Natural Radioactivity In Rocks Research Articles

Reviewing 39Ar and 37Ar underground production in shallow depths with implications for groundwater dating

Argon-37 (37Ar) and Argon-39 (39Ar) are used for groundwater dating on timescales from weeks to centuries. For both isotopes, the quantification of underground sources is essential to accurately infer water residence times from sampled dissolved activities. Subsurface production resulting from interactions with neutrons from the natural radioactivity in rocks and with primary cosmogenic neutrons has been known for a long time. More recently, the capture of slow negative muons and reactions with muon-induced neutrons were documented for 39Ar subsurface production in the context of underground particle detectors (e.g. for Dark Matter research). However, the contribution from these particles was never considered for groundwater dating applications. Here, we reevaluate the importance of all potential depth-related production channels at depth ranges relevant for 39Ar groundwater dating [0 − 200 meters below the surface (m.b.s)]. The production of radioargon by muon-induced processes is considered in this depth range for the first time. The uncertainty on the total depth-dependent production rate is estimated with Monte Carlo simulations assuming a uniform distribution of the parameter uncertainties. This work aims to provide a comprehensive framework for interpreting 39Ar activities in terms of groundwater residence times and for exposure age dating of rocks. The production of 37Ar is also addressed since this isotope is relevant as a proxy for 39Ar production, for the timing of river-groundwater exchanges, and in the context of on-site inspections (OSI) within the verification framework of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). In this perspective, we provide an interactive web-based application for the calculation of 37Ar and 39Ar production rates in rocks.

Natural radioactivity of rocks from the historic Jeron\xfdm Mine in the Czech Republic

This study reports the natural radioactivity of characteristic rocks found in the historic Jeroným Mine of the Czech Republic as measured under the laboratory conditions. The rocks analyzed included granites and schists weathered to varying degrees and collected from different levels of the underground workings of the Jeroným Mine. The mine itself has been subject to metal extraction (mainly tin and tungsten) since the sixteenth century and has recently been developed as a cultural and scientific attraction open to the public. Activity concentrations of 40K, 232Th and 238U were measured from nine rock samples using gamma-ray spectrometry. The activity concentrations of 40K varied from 595 Bq kg−1 to 1244 Bq kg−1, while 232Th varied from 25 Bq kg−1 to 55 Bq kg−1. The activities associated with 238U ranged from 46 Bq kg−1 to 386 Bq kg−1. The measured activities were used to estimate two radiation hazard indices typically applied to building materials, the activity concentration index I and the external hazard index Hex. Mean respective values of 1.02 and 0.77 for I and Hex indicate that the rocks found in the Jeroným Mine meet radiological safety standards for building materials and do not pose a risk to potential tourists and staff.

Uran, thorium a draslík v krystaliniku a paleozoických sedimentech na mapovém listu 14-33 Polička – laboratorní gamaspektrometrie a parciální chemické složení variských plutonitů

The paper deals with natural radioactivity of metamorphic and igneous rocks and Palaeozoic sediments within the map sheet 14-33 Polička. Studied rocks belong to three geological units: the Hlinsko Zone (phyllites and quartzites of the Mrákotín Fm., flysch sediments of the Hlinsko-Rychmburk Fm.), the Svratka Crystalline Complex (mainly mica schists, paragneisses, orthogneisses and migmatites, also amphibolites, skarns, erlans and quartzites) and the Polička Crystalline Complex (mica schists, paragneisses to migmatites and the Variscan granitoids are dominant). Concentrations of potassium, uranium and thorium were measured using a laboratory gamma-ray spectrometer in 805 rock samples. Data are tabled and discussed. Natural radioactivity of rocks is evaluated on the basis of the calculated values of mass activity of 226Ra equivalent (am). Slightly increased am values were found in migmatites and orthogneisses of the Svratka Crystalline Complex (187 Bq.kg-1 on average), granites and granodiorites of the Budislav Pluton (216 Bq.kg-1), granodiorites and rocks of a tonalite suite of the Miřetín Pluton (199 and 194 Bq.kg-1). Increased concentrations of uranium and thorium were found in some samples of pegmatite and aplite. Radioactivity of rocks of the Hlinsko-Rychmburk and Mrákotín Fms. can be assessed as relatively low.

