Application of the Monte Carlo Method for spectrometer calibration to determine the surface activity of radionuclides deposited on the ground.
The results of efficiency calibration and verification of the in-situ method with application of a handheld spectrometer with high-purity germanium detector are presented. The conducted studies show that the calibration of spectrometer efficiency with the use of the Monte Carlo method can be applied for measurement of the surface activity of radionuclides deposited on the ground with an uncertainty of not more than 22%.
The performance of hand-held radioisotope identification devices (RIDs) is still hampered by the performance of the NaI(Tl) detectors, which are commonly used in such instruments. In this paper, we continue the search for better detector options. One of the largest single elements ever made, a coplanar CdZnTe (CZT) detector (30x15x12.1 mm volume 5.45 cm^3 designed by University of Michigan) is compared with a commercially available LaBr3(Ce) detector (1"x1" volume 12.9 cm^3). Parameters that are relevant to the performance of isotope identification devices, such as resolution and efficiency as function of the gamma-ray energy, temperature shift, linearity and others are measured and compared. According to measurement results, it seems that for this application LaBr3(Ce) detectors are a viable alternative to CZT detectors; even more so if one bears in mind that LaBr3(Ce) became commercially available only recently and detectors with larger volumes are likely to appear in the near future.
The present work shows the results of the development of a mobile spectrometric system based on a LaBr3(Ce) spectrometer intended for measuring the energy distribution of gamma radiation and the identification of gamma radionuclides, as well as for defining the specific and surface activity of gamma radionuclides in natural occurrence, distributed over large areas, locally, in urban housing and industrial zones, as well as on open natural territories. The application of such a mobile radiation system is invaluable for their ecological rehabilitation and control release.
Rapid analysis of radionuclide composition (screening) of liquid samples via deconvolution of their LS spectra
Liquid scintillation (LS) spectrometry based on an original method for processing initial LS spectra is presented. The algorithm used is based on the modeling of spectra transformed by a convolution into group form by the superposition of individual reference spectra taken from a previously created nuclide library. In this library, for each radionuclide (or radionuclide + DP), there is a set of at least 10 spectra measured at different quenching parameters. The model spectrum is presented as a sum of elemental spectra with weight coefficients (cj) that are adjusted during the modeling procedure so that the model spectrum will coincide with the sample spectrum to a maximum degree. Due to the development of new approaches for interpreting LS spectra realized in the software RadSpectraDec, the possibilities of this method for implementing a rapid analysis (screening) of samples with unknown radionuclide composition has been considerably extended. The software now allows us to analyze actual complex radionuclide mixtures of environmental or technological origin. The reliability of the proposed procedures has been confirmed by “added-measured” tests, comparative radiochemical analysis, and by analyzing materials with a regulated content of radionuclides (IAEA, RM, and PT). In this work, data are presented that have been obtained with the given approach for analyzing different materials, such as liquid waste, drill water, liquid discharge, potable water, etc. The limitations regarding sample screening operations are considered as well.