Anthropogenic emissions of210Po,210Pb and226Ra in an estuarine environment

An extensive study on the distribution of natural radionuclides in an estuarine ecosystem located in Southwestern Spain is presented. This environment is highly affected by the wastes released by a phosphoric acid industry which uses phosphate rocks as raw material for fertilizer production. This rock has generally high concentrations of U and its daughters. The estuary is formed by two rivers, Odiel and Tinto, which have a common mouth into the Atlanic Ocean and a salt marsh (Odiel marsh) affected by the income of Odiel riverwaters. This river receives directly the liquid and part of the solid (gypsum) wastes released from the industries. Besides that, most of the phosphogypsum wastes are stored in uncovered piles at the right margin of the Tinto river. The study has concluded that the wastes from such industries are the cause of the enhanced concentrations found at the bed of both river channels as well as the enhancement found in surface soils in certain zones of the Odiel wet marshland. Indeed, the Northern marsh and the Mojarrera channel at the Odiel marsh seem to be the main sinks of the contaminant released by the phosphoric acid industry.     

Anthropogenic contamination analyzed by TTPIXE in samples from the Odiel salt marsh at the SW Spain

The studied marsh area is located at the southwest of Spain in an estuarine system formed by the confluence of the Odiel river and the Atlantic ocean. 23 samples collected in the marsh have been analysed by Thick Target Proton Induced X-ray Emission using 2 MeV protons from the 3 MV Van de Graaff accelerator of the ITN. Elemental concentrations in the samples are affected by the Atlantic ocean, the materials transported by the Odiel river and the wastes discharged by the factories of a nearby industrial area. The study has shown that certain areas of the estuary present high concentrations of P, Cu, Zn, As and Pb, which were attributed to the operation of a phosphate fertilizer factory and a Cu extraction factory. The mining activity carried out near the source of the river could be also responsible of part of this contamination. Finally, the spatial distribution of the contamination has reflected the dinamic of the Odiel river waters, due to tidal movements, into the marsh area.     

Rapid sequential separation of actinides using Eichrom's extraction chromatographic material

The presence of ²²⁶ Ra in an estuary formerly affected by direct discharges of waste from a phosphate fertilizer complex has been investigated. Specific activities ranging from 3.6 to 45.2 mBq/l have been detected. In general, activity levels are lower than those detected when direct discharges were carried out. However, there is still a clear contamination due to the disposal of phosphogypsum in open air piles by the river. Moreover, it seems that ²²⁶ Ra is being redissolved from the contaminated bed sediments, which also contributes to an enhancement in the activity levels of the estuary waters.     

Application of a Liquid Scintillation Technique to the Measurement of 226Ra and 224Ra in Samples Affected by Non-Nuclear Industry Wastes

Experiment procedures have been developed for the determination of ²²⁶Ra and ²²⁴Ra activity concentration in solid and liquid samples collected around a non-nuclear industrial area, by liquid scintillation counting. The different radiochemical procedures developed in this work, have been adaptations of a radiochemical procedure previously used, for ²²⁶Ra and ²²⁴Ra determinations by LSC in drinking water, which was improved, refined up and adapted to the type of sample to be applied. These improved radiochemical methods have been applied to waste samples (phosphogypsum) produced by two factories which are engaged in phosphoric acid production, and to waters collected from the Odiel river, where during the sampling period a fraction of these wastes were released. ²²⁶Ra activity concentrations in the phosphogypsum ranged from 673 to 1178 Bq/kg dry weight, indicating that the wastes are particularly enriched in this radionuclide. Consequently, high ²²⁶Ra levels were easily found in the river waters analysed, especially in the neighbouring zones of the waste discharges.     

The <Superscript>137</Superscript>Cs distribution in sediment profiles from the Yangtze River estuary: a comparison of modeling and experimental results

It has been generally accepted when estimating sedimentation rates using the ¹³⁷Cs dating method that the position of the ¹³⁷Cs maximum in a sediment profile represents the year 1963. In this paper we validated this approach by developing a model in which the annual ¹³⁷Cs global fallout flux for the Yangtze River estuary was established on the basis of the Tokyo flux corrected for precipitation rates observed in Shanghai. As the ¹³⁷Cs maxima in the sediment deposition profiles depend on the sedimentation rates, the sub-sampling intervals were calculated accordingly. Higher measured than the calculated values were found in some cores, what may be due to fluctuating sedimentation rates and an additional deposition of ¹³⁷Cs from land-based sources. The study provides useful information on the reliability of the measured ¹³⁷Cs maxima in sediment profiles frequently used for dating of sediments in marine (coastal regions, open seas) as well as in terrestrial (lakes) environments.     

