This work presents the study of the solubility of selenium under cementitious conditions and its diffusion, as SeO32?, through monolithic cement samples. The solubility studies were carried out under alkaline conditions similar to those anticipated in the near-field of a cement-based repository for low- and intermediate-level radioactive waste. Experiments were conducted in NaOH solution, 95%-saturated Ca(OH)2, water equilibrated with a potential backfill material (Nirex reference vault backfill, NRVB) and in solutions containing cellulose degradation products, with and without reducing agents. The highest selenium concentrations were found in NaOH solution. In the calcium-containing solutions, analysis of the precipitates suggests that the solubility controlling phase is Ca2SeO3(OH)2·2H2O, which appears as euhedral rhombic crystals. The presence of cellulose degradation products caused an increase in selenium concentration, possibly due to competitive complexation, thereby, limiting the amount of calcium available for precipitation. Iron coupons had a minor effect on selenium solubility in contrast to Na2S2O4, suggesting that effective reduction of Se(IV) occurs only at Eh values below ?300 mV. Radial through-diffusion experiments on NRVB and in a fly ash cement showed no evidence of selenium breakthrough after one year. However, autoradiography of the exposed surfaces indicated that some migration had occurred and that selenium was more mobile in the higher porosity backfill than in the fly ash cement.
The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH)2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40µm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite.
Lead-210 (210Pb) can be present at high activity concentrations, in residues arising from the petroleum, mineral processing and chemical industries. Although 210Pb itself poses a low radiological risk, the nuclide decays via 210Bi to the alpha emitting and highly radiotoxic 210Po. Therefore, rapid, accurate determination of 210Pb is essential for assessing the radiological risk to plant operators and appropriate sentencing of waste. Unfortunately, direct measurement of 210Pb by gamma spectrometry is hindered by its weak gamma-ray emission at 46.5 keV, which is readily attenuated by mineral matrices. This paper demonstrates the extent to which 210Pb can be underestimated during routine analysis by an inter-laboratory exercise involving five accredited laboratories and a wide range of scales from diverse industrial sources. Two methods of addressing errors in 210Pb analysis are highlighted; the first, involving lithium tetraborate fusion prior to gamma spectrometry shows promise but is not suitable for all 210Pb-containing phases. The second method, requiring calculation of matrix attenuation factors for a representative fingerprint sample, was applied successfully to deposits from the steel and gas industries. However, its wider application depends on detailed chemical and mineralogical characterisation for each of the major categories of mineral scale found and at present, there is an acute lack of suitable certified reference materials.
Radiological exposures due to naturally occurring radioactive material (NORM) can occur during a wide range of work-related activities in the mineral processing and chemical industries. However, evaluation of such exposures in industrial settings remains a difficult exercise owing inter alia to the large number of personnel, operations and plants affected; assumptions that often have to be made concerning the actual duration and frequency of exposures; the complex chemistry and radioactive disequilibria involved and typically, the paucity of historical data. In our study, the challenges associated with assessing chronic exposure to fugitive dust enriched in 210Pb and 210Po and the determination of the associated internal dose by inhalation and ingestion are described by reference to a case study undertaken at an iron ore sintering plant between June 2013 and July 2015. The applicability of default dose coefficients and biokinetic models provided by the International Commission for Radiological Protection (ICRP) was verified by combining air and dust monitoring with information on the characteristics of the aerosols and in-vitro solubility experiments. The disparity between particulate matter 100 microns or less in diameter (PM100), particulate matter 10 microns or less in diameter (PM10) and 210Pb/210Po activity concentrations observed over the different monitoring campaigns and sampling locations confirmed that use of positional short-term monitoring surveys to extrapolate intake over a year was not appropriate and could lead to unrealistic intake and dose figures. Personal air sampling is more appropriate for estimating the dose in such situations, though it is not always practical and may collect insufficient quantities of material for radiochemical analysis; this is an important constraint when dealing with low specific activity materials.
