RESUMO
Calibration sources based on the primordial isotope potassium-40 (K) have reduced controls on the source's activity due to its terrestrial ubiquity and very low specific activity. Potassium-40's beta emissions and 1,460.8 keV gamma ray can be used to induce K-shell fluorescence x rays in high-Z metals between 60 and 80 keV. A gamma ray calibration source that uses potassium chloride salt and a high-Z metal to create a two-point calibration for a sodium iodide field gamma spectroscopy instrument is thus proposed. The calibration source was designed in collaboration with the Sandia National Laboratory using the Monte Carlo N-Particle eXtended (MCNPX) transport code. Two methods of x-ray production were explored. First, a thin high-Z layer (HZL) was interposed between the detector and the potassium chloride-urethane source matrix. Second, bismuth metal powder was homogeneously mixed with a urethane binding agent to form a potassium chloride-bismuth matrix (KBM). The bismuth-based source was selected as the development model because it is inexpensive, nontoxic, and outperforms the high-Z layer method in simulation. Based on the MCNPX studies, sealing a mixture of bismuth powder and potassium chloride into a thin plastic case could provide a light, inexpensive field calibration source.
Assuntos
Modelos Estatísticos , Isótopos de Potássio/análise , Isótopos de Potássio/normas , Contagem de Cintilação/instrumentação , Contagem de Cintilação/normas , Iodeto de Sódio/efeitos da radiação , Calibragem/normas , Simulação por Computador , Método de Monte Carlo , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Activity concentrations of main terrestrial radioisotopes (226)Ra, (232)Th and (40)K were measured in geological samples collected in Libya's Jabal Eghei area, in order to contribute to the establishment of a baseline map of the environmental radioactivity levels and to estimate the associated environmental risk to the population. Activity concentrations ranged from 22 to 5256 Bq kg(-1) for (226)Ra, from 11 to 221 Bq kg(-1) for (232)Th and from 132.0 to 2304 Bq kg(-1) for (40)K. Using these results, representative risk factors were calculated: the total absorbed gamma dose rate in air (ranged from 25.5 to 2434.3 nGy h(-1) with a mean value of 251.8 nGy h(-1)), the radium equivalent activity (55-5281 Bq kg(-1), with the mean value of 537 Bq kg(-1)), external hazard index (0.149-14.24, with a mean value of 1.451) and annual outdoor effective dose (31.3-2985.4 µSv, with a mean value of 308.9 µSv). Accordingly, the radiation risk is above the world average, mainly as the consequence of discovered uranium anomalies.
Assuntos
Radiação de Fundo , Isótopos de Potássio/análise , Monitoramento de Radiação/métodos , Rádio (Elemento)/análise , Poluentes Radioativos do Solo/análise , Tório/análise , Exposição Ambiental , Raios gama , Geografia , Humanos , Líbia , Modelos de Riscos Proporcionais , Radioatividade , Radioisótopos/análise , Medição de Risco/métodos , Fatores de Risco , Urânio/análiseAssuntos
Composição Corporal , Água Corporal/análise , Lipídeos/análise , Adolescente , Adulto , Custos e Análise de Custo , Densitometria , Deutério , Estudos de Avaliação como Assunto , Feminino , Humanos , Masculino , Métodos , Pessoa de Meia-Idade , Militares , Isótopos de Potássio , Radioisótopos , Fatores Sexuais , Fatores de Tempo , Estados Unidos , Contagem Corporal TotalRESUMO
Total Exchangeable Potassium (TEK) was measured in 31 elderly patients admitted to a geriatric assessment unit. The value in control cases ranged between 26 mEq/kg to 45.5 mEq/kg; the mean values for men and women were 35.5 mEq/kg and 28.4 mEq/kg, respectively. The test was repeated after one week in eight cases, the standard deviation between the two estimations ranged from 0.35 to 1.13 with the exception of one case which was 2.55. Estimations were made in six cases of myxoedema, the initial value was low and on treatment rose by 22.6 per cent to 36.4 per cent which coincided with the clinical improvement.