Radiological and chemical risks by waste scales generated in the titanium dioxide industry.

Along the industrial process devoted to the production of titanium dioxide pigments by using ilmenite as main raw material, small residues amounts are generated, remaining clearly enriched in natural radionuclides and chemical pollutants. Between them, we can remark the scales enriched in both radium isotopes and lead, which are formed in the internal walls of pipes and some equipment. These scales are radiological anomalies that demand its mineralogical, elemental and radiometric characterization as a basis for a detailed radiological and toxicological assessment from the occupational and public point of view. In this work, several scales collected in a TiO2 pigment production plant in South of Spain have been mineralogically characterized by XRD, while information about their elemental composition and morphology have been obtained by applying the XRF and SEM techniques. In addition, radiometric determinations have been performed by gamma-ray and alpha-particle spectrometry. The performed study indicates that the radiological doses received due to the scales by the workers performing its conventional activities are clearly lower than 1 mSv/y. Special dosimetric and chemical controls could be needed for the workers in charge of the maintenance labours (which include the removal of the scales) if these workers belong to an external company devoted to perform maintenance operations in several NORM industries.

Radiological and physico-chemical characterization of materials from phosphoric acid production plant to assess the workers radiological risks.

The industry devoted to the production of phosphoric acid by using as raw material sedimentary phosphate rock (PR) is considered as a NORM activity (Naturally Occurring Radioactive Materials), due to the high levels of U-series radionuclides contained in this ore, which are 1-2 orders of magnitude higher than those in unperturbed soils. This fact allowed us to develop a deep characterization of the raw materials, wastes, main intermediate materials, and final products obtained at a typical phosphoric acid factory. The elemental composition (major, minor and trace elements), radionuclide concentrations, grain size distribution, mineralogy and micro-structural composition were analyzed. The aim of this characterization was to obtain information for operators and maintenance personnel involved in clean-up and waste management operations. The highest concentrations of some heavy metals and radionuclide activity concentrations were found in the "scales" (or internal incrustations)from the pipes that carry either phosphoric acid (PA) or the phosphogypsum waste (PG). The highest concentrations where found for 226Ra and 40K,with values up to 9 and 5 Bq g-1, respectively. In addition, high concentrations of many toxic heavy metals and trace elements, such as Cd, Cr, Ni, Sr, Y, V, Zn, Th, and U, were found in some sludge samples. The shielding effect of the containers/vessels/pipes has an essential role in the measured external dose in the intermediate products. The radiological implications of natural radionuclides with higher activity showed that if the maximum particulate matter concentration established in the Spanish regulation is verified, and taking into account the most conservative scenario, the annual limit of 1 mSv y-1 is not exceeded.

Radioactive characterization of leachates and efflorescences in the neighbouring areas of a phosphogypsum disposal site as a preliminary step before its restoration.

After the recent closure of certain phosphoric acid plants located in the South-West of Spain, it has been decided to restore a big extension (more than six hundred hectares) of salt-marshes, where some million tonnes of phosphogypsum (PG), the main by-product generated by these plants, had been disposed of. This PG is characterized by its content of high activity concentrations of several radionuclides from the uranium series, mainly (226)Ra, (210)Pb, and (210)Po and, to a lesser extent, U-isotopes. The PG disposal area can be considered as a potential source of radionuclides into their nearby environment, through the waters which percolate from them and through the efflorescences formed in their surroundings. For this reason, a detailed radioactive characterization of the mentioned waters and efflorescences has been considered essential for a proper planning of the restoration tasks to be applied in the near future in the zone. To this end, U-isotopes, (234)Th, (230)Th, (226)Ra, (210)Pb and (210)Po activity concentrations have been determined by applying both alpha-particle and gamma-ray spectrometric techniques to selected water and efflorescence aliquots collected in the area. The analysis of the obtained results has enabled to obtain information about the geochemical behaviour in the area of the different radionuclides analyzed; and the conclusion to be drawn that, in the restoration plan under preparation, both the prohibition of outflowing waters from the disposal area to the neighbouring salt-marshes, and the removal of all the efflorescences now disseminated in their surroundings are essential.

Occupational exposures in two industrial plants devoted to the production of ammonium phosphate fertilisers.

In order to fill a gap in the open literature, occupational exposures and activity concentrations have been assessed in two NORM industrial plants, located in the south-west of Spain, devoted to the production of mono-ammonium phosphate (MAP) and di-ammonium phosphate (DAP) fertilisers. The annual effective doses received by the workers from these plants are clearly below 1 mSv yr(-1) and the contribution due to external radiation is similar to that due to inhalation. The contribution to the maximum effective doses due to inhalation of particulate matter has been estimated to be about 0.12 mSv yr(-1), while the (222)Rn concentrations inside the plants are of no concern. Consequently, no additional actions or radiological protection measures need to be taken to decrease the natural radiation received by the workers in these facilities.

