Improvement of a low-level mesurement system used at LNHB.

In this new approach, the active shielding of a low level spectrometer is monitored by an extendable dead time used as an "extendable GATE" signal. This concept is directly inspired from the live-timed anti-coincidence system implemented at LNE-LNHB (MTR2 modules). This allows a significant reduction in the cost and complexity of the system since several electronic modules are replaced by only one module dedicated specifically to this type of experiment. Settings of this new approach are detailed and results are discussed.

(60)Co in cast steel matrix: A European interlaboratory comparison for the characterisation of new activity standards for calibration of gamma-ray spectrometers in metallurgy.

Two series of activity standards of (60)Co in cast steel matrix, developed for the calibration of gamma-ray spectrometry systems in the metallurgical sector, were characterised using a European interlaboratory comparison among twelve National Metrology Institutes and one international organisation. The first standard, consisting of 14 disc shaped samples, was cast from steel contaminated during production ("originally"), and the second, consisting of 15 similar discs, from artificially-contaminated ("spiked") steel. The reference activity concentrations of (60)Co in the cast steel standards were (1.077±0.019) Bqg(-1) on 1 January 2013 12h00 UT and (1.483±0.022) Bqg(-1) on 1 June 2013 12h00 UT, respectively.

A tunable monochromatic X-ray source for metrological studies in the 1-20 keV energy range: application to the measurement of attenuation coefficients.

A tunable monochromatic X-ray source operating in the 1-20 keV energy range is described. An X-ray tube provides initial photons. A dispersive crystal performs the energy selection, according to Bragg's law. An X-ray detector is connected to the monochromator fixed exit. This setup can be used for metrological studies. A first application consists in measuring attenuation coefficients in the 4-10 keV energy range. Results for aluminum and copper are given, with average relative uncertainties (1sigma) of 1% and 3% respectively.

On scattering effects for volume sources in low-energy photon spectrometry.

In this study, different aspects of the Compton scattering inside volume sources are illustrated using experimental approach and Monte Carlo simulation. For the low-energy range (below 100 keV) scattered events represents around 30% of the whole spectrum. Influence of the source-detector geometry is discussed. The scattering effects induce strong differences in spectrum shape for different geometrical conditions. This should influence efficiency transfer factors. A new approach is proposed, including the scattered events, to avoid complex peak area determination.

Validation of efficiency transfer for Marinelli geometries.

In the framework of environmental measurements by gamma-ray spectrometry, some laboratories need to characterize samples in geometries for which a calibration is not directly available. A possibility is to use an efficiency transfer code, e.g., ETNA. However, validation for large volume sources, such as Marinelli geometries, is needed. With this aim in mind, ETNA is compared, initially to a Monte Carlo simulation (PENELOPE) and subsequently to experimental data obtained with a high-purity germanium detector (HPGe).

Characterization of a cosmic suppression spectrometer.

In this work, PENELOPE2008 and MCNP5 software packages were used to investigate the effect of simulation parameters such as cut-off energy of photons and electrons on the detector response function and peak escape intensity to assess their influence on the efficiency determination. The results showed a general agreement between the two codes, however both the intensity of escape peaks and total efficiency computed with PENELOPE2008 are higher than those obtained with MCNP5. Moreover, the calculated efficiencies are typically 8% higher than what is experimentally found in the low energy range. Further investigation was required to obtain better agreement and lead to better estimate of the real germanium crystal dimensions and dead layer.

Coincidence summing corrections applied to volume sources.

The numerical calculation of coincidence summing corrections requires both the total and full-energy peak efficiencies to be included in the corrective factors. Moreover, in the case of volume sources, the coincidence probability depends on the position of the photon emission inside the radioactive sample, thus it is necessary to calculate the coincidence summing corrective factors by integrating the elemental contributions for the entire volume. The software ETNA calculates coincidence summing corrective factors according to a deterministic method, for volume sources, two approaches are included in the software: the "simplified" calculation uses directly the efficiency of the volume source like in the case of point source, and the "complete" calculation performs the volume integration. To assess the difference between these, different geometrical cases are tested for several radionuclides using both methods.

Measurement of beta-plus emitters by gamma-ray spectrometry.

The activity measurement of beta-plus emitters by gamma-ray spectrometry is studied. Experimental measurements are performed with (22)Na, (65)Zn and (64)Cu with sources included in a lead container. For these nuclides, the activity can be derived both from one photon emission peak and from the 511 keV annihilation peak, including annihilation in-flight correction and geometry correction computed by Monte Carlo simulation. The activity values obtained using the two types of peaks show satisfying agreement. The extension of the method to volume sources is discussed.

Measurement of natural radionuclides in phosphgypsum using an anti-cosmic gamma-ray spectrometer.

Gamma-ray spectrometry measurements have been carried out to determine the activity of natural radionuclides in a phosphogypsum sample included in a specific tight container. The gamma spectrometer includes an N-type coaxial high-purity germanium (HPGe) detector equipped with an anti-cosmic system. This measurement required the determination of linear attenuation coefficients of phosphogypsum to calculate self-absorption correction between efficiency calibration conditions and measurement ones. The results are given for the three natural chains and for (40)K, in term of specific activity/g of dry material, ranging from a few Bq kg(-1) to a few hundreds Bq kg(-1). The equilibrium within the different families and the (235)U/(238)U ratio are discussed.