Studies on natural radioactivity in rocks of Coorg district, Karnataka state, India

The paper deals with the study of natural radioactivity in the rocks of Coorg district, Karnataka state. The samples were analyzed by NaI(Tl) based gamma ray spectrometer. The activity of 232Th varies from 16.46 Bq kg−1 to 160.84 Bq kg−1 with mean value of 79.05 Bq kg−1. The activity of 40K varies from 96.72 Bq kg−1 to 933.68 Bq kg−1 and that of 226Ra was found to vary from BDL to 34.36 Bq kg−1. A correlation coefficient of R = 0.81 was found between 232Th activity and 40K activity. The correlation between 226Ra activity and 232Th activity is R = 0.59. The correlation between 40K and 226Ra is R = 0.51. The Radium Equivalent Activity (Raeq) ranges from 46.78Bq kg−1 to 315.55Bq kg−1. The absorbed gamma dose rate (D) ranges from 21.28 nGy h−1 to 141.45 nGy h−1, with an average of 73.37 nGy h−1. The radionuclides activity was compared with world average values. The external Hazard index (Hex) varies from 0.12 to 0.84. The internal hazard index (Hin) is in the range 0.15–0.89. The hazard indices were found to be within safety limits.

Evaluation of environmental hazards resulted from natural radioactivity in rocks from catchment area in Delta Tuban in Yemen

The knowledge of environmental hazards resulted from natural radioactivity and human activities are very important for monitoring environmental contamination. In this study the environmental hazards due to the natural radioactivity in rocks from catchment area of Tuban delta in Yemen were discussed and evaluated. Eight rocks samples were collected from the study area. The results showed that the mean activity concentrations of 238U series (226Ra), 232Th, and 40K were 29.52  1.5, 32.29  2.3, and 817.5  30.1 Bq kg-1, respectively. Also, the physical and chemical properties of some rock samples were examined and evaluated. Radiological parameter, such as absorbed dose rate in air, annually effective dose, the radium equivalent activity (Raeq), gamma index (Iɤ), external hazard index (Hex), and internal hazard index (Hin), were calculated and evaluated. The results were compared with those of literatures.

Borehole Logging in Alpine Periglacial Talus Slopes (Valais, Swiss Alps)

Geophysical measurements were carried out in six boreholes at three periglacial talus slopes in the Swiss Alps in order to determine the talus structure and the geological and permafrost stratigraphy. These are important elements of interpretation of the palaeoclimatic significance of Alpine talus slopes. This study combined three nuclear well logging methods. Natural radioactivity of rocks and ice-rich permafrost were determined by using natural gamma-ray logs through the lack of radioactivity of massive ice. Quantification of the ice content in frozen layers and the air content in unfrozen layers by variations in bulk density was provided by the application of gamma-gamma logs. Neutron-thermal neutron logs were used to calculate the water content, linked with the porosity of the formation. Combination of the three logs allowed three-phase models (rock, ice and air/water) of the subsurface to be obtained. Results show that the air content decreases with depth because of the increasing in-situ stresses that cause compression of the rock debris and the existence of a fine matrix filling the voids. Calculation of the ice content variations shows that talus slopes are frequently partially saturated with ice or, at most, slightly supersaturated with ice. All three logs provide complementary information on the progressive infilling of the voids with depth and the occurrence of ice-rich layers. A similar trend in ice content and the apparent porosity was highlighted by the joint application of gamma-gamma and neutron-neutron logs, which provide a mirror image of these two parameters. Copyright © 2015 John Wiley & Sons, Ltd.

Evaluation of natural radioactivity in rocks of Nilgiri hills and their radiation hazard to mankind

Twenty three rock samples were collected from various altitudes of Nilgiri hills, Tamil Nadu, India. A survey was carried out to determine the activity concentration of selected radionuclides ( 238 U, 232 Th, 40 K) by means of gamma-ray spectroscopy using NaI (Tl) detector. From the measured spectra, the mean activity of 238 U, 232 Th, 40 K are 7.13 Bq kg -1 , 30.47 Bq kg -1 and 346.06 Bq kg -1 , respectively. To evaluate the radiological effects, the absorbed dose rate, effective absorbed dose rate, radium equivalent activity, external and internal hazard indices, and radioactivity level index are also calculated. The mean absorbed dose rate of gamma radiation ranged from 11.90 nGy h -1 to 108.22 nGy h -1 . The activity concentration of 238 U, 232 Th, 40 K and the various radiological effects are below the internationally recommended maximum values.

