Estudio del proceso de dispersión electrón-núcleo en la aproximación de impulso

En este trabajo realizaremos un estudio de la dispersión de electrones con núcleos. Nos centraremos principalmente en la denominada aproximación de impulso de ondas planas (PWIA), en la cual se considera que tras la colisión del electrón inicial con el núcleo, el fotón intercambiado interacciona con un único nucleón. Así pues, dicho nucleón será eyectado y se detectará en coincidencia con el electrón dispersado. Con el fin de simplificar el proceso, la descripción del nucleón en el estado final se realizará en la aproximación de ondas planas, es decir, no consideraremos efectos asociados a la interacción de estados finales entre el nucleón emitido y el núcleo residual. Por último, analizaremos los efectos ‘‘off-shell’’ debidos al carácter del nucleón ligado (se encuentra fuera de la capa de masas), y los efectos nucleares producidos por el modelo nuclear.Universidad de Sevilla. Máster Universitario en Física Nuclea

A practical and general methodology for efficiency calibration of coaxial Ge detectors

The correct determination of artificial and natural radionuclides like 152Eu, 137,134Cs, 60,57Co, etc., and 234,228Th, 228,226Ra, 210Pb and 40K, respectively, is essential for many environmental science fields. For this, a general function was obtained for the full-energy peak efficiency (FEPE) by gamma-ray spectrometry using coaxial Ge detectors. Then, the experimental FEPE values, obtained fixing the energy, Eγ, were fitted varying the thickness, h, of cylindrical standards. The parameters resulted from these fittings were fitted, in turn, versus Eγ, obtaining a general efficiency function, εc (Eγ, h). εc (Eγ, h) was validated, obtaining very good zscore, except for Eγ affected by TCS effects. Consequently, a practical and general method was developed, recalibrating the detector by varying the sample-detector distance, d. εc (Eγ, h, d) was obtained, achieving very good zscore. Furthermore, this practical method was also employed to correct high self-absorptions and high dead times.This research has partially funded by the projects of the Regional Government of Andalusia called “Basic processes regulating the fractionations and enrichments of natural radionuclides under acid mine drainage conditions” (Ref.: UHU-1255876), and “Treatment of acid leachates from phosphogypsum piles located at Huelva, and transport modelling of the released radionuclides” (Ref.: P20_00096), the project funded by the Spanish Ministry of Science, Innovation and Universities’ Research Agency “Development and optimization of a process for removing natural radionuclides in phosphogypsum leachates” (Ref.: PID2020-116461RB-C21), and the Project for Novel Principal Investigators “Quantitative study of the variables involved in the radonexhalation rate for granular solids; application to rafts of granular solid phosphogypsum” (Ref.: UHUPJ-00005-632). The authors acknowledge the funding for open access charge provided by Universidad de Huelva/CBUA

A new efficiency calibration methodology for different atmospheric filter geometries by using coaxial Ge detectors

The study of the different pollutants present in atmospheric aerosols such as trace elements and radionuclides is essential to assess the air quality. To analyze the particulate matter (PM), atmospheric filters with different dimensions and geometries (rectangular, circular, slotted, and square filters) are usually employed. Regarding the pollutants existing in atmospheric aerosols, radionuclides are usually analyzed due to their multiple applications such as either in the environmental radiological control or as tracers of atmospheric processes. Therefore, this study aims to develop a new and general methodology to calibrate in efficiency coaxial Ge detectors to properly determine radionuclides present in the PM by gamma-ray spectrometry for several filter types. For this, granular certified reference materials (CRM) containing only natural radionuclides (²³⁸U-series, ²³²Th-series, and ⁴⁰ K) were selected. Several granular solid CRMs were chosen allowing us to reproduce the same PM deposition geometry and to assure the homogeneity of the added CRMs. These are the main advantages in relation to the typical methods that use liquid CRMs. Furthermore, for filters whose surfaces are relatively large, they were cut in several pieces and placed one on top of the other, achieving the same geometry than the PM deposited onto the filter. Then, the experimental full-energy peak efficiencies (FEPEs) were obtained for each energy of interest (Eγ) and they were fitted versus Eγ, finding a general FEPE function for each filter type. Finally, this methodology was validated for both natural and artificial radionuclides (from 46 to 1332 keV) by using different filter types employed in proficiency test exercises, obtaining |zscore|< 2 for all cases.Funding for open access publishing: Universidad de Huelva / CBUA This research has partially funded by the projects of the Regional Government of Andalusia called “Treatment of acid leachates from phosphogypsum piles located at Huelva, and transport modelling of the released radionuclides” (Ref.: P20_00096) and “Valorization of inorganic wastes enriched in natural radioactivity for sustainable building materials” (Ref.: FEDER-UHU-202020); the project funded by the Spanish Nuclear Safety Council (CSN) “Radon exhalation from building materials; radiological impact and corrective measures” (Ref.: SUBV-4/2021); the project funded by the Spanish Ministry of Science, Innovation and Universities’ Research Agency “Development and optimization of a process for removing natural radionuclides in phosphogypsum leachates” (Ref.: PID2020-116461RB-C21); and the Project for Novel Principal Investigators “Quantitative study of the variables involved in the radon exhalation rate for granular solids; application to rafts of granular solid phosphogypsum” (Ref.: UHUPJ-00005–632)

