Detailed MCNP Simulations of Gamma-Ray Spectroscopy Measurements With Calibration Blocks for Uranium Mining Applications

Marchais, T.; Pérot, B.; Carasco, C.; Allinei, Pierre-Guy; Chaussonnet, P.; Ma, Jean-Luc; Toubon, H.

doi:10.1109/tns.2018.2797312

Cited by 6 publications

(5 citation statements)

References 2 publications

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“…These calculations (not reported here) show that if the contaminated area is smaller (for instance a hot spot or a 10 cm × 10 cm surface) than the detector field of view, the efficiency can be almost twice than that used for interpretation (calculated for a contaminated area of 25 cm × 25 cm) or those calculated with surfaces larger than the field of view (we studied from 20 cm × 20 cm to 30 cm × 30 cm). From this study and due to the lack of knowledge of the real contamination distribution, we consider an arbitrary relative uncertainty of 50 % on efficiency, this last also includes the uncertainty on the HPGe detector MCNP model, which is however less than 10 % from our feedback [10]. Even if this uncertainty is much smaller than the previous one, we will check the HPGe detector model through MCNP vs. experiment comparisons of precise measurements with calibration point sources, on the wide energy range of interest (53.2 keV peak of 234 U up to 1001 keV peak of 234m Pa), the other uncertainties on the MCNP model, such as the limited knowledge of the concrete block density and chemical composition, are smaller and also included in the abovementioned 50 % relative standard deviation, statistical uncertainties, including the variability associated to the net area extraction for the small 53.2 keV peak of 234 U, and the dispersion of the activities obtained with the different peaks of multi-gamma emitters, calculated through the weighted average (2).…”

Section: Withmentioning

confidence: 99%

Gamma-ray spectroscopy for the characterization of uranium contamination in nuclear decommissioning

Salvador,

Marchais,

Pérot

et al. 2023

EPJ Web Conf.

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Decommissioning is the last step in the life cycle of a nuclear facility. After the evacuation of the facility components, the remaining structures such as concrete walls and floors must be surveyed to ensure that no residual contamination remains. It is a costly and time consuming activity, for which CEA develops fast alpha and beta detection methods allowing a full scanning of very large areas (hundreds of thousands of square meters) in legacy uranium enrichment plants. To support these developments, we present here complementary high-resolution gamma-ray spectroscopy analyses of a contaminated area at the gaseous diffusion uranium enrichment facility UDG, currently under decommissioning at Pierrelatte nuclear plant, France. Long measurements are performed with a High-Purity Germanium (HPGe) detector on the contaminated surface, and in a clean area to assess the natural gamma background of the concrete ground. The surface activity of uranium is 16.6 ± 6.0 Bq.cm-2, mainly due to 234U and 238U, most of the uncertainty coming from the non-uniform distribution of the contamination on the ground. This measurements also allowed us estimating the uranium enrichment of the contamination, which amounts to (0.80 ± 0.13) % of 235U mass fraction, consistently with the range of the Low Enrichment Plant where this measure was performed. Eventually, the background spectrum allowed us to determine the mass fractions of natural uranium, thorium and potassium in the concrete ground, which respectively amount to 3.8 ± 0.2. ppmU (i.e. 3.8 mg of uranium per kg of concrete), 7.4 ± 0.7 ppmTh, and (2.6 ± 0.1) %K of potassium.

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Section: Withmentioning

confidence: 99%

Gamma-ray spectroscopy for the characterization of uranium contamination in nuclear decommissioning

Salvador,

Marchais,

Pérot

et al. 2023

EPJ Web Conf.

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“…The modelling of the high purity germanium (HPGe) detector efficiency was performed by using the Monte Carlo radiation transport code MCNP version 6.2 [14]. One area of applications of the code is widely used for detector design and analysis to investigate the performance data of the detector [15][16][17][18]. The geometry setup of Ge crystal and its shielding, used in the simulation, are presented in Figs.…”

Section: Monte Carlo Simulationsmentioning

confidence: 99%

Efficiency calibration of high-purity germanium detector using Monte Carlo simulations including coincidence-summing corrections: volume source case

Konstantinova¹,

Germanas²,

Gudelis³

et al. 2021

physics

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The gamma-ray spectrometry by the instrumentality of Ge detectors is used for the detection of low activity environmental samples of different geometry (soil samples, air filters with aerosols, milk powder, etc.). Such measurements require separate calibration of the detector. The high purity germanium (HPGe) gamma-ray spectrometer of GC2520 series was used for experiments. For the efficiency calibration, three cylindrical containers filled with different 60Co water solution levels were used, and the gamma-ray coincidence summing was modelled using MCNP6. The dimensions of the pure germanium crystal, provided by Canberra, were used for the simulations. The true coincidence summing takes place when two or more gamma quanta, which are emitted in a cascade from an excited nucleus, are detected within the resolving time of the detector. However, there is often a mismatch between the simulated and experimental efficiencies. The experimentally obtained and modelled spectra were compared: a good consistency of experimental and modelled results allows investigating the volume sources. During the simulation it was found that the factors affecting the accuracy of modelling are the thickness of the dead layer, crystal dimensions and the thickness of the Al detector cap. The analysis allows measuring the radionuclides activity concentration of samples placed in the containers with different filling heights having only standard shape calibration sources. The obtained accuracy is sufficient to fulfil criteria of 5–10% for such type of simulation to be applied for measurements of real samples in standard BURK-60 containers of various sample filling heights.

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“…in mg of uranium per kg of ore, dimensionless unit). This equation has been already used and validated during a measurement campaign in Bessines (France) calibration facility [3].…”

Section: Analysis Of the Gamma Spectrummentioning

confidence: 99%

“…This detector is equipped with a planar HPGe crystal, which will be finely characterized with a multi-energy highly collimated 152 Eu gamma source. This narrow photon beam will allow precisely estimating the dead layers vs. active area of the germanium crystal [3]. We will also measure 38 additional ore samples provided by ORANO Mining, on a wider range of uranium concentrations, to fully qualify the method in the Nuclear Measurement Laboratory of CEA, DEN, Cadarache.…”

Section: Conclusion and Prospectsmentioning

confidence: 99%

The use of self-induced X-ray fluorescence in gamma-ray spectroscopy of uranium ore samples

Marchais¹,

Pérot²,

Carasco³

et al. 2020

EPJ Web Conf.

Self Cite

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Gamma logging for uranium exploration are currently based on total counting with Geiger Müller gas detectors or NaI (TI) scintillators. However, the total count rate interpretation in terms of uranium concentration may be impaired in case of roll fronts, when the radioactive equilibrium of the natural 238U radioactive chain is modified by differential leaching of uranium and its daughter radioisotopes of thorium, radium, radon, etc. Indeed, in case of secular equilibrium, more than 95 % of gamma rays emitted by uranium ores come from 214Pb and 214Bi isotopes, which are in the back-end of 238U chain. Consequently, these last might produce an intense gamma signal even when uranium is not present, or with a much smaller activity, in the ore. Therefore, gamma spectroscopy measurements of core samples are performed in surface with high-resolution hyper-pure germanium HPGe detectors to directly characterize uranium activity from the 1001 keV gamma ray of 234mPa, which is in the beginning of 238U chain. However, due to the low intensity of this gamma ray, i.e. 0.84 %, acquisitions of several hours are needed. In view to characterize uranium concentration within a few minutes, we propose here a method using both the 92 keV gamma ray of 234Th and the 98.4 keV uranium X-ray. This last is due to uranium self-induced fluorescence caused by gamma radiations of 214Pb and 214Bi, which create a significant Compton scattering continuum acting as a fluorescence source and resulting in the emission of uranium fluorescence X-rays. The comparison of the uranium activity obtained with the 92 keV and 98.4 keV lines allows detecting a uranium heterogeneity in the ore. Indeed, in case of uranium nugget, the 92 keV line leads to underestimated uranium concentration due to gamma self-absorption, but on the contrary the 98.4 keV line leads to an overestimation because of increased fluorescence. In order to test this new approach, several tens of uranium ore samples have been measured with a handheld HPGe FALCON 5000 detector.

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Detailed MCNP Simulations of Gamma-Ray Spectroscopy Measurements With Calibration Blocks for Uranium Mining Applications

Cited by 6 publications

References 2 publications

Gamma-ray spectroscopy for the characterization of uranium contamination in nuclear decommissioning

Gamma-ray spectroscopy for the characterization of uranium contamination in nuclear decommissioning

Efficiency calibration of high-purity germanium detector using Monte Carlo simulations including coincidence-summing corrections: volume source case

The use of self-induced X-ray fluorescence in gamma-ray spectroscopy of uranium ore samples

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