Measurement of <Superscript>99</Superscript>Tc in Savannah River Site high activity waste

Summary Waste cleanup efforts currently underway at the Savannah River Site have created a need to characterize ⁹⁹Tc in the various high activity waste matrices currently in Site inventories. The traditional method our laboratory used for analyzing ⁹⁹Tc in higher activity matrices was a solvent-solvent extraction method using Aliquat-336 in xylene. In an effort to eliminate the resulting generation of mixed wastes, a variety of different separation methodologies have been studied. Eichrom TEVA solid phase extractions using column technology have been employed in a case by case basis over the last several years. More recently, applications using Eichrom TEVA extraction discs and 3M Empore Tc extraction discs have also been explored.     

Magnesium-Potassium Phosphate Matrix for Immobilization of <Superscript>14</Superscript>C

Possibility of using a low-temperature magnesium-potassium phosphate matrix to solve the problem of immobilizing the radioactive wastes containing radioactive carbon (¹⁴C) in the form of calcium carbonate was examined. The physicochemical characteristics of the compounds obtained were determined. Large values of the ultimate compression strength (22 ± 5 MPa), which satisfy the technical requirements for cemented radioactive wastes (no less than 4.9 MPa), were obtained. The minimum carryover of carbon dioxide into the atmosphere in the course of synthesis and in keeping of samples for 14 days was noted: not more than 3 wt % relative to the starting CaCO₃. The leaching rate of carbonate ions from magnesium-potassium compounds by 28th day of contact with air does not exceed 10?9 g cm^?2 day^?1, with this value for the rest of the compound components not exceeding 10^?4 g cm^?2 day^?1. Thus, it was found that the magnesium?potassium phosphate matrix is an alternative to the cementation for solidification of radioactive wastes containing ¹⁴C.     

Determination of <Superscript>93</Superscript>Zr and <Superscript>237</Superscript>Np in nuclear power plant wastes

A combined radioanalytical method for determination of ⁹³Zr and ²³⁷Np (as well as other actinoids) in radioactive wastes has been developed. Analytes were co-precipitated on iron(II)-hydroxide, separated and purified on UTEVA columns, and detected by inductively coupled plasma mass spectrometry. According to Zr and Np, 65 and 75% yields were achieved, respectively.     

Thermal behavior of Cd<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd²⁺ and Co²⁺ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion. The kinetic analysis of the TG non-isothermal data was performed by the isoconversional methods suggested by Friedman and Flynn, Wall and Ozawa, as well as by the non-parametric (Sempere-Nomen) method. All processes put in evidence in TG curves exhibit strong changes of the activation energy values with the conversion degree, which mean that these processes are complex ones. Assuming that each of these processes consists in two steps, the application of non-parametric method leads to average values of the activation energy close to the average values of this parameter obtained by isoconversional methods.     

Sequential separation of <Superscript>99</Superscript>Tc, <Superscript>94</Superscript>Nb, <Superscript>55</Superscript>Fe, <Superscript>90</Superscript>Sr and <Superscript>59/63</Superscript>Ni from radioactive wastes

A sequential separation procedure has been developed for the determination of ⁹⁹Tc, ⁹⁴Nb, ⁵⁵Fe, ⁹⁰Sr and ^59/63Ni in various radioactive wastes generated from nuclear power plants. Ion exchange and extraction chromatography were adopted for individual separation of the radionuclides. Precipitation was supplementarily utilized for both purification of the individual radionuclides and preparation of the radionuclide sources for use in a radioactivity measurement. The chromatographic separation behavior of the radionuclides both from the sample matrix metals and from one another was investigated using stable metals, Re (as a surrogate of ⁹⁹Tc), Nb, Fe, Sr and Ni. The validity of the procedure for reliability and applicability was evaluated by measuring the recovery of the metal carriers added to synthetic radioactive waste solutions. The recoveries by the chromatographic separation were in the range of 84.8 to 102.2% with 2s of less than 8.6%, the recoveries by the precipitation being in the range of 84.3 to 97.3% with 2s of less than 10.9%.     

Determination of Uranium in Natural Waters by Solid Phase Spectrometry

Abstract

A microdetermination method (at the μg1^?1 level) for uranium has been developed, based on Solid-Phase Spectrophotometry (SPS). The uranium reacts with pyridylazo-resorcinol in the presence of fluoride to form a 1:1:1 red ternary complex, which is fixed on an anion-exchange resin. The resin absorbance is measured directly, and allows the determination of uranium in the range of 1–10μg1^?1, with an RSD of 4%. The method has been applied to the determination of U(VI) in natural waters from wells located near the deposits of industrial wastes from a uranium mineral plant in Andujar (Spain).     

