47 research outputs found

    Contribuci贸n a la caracterizaci贸n de aerosoles radiactivos derivados del rad贸n

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    La existencia de una relaci贸n entre el riesgo a desarrollar un c谩ncer de pulm贸n y la exposici贸n al rad贸n y descendientes presentes en el aire se puso de manifiesto hace ya bastante tiempo en la poblaci贸n minera. Desde aquellas fechas se han desarrollado numerosos estudios encaminados a determinar el riesgo radiol贸gico por unidad de exposici贸n. En la actualidad, se pueden distinguir dos grandes v铆as para su evaluaci贸n: a) los estudios epidemol贸gicos, y b) la utilizaci贸n de modelos dosim茅tricos del sistema respiratorio. La utilizaci贸n de dichas v铆as en la evaluaci贸n del riesgo radiol贸gico por unidad de exposici贸n en la poblaci贸n minera muestran factores de riesgo que se diferencian en un factor de 2 a 3. En la utilizaci贸n de los modelos dosim茅tricos del sistema respiratorio, las incertidumbres que se introducen se pueden atribuir a cuatro or铆genes: a) caracter铆sticas fisico-qu铆micas del aerosol, b) par谩metros utilizados para describir el modelo dosim茅trico, c) hip贸tesis utilizadas en las c茅lulas irradiadas, y d) factores de ponderaci贸n utilizados en dosimetr铆a.La finalidad de este trabajo de investigaci贸n ha sido la determinaci贸n de par谩metros que caracterizan a los descendientes del rad贸n de vida corta en recintos cerrados para analizar en primer lugar su comportamiento f铆sico-qu铆mico y as铆 mejorar la estimaci贸n del riesgo radiol贸gico debido a su inhalaci贸n mediante la utilizaci贸n de modelos dosim茅tricos del tracto respiratorio. Para alcanzar este fin se han puesto a punto diversas t茅cnicas que permiten analizar, tanto en una instalaci贸n de laboratorio como en espacios habitados, el factor de equilibrio, la fracci贸n libre y el espectro dimensional de descendientes del rad贸n en estado libre. En referencia a los dos primeros par谩metros se ha desarrollado un equipo port谩til que permite realizar medidas de campo con una gran precisi贸n. En cuanto al sistema de medida del espectro dimensional de los descendientes del rad贸n en estado libre se ha realizado el dise帽o y construcci贸n de un nuevo sistema basado en las t茅cnicas de tubos de difusi贸n, que presenta un gran n煤mero de mejoras respecto a otros prototipos. Con este sistema se ha establecido, en una intercomparaci贸n realizada en la c谩mara de rad贸n, construida para este estudio, que el tama帽o m谩s probable del espectro dimensional de los descendientes en estado libre est谩 comprendido entre 0.8 nm y 0.9 nm. Con el sistema de media del factor de equilibrio y la fracci贸n libre se han llevado a cabo medidas experimentales de campo en cuatro lugares de la costa catalana. Se estableci贸 que dicho par谩metros var铆an de forma significativa, (0.03) y fp (0-0.72), en los distintos emplazamientos de acuerdo con sus caracter铆sticas del lugar y su clima. que Las medidas de F y fp muestran una correlaci贸n de tipo inversa mediante una ecuaci贸n del tipo logar铆tmico potencial, Ln(1/fp)=1.90*(Ln(1/F))-0.68, que puede ser utilizada para todo el rango de F, en lugar de la ecuaci贸n del tipo potencial sugerida por diversos autores, que s贸lo se ajusta correctamente para un reducido rango de F.Los resultados de campo y de laboratorio obtenidos se han introducido en dos modelos dosim茅tricos del tracto respiratorio de manera a evaluar su riesgo radiol贸gico. Estos resultados muestran que no existe un factor de dosis por unidad de exposici贸n de rad贸n constante sino que para una precisa estimaci贸n de dicha dosis es necesario la medida de los descendientes del rad贸n. La mejor estimaci贸n que se ha obtenido con los modelos dosim茅tricos, suponiendo como valor m谩s probable del factor de equilibrio de 0.4, es de 10 nSv por Bq m-3 h que difiere en un factor 3 respecto a los resultados epidemiol贸gicos tal como ya se recog铆a en otros trabajos anteriores.The knowledge of a relationship between the probability of develop a lung cancer and the exposure to radon and radon progeny in the air has been established years ago in the miner population. From this date different studies have been developed in order to determine the radiological risk per unit exposure. Nowadays, two different ways are used for its evaluation: a) epidemiologic studies and b) the use of dosimetric models of the respiratory tract. The use of these ways shows a difference of a factor 2 -3. In the use of dosimetric models, the uncertainties arise from four origins: a) physico-chemical aerosol properties, b) parameters used in the dosimetric model, c) hypothesis in the irradiated cells and d) weighted factors used in dosimetry.The aim of this research is the evaluation of different parameters that characterise indoors short-lived radon progeny in order to analyse its physico-chemical behaviour and therefore, improve the estimation in the radiological risk evaluation using respiratory tract dosimetric models.In order to achieve this objective different systems have been developed for determining the equilibrium factor, the unattached fraction and the unattached activity size distribution. Regarding the two first parameters a portable monitor has been developed in order to measure high accuracy field measurements. A new system based in the tube diffusion technology has been developed for measuring continuously the unattached activity size distribution. Intercomparison with the aerosol group of Brest in a radon-walk-chamber developed in this work has been carried out. The most probable value for the unattached activity size distribution has been established in the range from 0.8 nm and 0.9 nm.Continuous measurements of F and fp have been carried out in four dwelling of the Mediterranean Catalan Coast. It has been established that these parameters vary widely, F(0.03-0.87) and fp (0-0.72), from one site to another and with time, according to the characteristics of the site and climate. The measurements of F and fp show that fp is negatively correlated to F by a log-power equation, Ln(1/fp)=1.90*(Ln(1/F))-0.68 , which can be used in all the F range, instead of the commonly used power equation fp=a*Fb suggested other authors, which fits well for a reduced range of F.Both, laboratory and field measurements have been introduced in two dosimetric models in order to evaluate the radiological risk. The results show that there is variability in the risk estimation per unit exposure depending on the environmental conditions and therefore, an accurate estimation of radon progeny activity concentration should be measured. The best estimation, for an equilibrium factor of 0.4, is 10 nSv per Bq m-3 h, which still differs by a factor of 3 from the epidemiological estimation

