Gamma Spectrometry Measurements Research Articles

Novel integral expressions for computing the full energy peak efficiency of gamma spectrometry systems

A new theoretical approach was developed for computing the FEP efficiency of HPGe and scintillation detectors using the concept of probability function. Thus integral expressions for the FEP efficiency were developed using three probability functions. Starting from the integral expression of the FEP efficiency and using integral means and Chebyshev functional, new expressions of the FEP efficiency, detector response, and self-attenuation factors were obtained. Also, the new approach provides new insights useful for gamma spectrometry measurements. Two practical applications of this approach are described.

Study of Neutron Background in order to Improve Radioactive Waste Drum Characterization

A usual way of radioactive waste drums characterization combines gamma spectrometry measurements with passive neutron measurements. The CEA facility for waste drum characterization hereby described has been operated for more than 30 years. In this framework, a large variety of waste drums has been characterized in terms of spectra, densities, materials and radioactivity levels. As the facility was first dedicated to measure Intermediate-Level Long-lived Waste, the neutron background was not significant compared to expected neutron emitters from waste packages. These last years, Dismantling and Decommissioning operations have been advanced in this CEA site to the point where they are now associated with mostly Very Low Level Waste production. Therefore, neutron background is becoming significant. Using the large variety of past characterized drums brings the opportunity to study this background. The present study has been led over a sample of almost 1500 drums over a wide waste density range. These drums have been selected over the last 20 years by taking into account only one criterion: without any expected neutron emitters from the waste itself. This work first presents the technical settings of the measurement facility before describing the raw data of the measurements. Next, a statistical study over raw data enables to better acknowledge the neutron spallation background behavior in terms of time, density and materials. Ensues a way of using this new knowledge in order to improve how to take into account neutron spallation background in passive neutron measurements of packages of low actinides activities and high densities.

A practical approach to determining soil-sample detection efficiency in field gamma-ray spectroscopy

Field measurements of radionuclide activities in soil samples via gamma spectroscopy measurements are conducted for many applications. One example application space is on-site inspection for the Comprehensive Nuclear-Test-Ban Treaty. To extract isotopic activities from observed peak counting rates, it is necessary to understand the absolute efficiency of the detector system for a sample. In principle, this efficiency is a function of many parameters, such as sample geometry, soil elemental composition, and soil density. The demands of field measurements within the context of on-site inspections, however, places a premium on an easy-to-implement approach at the possible expense of accuracy given the need to process many samples in a short period of time. This paper presents a semi-empirical approach, using a calibrated standard and a correction that depends only on the relative differences in density of the sample and the standard. Field measurements were conducted to demonstrate the validity of the approach.

Characterization of two extraordinary AmLi neutron sources

Two legacy AmLi sources have been actively used across several projects within Pacific Northwest National Laboratory, however, applicability of source measurement data has been substantially limited due to the lack of original manufacturer documentation and cross comparison to other sources. This paper summarizes measurements conducted to better quantify source radionuclide content, neutron energy spectrum and emission rate of the AmLi sources. The measured neutron energy spectra of AmLi sources produced by Monsanto Research Corporation have not been found in open literature before and therefore the focus of the study was to obtain the high definition energy distribution of the sources. The initial gamma spectrometry measurements, aimed to estimate the radionuclide content and potential impurities, revealed a significant contamination of the source material with beryllium. Consequent neutron spectrum measurements confirmed beryllium contamination through the presence of a high energy tail contributing up to 17% to the total neutron emission rate. The obtained lithium-only portion of the measured source energy distribution was compared against other AmLi spectra discussed in the past and recent literature. Determination of the total neutron yields of the sources was made with measurements in a neutron well counter. Detection efficiency of the well counter was calculated specifically for these sources via detailed Monte Carlo simulations based on the obtained neutron energy distribution.

