Determination of long-lived radionuclides in environmental media around a nuclear fuel reprocessing plant

Methods for the analysis of¹²⁹I and²⁴¹Pu are described briefly. Neutron activation is necessary to achieve an adequate degree of sensitivity for the measurement of¹²⁹I, but otherwise all laboratory manipulations are straightforward and use commonly-found, well-tried techniques. With these methods, both radionuclides can be measured easily in the terrestrial environment around a nuclear fuel reprocessing plant;²⁴¹Pu is measureable elsewhere in integrating media such as undisturbed soil.     

Partitioning of natural radionuclides in sediments around a former uranium mine and mill

Partitioning of natural radionuclides in sediments from streams affected by the waste piles of the former uranium mine and mill located at ?irovski vrh, Slovenia, was performed by applying a sequential extraction procedure. The sediments were collected at three sites located upstream and three sites located downstream of the waste piles. Then the four-step Community Bureau of Reference (BCR) sequential extraction protocol was applied to the samples and the natural radionuclides ²³⁸U, ²³⁰Th, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po were analysed in each extraction fraction. It was expected that the fractionation of natural radionuclides originating from the waste piles would differ from that upstream of the influence of waste piles because their chemical environment had been altered during the processes of uranium extraction. This difference could allow tracing of the radionuclides coming from the waste piles downstream of the affected watercourses. The results definitely showed that the total activity concentrations at sites downstream of the influence of the waste piles were higher than at sites upstream of the piles. However, this difference was geographically very limited and could no longer be detected already at a distance of about 5 km downstream. Unexpectedly, the fractionation of radionuclides upstream and downstream of the area of influence of the waste piles did not appear to be significantly altered. The sole differences found were for ²³⁸U and ²²⁶Ra in the second fraction (the “Fe/Mn oxides” fraction) and for ²¹⁰Po in the fourth fraction (the “residue” fraction) of the BCR sequential extraction protocol.     

Analysis for naturally occuring radionuclides at environmental concentrations by gamma spectrometry

The analytical potential of low level, high resolution gamma-ray spectrometry for naturally occurring radionuclides at environmental levels is described, with particular emphasis on detector background levels and sensitivity. Comparisons are drawn between the performance of a specially designed low background detector system, and that of standard off the shelf devices. Sample characteristics, calibration procedures and checks, are described, and empirical minimum detection limits of between 0.4 Bq·kg^–1 (²²⁶Ra,²²⁸Th) and 10 Bq·kg^–1 (²¹⁰Pb) are derived for soil or sediment samples of about 250 g. Representative analyses of a variety of environmental samples, including water, plant material, animal tissue and sediment, are given to illustrate the routine use of the spectrometer.     

Spectrophotometric determination of uranium in process streams of a uranium extraction plant

This paper deals with the development and standardization of procedures for the determination of uranium on a routine basis in various process streams of a uranium extraction plant, covering a wide range of concentrations from 350 g 1(-1) down to 5 mg 1(-1) using only a spectrophotometric technique. The self-absorption of uranyl ion in dilute phosphoric acid and the violet-blue colour of the UO(2)(2+)-Arsenazo III complex in 4 M HC1 were exploited for high and low concentrations of uranium, respectively. The methods described were applied to samples of varying nature such as aqueous, organics and solids, involve minimal sample preparation and do not require prior separation of uranium from impurities. The interfering impurities in different process streams were also studied. Large quantities of silica as undissolved material poses a serious interference in the case of UNS and UNF. Considerable quantities of iron in UNS, UNF, UNR and UNRC cause interference. Possible remedies in these cases are suggested. Problems with the direct spectrophotometric measurement of organic samples is discussed. The effect of the presence of large quantities of ammonium nitrate and sodium nitrate in WD samples on the determination of uranium is also discussed. The results are compared with those obtained by volumetry and X-ray fluorescence spectrometry for higher concentrations of uranium and by extraction-spectrophotometry (ethyl acetate-thiocyanate method) for lower concentrations. Relative standard deviation of 1% and 5% for high and low concentrations, respectively, were obtained, which are adequate as far as process stream samples are concerned. The compared results are in fair agreement. The problems associated with the determination of uranium in these process streams are discussed. Experimental results for 10 different process streams normally encountered in a uranium extraction plant are tabulated.     

