Rn Emanation Rates Research Articles

Assessment of 222Rn emanation from ore body and backfill tailings in low-grade underground uranium mine

This paper presents a comparative study of (222)Rn emanation from the ore and backfill tailings in an underground uranium mine located at Jaduguda, India. The effects of surface area, porosity, (226)Ra and moisture contents on (222)Rn emanation rate were examined. The study revealed that the bulk porosity of backfill tailings is more than two orders of magnitude than that of the ore. The geometric mean radon emanation rates from the ore body and backfill tailings were found to be 10.01 × 10(-3) and 1.03 Bq m(-2) s(-1), respectively. Significant positive linear correlations between (222)Rn emanation rate and the (226)Ra content of ore and tailings were observed. For normalised (226)Ra content, the (222)Rn emanation rate from tailings was found to be 283 times higher than the ore due to higher bulk porosity and surface area. The relative radon emanation from the tailings with moisture fraction of 0.14 was found to be 2.4 times higher than the oven-dried tailings. The study suggested that the mill tailings used as a backfill material significantly contributes to radon emanation as compared to the ore body itself and the (226)Ra content and bulk porosity are the dominant factors for radon emanation into the mine atmosphere.

Validation of a model for radon-induced background processes in electrostatic spectrometers

The Karlsruhe Tritium Neutrino (KATRIN) experiment investigating tritium β-decay close to the endpoint with unprecedented precision has stringent requirements on the background level of less than 10−2 counts per second. Electron emission during the α-decay of 219, 220Rn atoms in the electrostatic spectrometers of KATRIN is a serious source of background exceeding this limit. In this paper we compare extensive simulations of Rn-induced background to specific measurements with the KATRIN pre-spectrometer to fully characterize the observed Rn-background rates and signatures and determine generic Rn emanation rates from the pre-spectrometer bulk material and its vacuum components.

A rapid method for radium regeneration from its sulfate

A single-phase alternative of frequently used carbonatization method was suggested as a procedure for radium regeneration from its sulfate. The procedure involves dissolution of RaSO4 in an alkaline solution of disodium dihydrogen ethylenediaminetetraacetate, addition of excess Na2CO3, and displacement of Ra from the complexes with solutions of Pb(II) salts. In a trial performed with 10.8 mg of RaSO4, the yield of Ra to the target fraction was about 91%. All the operations can be performed without heating, which decreases the Rn emanation rate and makes handling of Ra samples safer.

Soil gas radon emanometry: A tool for delineation of fractures for groundwater in granitic terrains

In several arid and semi-arid hard rock areas of the world, overexploitation of groundwater has caused de-saturation of the phreatic weathered zone. Attempts are now underway to draw supplies from deeper fracture zones. But random drilling often fails to encounter such productive zones. Further, currently available hydrogeological and geophysical methods are of limited applicability. Alternative geochemical methods, employing soil gas 222 radon (Rn) and helium ( 4 He) have been explored but not investigated sufficiently. This paper reports the results of a systematic survey of 222 Rn concentration in soil gas (at a depth of 60 and 160 cm) in a watershed located in a semi-arid granitic area in India. We were able to demarcate three high 222 Rn anomalies, which were supplemented by 4 He measurements. Drilling was carried out on the sites of these high 222 Rn anomalies as well as on low 222 Rn anomalies. The bore wells drilled at the site of high 222 Rn concentration were found to be quite productive and those drilled on low 222 Rn concentration sites were dry; those sites of the intermediate 222 Rn concentrations had intermediate yields. These preliminary results suggest that 222 Rn emanometry method may turn out to be useful. The method still needs to be investigated in detail and its usefulness in various settings still needs to be established on a statistical basis. We have made an attempt to understand the process that may cause such 222 Rn anomalies. Our observations of 222 Rn concentration in the soil gas and of 222 Rn emanation rates from the soil and uranium concentrations in the soil indicate that fracturing of the rock, rather than advection of 222 Rn from deeper strata may be responsible for such 222 Rn anomalies.