Performance of a novel BD stem cell enumeration kit on two flow cytometry systems.

INTRODUCTION: Hematopoietic stem cell transplantation, which requires accurate enumeration of stem cells, is routinely used in clinical settings. Flow cytometry provides a qualitative and quantitative assessment of CD34⁺ cells. Precision, linearity, and stability of the novel BD™ Stem Cell Enumeration (SCE) Kit were evaluated on two flow cytometry platforms using a modified ISHAGE gating strategy and including a viability dye for data acquisition and analysis. METHODS: Precision and linearity were evaluated on BD FACSCanto™ II and BD FACSCalibur™ systems. Stability was evaluated on the BD FACSCanto II system. Precision was tested using both high and low controls. Linearity was evaluated using dilutions from CD34⁺ cell pools, while stability was evaluated using fresh leukapheresis specimens. RESULTS: Both systems showed precision with limited variability in absolute counts and percentages of viable CD34⁺ cells. The linearity range of viable CD34⁺ cells in both systems was established at 0-1000 cells/µL, showing a linear relationship (R² = 0.99). Stability of CD34⁺ cells in mobilized leukapheresis samples was confirmed up to 24 h after collection and up to 60 min after the end of stain/lyse procedures. CONCLUSION: The BD SCE Kit on both flow cytometry systems shows consistent and reproducible results.

Contamination and restoration of an estuary affected by phosphogypsum releases.

The Huelva Estuary in Huelva, Spain, has been one of the most studied environmental compartments in the past years from the point of view of naturally occurring radioactive material (NORM) releases. It has been historically affected by waste releases, enriched in radionuclides from the U-decay series, from factories located in the area devoted to the production of phosphoric acid and phosphate fertilizers. Nevertheless, changes in national regulations forced a new waste management practice in 1998, prohibiting releases of phosphogypsum into the rivers. The input of natural radionuclides from phosphate factories to rivers was drastically reduced. Because of this there was a unique opportunity for the study of the response of a contaminated environmental compartment, specifically an estuary affected by tidal influences, after the cessation of the contaminant releases to, in this case, the Huelva Estuary (henceforth referred to as the Estuary). To investigate the environmental response to this new discharge regime, the specific activities of radionuclides 226Ra and 210Pb in water and sediment samples collected in four campaigns (from 1999 to 2005) were determined and compared with pre-1998 values. From this study it is possible to infer the most effective mechanisms of decontamination for the Estuary. Decontamination rates of 210Pb and 226Ra in the sediments and water have been calculated using exponential fittings and corresponding half-lives have been deduced from them. The cleaning half-life in the whole area of the Estuary is about 6 and 3.5 years for 226Ra and 210Pb respectively. The observed trend clearly shows that contamination of the Estuary by natural radionuclides is now decreasing and radioactive levels in waters and sediments are approaching the natural background references. This work attempts to evaluate whether it can be expected that the decontamination of the enhanced levels of natural radioactivity in the Estuary can be performed via natural processes.

Colour quenching corrections on the measurement of 90Sr through Cerenkov counting.

The determination of 90Sr through the Cerenkov radiation emitted by its descendant 90Y is a well-known method and firmly established in literature. Nevertheless, in order to obtain an accurate result based on a Cerenkov measurement, the experimental work must be extremely rigorous because the efficiency of Cerenkov counting is especially sensitive to the presence of colour. Any traces of colour in the sample produce a decrease in the number of photons detected in the photomultipliers and, therefore, this might cause a diminution in Cerenkov counting efficiency. It is essential not only to detect the effect of colour quenching in the sample but also to correct the decrease in counting efficiency. For this reason, colour quenching correction curves versus counting efficiency are usually done when measuring through Cerenkov counting. One of the most widely used techniques to evaluate colour quenching in these measurements is the channel ratio method, which consists of the measurement of the shift of the spectrum measuring the ratio of counts in two different windows. The selection of the windows for the application of the corrections might have an influence on the quality of the fitting parameters of the correction curves efficiency versus colour quenching degree and hence on the final 90Sr result. This work is focused on the calculation of the counting efficiency decrease using the channel ratio method and on obtaining the best fitting correction curve. For this purpose, empirical curves obtained through artificial quenchers have been studied and the results have been tested in real samples. Additionally, given that the Packard Tri-Carb 3170 TR/SL liquid scintillation counter is a novel detector for use in Cerenkov counting, the previous calibration of the Tri-Carb 3170 TR/SL detector, necessary for the measurement of 90Sr, is included.