    Contribuci贸n a la caracterizaci贸n de aerosoles radiactivos derivados del rad贸n

    Get PDF
    La existencia de una relaci贸n entre el riesgo a desarrollar un c谩ncer de pulm贸n y la exposici贸n al rad贸n y descendientes presentes en el aire se puso de manifiesto hace ya bastante tiempo en la poblaci贸n minera. Desde aquellas fechas se han desarrollado numerosos estudios encaminados a determinar el riesgo radiol贸gico por unidad de exposici贸n. En la actualidad, se pueden distinguir dos grandes v铆as para su evaluaci贸n: a) los estudios epidemol贸gicos, y b) la utilizaci贸n de modelos dosim茅tricos del sistema respiratorio. La utilizaci贸n de dichas v铆as en la evaluaci贸n del riesgo radiol贸gico por unidad de exposici贸n en la poblaci贸n minera muestran factores de riesgo que se diferencian en un factor de 2 a 3. En la utilizaci贸n de los modelos dosim茅tricos del sistema respiratorio, las incertidumbres que se introducen se pueden atribuir a cuatro or铆genes: a) caracter铆sticas fisico-qu铆micas del aerosol, b) par谩metros utilizados para describir el modelo dosim茅trico, c) hip贸tesis utilizadas en las c茅lulas irradiadas, y d) factores de ponderaci贸n utilizados en dosimetr铆a.La finalidad de este trabajo de investigaci贸n ha sido la determinaci贸n de par谩metros que caracterizan a los descendientes del rad贸n de vida corta en recintos cerrados para analizar en primer lugar su comportamiento f铆sico-qu铆mico y as铆 mejorar la estimaci贸n del riesgo radiol贸gico debido a su inhalaci贸n mediante la utilizaci贸n de modelos dosim茅tricos del tracto respiratorio. Para alcanzar este fin se han puesto a punto diversas t茅cnicas que permiten analizar, tanto en una instalaci贸n de laboratorio como en espacios habitados, el factor de equilibrio, la fracci贸n libre y el espectro dimensional de descendientes del rad贸n en estado libre. En referencia a los dos primeros par谩metros se ha desarrollado un equipo port谩til que permite realizar medidas de campo con una gran precisi贸n. En cuanto al sistema de medida del espectro dimensional de los descendientes del rad贸n en estado libre se ha realizado el dise帽o y construcci贸n de un nuevo sistema basado en las t茅cnicas de tubos de difusi贸n, que presenta un gran n煤mero de mejoras respecto a otros prototipos. Con este sistema se ha establecido, en una intercomparaci贸n realizada en la c谩mara de rad贸n, construida para este estudio, que el tama帽o m谩s probable del espectro dimensional de los descendientes en estado libre est谩 comprendido entre 0.8 nm y 0.9 nm. Con el sistema de media del factor de equilibrio y la fracci贸n libre se han llevado a cabo medidas experimentales de campo en cuatro lugares de la costa catalana. Se estableci贸 que dicho par谩metros var铆an de forma significativa, (0.03) y fp (0-0.72), en los distintos emplazamientos de acuerdo con sus caracter铆sticas del lugar y su clima. que Las medidas de F y fp muestran una correlaci贸n de tipo inversa mediante una ecuaci贸n del tipo logar铆tmico potencial, Ln(1/fp)=1.90*(Ln(1/F))-0.68, que puede ser utilizada para todo el rango de F, en lugar de la ecuaci贸n del tipo potencial sugerida por diversos autores, que s贸lo se ajusta correctamente para un reducido rango de F.Los resultados de campo y de laboratorio obtenidos se han introducido en dos modelos dosim茅tricos del tracto respiratorio de manera a evaluar su riesgo radiol贸gico. Estos resultados muestran que no existe un factor de dosis por unidad de exposici贸n de rad贸n constante sino que para una precisa estimaci贸n de dicha dosis es necesario la medida de los descendientes del rad贸n. La mejor estimaci贸n que se ha obtenido con los modelos dosim茅tricos, suponiendo como valor m谩s probable del factor de equilibrio de 0.4, es de 10 nSv por Bq m-3 h que difiere en un factor 3 respecto a los resultados epidemiol贸gicos tal como ya se recog铆a en otros trabajos anteriores.The knowledge of a relationship between the probability of develop a lung cancer and the exposure to radon and radon progeny in the air has been established years ago in the miner population. From this date different studies have been developed in order to determine the radiological risk per unit exposure. Nowadays, two different ways are used for its evaluation: a) epidemiologic studies and b) the use of dosimetric models of the respiratory tract. The use of these ways shows a difference of a factor 2 -3. In the use of dosimetric models, the uncertainties arise from four origins: a) physico-chemical aerosol properties, b) parameters used in the dosimetric model, c) hypothesis in the irradiated cells and d) weighted factors used in dosimetry.The aim of this research is the evaluation of different parameters that characterise indoors short-lived radon progeny in order to analyse its physico-chemical behaviour and therefore, improve the estimation in the radiological risk evaluation using respiratory tract dosimetric models.In order to achieve this objective different systems have been developed for determining the equilibrium factor, the unattached fraction and the unattached activity size distribution. Regarding the two first parameters a portable monitor has been developed in order to measure high accuracy field measurements. A new system based in the tube diffusion technology has been developed for measuring continuously the unattached activity size distribution. Intercomparison with the aerosol group of Brest in a radon-walk-chamber developed in this work has been carried out. The most probable value for the unattached activity size distribution has been established in the range from 0.8 nm and 0.9 nm.Continuous measurements of F and fp have been carried out in four dwelling of the Mediterranean Catalan Coast. It has been established that these parameters vary widely, F(0.03-0.87) and fp (0-0.72), from one site to another and with time, according to the characteristics of the site and climate. The measurements of F and fp show that fp is negatively correlated to F by a log-power equation, Ln(1/fp)=1.90*(Ln(1/F))-0.68 , which can be used in all the F range, instead of the commonly used power equation fp=a*Fb suggested other authors, which fits well for a reduced range of F.Both, laboratory and field measurements have been introduced in two dosimetric models in order to evaluate the radiological risk. The results show that there is variability in the risk estimation per unit exposure depending on the environmental conditions and therefore, an accurate estimation of radon progeny activity concentration should be measured. The best estimation, for an equilibrium factor of 0.4, is 10 nSv per Bq m-3 h, which still differs by a factor of 3 from the epidemiological estimation.Postprint (published version

    Comparison of methods for H*(10) calculation from measured LaBr3(Ce) detector spectra

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    The Universitat Politecnica de Catalunya (UPC) and the Centro de Investigaciones Energ茅ticas, Medioambientales y Tecnol贸gicas (CIEMAT) have evaluated methods based on stripping, conversion coefficients and Maximum Likelihood Estimation using Expectation Maximization (ML-EM) in calculating the H*(10) rates from photon pulse-height spectra acquired with a spectrometric LaBr3(Ce)(1.5驴 脳 1.5驴) detector. There is a good agreement between results of the different H*(10) rate calculation methods using the spectra measured at the UPC secondary standard calibration laboratory in Barcelona. From the outdoor study at ESMERALDA station in Madrid, it can be concluded that the analysed methods provide results quite similar to those obtained with the reference RSS ionization chamber. In addition, the spectrometric detectors can also facilitate radionuclide identification.Postprint (author's final draft

    Dose calculations in aircrafts after Fukushima nuclear power plant accident 鈥 Preliminary study for aviation operations

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    There is little information to decision support in air traffic management in case of nuclear releases into the atmosphere. In this paper, the dose estimation due to both, external exposure (i.e. cloud immersion, deposition inside and outside the aircraft), and due to internal exposure (i.e, inhalation of radionuclides inside the aircraft) to passengers and crew is calculated for a worst-case emergency scenario. The doses are calculated for different radionuclides and activities. Calculations are mainly considered according to International Commission on Radiological Protection (ICRP) recommendations and Monte Carlo simulations. In addition, a discussion on potential detectors installed inside the aircraft for monitoring the aerosol concentration and the ambient dose equivalent rate, H*(10), for during-flight monitoring and early warning is provided together with the evaluation of a response of a generic detector. The results show that the probability that a catastrophic nuclear accident would produce significant radiological doses to the passengers and crew of an aircraft is very low. In the worst-case scenarios studied, the maximum estimated effective dose was about 1驴mSv during take-off or landing operations, which is the recommended yearly threshold for the public. However, in order to follow the ALARA (As Low As Reasonably Achievable) criteria and to avoid aircraft contamination, the installation of radiological detectors is considered. This would, on one hand help the pilot or corresponding decision maker to decide about the potential change of the route and, on the other, allow for gathering of 4D data for future studiesPostprint (published version

    Intercomparison study of atmospheric 222Rn and 222Rn progeny monitors

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    The use of the noble gas radon (222Rn) as a tracer for different research studies, for example observation-based estimation of greenhouse gas (GHG) fluxes, has led to the need of high-quality 222Rn activity concentration observations with high spatial and temporal resolution. So far a robust metrology chain for these measurements is not yet available. A portable direct atmospheric radon monitor (ARMON), based on electrostatic collection of 218Po, is now running at Spanish stations. This monitor has not yet been compared with other 222Rn and 222Rn progeny monitors commonly used at atmospheric stations. A 3-month intercomparison campaign of atmospheric 222Rn and 222Rn progeny monitors based on different measurement techniques was realized during the fall and winter of 2016鈥2017 to evaluate (i) calibration and correction factors between monitors necessary to harmonize the atmospheric radon observations and (ii) the dependence of each monitor's response in relation to the sampling height and meteorological and atmospheric aerosol conditions. Results of this study have shown the following. (i) All monitors were able to reproduce the atmospheric radon variability on a daily basis. (ii) Linear regression fits between the monitors exhibited slopes, representing the correction factors, between 0.62 and 1.17 and offsets ranging between -0.85 and -0.23驴Bq驴m-3 when sampling 2驴m above ground level (a.g.l.). Corresponding results at 100驴m驴a.g.l. exhibited slopes of 0.94 and 1.03 with offsets of -0.13 and 0.01驴Bq驴m-3, respectively. (iii) No influence of atmospheric temperature and relative humidity on monitor responses was observed for unsaturated conditions at 100驴m驴a.g.l., whereas slight influences (order of 10-2) of ambient temperature were observed at 2驴m驴a.g.l. (iv) Changes in the ratio between 222Rn progeny and 222Rn monitor responses were observed under very low atmospheric aerosol concentrations. Results also show that the new ARMON could be useful at atmospheric radon monitoring stations with space restrictions or as a mobile reference instrument to calibrate in situ 222Rn progeny monitors and fixed radon monitors. In the near future a long-term comparison study between ARMON, HRM, and ANSTO monitors would be useful to better evaluate (i) the uncertainties of radon measurements in the range of a few hundred millibecquerels per cubic meter to a few becquerels per cubic meter and (ii) the response time correction of the ANSTO monitor for representing fast changes in the ambient radon concentrations.Postprint (published version

    Variability of methane fluxes at the Ebro Delta due to rice field: comparison between inventories and Radon Tracer Method based results.

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    The Ebro River Delta, in the northwestern Mediterranean basin, has an extension of 320 km2 and is mainly covered by rice fields. Rice fields are known to be one of the main sources of anthropogenic methane emissions, and a better estimation of its temporal variability in relation to the different rice cultivation phases is important to help with the implementation of emission reduction strategies (脌gueda et al., 2017), In the framework of the ClimaDat network, an atmospheric station was installed in the middle of the Ebro Delta in 2012. A Picarro G2301 for greenhouse gases (GHG) atmospheric concentrations and an ARMON (Atmospheric Radon Monitor) for atmospheric 222Rn concentrations were collocated among other instruments. Nocturnal hourly atmospheric observations of CH4 and 222Rn measured between 2013 and 2019 were used to apply the Radon Tracer Method (RTM) for retrieving CH4 fluxes over the footprint area. The Ebro River Delta has a reduced dimension and a complex meteorological regime highly influenced by the Ebro channelled winds and the sea breezes, making it difficult to calculate GHG fluxes using global or regional inversion models. However, the use of high-resolution backtrajectories (model WRF-Flexpart) coupled with the traceRadon daily radon flux maps for Europe (Karsten et al., 2022), with a resolution of 0.05 degrees, has allowed the use of the RTM in this complex area. Methane fluxes estimated by RTM were compared with fluxes directly measured with chambers in past studies (Mart铆nez-Eixarch et al., 2018) and with data obtained by the EDGAR inventory (Crippa et al., 2022). Results show a promising agreement between methane fluxes obtained with different methods, and a variability clearly governed by the rice crop cycle which is not reflected in the methane emissions values reported in EDGAR inventories.Peer ReviewedPostprint (published version

    Metrology for low-cost CO2 sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO2 fluxes observations