Ultra-traces of 226Ra in nylon used in the Borexino solar neutrino experiment

Abstract Borexino is a large-scale liquid scintillator detector for solar neutrinos with a low expected event rate, therefore requiring an extremely low radioactive background. In this paper we present a method, which makes it possible to measure the surface and bulk activities of 226 Ra in thin nylon foils for use in Borexino at unprecedented concentration levels, as low as 0.5 μBq/m 2 and 10 μBq/kg, respectively. It is based on high-sensitivity 222 Rn emanation detection, taking advantage of the fact that the permeability of nylon for radon is strongly enhanced in the presence of water. A mathematical diffusion model is outlined to distinguish the surface and bulk activity of 226 Ra from the 222 Rn emanation rates of dry and wet film. The experimental method is described in connection with screening measurements of nylon foils of different origin. One foil could be identified with a low 226 Ra contamination (corresponding to ∼10 −12 g/g 238 U-equivalent) for application in Borexino . This film will be used for the construction of a liquid scintillator containment vessel as the central part of the Borexino solar neutrino detector.

Distribution of radon sources and effects on radon emanation in granitic soil at Ben Lomond, California

The abundance and distribution of radioelements on bulk and microscopic scales were investigated in residual granitic-derived soil at a facility for investigating the movement of radon into structures. In bulk soil samples, Ra concentrations range from 0.6 to 1.3 pCi/g, and variations in Ra, Th, and K appear to be controlled mainly by heterogeneities inherited from the parent granitic rock, which contains abundant dikes and inclusions. U in soil and parent rock is concentrated in primary minerals (mainly zircon and sphene), and in secondary sites that are of greater importance for Rn emanation. The main U-bearing secondary sites are weathered sphene, grain boundary coatings, weathered biotite and plagioclase, as well as dense Fe-rich coatings and a REE-phosphate mineral present in near-vertical fracture zones in saprolite underlying shallow loam. Elevated U in these sites generally correlates with high Ti, Al, Fe, and/or P. Preferential distribution of U and Ra on grain boundaries and porous weathered minerals is reflected in relatively high Rn emanation rates in the soil. Highest emanation occurs between 1.3 and 2.3 m depth, where fine pedogenic phasesgibbsite and amorphous silica and Fe-OOH—are most abundant; it is related to fixation of Ra by these phases, which precipitate close to the surface and accumulate at these depths by illuviation. Separation of Ra from U may occur locally, given remobilization of U-series elements from secondary sites, and large differences between Ra and U sorption capabilities of several phases present in the soil. Concentration of U along permeable fracture zones in saprolite suggests that contribution of soil-gas Rn from depth (> 2 m) could be significant to Rn availability near the surface.

Radon-Thoron estimation using LR-115 plastic track detector

LR-115 plastic track detector and a Radon-Thoron discriminator has been used to estimate the radon (Rn) and thoron (Tn) contents in the soil of Guru Nanak Dev University Campus area. Track production rates in the soil at different depths have been studied. Uranium estimation in the soil samples from the experimental site have also been made to establish some correlation with Rn emission. Rn-emanation rates from the plants growing around the experimental site have also been studied using LR-115 plastic track detector. Plant leaves have been found to emanate more Rn than stems.

Theory of alpha recoil effects on radon release and isotopic disequilibrium

Using the present understanding of the mechanisms of release from rocks and soils of recoiling products of alpha emission, physical predictions can be made of the fraction of these nuclei that are directly freed and the fraction that can subsequently be freed by the action of water. The fractions depend on the size and nature of the grains in which the recoiling nuclei originate, the size and shape of the pore spaces, the nature of the surrounding grains, the decay lifetime of the recoiling nuclei, and the time sequence of the presence of water. For simplified assumptions quantitative predictions are made of Rn emanation rates and of isotopic disequilibrium.

An apparatus for the measurement of the rates of emanation of radon from rock specimens and powders

Specimens are placed in sealed chambers to which scintillation cells are attached and radon concentrations, R, are measured in the air of the chambers at intervals thereafter by inserting the cells into scintillation counters. The Rn emanation rate is calculated from the rate at which R increases, or from the maximum R reached. Uncertainties are estimated to be 10%–25%, detection limits 10−19 Ci cm−2 s−1 or 5×10−19 Ci g−1 s−1. Effects of disequlibrium in the Rn decay chain, or the diffusion rate of Rn, and of Rn leakage are considered. Powdering a rock usually has little effect on its emanation rate per gram.