An upgraded lab-based method to determine natural γ-ray emitters in NORM samples by using Ge detectors

The regulation existing on NORM activities requires the accurate and quick measurement of natural radionuclides in a wide range of matrices by gamma spectrometry. The aim of this work has been to develop a comprehensive and accurate methodology to determine natural long-lived radionuclides (210Pb, 228,226Ra, 234,228Th and 40K) by gamma spectrometry with Ge detectors in NORM samples. An exhaustive calibration method to obtain the full-energy peak efficiency (FEPE), for each gamma emission energy, as a function of the thickness, apparent density and matrix composition of the cylindrical sample, has been developed. The selected certified calibration standards contain only natural radionuclides belonging to the 238U- and 232Th-series as well as 40K (codes RGU-1, RGTh-1 and RGK-1 from IAEA). Then, the obtained FEPE curves were validated using Genie 2000 simulations and Certified Reference Materials, for which the self-attenuation corrections were considered. Finally, a study on 222Rn losses was done for several samples.Funding for open access charge: Universidad de Huelva / CBU

Development of a robust and precise methodology for the measurement of the radon diffusion coefficient in diverse materials

The main sources of radon indoors are the infiltration from the soil through the building materials and the materials themselves. These pathways are significantly influenced by the radon diffusion coefficient, D, of those elements, playing an important role when trying to mitigate radon accumulation. Current methodologies developed to determine D are difficult to apply. ISO 11665-13 imposes restrictive conditions on the experimental system and requires the application of numerical methods. In the methodology the problem material is placed between a chamber containing a radon source and an empty one and radon concentration is measured in the chambers. The D closer to the experimental data is then selected. In this work, the methodology was improved, and an algorithm was developed to complement the ISO. The algorithm solves for the physical governing equations and finds the value of D that best fits the data by minimising the differences between the predicted and experimental concentrations. Various statistical parameters and stop conditions were studied to determine when an optimal D was found. A validation procedure was developed for internal validation, and results were compared with the literature for external validation. Additional results are presented for materials not found in the literatureThis research was partially funded by the Nuclear Safety Council (CSN) by the project “Radon exhalation from building materials; Radiological impact and corrective measures (EXRADON)” (Ref.: PR- 047-2021) and the project funded by the Spanish Ministry of Science, Innovation and Universities’ Research Agency “Development and optimization of a process for removing natural radionuclides in phosphogypsum leachates (RAD-REMOVE)” (Ref.: PID2020-116461RB-C21

Sedimentary environmental quality of a biosphere reserve estuary in southwestern Iberian Peninsula