Reconstructing the impact of nickel mining activities on sediment supply to the rivers and the lagoon of South Pacific Islands: Lessons learnt from the Thio early mining site (New Caledonia)

Opencast mining has exacerbated land degradation in New Caledonia, a French archipelago located in the south-west Pacific Ocean. Developed since the 1880s, mining has become the major economic activity in some catchments, which strongly disrupted sediment dynamics. Reconstructing the temporal changes of sediment source contributions is essential to understand the driving factors of soil erosion in response to i) the occurrence of cyclones, ii) the changes in mining practices during the last several decades, and iii) other soil degradation processes such as extensive soil erosion induced by fires, overgrazing and trampling of invasive species, and landslides. Accordingly, a multi-parameter analysis including gamma spectrometry, color and X-ray fluorescence measurements was conducted on a sediment core collected in a deltaic floodplain at the outlet of one of the first areas exploited for nickel mining, the Thio River catchment (397-km2). One geochemical tracer (i.e. K) has been used to quantify changes in sediment sources in the successive sediment layers deposited since the beginning of mining activity. The results showed that the contribution of mining tributaries largely dominated, with a mean contribution of 74% (SD 13%) of material sampled in the sediment core. This contribution notably increased after the mechanization of mining activities (i.e. from 1950s; increase of 18%). The occurrence of Cyclone Alison in 1975 triggered the progressive transfer of mining waste accumulated on the foothills over 25 years into the river system. This tipping point could be identified in the sediment sequence, which demonstrates that over the last 41 years (i.e. 1975–2016), a ~84-cm deep sediment deposit has accumulated in the alluvial floodplain of the Thio River catchment (mean annual deposition rate of 2 cm yr−1). Currently, the progressive release and downstream transfer of this mining waste is still ongoing ~45 years after Cyclone Alison. Although environmental legislation was introduced in 1975, mining tributary contributions to sediment still dominate (80%, SD 5%). Overall, this multi-proxy approach to examining the cumulative effects of mining activities on downstream sediment dynamics could be implemented in other mining catchments of New Caledonia and around the world to compare the respective mining source contributions to sediment and their evolution throughout time in these contrasted areas.

Qualification of gamma spectrometry measurement for the radiological characterization of mixed VLLW cables in particle accelerators

In the framework of maintenance activities in particle accelerators, such as upgrades and dismantling, a large number of activated equipment are removed from the accelerator complex and require characterization in view of their disposal as radioactive waste. In particular, cables can be of different types. This feature induces variations of the efficiency calibration curves due to the variation of the material composition, source distribution and density. Hence, quantifying the activities of the gamma-emitting radionuclides can be quite challenging for mixed cables. In this article, we propose a new qualification methodology, based on gamma spectrometry, in order to assess the activity results uncertainties of gamma-emitting radionuclides. This new methodology is developed to define the envelop efficiency calibration curves and allows for the establishment of more accurate activity values with their corresponding uncertainties.

Radiation survey around “the 30th shipyard” company: 30 years after the accident

Introduction. The objective of this work was the radiation survey in the vicinity of “The 30th Shipyard” Company. The studies were carried out during the period between 2014 and 2016 within the supervision area and in the area of the radioactive trace formed after the accident of 1985 in the nuclear submarine.Material and methods. The following methods were used in the course of the survey: pedestrian gamma surveys, gamma spectrometry measurements of radionuclides using a gamma spectrometer, and radiochemical extraction of 90Sr, followed by measurement of its activity at radiometric installations.Results. Gamma ambient dose equivalent rate within the supervision area beyond the radioactive trace varies within the range between 0.09 and 0.18 µSv/h. The specific activities of 90Sr, 137Cs, and 235U in soil do not exceed 11, 34, and 5.8 Bq/kg, respectively. The specific activity of 60Co in the soil of the Dunay village is lower 0.42 Bq/kg and does not exceed 4.9 Bq/kg at the rest part of the supervision area. The area of the radioactive trace limited by 0.13 µSv/h iso-line does not exceed 0.5 km2, while that limited by 0.3 µSv/h iso-line - 0.0063 km2. Within the area of the trace, the highest value of the gamma dose rate accounts for 0.60 µSv/h. Soils contaminated with emergency radionuclides do not belong to solid radioactive waste. Emergency radionuclides migrated in soil up to 20 cm depth. Today, 137Cs is firmly fixed in the soil. 40-45% of 60Co activity is in acid-soluble form. Under specific conditions, it can migrate deep into the soil and be accessible to plants.Conclusions. Within the supervision area of “The 30th Shipyard” Company, except for the area of the radioactive contamination trace induced by the accident, the radiation situation is the same as that in the area of the Primorskiy Krai. The soil of the radioactive trace does not belong to solid radioactive waste. In the future, the improvement of the radiation situation on the trace will be mainly due to the physical decay of radionuclides.