Systematic radiochemical separation for the determination of <Superscript>99</Superscript>Tc, <Superscript>90</Superscript>Sr, <Superscript>94</Superscript>Nb, <Superscript>55</Superscript>Fe and <Superscript>59,63</Superscript>Ni in low and intermediate radioactive waste samples

A simple and rapid separation procedure was systemized for the determination of ⁹⁹Tc, ⁹⁰Sr, ⁹⁴Nb, ⁵⁵Fe and ^59,63Ni in low and intermediate level radioactive wastes. The integrated procedure involves precipitation, anion exchange and extraction chromatography for the separation and purification of individual radionuclide from sample matrix elements and from other radionuclides. After separating Re (as a surrogate of ⁹⁹Tc) on an anion change resin column, Sr, Nb, Fe and Ni were sequentially separated as follows; Sr was separated as Sr (Ca-oxalate) co-precipitates from Nb, Fe and Ni followed by purification using Sr-Spec extraction chromatographic resin. Nb was separated from Fe and Ni by anion exchange chromatography. Fe was separated from Ni by anion exchange chromatography. Ni was separated as Ni-dimethylglyoxime precipitates after the removal of ^134,137Cs and ^110mAg by Cs-phosphotungstate and AgCl precipitation, respectively. Finally, the radionuclide sources were prepared by precipitation for their radioactivity measurements. The reliability of the procedure was evaluated by measuring the recovery of chemical carriers added to a synthetic radioactive waste solution.     

Equilibrium in adsorption of lead (Pb<Superscript>2+</Superscript>) and manganese (Mn<Superscript>2+</Superscript>) ions from solutions onto natural and synthetic sorbents

The patterns of static equilibrium sorption of Pb²⁺ and Mn²⁺ ions from solutions simulating a composition of industrial liquid waste, onto modified bentonite and zeolite were researched. Na-bentonite and Na-clinoptilolite demonstrate high sorption activity with respect to Pb²⁺ and Mn²⁺ ions are recommended instead of a commercial synthetic KU-2-8 for a sorption after-treatment of liquid wastes from toxic Pb²⁺ and Mn²⁺ ions.     

Migration processes of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr in compartments of a lake ecosystem

Summary The dispersion of radioactive substances in the environment following nuclear weapon tests in atmosphere since 1954 and accidents to nuclear plants, like that in Chernobyl in 1986, have allowed us to study the migration processes of some radionuclides in complex ecosystems such as lakes are. In the present paper the behavior of ¹³⁷Cs and ⁹⁰Sr in different compartments of the Monterosi Lake (central Italy) was assessed. The ¹³⁷Cs concentration was measured in lake water as well as sediment, stream water, aquatic plant and fish samples. ⁹⁰Sr concentration in water and sediments was also determined. A total inventory of 4206±76 Bq ^. m^-2 and 958±79 Bq ^. m^-2 (on 27/6/01) has been found for ¹³⁷Cs and ⁹⁰Sr, respectively. The experimental data presented here allow to calibrate theoretical models predicting the temporal trend of radionuclide concentration in similar ecosystems. Moreover, information on cesium and strontium migration processes can be extended to other pollutants having similar environmental behavior.     

Determination of <Superscript>237</Superscript>Np, <Superscript>93</Superscript>Zr and other long-lived radionuclides in medium and low level radioactive waste samples

The majority of long-lived radionuclides produced in the nuclear fuel cycle can be regarded as “difficult-to-measure” nuclides, hence chemical separation is needed before the nuclear measurement of them. A combined radiochemical procedure that enables the simultaneous determination of some “difficult-to-measure” nuclides in medium and low level radioactive wastes has been developed in our laboratory. Recently, this method has been extended for determination of ²³⁷Np and ⁹³Zr. ²³⁷Np and ⁹³Zr are pre-concentrated by co-precipitation on iron(II) hydroxide and zirconium oxide, separated by extraction chromatography using UTEVA, and measured by inductively coupled plasma mass spectrometry (ICP-MS). As even traces of polyatomic ions and isotopes at m/z 237 or 93 cause considerable interferences during ICP-MS detection, a purification step by extraction chromatography was needed. Analyzing real samples (evaporation concentrates of a nuclear power plant) 66–99% and 31–99% chemical yields were achieved for Np and Zr, respectively.     

Separation and determination of <Superscript>90</Superscript>Sr in low- and intermediate-level radioactive wastes using extraction chromatography and LSC

A methodology for the determination of ⁹⁰Sr in low- and intermediate-level radioactive wastes from nuclear power plants is presented in this work. It is a part of a methodology developed for the sequential radiochemical separation of radionuclides difficult-to-measure directly by gamma spectrometry in these radioactive wastes. The separation procedure was carried out using precipitation and extraction chromatography with Sr Resin, from Eichrom and the ⁹⁰Sr was measured by liquid scintillation counting (LSC). Optimum conditions for the pretreatment, separation and LSC measurements were determined using simulated samples, which were prepared using standard solutions and carriers. The procedure showed to be rapid and achieved a good chemical yield, in the range 60–90%, and a detection limit of 6.0 × 10⁻⁴ Bq g⁻¹. The method was also tested by participation in a national intercomparison program, with aqueous samples, with good agreement of results.     