The Huelva estuary is formed by the common mouths of the Odiel and Tinto Rivers, and inside this ecosystem is the biosphere reserve of the Odiel saltmarshes. This ecosystem has been historically affected by acid mine drainage (AMD) and by releases of pollutants from five phosphoric acid industrial plants and phosphogypsum (PG) waste stacks located in the area. This study carried out a comprehensive assessment of the environmental impact of the biosphere reserve of the Odiel saltmarshes. To this end, it was necessary to find a suitable sedimentary background (Piedras River in our case). To quantify this impact, several pollution indexes were used. According to the values reached by the indexes, this impact was classified as "serious" pollution for most trace elements, excepting the deepest layers, and "low-moderate" pollution for the 238U-series radionuclides, while no pollution for the 232Th-series and 40K radionuclides was found as expected.This research was partially funded by the University of Huelva and the Operative FEDER Program-Andalusia 2014-2020 (UHU-1255876, UHU-202020); The European Regional Development Fund through the Spanish Ministry of Science, Innovation and Universities' Research Agency (research grants PID2020-116461RB-C21 and 116461RA-C22); and the Andalusian government (I + D + i-JAPAIDI-Retos, project Ref.: PY20_00096, and Diagnosis and proposals for the environmental recovery of areas affected by industrial and mining activities; Implications for the Huelva estuary (RESTOREHU), Ref.: TED2021-130361B-I00). Jos´e Luis Guerrero thanks the Spanish Ministry of Universities for the Margarita Salas research grant.Departamento de Física Aplicad

A simple and precise methodology to determine particulate matter mass in atmospheric filters; validation and application cases

In the past decades, particulate matter (PM) measurements have been used extensively in atmospheric sciences, as it allows studying the evolution of tracers for different atmospheric processes and the effects of atmospheric pollution on human health. However, measuring PM mass requires a constant control of the laboratory conditions due to its capacity to absorb humidity. For this reason, this study was focused on developing a novel, simple and precise methodology to determine the corrections of the filter mass due to humidity changes. The control and corrections are possible using a “control filter”, which is always adapted to the environmental conditions of the laboratory. To check the consistency of this method, it was proved that the mass of any problem filter and that of the control filter behave in a very similar way. This allows quantifying the mass changes of any problem filter by using the control filter, where the problem filters and the control filter must have the same chemical composition and dimensions. To validate this methodology, a comparison was made between the methodology proposed in this study (Method-1) and the one proposed by the EPA (Method-2), which is generally applied. The particulate matter mass (m) was obtained for a problem filter for different weights, achieving similar values using both methods. However, Method-1 still provided reliable mass measurements for relative humidities very different from 50%, even as low as 18%. It was also proved that the adsorption or loss of water by the particulate matter can be neglected, since m is much smaller than the blank filter mass. Method-1 was also employed in several samplings carried out using three PM10 samplers to determine contaminants, such as 7Be and 210Pb, obtaining a good agreement between all particulate masses and activities measured by the three samplers for all samplings.This research has partially funded by the projects of the Regional Government of Andalusia called “Basic processes regulating the fractionations and enrichments of natural radionuclides under acid mine drainage conditions” (Ref.: UHU-1255876), and “Treatment of acid leachates from phosphogypsum piles located at Huelva, and transport modelling of the released radionuclides” (Ref.: P20_00096), the project funded by the Spanish Ministry of Science, Innovation and Universities’ Research Agency “Development and optimization of a process for removing natural radionuclides in phosphogypsum leachates” (Ref.: PID2020-116461RB-C21), and the Project for Novel Principal Investigators “Quantitative study of the variables involved in the radon exhalation rate for granular solids; application to rafts of granular solid phosphogypsum” (Ref.: UHUPJ-00005-632). The authors acknowledge the funding for open access charge provided by Universidad de Huelva / CBUA. The authors would like to thank A.M. Padilla for his great help provided in order to make this study possible

Behavior of heavy metals and natural radionuclides along the Moroccan phosphogypsum carbonation process with several alkaline reagents

