Precise measurement of the half-life of ⁶¹Cu.

The decay characteristics of (61)Cu allow for a precise determination of its half-life. In order to search for a possible influence of the chemical environment on the decay rate, the half-life of (61)Cu in nickel and nickel-oxide was measured with high precision. The results show a small difference in the half-life that can be explained by the differences in electron density at the site of the nucleus.

Analysis of HPGe spectra by spectrum matching--experimental verification.

A new approach to spectrum analysis in gamma-ray spectrometry has recently been proposed, based on channel-by-channel matching of the measured spectrum with calculated synthetic spectra. In this paper, verification of the new method against experimental data and a comparison with the standard approach to the analysis of HPGe spectra is presented.

Twenty-year follow-up study of radiocesium migration in soil.

The profile of (137)Cs present in undisturbed soil due to the Chernobyl accident was measured repeatedly for approximately 20 y. The vertical migration of (137)Cs in soil is a very slow process. The mean vertical migration velocity is estimated at approximately 0.

Monte Carlo calculation of entire in situ gamma-ray spectra.

We present a method for the synthesis of entire in situ gamma-ray spectra based on Monte Carlo calculations and measured data that characterize the detector properties. The method can serve for the determination of the effective depth of 137Cs in soil based on the information contained in the low-energy part of an in situ spectrum. Effective depth is defined as the depth of a plane distribution of 137Cs beneath the surface that reproduces the fluence energy and angular distribution at 1 m above the ground of gamma rays belonging to the real 137Cs distributions.

On the invariability of the total-to-peak ratio in gamma-ray spectrometry.

It is demonstrated that the assumption on the independence of the total-to-peak ratio of the source position in gamma-ray spectrometry holds for coaxial detectors with sufficient accuracy to make it applicable to the determination of the full energy peak efficiencies in environmental measurements via the so-called efficiency transfer method. The calculations show that for planar detectors the assumption breaks down at higher gamma-ray energies and that for such detectors the use of the efficiency transfer method is only warranted for gamma-ray energies up to 200 keV.

Analysis of gamma-ray spectra from HPGe detectors in field conditions without explicit energy calibration.

A novel approach to the analysis of high-resolution gamma-ray spectra from HPGe detectors is presented. Identification of the nuclides contributing to the spectrum is performed in an energy-calibration-free manner by a correlation technique. The performance of the system proves to be robust with a possibility of integrating a high degree of expertise.

Automated construction of detector models for efficiency interpolation in gamma-ray spectrometry.

A method was developed for automated construction of detector models in gamma-ray spectrometry, which can be used in Monte Carlo calculations of efficiency calibration curves. Full-energy peak efficiencies were first measured for different gamma-ray energies and for a given sample-detector arrangement and then calculated by the Monte Carlo method. For these calculations a detector model was employed along with a computer algorithm, which seeks agreement between the experimental efficiencies and the calculated ones by automatically determining the parameters of the model.

A theoretical description of diffusion and migration of 137Cs in soil.

Careful measurements of activity concentrations of 137Cs in soil samples taken layer by layer in autumn of 1999 in Slovenia are confronted with a prediction based on the diffusion-convection equation with a boundary condition which--unlike the boundary conditions applied in the literature so far--conserves the deposited activity over time, except for the natural decay. It is shown that it is essential to consider the deposits from atmospheric nuclear weapons tests and the Chernobyl accident to arrive at a good fit to the measured data. The corresponding Green's function as well as the diffusion constant and migration speed based on the analysis are given.

Monte Carlo determination of gamma-ray dose rate with the GEANT system.

Conversion factors for the dose rate 1 m above the ground level from the measured activities for different gamma-ray emitters in soil are calculated using the Monte Carlo method. The calculations are based on the GEANT system developed at CERN, Geneva. Results for the uniform and surface distribution of the emitters in the soil are given for gamma-ray energies in the interval between 20 keV and 3 MeV.