Advances in <Superscript>79</Superscript>Se analyses on Savannah river site radioactive waste matrices

Waste cleanup efforts underway at the United States Department of Energy’s (DOE) Savannah River Site (SRS) in South Carolina, as well as other DOE nuclear sites, have created a need to characterize ⁷⁹Se in radioactive waste inventories. Successful analysis of ⁷⁹Se in high activity waste matrices is challenging for a variety of reasons. As a result of these unique challenges, the successful quantification of ⁷⁹Se in the types of matrices present at SRS requires an extremely efficient and selective separation of ⁷⁹Se from high levels of interfering radionuclides. A robust ⁷⁹Se radiochemical separation method has been developed at the Savannah River National Laboratory (SRNL) which is routinely capable of successfully purifying ⁷⁹Se from a wide range of interfering radioactive species. In addition to dramatic improvements in the K_d, ease, and reproducibility of the analysis, the laboratory time has been reduced from several days to only 6 h.     

Synthesis of a <Superscript>188</Superscript>Re–DTPMP complex using carrier-free <Superscript>188</Superscript>Re and study of its stability

Labeling of diethylenetriamine-N,N,N′,N″,N″-pentakis(methylenephosphonic) acid (DTPMP) with rhenium-188 using stannous chloride as a reducing agent has been investigated. Dependence of the yield of the ¹⁸⁸Re–DTPMP complex on the concentration of the reducing agent, pH, reaction time, temperature, ascorbic acid and amount of carrier added has been studied. Under optimum conditions, the labeling yield of ¹⁸⁸Re–DTPMP complex is 95% for the carrier-free ¹⁸⁸Re but with the carrier-added ¹⁸⁸Re the labeling yield is more than 97%. Furthermore, the stability of the ¹⁸⁸Re–DTPMP complex against pH change and dilution with saline has been also studied. It is found that the addition of carrier stabilizes the ¹⁸⁸Re–DTPMP complex against pH change and dilution.     

Preparation of <Superscript>26</Superscript>Al, <Superscript>59</Superscript>Ni, <Superscript>44</Superscript>Ti, <Superscript>53</Superscript>Mn and <Superscript>60</Superscript>Fe from a proton irradiated copper beam dump

The station for pions cancer therapy was operated at PSI from 1980 to 1992. After a cooling time of 12 years it’s made of copper beam dump was cut and samples were taken for analytical purposes. The sampling collected about 500 g of high active copper chips that can be used for separation of exotic radionuclides. The analyses by gamma spectrometry, LSC and AMS showed main nuclides present to be ⁶⁰Co, ⁵⁴Mn, ²²Na, ⁶⁵Zn, ²⁶Al, ⁵³Mn, ⁵⁹Ni, ⁶³Ni, ⁵⁵Fe and ⁶⁰Fe and ⁴⁴Ti with a daughter nuclide ⁴⁴Sc. In the frame of ERAWAST project a procedure combining selective precipitation and ion exchange for the separation of the rare radionuclides from the copper beam dump was developed. The proposed separation procedure is easy for remote controlled implementation in a hot cell. The ion exchange separation of Ni, Al, Mg, Ti and Fe was complete and high decontamination factors for copper and cobalt were achieved. Based on the developed procedure a remotely controlled system for separation of exotic radionuclides from the copper chips was set up. The full scale system was installed in a hot cell where high activity levels can be handled. In order to evaluate the reliability and functionality of the system extensive tests have been done. During the test period 13.86 g in total of the proton irradiated copper beam dump were processed for separation of ²⁶Al, ⁵⁹Ni, ⁵³Mn, ⁴⁴Ti and ⁶⁰Fe. The results showed that the system was operational and the radionuclide separation was selective with high chemical yield. The procedure manages as well the generated liquid wastes containing high level of ⁶⁰Co activity.     

Determining <Superscript>222</Superscript>Rn daughter activities by simultaneous alpha- and beta-counting and modeling

The introduced method to determine the individual activities of the short-lived radon daughters in air is based on simultaneous α- and β-counting of the sampled air collected on a filter. The measured curves of gross-α and gross-β intensities were decomposed by sum of exponentials and the individual activities of the progenies were assessed. Furthermore, computer simulations were carried out supplemented with aerosol measurements to describe the physical processes of radon progenies in air during the experiments and to verify the suitability of the method.