In order to exploit 222Rn as a naturally-occurring tracer in soils we need to sample and measure radon isotopes in soil gas with high spatial and temporal resolution, without disturbing in situ activity concentrations and fluxes. Minimization of sample volume is key to improving the resolution with which soil gas can be sampled; an analytical method is then needed which can measure radon with appropriate detection limits and precision for soil gas tracer studies. We have designed a soil gas probe with minimal internal dead volume to allow us to sample soil gas volumes of 45 cm3. Radon-222 is extracted from these samples into a mineral oil-based scintillation cocktail before counting on a conventional liquid scintillation counter. A detection limit of 320 Bq m-3 (in soil gas) is achievable with a one hour count. This could be further reduced but, in practice, is sufficient for our purpose since 222Rn in soil gas typically ranges from 2,000 - 50,000 Bq m-3. The method is simple and provides several advantages over commonly used field-portable instruments, including smaller sample volumes, speed of deployment and reliability under field conditions. The major limitation is the need to count samples in a liquid scintillation counter within 2 ? 3 days of collection, due to the short (3.824 day) radioactive half-life of 222Rn. The method is not applicable to the very short-lived (55 second half-life) 220Rn.
Organic superplasticisers improve the flow properties of cement, offering operational advantages for the disposal of radioactive wastes. However, there are concerns that they could increase the mobility of encapsulated contaminants significantly. The effect of polycarboxylate ether superplasticisers on the solubility of Ni(II), Am(III), Pu(IV) and U(VI) in two cement-equilibrated waters (ordinary Portland cement/pulverised fuel ash (OPC/PFA) and OPC/ground granulated blast-furnace slag (GGBS)) has been assessed. The study included four commercial superplasticisers, three adjuncts (a de-foaming agent, biocide and viscosity modifier) and a bespoke, synthesised superplasticiser from which residual monomer had been removed by dialysis. The commercial products (0·5% w/w dosage) had a much greater effect on metal solubility than the dialysed equivalent, increasing solubility by 2?3 orders of magnitude. As the adjuncts alone showed no effect, the difference between the commercial and synthesised superplasticisers is attributed to small molecules, primarily residual monomers, in the commercial formulations owing to incomplete polymerisation. The distribution of radionuclides in hardened cement pastes corresponds closely to the distribution of superplasticiser, as shown by 14C-labelling in combination with digital autoradiography and accounting for the bleed observed for certain slag-rich formulations.
Most of the materials found on the Earth?s surface, such as iron ores and all other materials entering the integrated steel-making process, contain measurable amounts of natural radioactivity mainly due to the presence of uranium-238 (238U), thorium-232 (232Th) and their respective daughter decay products. Some materials after being processed can present a relatively high concentration of natural radionuclides. These materials are defined as Naturally Occurring Radioactive Materials (NORM). Since 2010, in the United Kingdom, industries producing NORM are subject to a new permitting regime. The current regime is named Environmental Permitting Regulations 2010 (EPR 2010), recently amended and replaced by EPR2016 and is directly derived from the European Directive EURATOM 1996, itself reviewed in 2013 and replaces the previous exemption limits defined in the previous regime Radioactive Substances Act 1993 (RSA93). As a result, the steel industry is now potentially producing materials above the new exemption levels to dispose of and therefore has a new environmental duty to accurately determine the radioactivity content of a wide range of iron- and steel-making materials used on site within the processes and/or sold off to third parties. In the steel industry, the main isotopes of concern are polonium-210 (210Po) and lead-210 (210Pb), which concentrate in the waste off-gas dusts from the iron ore sintering and blast furnaces processes, and radium-226 (226Ra) which can be found in slag materials from the blast furnace process. NORM can also result in potential exposure of the workforce to radioactive substances, mainly in workplaces where NORM are handled, stockpiled or processed. The UK steel industry has a duty of care to protect the workers and assess the potential occupational exposure to natural radioactivity in its workplaces in accordance with the Ionising Radiations Regulations 1999 (IRR99), recently replaced by IRR17 since 1st January 2018.
The behaviour of base metals Ni, Zn, Cu, Co, Fe, and Mn, potentially toxic metals Pb, Cr, and Cd, and the radioactive elements, U and Th, in the Talvivaara mining process, Finland has been studied by tracing metal concentrations from the black schist ore, through ores subjected to bioheap leaching of varying duration, to pregnant leach solution (PLS), and solid process waste material deposited on site in gypsum waste ponds. It is apparent that Zn, Cu, Co, and Cd are leached from the ore in a similar manner and recovered efficiently in the PLS; however, Ni, though leached, was also found in the gypsum pond at relatively high concentrations. Relatively little Pb is released from the ore, but the small fraction that is mobilised accumulates in the gypsum pond. Of the radioactive constituents, Th is essentially immobile, whereas U is readily leached from the ore, again accumulating in gypsum pond waste. In addition, a laboratory-based sequential leach test was applied to assess the future leaching potential of metals from residual ore and process waste material under different environmental conditions.
