External occupational exposures in some NORM industries located at the south-west of Spain

Detailed mappings of the external exposures which can be received by the workers in two NORM industrial factories located at the South-West of Spain have been performed: one devoted to the production of phosphoric acid, and the other devoted to the production of titanium dioxide pigments. In most places of the analyzed factories, the external exposures are moderated, although in some specific points, and associated to the presence of scales, their values are clearly higher. Nevertheless, under normal running conditions, the contribution of the external exposures to the effective doses received by the workers is lower than 1 mSv/y because the worker occupancy factors values are very low in the places with the highest external exposures

Editorial

In this editorial a summary of the main contributions and outcomes of the conference celebrated in Seville about Radioecological Concentration processes during six intense sessions is given. It was quite remarkable in addition to the good quality of the communications presented, the active participation of the delegates and the good working atmosphere created during the conference as well as the participation of a good set of young researchers that will construct the future of the radioecology. In addition, it was possible to obtain as a main conclusion of the conference that the radioecology is in good health with a set of emerging new topics under development

Determination of U isotopic ratios in environmental samples by ICP-MS

Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the determination of trace elements in a variety of materials. For uranium, the concentration of 238U can be measured with a detection limit of less than 0.1 ppt in a few minutes. However, because of the extremely low 234U concentrations in environmental materials, it is necessary to separate U from the matrices and to remove interfering elements from the sample solution for measurement of the 238U/234U ratio by ICP-MS. In this study, a simple and rapid separation method for U with an extraction chromatographic resin (TEVA resin) was developed for ICP-MS and the U isotopic ratios in phosphogypsum samples, collected in Spain, were measured. The resin efficiently retained U in 6 M HCl medium and more than 98% of the U was easily eluted with the first 30 mL of 0.1 M HNO3. The separated solutions were free from most of the matrix elements and the concentrations of U in the solutions ranged from 35 to 70 ppb. The 238U/234U isotopic ratios in the solutions were measured by ICP-MS. Moreover, due to the presence of a higher number of 235U atoms in comparison with 234U, the 238U/235U isotopic ratios were also determined with high precision by ICP-MS. The results obtained agreed well with the ratios measured by alpha-spectrometry. The method for this determination is more rapid than alpha-spectrometry, and is considered to be more suitable for environmental monitoring

Measurement of Pu and U isotopes on the 1 MV AMS system at the Centro Nacional de Aceleradores

In the last decade, compact AMS systems have demonstrated their potential to measure actinides (236U, 239,240,244Pu, 237Np). With an appropriate detection system, kinematic filters with enough mass resolution, and a simple chemical procedure, the determination of plutonium isotopes and 237Np at environmental levels is currently possible with this new generation of facilities with even better performance than with conventional AMS systems. However, the measurement of 236U (T1/2=23.4 My), produced by neutron capture on 235U, is still a challenge, due to the interference caused by 235U and 238U. In this work, we will explore the possibilities that the 1 MV AMS system at the CNA offers for the measurement of uranium isotopes at environmental levels, in terms of detection limit, efficiency, and precision. Considering the very promising 239Pu/238U mass suppression factor achieved with our system, of about 10-9, a limiting 236U/238U atomic ratio of about 10-11 was expected, approaching the levels expected in natural uranium. However, to date, only the 10-9 level has been obtained, possibly due to the lack of an appropriate uranium material. Currently, different natural uranium materials are being studied, in order to elucidate the origin of the interference. On the other hand, we will discuss the status of the plutonium measurements at our facility, based on the experience we have accumulated in recent years from the analysis of different matrixes over a wide range of plutonium concentrations

Monte Carlo simulation of a liquid scintillation counter using geant4 code

This paper presents a first approach to the use of the GEANT4 Monte Carlo (MC) technique in liquid scintil-lation counting (LSC) applied to measurements in radiological laboratories. The GEANT4 software was developed by RD44,a worldwide collaboration of national institutes, laboratories, and large high-energy physics experiments. GEANT4 is a pub-lic software package composed of tools that can be used to accurately simulate the passage of particles through matter. TheGEANT4 catalog of processes at optical wavelengths includes refraction and reflection at medium boundaries, bulk absorp-tion, and Rayleigh scattering. Processes that produce optical photons include the Cherenkov effect, transition radiation, andscintillation.The simulated setup includes a vial containing the scintillation cocktail in between 2 opposite photomultipliers tubes (PMTs)working in sum-coincidence mode. The decay of several beta emitters (such as 14C and 3H) can be simulated, as well as alphaor EC emitters. Additionally, significant information could be obtained, such as the energy deposited by decay into the scin-tillation cocktail or the light output generated into the scintillation cocktail. GEANT4 is a useful tool for efficiency calibra-tion, stopping power calculations, or wall effect studies for different scintillation cocktails and geometries.Junta de Andalucia Excellence Project RNM-0256