Activity concentrations of 131I and other radionuclides in cow's milk in Belarus during the first month following the Chernobyl accident

The accident at the Chernobyl nuclear power plant (NPP) in Ukraine on April 26, 1986 led to a considerable release of radioactive material resulting in environmental contamination over vast areas of Belarus, Ukraine and western Russian Federation. The major health effect of the Chernobyl accident was an increase in thyroid cancer incidence in people exposed as children and adolescents, so much attention was paid to the thyroid doses resulting from intakes of 131I. Because cow's milk consumption was the main source of 131I intake by people, it was important to measure the 131I activity concentrations in cow's milk to calculate, or to validate, the thyroid doses to the exposed population. Almost 11,000 measurements of total beta-activity in cow's milk were performed using a DP-100 device during the first month after the Chernobyl accident in the most contaminated regions of Belarus. Using an ecological model and calibration coefficients for the DP-100 device the activity concentration of 131I in cow's milk was derived as well as the activity concentrations of the other radiologically important radionuclides, namely 134Cs, 137Cs, 89Sr and 90Sr. The activity concentrations of other radionuclides, such as 90Y, 132Te, 132I, 133I, 136Cs, 140Ba, 140La, 141Ce and 144Ce, in cow's milk were also estimated and were shown to be of minor importance. The concentrations of 95Zr, 95Nb, 103Ru and 106Ru in cow's milk were negligible. The data obtained in this study were validated by comparing derived 131I and 137Cs concentrations in cow's milk with gamma-spectrometry measurements performed in milk produced in the same location close to the same date. The results of this study were essential to assess and validate the radiation doses received by the subjects of epidemiological studies related to the health consequences of the Chernobyl accident.

PROCEDURES TO MEASURE MEAN AMBIENT DOSE EQUIVALENT RATES USING ELECTRET ION CHAMBERS.

The capabilities of electret ion chambers (EICs) to measure mean ambient dose equivalent rates were investigated by performing both laboratory and field studies of their properties. First, EICs were ‘calibrated’ to measure ambient gamma dose equivalent in the Ionizing Calibration Laboratory of the Greek Atomic Energy Commission. The EICs were irradiated with different gamma photon energies and from different angles. Calibration factors were deduced (electret’s voltage drop due to irradiation in terms of ambient dose equivalent). In the field studies, EICs were installed at eight locations belonging to the Greek Early Warning System Network (which is based on Reuter-Stokes ionization chambers) for three periods, averaging 5 months each. In the same locations, in situ gamma spectrometry measurements were performed with portable germanium detectors. Gamma ambient dose equivalent rates were deduced by the in situ gamma spectrometry measurements and by soil sample analysis. The mean daily electret potential drop (in Volts) was compared with the mean daily ambient dose equivalent, measured with a portable HPGe detector and Reuter-Stokes high-pressure ionization chambers. From these measurements, ‘field’ calibration factors (electret’s voltage drop due to gamma radiation in terms of ambient dose equivalent) were deduced and found in very good agreement with the values deduced in Laboratory. The influence of cosmic radiation and the intrinsic voltage loss when performing long-term environmental gamma measurements with EICs, was estimated.

Determination of radon leakage from sample container for gamma spectrometry measurement of 226Ra

Gamma spectrometry is widely used for radionuclide activity measurement of environmental sample including 226Ra in soil because it is versatile, easy to implement, non-destructive, and relatively cheap compared to other methods. By gamma spectrometry, 226Ra can be determined directly using its energy peak of 186.2 keV or indirectly by its decay products which are in secular equilibrium with 226Ra, i.e. 214Bi and 214Pb. However, both methods have challenges where for direct measurement, interfering from 235U energy peak of 185.7 keV can add significant contribution to the 186.2 keV of 226Ra gamma peak while for indirect measurement using energy peaks of 214Bi and 214Pb, decay products of 222Rn gas, longer time (at least 21 days) for their equilibrium ingrowth is needed and radon tightness of sample container must be ensured. In some measurements, the equilibrium could not be reached due to radon leakage from sample container. Therefore, in this paper, the radon leakage fraction from three different sealing methods of Marinelli beaker used in soil activity measurement were studied using HPGe detector and radon accumulation chamber with RAD7. The three sealing methods were only lid without sealing (MB1), sealed with paraffin film (MB2), sealed with silicone glue and vacuumed plastic bag (MB3) and their leakage fractions were 53%, 30%, and negligible leakage, respectively. Significant radon leakage from MB1 and MB2 have caused underestimation of 226Ra activity concentration measured by indirect gamma spectrometry. The study result recommends using MB3 sealing method for gamma spectrometry measurement because it is simple and cheap and has negligible leakage, moreover, its vacuumed plastic bag facilitates visual inspection to possible radon leakage.

Radioactivity induced in new-generation cardiac implantable electronic devices during high-energy X-ray irradiation

This study provides the first insight into the problem of the induced radioactivity of the construction materials of the new-generation cardiac implantable electronic devices (CIEDs). Its aim was to identify nuclear reactions and the resulting radioisotopes induced in the CIEDs by high-energy X-ray therapeutic beams generated by medical linear accelerators. The presented results allow to verify the rightness of choice of materials for investigated CIEDs. Such analysis is currently available only for the older types of the CIEDs, but not for those of the new generation. Gamma spectrometry measurements have been performed using a high-purity germanium detector (HPGe). The identification and activities of the generated radioisotopes were obtained from the measured spectra of gamma - rays from decays of the produced unstable radioisotopes. 21 radioisotopes originating from 24 nuclear reactions were identified. For all considered models of CIEDs the highest activities are from the tin isomer 117mSn. The induced activities were relatively small, not exceeding 3.1 Bq per a 1 Gy X-ray dose to a target volume.

Characterization of Uranium Ore Samples by HPGe Gamma-Ray Spectroscopy

Gamma logging for uranium exploration is currently based on total counting with the Geiger–Muller gas detectors or NaI(Tl) 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 the differential leaching of uranium and its daughter radioisotopes radium, radon, and so on. Indeed, in the case of secular equilibrium, more than 95% of gamma rays emitted by uranium ores come from 214Pb and 214Bi isotopes that are in the back end of the 238U decay chain. These two isotopes 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 on the surface with HPGe detectors to directly characterize uranium activity from the 1001-keV gamma ray of 234mPa that is at the beginning of the 238U chain. However, due to the low intensity of this gamma ray, acquisitions of several hours are needed. In view to characterize uranium concentration within a few minutes, we propose a method using both the 92 keV gamma rays of 234Th and 235U and the 98.4-keV uranium X-ray. This last is due to uranium self-induced fluorescence caused by gamma rays of the uranium chain, mainly 214Pb and 214 Bi. The gamma rays of 214Pb and 214Bi undergo scatterings in the sample leading to photons with energy in the 100-keV range that favor photoelectric interactions and, thus, fluorescence. The comparison of the uranium activity obtained with the 92- and 98.4-keV lines allows detecting a uranium heterogeneity in the ore. Indeed, in the case of uranium nugget, the 92-keV peak leads to underestimated uranium concentration due to the gamma self-absorption, but on the contrary, the 98.4-keV peak leads to an overestimation because of increased fluorescence. In order to test this new approach, tens of uranium ore samples have been measured with a handheld HPGe FALCON 5000 detector.

Radioactive uranium and cesium levels in Kuwait Bay seawater

The development of a continuous radioisotope monitoring program has an extreme significance in maintaining the marine environment’s radiological safety. This study aimed to evaluate the radiological safety of locally sourced desalinated water and seafood. The establishment of baseline data for observing the nuclear activities already existing in the Gulf region was also targeted. While natural uranium radioisotopes are naturally occurring in the environment, there is a rising concern in Kuwait due to the depleted uranium (DU) presence after the Gulf War in 1991. The anthropogenic radionuclide (137Cs) serves as among the most important indicator of the radioactivity releases. The present work focused on determining the concentration of 137Cs and uranium isotopes in Kuwait Bay (KB) seawater. The concentrations of 137Cs were determined by the ammonium molybdenum phosphate (AMP) co-precipitation method followed by gamma spectrometry measurement, whereas a radiochemical separation using anion exchange chromatography and alpha spectrometry measurement was used for uranium isotope determination. The average concentration levels of 235U, (234U and 238U), and 137Cs were 2.3 mBq l−1 ± 0.4, 45.3 mBq l−1 ± 3.5, and 1.24 mBq l−1 ± 0.5, respectively, and these figures are comparable to those reported worldwide. The concluded isotopic ratio of 235U/238U and 234U/238U indicated that the existing uranium in seawater of KB is only natural and no indication of the DU. The produced radiological data are considered as a beneficial baseline for monitoring the regional marine environment.