This paper describes some of the challenges faced by testing laboratories when conducting compliance measurements for NORM wastes. Focus is placed on solid materials as these comprise by far the most common samples of this type sent for commercial analysis. The importance of understanding the industrial processes giving rise to the waste and the need for representative sampling are emphasised. The market for analysis of NORM will undoubtedly grow, driven by more rigorous, modern legislation; however, existing capacity is limited. Future needs are discussed with reference to hydraulic fracturing for shale gas, already a mature technology in North America and one that is set to play an increasing role in the UK and continental Europe.
The influence of anthropogenic organic complexants (citrate, EDTA and DTPA from 0.005 to 0.1 M) on the solubility of nickel(II), thorium(IV) and uranium (U(IV) and U(VI)) has been studied. Experiments were carried out in 95%-saturated Ca(OH)2 solutions, representing the high pH conditions anticipated in the near field of a cementitious intermediate level radioactive waste repository. Results showed that Ni(II) solubility increased by 2?4 orders of magnitude in the presence of EDTA and DTPA and from 3 to 4 orders of magnitude in the case of citrate. Citrate had the greatest effect on the solubility of Th(IV) and U(IV)/(VI). XRD and SEM analyses indicate that the precipitates are largely amorphous; only in the case of Ni(II), is there some evidence of incipient crystallinity, in the form of Ni(OH)2 (theophrastite). A study of the effect of calcium suggests that U(VI) and Ni(II) may form metal-citrate-OH complexes stabilised by Ca2+. Thermodynamic modelling underestimates the concentrations in solution in the presence of the ligands for all the elements considered here. Further investigation of the behaviour of organic ligands under hyperalkaline conditions is important because of the use of the thermodynamic constants in preparing the safety case for the geological disposal of radioactive wastes.
The Talvivaara mine in Eastern Finland utilizes microbe-induced heap leaching to recover nickel and other valuable metals (Zn, Cu, Co) from a black schist ore. In addition to the target metals, the ore contains uranium at a concentration of 17 mg/kg, incorporated as uraninite (UO2). Uranium oxidizes from the U(IV) to U(VI) state during leaching and dissolves as the uranyl ion (UO22+) in the acidic pregnant leach solution. Mobilisation of uranium has caused sufficient concern that plans have been developed for uranium recovery. The aim of this study is to generate new data leading to a better understanding of the fate of its radiotoxic daughter nuclides, primarily 226Ra, 210Pb and 210Po, in the mining process.
It is shown that uranium daughters mostly remain in the heaps during the leaching process and are associated with secondary minerals, including jarosite, goethite and gypsum. Thorium and progeny (232Th plus 228Th, 228Ra) are also mainly retained. High sulphate concentrations in the acidic solutions limit the solubility of radium by incorporation in the crystal lattices of precipitated secondary sulphates. Electron probe microanalysis shows that goethite in the heaps is uraniferous, resulting from the adsorption of U(VI).
After recovery of target metals, the pregnant leach solution is neutralized to further remove metal contaminants and the resulting slurries stored in a bunded tailings pond. The activity concentrations of thorium, radium, lead and polonium isotopes are generally low in the pond owing to prior retention by secondary minerals in the heaps. However, 238U activity concentrations range up to 3375 Bq/kg, which exceeds the permitted value (1000 Bq/kg) for natural radionuclides of the 238U series.
Van Es Elsje, Hinchliff J., Felipe-Sotelo Monica, Milodowski A.E., Field L.P., Evans N.D.M., Read David (2015) Retention of chlorine-36 by a cementitious backfill, Mineralogical Magazine 79 (06) pp. 1297-1305
The Mineralogical Society of Great Britain and Ireland
Radial diffusion experiments have been carried out to assess the migration of 36Cl, as chloride, through a cementitious backfill material. Further experiments in the presence of cellulose degradation products were performed to assess the effect of organic ligands on the extent and rate of chloride diffusion. Results show that breakthrough of 36Cl is dependent on chloride concentration: as the carrier concentration increases, both breakthrough time and the quantity retained by the cement matrix decreases. Experiments in the presence of cellulose degradation products also show a decrease in time to initial breakthrough. However, uptake at various carrier concentrations in the presence of organic ligands converges at 45% of the initial concentration as equilibrium is reached. The results are consistent with organic ligands blocking sites on the cement that would otherwise be available for chloride binding, though further work is required to confirm that this is the case. Post-experimental digital autoradiographs of the cement cylinders, and elemental mapping showed evidence of increased 36Cl activity associated with black ash-like particles in the matrix, believed to correspond to partially hydrated glassy calcium-silicate-sulfate-rich clinker.
