Neutron spectra from Neutron Standards Laboratory (LPN/CIEMAT) sources with two Bonner sphere spectrometers

The Neutron Standards Laboratory (LPN: Laboratorio de Patrones Neutrónicos) of the Ionizing Radiation Metrology Laboratory (LMRI) of the CIEMAT (Centro de Investigaciones Energéticas Medioambientales y Tecnológicas) has two calibration neutron sources, 241Am-Be and 252Cf. Studies to verify the shielding of the facility and to characterize the neutron field in the irradiation room have been carried out using Monte Carlo methods. However, spectral measurements were not performed yet. In this study, we measured the total and direct neutron spectra of both calibration neutron sources. Two different Bonner Sphere Spectrometers (BSS) systems were allocated to 115 cm from the sources, on the calibration bench, with and without the shadow cones (SC). From the count rates obtained with both BSS systems (BSS-6LiI and BSS-3He), the total neutron spectrum and direct neutron spectrum were unfolded. Total and direct spectra obtained for the 241Am-Be and 252Cf sources with the MCNPX and different BSS systems, unfold codes and response matrices presented similar shape and are consistent with each other

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND: Disorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021. METHODS: We estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined. FINDINGS: Globally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer. INTERPRETATION: As the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Análisis Monte Carlo del Laboratorio de Patrones Neutrónicos del CIEMAT

Mediante métodos Monte Carlo se ha caracterizado el campo de neutrones producido por fuentes de calibración en el laboratorio de Patrones Neutrónicos del Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas. El laboratorio cuenta con dos fuentes de calibración de neutrones: 241AmBe y 252Cf que son almacenadas en una piscina de agua y se colocan sobre la bancada de calibración usando sistemas controlados a distancia. Para caracterizar el campo de neutrones se construyó un modelo tridimensional de la sala donde se incluyó la bancada de acero inoxidable, la mesa de irradiación y la piscina de almacenamiento. El modelo de las fuentes incluyó el doble encapsulado de acero, como encamisado. Con el fin de determinar el efecto que produce la presencia de los diferentes componentes de la sala, durante la caracterización se estimaron los espectros de neutrones, el flujo total y la rapidez de dosis equivalente ambiental a 100 cm de la fuente. La presencia de los muros, suelo y techo de la sala es la que causa la mayor modificación en los espectros y los valores integrales del flujo y la rapidez de dosis equivalente ambiental

Neutron field characteristics of Ciemat´s Neutron Standards Laboratoy

Monte Carlo calcultarions were carried out to characterized the neutron field produced by the calibration neutron sources of the Neutron Standards Laboratory at the Research Center for Energy, Environment and Technology (CIEMAT) in Spain. For 241 AmBe and 252 Cf neutron sources, the neutron spectra, the ambien dose equivalent rates and the total neutron fluence were estimated. In the calibration hall, there are everal itmes that modify the neutron field. To evaluate their effects different cases were used, front point-like source in vacuum upto the full model. Additionally, using the full model, the neutron spectra were estimated to different distances along the bench; with these spectra, the total neutron fluence and the ambient dose equivalent rates were calculated. The hall walls induce tha largest changes in the neutron spectra and the respective integral quantities. The free-field neutron spectrum is modified due the room return effect

Laboratorio de patrones neutrónicos del CIEMAT

Mediante una serie de cálculos con métodos Monte Carlo con el código MCNPX se ha caracterizado el campo de neutrones producido por las fuentes de calibración existentes en el laboratorio de Patrones Neutrónicos, LPN, del Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT. El laboratorio cuenta con dos fuentes de calibración de neutrones una de 241AmBe y una 252Cf que son almacenadas en una piscina de agua. Se construyó un modelo tridimensional detallado de la sala con la bancada de acero inoxidable puntualizando en el seleccionador de las fuentes que las coloca en su posición de irradiar a 4 m del suelo, en la mesa de irradiación y la piscina de almacenamiento. Cada una de las fuentes se definió en el modelo en su doble encapsulado de acero. Se calcularon los espectros con distintos casos con el fin de calcular la aportación de cada elemento que impacta al transporte de los neutrones. Se calcularon los espectros de las fuentes de calibración a diferentes distancias colocadas respecto a la fuente desde 0, 15, 35, 50 a 300 cm sobre la bancada y de igual manera los valores de la dosis equivalente ambiental utilizando los criterios del ICRP 74. Los resultados muestran claramente que la mayor contribución en la modificación del espectro se le atribuye a las paredes, y suelo del recinto del LPN

Estudio de un detector de neutrones de centelleo de 10B+ZnS(Ag) como alternativa a los detectores de 3He: Modelo MCNPX y validación