Possible Factors Influencing the Accumulation of Different Radionuclides in Sludge from a Drinking Water Treatment Plant Located in Southern Catalonia Between 2002 and 2018

The drinking water treatment plant (DWTP) in L’Ampolla collects water from the River Ebro. The sludge generated during the water treatment processes applied accumulates some of the radionuclides present in the ingoing water. Gamma spectrometry measurements of the sludge were carried out monthly for a period of 17 years (2002–2018) to evaluate possible factors that might influence the radioactive content. These included the geology, river flow rate, suspended particulate matter, turbidity, water treatment processes, and industrial activities in the area of the river basin. The activity concentrations of 214Pb, 214Bi, 228Ac, 228Ra, and 226Ra from both the 238U and 232Th decay chains decreased significantly from 2012 onwards. This may be related to a change in the water treatment process in the L’Ampolla DWTP, and in particular, that potassium permanganate was no longer added to the raw water from 2011. Other isotopes such as 40K, 7Be, and 234U/238U have not displayed the same behavior, which could support our hypothesis that the accumulation of radium isotopes in the sludge could be influenced by the use and nonuse of permanganate. A number of artificial radionuclides were also determined, which is consistent since L’Ampolla DWTP is located 70 km from a nuclear power plant, and the activities found for some of these radionuclides correlate with its annual liquid discharges into the river. The results therefore indicate that a relationship exists between the different factors in connection with the raw water and the radioactive content of the sludge generated by the plant under study.

Distribution of uranium and thorium chains radionuclides in different fractions of phosphogypsum grains

This work presents results obtained using gamma spectrometry measurements of phosphogypsum samples on a non-fractionated (native) and fractionated phosphogypsum byproduct. The phosphogypsum was divided into particles size fractions within the range of < 0.063, 0.063–0.090, 0.090–0.125, 0.125–0.250, and over 0.250 mm and analyzed after reaching radioactive equilibrium using high-resolution gamma spectrometry technique. It was found that there is no significant differentiation between 226Ra distribution among particular grain size fractions of this material; however, tendency for preferential retention of radionuclides in particular grain size fractions is observed. The detailed analysis of results revealed that radium is preferentially retained in smaller grain size fractions, whereas lead and thorium in coarse fractions. The results indicate that overall 226Ra activity concentrations between particular fractions of phosphogypsum vary globally between − 34 and + 47% regarding non-fractionated material, and for 210Pb activity concentration, fluctuations are found between − 26 up and + 38%. Presumably, the mechanism of radium incorporation into gypsum phase is based on a sequence of radium bearing sulfate phases formation followed by a surface adsorption of these phases on the calcium sulfate crystals, whereas for lead and thorium ions, rather incorporation into crystal lattice should be expected as more likelihood process.

The application of 137 Cs and 210 Pb ex methods in soil erosion research of Titel loess plateau, Vojvodina, Northern Serbia

Abstract Soil erosion is one of the largest global problems of environmental protection and sustainable development, causing serious land degradation and environmental deterioration. The need for fast and accurate soil rate assessment of erosion and deposition favors the application of alternative methods based on the radionuclide measurement technique contrary to long-term conventional methods. In this paper, we used gamma spectrometry measurements of 137Cs and unsupported 210Pb ex in order to quantify the erosion on the Titel Loess Plateau near the Tisa (Tisza) River in the Vojvodina province of Serbia. Along the slope of the study area and in the immediate vicinity eight representative soil depth profiles were taken and the radioactivity content in 1 cm thick soil layers was analyzed. Soil erosion rates were estimated according to the profile distribution model and the diffusion and migration model for undisturbed soil. The net soil erosion rates, estimated by 137Cs method range from −2.3 t ha−1 yr−1 to −2.7 t ha−1 yr−1, related to the used conversion model which is comparable to published results of similar studies of soil erosion in the region. Vertical distribution of natural radionuclides in soil profiles was also discussed and compared with the profile distribution of unsupported 210Pb ex measurements. The use of diffusion and migration model to convert the results of 210Pb ex activities to soil redistribution rates indicates a slightly higher net erosion of −3.7 t ha−1 yr−1 with 98% of the sediment delivery ratio.