Superplasticisers improve the flow properties of cement and offer a number of operational advantages to producers of radioactive waste. Research is underway to clarify their mode of interaction using a bespoke, purified polycarboxylate ether (PCE) superplasticiser in controlled trials. A large-scale (200 dm3) product was prepared with a mix of ground granulated blast-furnace slag and ordinary Portland cement (9:1 mix) and tested using methods established by the UK nuclear industry to assess grout performance. The product met the essential criteria for a radioactive waste encapsulation grout. Laboratory-scale studies utilising a 14C-labelled superplasticiser and its components were employed to better understand the mechanisms involved and to determine the location and distribution of the superplasticiser within cured cement monoliths. The results suggest that a PCE superplasticiser may enable the use of cement industry standard powders for encapsulation processes, allowing lower water content matrices and mitigating the risk of future powder supply issues.
Three different methods for determining uranium and four for determining thorium in an apatite ore, black schist and mill tailings are compared. The aim of the comparative study is to obtain analytical verification of field results so that site characterization could be optimized without compromising reliability of the analysis. The samples were collected from a former pilot scale phosphate mine in Sokli, northern Finland and the Talvivaara nickel mine in Eastern Finland. A non-destructive, portable X-ray fluorescence (XRF) spectrometer was used on site to measure, semi-quantitatively, the composition of major elements, including thorium in each material. The samples were then analyzed by X-ray diffraction (XRD) to identify the main mineral components and electron probe micro-analysis (EPMA) used to identify the uranium and thorium-bearing minerals. Gamma spectrometry was used for direct determination of uranium and thorium isotopes in powdered samples. Thereafter, sample digestion experiments were performed with various acids to optimize the method for microwave digestion allowing determination of uranium and thorium by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and alpha spectrometry. For the latter method, uranium and thorium were separated using anion exchange resin filled in a column. The results show that overall a sample mass of 0.1?0.5 g with addition of 20 mL concentrated nitric acid is the most efficient means for extracting uranium and thorium simultaneously from apatite ore, black schist and mill tailings. The results for uranium and thorium concentrations determined by gamma spectrometry, alpha spectrometry and ICP-MS were in good agreement. Also the on-site measurements with portable XRF gave comparable results to other methods used in this study for thorium even without prior sample preparation.
The Paukkajanvaara mine in Eno, eastern Finland, started to operate in 1959. The mine was a test site for assessing the feasibility of larger-scale uranium extraction. Pilot-scale mining and milling were carried out between 1958 and 1961, and the mine site was rehabilitated in the early 1990s. The aim of this study was to examine the potential for further mobilization of radionuclides after remediation. There are two primary sources of contamination at the site, the waste-rock pile and the tailings. Our study indicates that 226Ra leached from the waste-rock pile and accumulated in surrounding soil. In run-off sediment samples collected from a dry stream bed near the waste-rock pile, the activity concentrations of 226Ra and 238U were higher than in soil samples. From the tailings, radionuclides can leach directly to the lake and to another small stream, which flows to the east of the waste-rock pile. In the water samples collected from this stream, uranium concentrations increased at the outlet to the lake. The results from the soil samples collected between the tailings area and the stream indicate leaching of 238U and 226Ra with the surface flow. Sediment samples collected from the bottom of the lake displayed pronounced uranium series disequilibrium with fractionations of 210Pb and 226Ra relative to the parent 238U. The results therefore indicate that leaching and accumulation of at least 226Ra from the waste-rock pile and possibly tailings is still ongoing.
Accurate, low-level measurement of 226Ra in high volume water samples requires rapid pre-concentration and robust separation techniques prior to measurement in order to comply with discharge limits and drinking water regulations. This study characterises the behaviour of 226Ra and interfering elements on recently developed TK100 (Triskem International) extraction chromatography resin. Distribution coefficients over a range of acid concentrations are given, along with an optimised procedure that shows rapid pre-concentration and separation of 226Ra on TK100 resin is achievable for high volume (1 L) water samples without the need for sample pre-treatment.