Mediante métodos Monte Carlo con el código MCNPX, se ha estimado la respuesta de un detector de neutrones de centelleo de ZnS(Ag) con un mezcla de 10B de alto enriquecimiento. El detector consiste en cuatro placas de polimetil metacrilato (PMMA) y cinco capas de ~0,017 cm 10B+ZnS(Ag) en contacto con el PMMA. Se calculó la respuesta del detector desnudo y con distintos espesores de moderador de polietileno de alta densidad, PEAD, para 29 fuentes monoenergeticas y para las fuentes de 241AmBe y 252Cf de neutrones. En dichos cálculos se estimaron las reacciones 10B(n,α)7Li y la fluencia de neutrones en la zona sensible del detector, 10B+ZnS(Ag). Se realizaron medidas en el laboratorio de medias neutrónicas, LMN-UPM, para cuantificar las detecciones en cuentas por segundo ante una fuente de neutrones de 252Cf a 200cm sobre la bancada, modelando con MCNPX, dichas medidas se compararon validando el modelo y se estimó la eficiencia del ZnS(Ag) de detección α. Se realizaron cálculos en el LPN-CIEMAT. A partir de la validación se realizaron nuevos modelos con geometrías que mejoran la respuesta del detector tratando de alcanzar la detección de 2,5 cps-ng de 252Cf requisito para ser equiparable en respuesta a los equipos instalados de 3He en los Monitores de Radiación tipo Pórtico, “Radiation Portal Monitor, RPM’s”. Este tipo de detector se puede considerar alternativa a los detectores de 3He para la detección de “Special Nuclear Material, SNM”, Material Nuclear Especial

A 222 Energy Bins Response Matrix fora 6LiI Scintillator BSS system

A new response matrix was calculated for a Bonner Sphere Spectrometer (BSS) with a 6LiI(Eu) scintillator. We utilized the Monte Carlo N-Particle radiation transport code MCNPX, version 2.7.0, with ENDF/B-VII.0 nuclear data library to calculate the responses for 6 spheres and the bare detector, for energies varying from 9.441E(-10) MeV to 105.9 MeV, with 20 equal-log(E)-width bins per energy decade, totalizing 222 energy groups. A BSS, like the modeled in this work, was utilized to measure the neutron spectrum generated by the 241AmBe source of the Universidad Politécnica de Madrid (UPM). From the count rates obtained with this BSS system we unfolded neutron spectrum utilizing the BUNKIUT code for 31 energy bins (UTA4 response matrix) and the MAXED code with the new calculated response functions. We compared spectra obtained with these BSS system / unfold codes with that obtained from measurements performed with a BSS system constituted of 12 spheres with a spherical 3He SP9 counter (Centronic Ltd., UK) and MAXED code with the system-specific response functions (BSS-CIEMAT). A relatively good agreement was observed between our response matrix and that calculatedby other authors. In general, we observed an improvement in the agreement as the energy increases. However, higher discrepancies were observed for energies close to 1E(-8) MeV and, mainly, for energies above 20 MeV. These discrepancies were mainly attributed to the differences in cross-section libraries employed. The ambient dose equivalent (H*(10)) calculated with the 6LiI-MAXED showed a good agreement with values measured with the neutron area monitor Berthold LB 6411 and within 12% the value obtained with another BSS system (BSS-CIEMAT). The response matrix calculated in this work can be utilized together with the MAXED code to generate neutron spectra with a good energy resolution up to 20 MeV. Some additional tests are being done to validate this response matrix and improve the results for energies higher than 20 MeV

Espectrometría y Dosimetría Neutrónica con Redes Neuronales y Esferas Bonner: Un Estudio para Reducir el Número de Esferas

Para la espectrometría y dosimetría de neutrones el Sistema Espectrométrico de Esferas Bonner ha sido el sistema más usado, sin embargo, el número, tamaño y peso de las esferas que componen al sistema, la necesidad de utilizar un código de reconstrucción y los largos periodos de tiempo empleados para realizar las mediciones, son algunos de los inconvenientes que este sistema presenta. Para la reconstrucción de los espectros se han usado diferentes técnicas como las redes neuronales artificiales de propagación inversa. El objetivo de este trabajo fue reducir el número de esferas Bonner y usar las rapideces de conteo en una red neuronal de propagación inversa, optimizada por medio de la metodología de diseño robusto, para reconstruir los espectros de neutrones. Para el diseño de la red neuronal (RN) se usaron los espectros de neutrones del OIEA y la matriz de respuesta de las esferas Bonner con detector de 6 LiI(Eu). Se comparó el desempeño de la red usando 7 esferas Bonner que se comparó con el caso donde solo se usan 2 esferas y 1 esfera. Las topologías de red se entrenaron 36 veces para cada caso manteniendo constante el error objetivo (1E(-3)), el algoritmo de entrenamiento fue trainscg y la metodología de diseño robusto para determinar las mejores arquitecturas de red. Con éstas, se compararon los mejores y peores resultados. Se encontró que los resultados que se obtienen usando 7 esferas son semejantes a los obtenidos con la esfera de 5 in, sin embargo aún se encuentra en una etapa de análisis de información