RESUMEN
Detection of two and more γ-rays in coincidence by two NaI(Tl) detectors with almost 4π geometry allows absolute characterization of radionuclides emitting coincidence gammas. The method is a generalization of the Eldridge-Crowther method developed originally for x-rays and low energy γ-rays. This method is applied to the case of (94)Nb decay with two coincident gamma-rays emitted in one cascade. The application of this method for the case of coincident positron-gamma emission ((22)Na and (26)Al sources) meets some difficulties. In these decays, two 511 keV gamma quanta produced in positron annihilation are strongly correlated. Despite the fact that the third gamma emitted in (22)Na and (26)Al decays is not correlated with two annihilation quanta, the number of independent observables for (22)Na and (26)Al decays is less than the number of unknowns. The small parameter ω(00), the probability that both annihilation quanta escape detection in both NaI(Tl) detectors, cannot be determined. However, if this parameter is defined from experimental data for one source with known activity ((22)Na), the activity of the other source ((26)Al) can be calculated from experimental data for (26)Al decay.
Asunto(s)
Algoritmos , Radiometría/instrumentación , Yoduro de Sodio/efectos de la radiación , Diseño de Equipo , Análisis de Falla de Equipo , Estudios de Factibilidad , Rayos gamma , Internacionalidad , Dosis de RadiaciónRESUMEN
A method for assessing the impurity 210At in cyclotron-produced 211At via isotope dilution alpha spectrometry is presented. The activity of 210At is quantified by measuring the activity of daughter nuclide 210Po. Counting sources are prepared by spontaneous deposition of Po on a silver disc. Activity of 210At (at the time of 210Po maximum activity) is found to be 83.5+/-9.0 Bq, corresponding to an atom ratio (210At:211At at the time of distillation) of 0.010+/-0.007% (k=2). The method produces high-quality alpha spectra, with baseline alpha-peak resolution and chemical yields of greater than 85%.
Asunto(s)
Partículas alfa , Astato/análisis , Polonio/análisis , Técnica de Dilución de Radioisótopos , Radiometría/métodos , Análisis Espectral/métodos , Astato/química , Astato/uso terapéutico , Evaluación de Medicamentos/métodos , Polonio/química , Dosis de Radiación , Radiofármacos/análisis , Radiofármacos/síntesis química , Radiofármacos/uso terapéutico , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
The Department of Homeland Security is supporting the development of a large number of standards for first responders. In the area of detection of radioactive and nuclear materials, four new standards (ANSI N42.32, N42.33, N42.34, and N42.35) and their corresponding test and evaluation protocols were developed to meet Department of Homeland Security needs. Testing of the standards and protocols was carried out at the National Institute of Standards and Technology, Oak Ridge National Laboratory, Pacific Northwest National Laboratory, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory.
Asunto(s)
Monitoreo de Radiación/métodos , Protección Radiológica , Liberación de Radiactividad Peligrosa , Terrorismo , Humanos , Monitoreo de Radiación/normasRESUMEN
The massic activity of a solution containing 188W in equilibrium with its daughter, 188Re, has been standardized by the National Institute of Standards and Technology using 4pi beta liquid scintillation counting with efficiency tracing using the CIEMAT NIST method. Confirmatory measurements were carried out with gamma-ray spectrometry using high purity germanium detectors and a 4pi gamma NaI(Tl) system. A calibration factor of 1.68 MBq pA(-1) +/-0.03 MBq pA(-1) (expanded, k = 2, uncertainty) for the 188W in the solution was determined, along with correction factors for activity determinations using Capintec dose calibrators. A half-life value of 69.78 d +/- 0.05 d (standard uncertainty) was determined by measurement in the NIST 4pi gamma ionization chamber and is consistent with currently recommended values.