This work describes the solubility of nickel under the alkaline conditions anticipated in the near field of a cementitious repository for intermediate level nuclear waste. The measured solubility of Ni in 95%-saturated Ca(OH)2 solution is similar to values obtained in water equilibrated with a bespoke cementitious backfill material, on the order of 5 × 10?7 M. Solubility in 0.02 M NaOH is one order of magnitude lower. For all solutions, the solubility limiting phase is Ni(OH)2; powder X-ray diffraction and scanning transmission electron microscopy indicate that differences in crystallinity are the likely cause of the lower solubility observed in NaOH. The presence of cellulose degradation products causes an increase in the solubility of Ni by approximately one order of magnitude. The organic compounds significantly increase the rate of Ni transport under advective conditions and show measurable diffusive transport through intact monoliths of the cementitious backfill material.
The elemental composition of 37 bottled waters from the UK and continental Europe has been determined. Ca, K, Mg, Na, Al, As, Ba, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sr, U, V and Zn were determined by ICP-OES and ICP-MS, in addition to inorganic and total organic carbon. The composition of all the waters analysed fell within the guideline values recommended by the World Health Organization. Na, Ca, Sr and Ba showed the widest variation in concentrations, ranging over two orders of magnitude. Levels of Fe were below the limit of detection (30 ¼g L?1) in all samples analysed. Waters produced in the UK generally showed lower levels of most major elements and trace metals, with the exception of Ba (up to 455 ¼g L?1). Italian waters showed the highest concentrations of Sr (3000?8000 ¼g L?1) and U (8?13 ¼g L?1), whereas waters produced in Slovakia and the Czech Republic showed the highest levels of Pb (0.7?4 ¼g L?1). The use of multivariate analysis reveals an association between high alkaline metal content and high concentrations of As and Cr. There also appears to be a correlation between high Ca and Sr content and high levels of U. Analysis of variance (ANOVA) indicates that the composition of bottled water can be distinguished primarily by the country of origin, over other factors including the geological environment of the source. This would suggest that composition reflects, and is biased towards, consumer preferences.
Naturally occurring radioactive material (NORM) is a common feature in North Sea oil and gas production offshore but, to date, has been reported from only one production site onshore in the United Kingdom. The latter, Wytch Farm on the Dorset coast, revealed high activity concentrations of 210Pb in metallic form but little evidence of radium accumulation. NORM has now been discovered at two further onshore sites in the East Midlands region of the UK. The material has been characterized in terms of its mineralogy, bulk composition and disequilibrium in the natural uranium and thorium series decay chains. In contrast to Wytch Farm, scale and sludge samples from the East Midlands were found to contain elevated levels of radium and radioactive progeny associated with crystalline strontiobarite. The highest 226Ra and 228Ra activity concentrations found in scale samples were 132 and 60 Bq/g, with mean values of 86 and 40 Bq/g respectively; somewhat higher than the mean for the North Sea and well above national exemption levels for landfill disposal. The two East Midlands sites exhibited similar levels of radioactivity. Scanning electron microscope imaging shows the presence of tabular, idiomorphic and acicular strontiobarite crystals with elemental mapping confirming that barium and strontium are co-located throughout the scale. Bulk compositional data show a corresponding correlation between barium-strontium concentrations and radium activity. Scales and sludge were dated using the 226Ra/210Pb method giving mean ages of 2.2 and 3.7 years, respectively. The results demonstrate clearly that these NORM deposits, with significant radium activity, can form over a very short period of time. Although the production sites studied here are involved in conventional oil recovery, the findings have direct relevance should hydraulic fracturing for shale gas be pursued in the East Midlands oilfield.
This paper presents details of the challenges encountered when measuring 210Po and 210Pb, originally present in trace amounts in raw materials and then concentrates in the form of dusts during iron ore sintering, and validating radioanalytical methods in the absence of suitable reference materials. In-house radioanalytical methods for the measurement of these two radionuclides in a wide range of iron and steel-making materials including raw materials, waste dusts and emission samples have been developed. The methods have been validated and accredited by the United Kingdom Accreditation Service (UKAS) according to the International Standard Organisation (ISO) 17025.
A new phosphate mine is being planned at Sokli in northern Finland. In the late 1970s, pilot-scale mining and mineral processing took place at the site. The mobilisation of radionuclides and heavy metals from the mill tailings was examined in order to assess the potential environmental impact of past and future mining activities. Given the considerable amount of apatite still present, the waste material does not represent true tailings. Variations in abundance probably represent material discharges to the tailings rather than mobilization of the elements from the tailings themselves. No indication of heavy-metal migration was found. Extraction results suggest that only a small proportion of cadmium is in exchangeable form. Elements that are partly soluble under weakly-acidic conditions include copper, zinc, cadmium, uranium and lead. However, most of the elements are tightly bound to the sample matrix and therefore not easily released to the environment.
