²³²Th source of knowsn disintegration rate and in secular equilibrium was measured to determine the absolute -ray emission intensities of members of its decay chain. Similar measurements were made on sources of highly-enriched²³⁵U and of normal uranium metal. The results are compared with values from the literature.