MOX fuel microstructural evolution during the VERDON-3 and 4 tests

The VERDON-3 and -4 tests were part of the VERDON-ISTP programme that aimed at studying the fuel and fission products (FP) behaviour in severe accident conditions. The main objective of these two complementary tests was the study of MOX fuel behaviour and FP release under oxidising (VERDON-3) and reducing (VERDON-4) conditions at very high temperature (>2300 °C). Complementary to the on-line gamma spectrometry measurements performed during the two tests, post-test characterisations were carried out in order to tackle these tasks. The two samples recovered after the VERDON-3 and -4 tests were compared to a third one extracted from the same father rod and left as irradiated. This comparison enabled to highlight the effect of temperature and atmosphere on the fuel behaviour. These three samples were characterised by several techniques available at the LECA-STAR facility of the CEA Cadarache. Experimental observations showed that an interaction between the fuel and the cladding occurred in both types of conditions by interdiffusion mainly between U and Zr. This phenomenon led to the formation of a UyZr1-yO2±x cubic phase at the periphery of the fuel pellet which melted in the VERDON-4 test conditions, penetrating through the cracks of the sample and dissolving the fuel matrix. No liquid was formed during the VERDON-3 test despite the formation of a large fuel-cladding interaction zone.

INSIDER UC2: the BR3 biological shield preliminary results and future work

Aiming at economical optimization, the characterisation of the biological shield of the Belgian Reactor 3 is one of the three use cases intended to validate the integrated characterization methodology developed within the INSIDER project. Pre-existing data were used to define the sampling design strategy. The additional sampling and analysis program consisted of total gamma measurements at the inner surface of the biological shield (secondary data) and gamma spectrometry measurements on drill core samples (primary data). The newly acquired data is supplemented with the historical available data. The full data set currently consists of a total of 283 secondary and 379 primary data points. Preliminary calculations already provide a clear-cut representation of the three different end-stage classes: unconditional clearance, conditional clearance and radioactive waste. On the short term, the current model will be further refined and completed with proper risk evaluation. On the longer term, we envisage a global uncertainty calculation and sensitivity analysis of the entire process.

Ozračenost pripadnika vojske SR Jugoslavije na Kosovu i Metohiji u toku NATO agresije 1999. godine

Introduction/purpose: The paper indicates the radiation doses the military personnel of the Federal Republic of Yugoslavia were exposed to, and in particular the military personnel of the motorized brigades in the territory of Kosovo and Metohia on the Albanian-Yugoslav border. Methods: Gammaspectrometry measurements have confirmed that round penetrators contained depleted uranium, and the presence of alpha, beta and gamma radiation was determined by the method of dosimetric measurement. Results: The use of ammunition with 238U depleted uranium, with added plutonium, pollutes the environment, water, and soil in the long term, causing various disorders and diseases, primarily malignant ones. The radioactivity of 239Pu, compared to its toxicity, is several thousand times higher and the inhalation of plutonium dust is harmful and causes cancer. Uranium is a pyrophoric metal, toxic, radioactive and easy to ignite. Its oxides are toxic and partially soluble in water. After ignition, the round releases radioactive aerosol particles which burn in contact with the air causing short or long term damage when inhaled. In Kosovo and Metohia, a large amount of radioactivity was measured during the NATO aggression against the FR Yugoslavia. In Metohia, radioactivity was 1,100 times that of natural background radiation. Conclusion: During the war, the Army of the FR Yugoslavia was exposed to high radioactive doses, so that among the members of the army after the war there was an increased incidence of various malignancies, many of them lethal.

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

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.