Rapid, routine chemical analysis methods are available for most radionuclides. However, for Ra-226 methods are available, but these are far less routine and are therefore generally cost and time intensive. This is particularly true for the analysis of Ra-226 in environmental waters, as the activity concentrations of this sample type is comparatively low. To address this, accurate and traceable analytical methods for measuring Ra-226 in environmental water samples (1 L), in
Initial investigations were focused on gamma and alpha spectrometry with a view of them being implemented in a mobile facility. On site analysis, using a mobile facility, has the potential to increase the time and cost efficiency of analysis through negating the need for sample dispatch and transport.
Investigations showed that non-destructive gamma spectrometry, on a portable ORTEC HPGe detector provided a minimum detectable activity (MDA) of 3.6 ± 0.5 Bq/L. These measurements were subject to U-235 interferences, corrections for which are discussed within the text. Investigation were also carried out into using co-precipitation with barium sulphate prior to measurement by gamma spectrometry. Co precipitation removed the U-235 interference by providing separation of Ra-226 from U-235 prior to measurement. Co-precipitation of Ra as Ba(Ra)SO4 gave chemical recoveries > 90% and increased the counting efficiency, through improving the sample-detector geometry. This combination allowed for an MDA of 31 ± 4.5 mBq to be achieved. Alpha spectrometry was also investigated as a portable technique. The developed method pre-concentrated samples using manganese dioxide resin and separated Ra from the sample matrix using barium sulphate micro co-precipitation. The optimised method provided MDAs 75%.
The procedural time for non destructive gamma spectrometry was less than that for alpha spectrometry, 1.5 h and 8 h respectively. Gamma spectrometry with co precipitation required operator times of
Direct measurement by inductively coupled mass spectrometry (ICP-MS), using an Agilent 8800 ICP-QQQ-MS (Agilent Technologies, UK), was considered. Although it is not field deployable, it provided a means of eliminating the count times associated with radiometric techniques which proved to be the limiting factor in sample throughput. The instrument?s collision reaction cell was optimised to allow for online separation of interferences reducing the background to 0 at a mass to charge ratio of 226 (m/z 226) resulting in a limit of detection of 0.01 Bq L 1 based on the signal to noise ratio. Handling of complex matrices was achieved through use of the instrument?s high matrix introduction system. Direct analysis of Ra-226 in samples of 10 and 100 Bq/L provided measurement uncertainties of
Combining ICP-MS with a suitable pre-concentration technique was also investigated. To do this, the extraction chromatography and ion-exchange resins (TK
Accurate measurement of natural and anthropogenic radionuclide concentrations is of critical importance to end users in the nuclear sector to ensure correct classification prior to storage, recycling, reprocessing or disposal. Uncertainties in the characterisation of solid matrices and materials could lead to safety, quality and financial implications. Robust sample preparation methods are vital, in particular effective sample digestion, as under-estimated chemical yield recovery results in a corresponding under-estimation of activity levels. Borate fusion has been proven to effectively digest a range of complex sample matrices in the geosciences but is not used routinely elsewhere. In this study, we describe an automated procedure for borate fusion of multiple matrices encountered in nuclear decommissioning, containing diverse radionuclides over a range of activity concentrations. The impact of digestion flux, sample mass and sample to flux ratios are described, as well as the subsequent separation and measurement techniques. The results contribute to accurate and precise measurement of radionuclides in various matrices, as well as to characterisation of reference materials, providing greater confidence in nuclear industry programmes worldwide.
Four terbium radioisotopes (149, 152, 155, 161Tb) constitute a potential theranostic quartet for cancer
treatment but require any derived radiopharmaceutical to be essentially free of impurities. Terbium-155
prepared by proton irradiation and on-line mass separation at the CERN-ISOLDE and CERN-MEDICIS
facilities contains radioactive 139Ce16O and also zinc or gold, depending on the catcher foil used. A
method using ion-exchange and extraction chromatography resins in two column separation steps
has been developed to isolate 155Tb with a chemical yield of e95% and radionuclidic purity e99.9%.
Conversion of terbium into a form suitable for chelation to targeting molecules in diagnostic nuclear
medicine is presented. The resulting 155Tb preparations are suitable for the determination of absolute
activity, SPECT phantom imaging studies and pre-clinical trials.