Phosphogypsum (PG) is the main by-product from the phosphoric acid (PA) production industry being the PA production the basic raw material for producing the modern fertilizers. Because of its high calcium and sulfate content, it is important to emphasize that ecological benefits come from recycling and eventually converting PG into value-added compounds are obtained. This work aims to remedy the environmental problems associated to the large quantities of PG generated in Morocco. Furthermore, three procedures for PG conversion into Ca(OH)2, CaCO3, Na2SO4, K2SO4 and (NH4)2SO4 using hydroxide aqueous mediums were studied. The impurity traces contained in the PG were generally found to be completely transferred into the final calcite. The sulfates produced here are recommended for the use as a fertilizer (K2SO4 and (NH4)2SO4) and in the manufacture of detergents (Na2SO4), and the obtained calcite could be used in cement production, concretes, permeable reactive barriers for pollutants removing, etc.Funding for open access charge: Universidad de Huelva / CBU

Behavior of 222Rn, 220Rn and their progenies along a daily cycle for different meteorological situations: Implications on atmospheric aerosol residence times and Rn daughters' equilibrium factors

The correct assessment of the radiological hazard from radon and daughters, external and internal doses, residence times and equilibrium factors, implies the need to properly determine 222Rn (radon), 220Rn (thoron) and their respective short-lived progenies (214Pb and 214Bi, and 212Pb and 212Bi, respectively), where the precise measurements of both progenies are quite complex due to their very short half-lives. In addition, it is important to study the temporal behavior of all these radionuclides along daily cycles. Therefore, the aim of this study was to analyze the temporal evolution of radon, thoron and their progenies, and of their activity ratios along daily cycles for two different meteorological situations (synoptic and mesoscale processes). Radon and thoron were measured using a radon monitoring system, while their respective progenies were collected onto atmospheric filters using an ASS-500 sampler, and then measured by gamma-ray spectrometry. Furthermore, the different relationships between the concentrations of radionuclides and the different meteorological variables of interest (temperature, ABL height, and speed and direction of the wind) were found. Finally, the atmospheric aerosol residence times and Rn daughters’ equilibrium factors were estimated for each sampling carried out along the two daily cycles, finding results consistent with previous studies.This research was partially funded by the University of Huelva and the Operative FEDER Program-Andalusia 2014–2020 (Refs.: UHU- 1255876, and UHU-202020), the European Regional Development Fund through the Research State Agency (Ref.: PID2020-116461RB-C21), the Andalusian Government (Ref.: PY20_00096), and the CSN (Nuclear Safety Council) projects with Refs.: SUBV-4/2022 (CLIMATOR) and SUBV-4/2021 (EXRADON).Departamento de Física Aplicad

A comparative study of alternative methods for 210Pb determination in environmental samples

The accurate determination of the levels of 210Pb in environmental samples (e.g. atmospheric aerosols, waters, soils, biota, etc.) is essential due to its multiple applications in geochronology, radiation protection, groundwaters flows, air masses movement, etc. For this purpose, it has been developed a novel and thorough study of three alternative radiometric measuring methods of 210Pb activity concentrations in several types of samples. The three selected methods were low-level gamma spectrometry (210Pb), alpha-particle spectrometry (via 210Po), and Cherenkov counting (via 210Bi). This study has been performed in terms of precision, linearity and proportionality as well as spent time, type of matrix, and showing the most appropriate method of measure in each case. Several kinds of samples were analyzed such as atmospheric filters, soils, sediments and phosphogypsum (PG) matrices. These samples contain different 210Pb activity concentrations and were measured by the three techniques carrying out radiochemical procedures when necessary. There were not significant differences in the results obtained for the samples analyzed by the three methods. The major precision was obtained by using alpha-particle spectrometry, but this method is more expensive and time consuming.This research was partially funded by a project of the Regional Government of Andalusia “Basic processes regulating the fractionations and enrichments of natural radionuclides under acid mine drainage conditions” (Ref.: UHU-1255876), and a project of the Projects for Novel Principal Investigators “Quantitative study of the variables involved in the radon exhalation rate for granular solids; application to rafts of granular solid phosphogypsum” (Ref.: UHUPJ-00005-632). A.B.L. ac- knowledges support from funds provided by the Spanish Ministry of Science, Innovation and Universities’ Research Agency and co-financing provided by the European Social Fund (ESF) and the Spanish National Youth Guarantee Implementation Plan under Contract No. PEJ2018- 002676-A. The authors acknowledge the funding for open access charge provided by Universidad de Huelva / CBU