Specific activities of natural rocks and soils at quaternary intraplate volcanism north of Sana'a, Yemen.

The level of natural radioactivity in rocks and soil of 32 samples collected from locations at North Sana′a in Yemen was measured. Concentrations of radionuclides in rocks and soils samples were determined by gamma-ray spectrometer using high purity germanium (HPGe) detector with specially designed shield. The average radioactivity concentrations of 226Ra, 232Th, 40K were determined and expressed in Bq/kg. The results showed that these radionuclides were present in concentrations of 21.79 ± 3.1, 19.5 ± 2.6 and 399.3 ± 16 Bq/kg, respectively, for rocks. For soil, the corresponding values were 48.2 ± 4.4, 41.7 ± 4.5 and 939.1 ± 36 Bq/kg, respectively. Also, the radiological hazard of the natural radionuclide content, radium equivalent activity, total dose rates, external hazard index and gamma activity concentration index of the (rocks/soils) samples in the area under consideration were calculated. The dose rates at 1 m above the ground from terrestrial sources were 38.39 and 86.89 nGy/h for rocks and surface soil, respectively, which present no significant health hazards to humans.

Natural radioactivity in rocks of the Modane-Aussois region (SE France).

The activity concentrations of 40K, 232Th, and 238U in the characteristic rocks of the Modane-Aussois region (Western Alps, France) were determined using an HPGe gamma-ray spectrometry system. The activity concentrations of 40K varied from 18 Bqkg−1 (limestone dolomite) to 392 Bqkg−1 (calcschist), while those of 232Th varied from 0.7 Bqkg−1 (limestone dolomite) to 18 Bqkg−1 (calcschist). The activities associated with 238U ranged from 9 (quartzite) to 29 Bqkg−1 (dolomite). In the investigated rock samples, concentrations of 238U (ppm) and 40K (%) had a strong negative correlation.

Natural radioactivity in the volcanic field north of Sana′a, Yemen

The level of natural radioactivity in rocks and soil of 32 samples collected from locations at North Sana'a in Yemen was measured. Concentrations of radionuclides in rocks and soils samples were determined by gamma-ray spectrometer using HPGe detector with specially designed shield. The average radioactivity concentrations of 226 Ra, 232 Th and 40 K were determined and expressed in Bq kg −1 . The results showed that these radionuclides were present in concentrations of 21.79 ± 3.1, 19.5 ± 2.6 and 399.3 ± 16 Bq kg −1 , respectively, for rocks. For soil, the corresponding values were 48.2 ± 4.4, 41.7 ± 4.5 and 939.1 ± 36 Bq kg −1 . Also, the radiological hazard of the natural radionuclides content, radium equivalent activity, total dose rates, external hazard index and gamma activity concentration index of the (rocks/soils) samples in the area under consideration were calculated. The data were discussed and compared with those given in the literature.

Study of inhomogeneous distribution of natural radioactivity in rock

Study of inhomogeneous distribution of natural radioactivity in rock

Specific features in distribution of natural radioactivity in rocks of the Bazhenovo Formation on the western slope of the Surgut Dome, West Siberia

This paper presents an analysis of the radioactivity distribution in the Bazhenovo Formation rocks on the western slope of the Surgut Dome. The maximum uranium concentrations are confined to accumulations of organic matter and are proportional to its concentration in the rocks. The lowermost part of the section has lower radioactivity values than the upper one. The value of radioactivity varies throughout the area of the Surgut Dome. Coeval analogs of the Bazhenovo Formation show lower radioactivity values.

Smoothing and Change Point Detection for Gamma Ray Count Data

Gamma ray detectors are used to measure the natural radioactivity of rocks. For a number of boreholes drilled at a site the gamma ray detector is lowered into each borehole and counts of gamma ray emissions at different depths are recorded as the instrument is gradually raised to ground level. The profile of gamma counts can be informative about the geology at each location. The raw count data are highly variable, and in this paper we describe the use of adaptive smoothing techniques and change point models in order to identify changes in the geology based on the gamma logs. We formulate all our models for the data in the framework of the class of generalized linear models, and describe computational methods for Bayesian inference and model selection for generalized linear models that improve on existing techniques. Application is made to gamma ray data from the Castelreagh Waste Management Centre which served as a hazardous waste disposal facility for the Sydney region between March 1974 and August 1998. Understanding the geological structure of this site is important for further modelling the transport of pollutants beneath the waste disposal area.