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    Soil CO2 emissions are one of the largest contributions to the global carbon cycle, and a full understanding of processes generating them and how climate change may modify them is needed and still uncertain. Thus, a dense spatial and temporal network of CO2 flux measurements from soil could help reduce uncertainty in the global carbon budgets. In the present study, the design, assembly, and calibration of low-cost air enquirer kits, including CO2 and environmental parameters sensors, is presented. Different types of calibrations for the CO2 sensors and their associated errors are calculated. In addition, for the first time, this type of sensor has been applied to design, develop, and test a new steady-state through-flow (SS-TF) chamber for simultaneous measurements of CO2 fluxes in soil and CO2 concentrations in air. The sensors鈥 responses were corrected for temperature, relative humidity, and pressure conditions in order to reduce the uncertainty in the measured CO2 values and of the following calculated CO2 fluxes based on SS-TF. CO2 soil fluxes measured by the proposed SS-TF and by a standard closed non-steady-state non-through-flow (NSS-NTF) chamber were briefly compared to ensure the reliability of the results. The use of a multiparametric fitting reduced the total uncertainty of the CO2 concentration measurements by 62 %, compared with the uncertainty that occurred when a simple CO2 calibration was applied, and by 90 %, when compared to the uncertainty declared by the manufacturer. The new SSTF system allows the continuous measurement of CO2 fluxes and CO2 ambient air with low cost (EUR ~ 1200), low energy demand (< 5 W), and low maintenance (twice per year due to sensor calibration requirements).Peer ReviewedPostprint (published version

    An unmanned aircraft system to detect a radiological point source using RIMA software architecture

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    Unmanned Aircraft Systems (UASs), together with the miniaturisation of computers, sensors, and electronics, offer new remote sensing applications. However, there is a lack of hardware and software support to effectively develop the potential of UASs in different remote sensing applications, such as the detection of radioactive sources. This paper presents the design, development and validation of a UAS for the detection of an uncontrolled and point radioactive source. The article describes a flexible and reusable software architecture for detecting the radioactive source (NaTcO 4 , containing 99m Tc) with a gamma-ray Cadmium Zinc Telluride (CZT) spectrometer as a proof of concept. The UAS is equipped with multichannel air-ground communications to perform missions beyond line of sight and onboard computation to process samples in real time and thus react to any anomaly detected during the mission. An ad hoc ground control station (GCS) has also been developed for the correct interpretation of the radioactive samples taken by the UAS. Radiological spectra plots, contour mapping and waterfall plots are some of the elements used in the ad hoc GCS. The article shows the results obtained in a flight campaign performing different flights at different altitudes and speeds over the radiological source, demonstrating the viability of the system.Peer ReviewedPostprint (published version

    REFLECT 鈥 Research flight of EURADOS and CRREAT: Intercomparison of various radiation dosimeters onboard aircraft

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    Aircraft crew are one of the groups of radiation workers which receive the highest annual exposure to ionizing radiation. Validation of computer codes used routinely for calculation of the exposure due to cosmic radiation and the observation of nonpredictable changes in the level of the exposure due to solar energetic particles, requires continuous measurements onboard aircraft. Appropriate calibration of suitable instruments is crucial, however, for the very complex atmospheric radiation field there is no single reference field covering all particles and energies involved. Further intercomparisons of measurements of different instruments under real flight conditions are therefore indispensable. In November 2017, the REFLECT (REsearch FLight of EURADOS and CRREAT) was carried out. With a payload comprising more than 20 different instruments, REFLECT represents the largest campaign of this type ever performed. The instruments flown included those already proven for routine dosimetry onboard aircraft such as the Liulin Si-diode spectrometer and tissue equivalent proportional counters, as well as newly developed detectors and instruments with the potential to be used for onboard aircraft measurements in the future. This flight enabled acquisition of dosimetric data under well-defined conditions onboard aircraft and comparison of new instruments with those routinely used. As expected, dosimeters routinely used for onboard aircraft dosimetry and for verification of calculated doses such as a tissue equivalent proportional counter or a silicon detector device like Liulin agreed reasonable with each other as well as with model calculations. Conventional neutron rem counters underestimated neutron ambient dose equivalent, while extended-range neutron rem counters provided results comparable to routinely used instruments. Although the responses of some instruments, not primarily intended for the use in a very complex mixed radiation field such as onboard aircraft, were as somehow expected to be different, the verification of their suitability was one of the objectives of the REFLECT. This campaign comprised a single short flight. For further testing of instruments, additional flights as well as comparison at appropriate reference fields are envisaged. The REFLECT provided valuable experience and feedback for validation of calculated aviation doses.Postprint (published version
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