Radioactive impact in sediments from an estuarine system affected by industrial wastes releases

A big fertilizer industrial complex and a vast extension of phosphogypsum piles (12 km2), sited in the estuary formed by the Odiel and Tinto river mouths (southwest of Spain), are producing an unambiguous radioactive impact in their surrounding aquatic environment through radionuclides from the U-series. The levels and distribution of radionuclides in sediments from this estuarine system have been determined. The analyses of radionuclide concentrations and activity ratios have provided us with an interesting information to evaluate the extension, degree and routes of the radioactive impact, as well as for the knowledge of the different pathways followed for the radioactive contamination to disturb this natural system. The obtained results indicate that the main pathway of radioactive contamination of the estuary is through the dissolution in its waters of the radionuclides released by the industrial activities and their later fixation on the particulate materials. Tidal activity also plays an important role in the transport and homogenization along the estuary of the radioactivity released from the fertilizer plants. D 2002 Elsevier Science Ltd. All rights reserved.Junta de Andalucia (España) project 1FD97-0900-C02-02 (AMB

A review of the production cycle of titanium dioxide pigment

Titanium is a very important element for several industrial applications, being one of the ninth most abundant elements in the Earth’s crust (0.63% wt). In this work it will discuss the different mining and industrial activities involved in the production of titanium dioxide. The first step ana-lyzed will treat about the beneficiation mining process of titanium mineral, and secondly, it will discuss the two main processes of the TiO2 manufacturing (sulphate and chloride routes). In addi-tion, we will show different uses of the titanium dioxide pigment as filler in paper, plastics and rubber industries and as flux in glass manufacture, etc. Finally, we will show that the old wastes are currently called co-products since they were valorized, being commercialized by the Spanish industry of TiO2 production in different fields such as agriculture, civil engineering, or cement manufacturing.Government of Andalusia’s project “Characterization and modelling of the phosphogypsum stacks from Huelva for their environmental management and control” (Ref.: RNM-6300

129I, 236U, 239Pu and 240Pu profiles in a peatbog from the Southern Hemisphere

129I, 236U, 239Pu and 240Pu isotopes have been analyzed in the different layers of a peatbog core collected in Madagascar Island (South Hemisphere) and representing at least the last 100 years of atmospheric deposition. The determination of ultra-low levels of these isotopes has been possible by applying the Accelerator Mass Spectrometric Technique (AMS) by using the 1 MV Tandetrom AMS facility located at CNA (Seville, Spain). The elements of interest were extracted and isolated previous to the measurements by applying validated radiochemical procedures. In this contribution, the behavior along the core of the different isotopes under analysis will be discussed, evaluating in particular the magnitude of their post-depositional retention/migration. In this sense, it will be highlighted the great mobility of the 129I with a near uniform profile along the core, in opposition for example with the preservation for the Pu isotopes of the fallout bomb peak. In the case of 236U, the 236U/239Pu atomic ratios determined in a total of eight layers of the core are ranging in the interval 0.02 – 0.29 with an average value of 0.15. As far as we know, these are the first 236U results seeing the light that were obtained in deposits as peatbogs collected in the southern hemisphere.Spanish Ministry MINECO project FIS2015-69673-

Characterization of terrestrial hot particles from the Palomares accident using destructive and non-destructive analytical techniques

Several radioactive particles from the Palomares area have been analyzed with the nuclearmicroprobe of the National Accelerator Centre (CNA) in Seville exploring the advantages of combining -PIXE using a 5.5 MeV4He beam with conventional -PIXE analysis using 3 MeV protons. Themeasurements performed with the -particles are more sensitive to the sample surface, while the resultscollected with protons are indicative of the average composition of the hot particle. In this way, importantinformation about the depth distribution of Pu and U in the particles has been obtained. In addition, theparticles have been analyzed by SEM (EDX) and one of them has been sacrificed for the determinationof its U and Pu isotopic composition by ICP-MS and -spectrometry, being gained in this way importantinformation about the composition of the weapons involved in the Palomares accident.Junta de Andalucía Excellence Project TU-DRAMA (Ultra-sensitive techniques for radionuclides determination in environmental materials

Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leonreservoirs, Chihuahua, Mexico

Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. 232Th-series, 238U-series, 40K and 137Cs activity concentrations (AC, Bq kg-1) were determined by gamma spectrometry with a high purity Ge detector. 238U and 234U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating of core sediments was performed applying CRS method to 210Pb activities. Results were verified by 137Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High 238U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento – Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) 234U/ 238U and 238U/226Ra in sediments have values between 0.9-1.2, showing a behavior close to radioactive equilibrium in the entire basin. 232Th/238U, 228Ra/226Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs