Consistency test of coincidence-summing calculation methods for extended sources

An internal consistency test of the calculation of coincidence-summing correction factors F_C for volume sources is presented. The test is based on exact equations relating the values of F_C calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of F_C values sent by 21 teams. Most sets passed the test, but not the results obtained using the quasi-point source approximation; in the latter case the test qualitatively indicated the magnitude of the bias of F_C.

A benchmark for Monte Carlo simulation in gamma-ray spectrometry

Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage.

Determination activity of radionuclides in marine sediment by gamma spectrometer with anti cosmic shielding

In this work, the activities of radionuclides in a marine sediment sample have been determined. The gamma spectrometer comprises an N type coaxial HPGe detector with active shielding to reduce cosmic background. The mass activities of radionuclides have been derived and found to be around a few Bq kg(-1) to several hundreds Bq kg(-1) with relative uncertainties in this paper quoted corresponding to the combined standard uncertainties (k=1).

Study of scattering effects in low-energy gamma-ray spectrometry

The photon-scattering effect was studied in the low-energy range 15-80keV with planar and coaxial germanium detectors. Different experimental tests have been conducted with a point source, progressively reducing the matter around the radioactive deposit, to investigate the origin and characteristics of the different spectrum components due to scattered photons (bumps). These tests were completed by Monte Carlo simulations. Finally, a peak-shape calibration was performed using several radionuclides ((109)Cd, (241)Am, (133)Ba, (137)Cs and (152)Eu). This allowed in identifying the main contributions to the bumps and improving the spectra processing.

Standardization of 222Rn by LSC and comparison with - and -spectrometry

Liquid scintillation counting (LSC) was used for the measurement of 222Rn in equilibrium with its daughters, with detection efficiency close to 5. The appropriate corrections were considered, including one related to the probability that the 165-micros half-life 214Po decays during the dead time of the counter initiated by the disintegration of his parent nuclide, 214Bi. The dead-time determination of a commercial LS counter is also presented using a 222Rn standard source. The LSC 222Rn sources were prepared by transfer of 222Rn produced by a solid 226Ra source into LSC cocktail frozen at 77K, flame-sealed afterwards. They were measured using the LNHB triple coincidence counter with adjustable extending-type dead-time unit, between 8 and 100 micros; two different procedures were used to calculate an effective dead time and then to deduce the counting rate extrapolated to zero dead-time value. The LSC results were compared with those obtained by cryogenic alpha-particle spectrometry (LNHB system) and by gamma-ray spectrometry for the same radon source in the LSC vial; the geometry transfer coefficient was calculated using the ETNA software. Measurement results and uncertainties are discussed.

Measurement of a 103Pd solution using the TDCR method by LSC

Palladium 103 is a radionuclide used in brachytherapy sources for the treatment of prostate cancers and also for other medical applications. It decays through electron capture to excited levels of 103Rh. This paper describes the calculation method used to compute the detection efficiency in the framework of the triple to double coincidence ratio model. The calculation of the energy transferred to the scintillator is made by considering the various atomic events following the electron capture and the electron conversion. The energy deposited in the scintillator after the absorption of X-rays is calculated using the PENELOPE stochastic calculation code. The main contributors to the final uncertainty and their covariance matrix are discussed. As the calculation method cannot be reduced to an explicit function, this paper describes the Monte Carlo method used for the evaluation of uncertainties.

Intercomparison of efficiency transfer software for gamma-ray spectrometry

The EUROMET project 428 examines efficiency transfer results for Ge gamma-ray spectrometers when the efficiency is known for a reference point source geometry. For this, different methods are used, such as Monte Carlo simulation or semi-empirical computation. The exercise compares the application of these methods to the same selected experimental cases to determine the usage limitations versus the requested accuracy. For carefully examining these results and trying to derive information for improving the computation codes, this study was limited to a few simple cases. The first part concerns the simplest case of geometry transfer, i.e., using point sources for 3 source-to-detector distances: 2, 5 and 20 cm; the second part deals with transfer from point source geometry to cylindrical geometry with three different matrices. The general conclusion is that the deviations between the computed results and the measured efficiencies are mostly within 10%. The quality of the results is rather inhomogeneous and shows that these codes cannot be used directly for metrological purposes. However, most of them are operational for routine measurements when efficiency uncertainties of 5-10% can be sufficient.