The chemistry of uranium and related radionuclides in Lake Ontario waters

The chemistry of uranium and its eight associated daughters has been considered in Lake Ontario water along with that of selected transuranic elements. These transuranics arise mainly from fallout, and to a lesser extent from nuclear fuel reprocessing. Most exist as free ions or oxides of various kinds, uranium probably exists as a strong uranyl carbonate complex.     

Spatial and seasonal variation of radionuclides in soils and waters near a coal-fired power plant of Northern Greece: environmental dose assessment

Journal of Radioanalytical and Nuclear Chemistry - The determination of the radionuclides of U- and Th-series as well as of 40K and 137Cs in soils and waters in a lignite mining area was performed....     

A study of radionuclides in vegetation on abandoned uranium tailings

A study has been carried out of the uptake of uranium and other radionuclides by plants growing on abandoned tailings from an uranium mining operation. Assay methods included instrumental neutron activation analysis, delayed neutron counting, fission track imaging, and counting of natural radioactivity. Care was taken to avoid contamination of the plant material and a number of methods are described to identify such contamination. All plants observed showed high uptake of radionuclides, compared to plants studied from naturally uraniferous and control areas. Graminoid (grass-like) plants showed significant uptake in the above-ground parts while woody plants showed exceedingly high uranium accumulation in the root portions. These results have significance in determination of the spread of radioactive material from such sites.     

Production of radionuclides for nuclear therapy and environmental studies

This work is devoted to the production of the radionuclides used in nuclear medicine and as radiotracers for environmental research. Production methods for high LET radionuclides (⁶⁷Ga, ⁷⁷Br, ¹¹¹In, ²¹¹At) that are promising for radioimmunotherapy are proposed. Production techniques for short-lived analogues of highly radiotoxic long-lived fission products (Tc, Se, Sr) are developed. The techniques are based on extraction and chromatographic separation from a cyclotron target irradiated by α-particles and deuteron beams.     

Disequilibrium of uranium series radionuclides in soil and plants of South India

Soil and plants of South India were analysed using standard methods for equilibrium state between radionuclides ²²⁶Ra, ²¹⁰Pb, and ²¹⁰Po of uranium series. A disequilibrium state was observed, with mean ²¹⁰Pb/²²⁶Ra, ²¹⁰Po/²²⁶Ra, and ²¹⁰Po/²¹⁰Pb as 21.71, 5.52, and 0.40; 10.01, 4.21, and 0.43; and 30.86, 9.34, and 0.35 in Coastal Karnataka, Malnad Karnataka, and Malnad Kerala, respectively. ²¹⁰Po/²¹⁰Pb in soil was 0.29, 0.30, and 0.49 respectively, for the three regions. Unsupported ²¹⁰Pb and ²¹⁰Po might have caused the observed disequilibrium state. The investigation helps to monitor radionuclide distribution and dynamics in soil and plants of the study area.

     

Analysis of natural radionuclides from uranium and thorium series in briney groundwaters

Analytical procedures for measuring various radionuclides in the²³⁸U and²³²Th chains in briney waters are described. Using methods such as mass spectrometry, and alpha, beta and gamma spectrometry, the desired measurement sensitivity required for each of the radionuclides is achieved.²³³U,²²⁸Th,²⁰⁸Po,²¹²Pb, and¹³³Ba are used as tracers for chemical yield recoveries. Typical precision of the results range from 5–20%.     

Sequential extraction as a tool to study the foliar uptake of radionuclides

In order to study the foliar uptake of radionuclides deposited from an aerosol released in an accidental situation, lettuce plants were contaminated with an aerosol containing⁸⁵Sr,¹³⁴Cs and^110mAg isotopes. The methodology chosen to carry out this study is based on a sequential extraction scheme using water, to evaluate the fraction possibly removed by rain or by washing, and an organic solvent, to distinguish between the fraction adhering to the cuticle and the one incorporated in the leaves. Two procedures are compared. Moreover, the different behavior of the radionuclides in their incorporation into the leaves is deduced from the results obtained.     

Incorporation of natural radionuclides and rare earth elements into a salt tolerant plant

A highly salt tolerant shrub, samphire (Halosarcia halocnemoides), found growing in the soild alkaline residues in an evaporation pond at a former uranium and monoazite treatment plant, has been analysed for natural radionuclides and rate earths. The data obtained have been copared with that for plants from the local natural environment. Vegetation-to-soil concentration ratios have been determined. The radionuclide concentration ratios for samples from the contaminated site are similar to those from the natural environment. Significant differences have been noted in the case of the rare earth elements with an apparent preferential incorporation of the light rare earth elements into the plant growing in the chemical residues.     

Determination of uranium in various matrices using EDXRF and excitation by different radionuclides

The synergistic extractions of uranium(VI) nitrate using HDEHP,^* PMBP^** and TBP^*** have been studied from benzene media. A new method is proposed to calculate the equilibrium constants for such kinds of ternary synergistic extraction systems. The extraction reactions and their equilibrium constants were found. Models for the extraction mechanism are also discussed.     

Defluorination behavior and mechanism of uranium dioxide

The residual fluorine in ammonium uranyl tricarbonate (AUC) cannot be removed, while a large part of residual fluorine in ammonium diuranate (ADU) can be removed, when AUC and ADU are decomposed and reduced under dry hydrogen atmosphere. UO₂ was prepared by decomposing and reducing AUC and ADU in dry hydrogen atmosphere. The defluorination kinetics of UO₂ at 500–700°C in atmosphere of 50% H₂-50% H₂O was investigated. The results show that the defluorination kinetics supports the Lindman's assertion that the residual fluorine forms a solid-solution in UO₂.     

Mobilization of radionuclides from uranium mill tailings and related waste materials in anaerobic environments

Specific extraction studies in our laboratory have shown that iron and manganese oxide- and alkaline earth sulfate minerals are important hosts of radium in uranium mill tailings. Iron- and sulfate-reducing bacteria may enhance the release of radium (and its analog barium) from uranium mill tailings, oil field pipe scale [a major technologically enhanced naturally occurring radioactive material (TENORM) waste], and jarosite (a common mineral in sulfuric acid processed-tailings). These research findings are reviewed and discussed in the context of nuclear waste forms (such as barium sulfate matrices), radioactive waste management practices, and geochemical environments in the Earth's surficial and shallow subsurface regions.     

Combined procedure using radiochemical separation of plutonium,americium and uranium radionuclides for alpha-spectrometry

Radiochemical separation of Pu, Am and U was tested from synthetic solutions and evaporator concentrate samples from nuclear power plants for isolation of each of them for alpha-spectrometry analysis. The separation was performed by anion-exchange chromatography, extraction chromatography, using TRU resin, and precipitation techniques. The aim of the study was to develop a sensitive analytical procedure for the sequential determination of ²⁴²Pu^{, 238}Pu, ^239+240Pu, ²⁴¹Am and ^{235, 238}U in radioactive wastes. ²³⁸Pu, ²⁴²Pu, ²⁴³Am and ²³²U were used as tracers. The measurements of α emitting radionuclides were performed by semiconductor detector that is used especially when spectrometric information is needed. For synthetic solutions the chemical recovery was based on associated iron concentration and was about 93%.     

Determination of uranium isotopes in environmental samples

The determination of isotopes of uranium by alpha spectrometry in different environmental components (sediments, soil, water, plants and phosphogypsum) is presented and discussed in this paper. The alpha spectrometry is a very convenient and good technique for activity concentration of natural uranium isotopes (²³⁴U, ²³⁵U, ²³⁸U) in environmental samples and provides the most accurate determination of isotopic activity ratios between ²³⁴U and ²³⁸U. The analysis were provided information about possible sources of high concentrations of uranium in the examined sites determined by anthropogenic sources. The calculation of values ²³⁴U/²³⁸U in all analyzed samples was applied to identifying natural or anthropogenic uranium origin. Activity concentration of uranium isotopes in analyzed environmental samples shows that measurement of uranium levels is of great importance for environmental and safety assessment especially in contaminated areas (phosphogypsum waste heap).     

Release behavior uranium and thorium in soil from a decommissioned uranium tailings in Jiangxi Province,China

Journal of Radioanalytical and Nuclear Chemistry - The purpose of this study was to systematically analyze the leaching process of radionuclides from a decommissioned uranium tailings. About 40% of...