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Characterisation of the neutron sources in use at STUK SSDL through a new transfer instrument with spectrometric capabilities
Get PDFCharacterising neutron sources for calibration or generic testing purposes is a complex task, as the neutron spectrum may depend, to some extent, on the construction characteristics of the source. Bonner spheres (BS) are the traditional spectrometric transfer instruments, but they are very sensitive to room scatter and required measurements are highly time consuming. The recently developed NCT-WES device, belonging to the family of the Single Moderator Neutron Spectrometers, has been proposed as a convenient alternative to BS. This work presents the results of a demonstration campaign organised at the STUK neutron metrology laboratory (Finland) in July 2023, where the spectra from two 252Cf and two 241Am-Be sources were determined. For the 241Am-Be sources, the results were compared to the spectra of two categories recently introduced by ISO 8529-1. Based on the results it was concluded that the “large” source category is an appropriate selection for STUK sources. The campaign also proved the operational advantages of NCT-WES as spectrometric transfer instrument
Measurement of the prompt fission -rays from slow neutron-induced fission of U with STEFF
No full textThe average energy and multiplicity of prompt γ-rays from slow neutron-induced fission of 235U have been measured using the STEFF spectrometer at the neutron time-of-flight facility n_TOF. The individual responses from 11 NaI scintillators were corrected for multiple γ-ray interactions, prompt fission neutrons and background counts before being deconvolved to estimate the emitted spectrum of prompt fission γ-rays. The results give an average γ-ray energy E ̄γ of 1.71(5) MeV and multiplicity ν ̄γ of 2.66(18) considering γ-rays emitted within the energy range 0.8–6.8 MeV. The n_TOF data has a slightly larger E ̄γ and smaller ν ̄γ than other recent measurements, however the product of the two is in agreement within quoted uncertainties
Study of impurity behavior in JET-ILW hybrid scenario with deuterium, tritium, and deuterium-tritium plasmas
Get PDFExperimental campaigns at the Joint European Torus with an ITER-like Be/W wall with pure deuterium (D), tritium (T), and deuterium-tritium (DT) were a unique opportunity to explore various aspects related to the ITER operation. One of the most important challenges in recent years was the development of the hybrid scenario for D-T, based on reference deuterium and tritium plasmas. This kind of scenario, one of the foreseen for ITER, is characterized by a low current plasma and a high normalized beta βN factor compared to the parallel optimized baseline scenario [Hobirk et al., Plasma Phys. Controlled Fusion 54, 095001 (2012)]. As the experiments have shown, controlling the plasma edge in the different phases of the hybrid scenario becomes more difficult with higher isotope mass, and therefore, are also in risk of impurity accumulation [Hobirk et al., Nucl. Fusion 63, 112001 (2023)]. For this reason, investigation of the impurity behavior, as well as their control, constituted the crucial issue. The present contribution aims to compare mid-Z and high-Z impurities behavior within H-mode hybrid discharges in D and T plasmas, as well as D and DT plasmas. Detailed analysis shows that in the H-mode regime in the hybrid scenario, higher impurity radiation is observed for DT in comparison to D plasmas, as well as for T compared to D plasmas. Additionally, it was noticed that the most significant contribution to the plasma radiated power comes from W and to a lesser extent from Ni (∼10%). Moreover, it was found that an earlier transition from small edge localized modes (ELMs) to ELM-free phase can result in the earlier increase in impurities
Assessment of Particulate Matter (PM2.5) and Air Quality Index (AQI) in Eight Locations of Lagos State, Nigeria
No full textAir pollution, particularly fine particulate matter (PM2.5), poses a significant threat to public health, especially in rapidly urbanizing areas like Lagos State. Despite the severity of the issue, there is a lack of comprehensive data on PM2.5 levels and the Air Quality Index (AQI) in Lagos. This study leverages data from AirQo, an innovative air quality monitoring network using low-cost sensors, to provide a detailed assessment of PM2.5 concentrations and AQI across eight locations in Lagos State, Nigeria. This approach offers real-time, continuous monitoring, filling a critical data gap in the region's air quality management efforts. This study uses AirQo data to assess the concentration levels and spatial distribution of PM2.5 and AQI across the selected eight locations. Data on PM2.5 concentrations were obtained from AirQo sensors deployed across the eight strategic locations in Lagos. The spatial distribution of PM2.5 levels and AQI were analyzed, and the results were compared with national and international air quality standards. The findings revealed that PM2.5 levels (minimum – 6.28 μg/m3 (Ikeja) and maximum - 204.68 μg/m3 (Banana Island) in many areas of Lagos exceed annual WHO and national air quality guidelines, indicating significant health risks. The spatial analysis identified pollution hotspots, particularly in densely populated and industrial regions. The data suggested vehicular emissions and industrial activities as major contributors to high PM2.5 levels. This study underscores the severe air quality issues in Lagos State, emphasizing the need for immediate and targeted interventions to mitigate PM2.5 pollution. The use of AirQo sensors proved effective in providing accurate and timely data for air quality assessment. It is recommended that Lagos State implements stricter emission controls, promotes cleaner technologies, and enhances
Environmental and economic assessment of industrial excess heat recovery collaborations through 4th generation district heating systems
Get PDFThe external use of excess heat from industrial processes is an important factor in the energy transition and 4th generation district heating is an enabling technology. This paper presents a calculation tool for assessing the economic feasibility and the environmental impact of collaborations between potential industrial sources and users. The tool supports the sizing of district heating pipe diameters, pumps, heat pumps, and heat storage systems. A distinctive feature of the model is the possibility of calculating carbon and blue water footprints, alongside economic indicators, for both existing stand-alone systems and potential collaborative configurations. Excess heat recovery from water-cooled condensers of refrigeration systems is evaluated for two case studies involving the space heating of offices in a food logistics hub and the heating of a greenhouse from a frozen pizza factory, respectively. Only the second collaboration is profitable with the baseline price of natural gas (0.04 €/kWh) and electricity (0.12 €/kWh), provided that the distance between the source and the user is less than 2 km. For higher gas prices, distances of approximately 8 km would be viable. However, for source-user distances above 5 km, the water footprint of the collaboration would be higher than that of stand-alone systems
Study of Cathode Materials for Na-Ion Batteries: Comparison Between Machine Learning Predictions and Density Functional Theory Calculations
Get PDFEnergy storage technologies have experienced significant advancements in recent decades, driven by the growing demand for efficient and sustainable energy solutions. The limitations associated with lithium’s supply chain, cost, and safety concerns have prompted the exploration of alternative battery chemistries. For this reason, research to replace widespread lithium batteries with sodium-ion batteries has received more and more attention. In the present work, we report cutting-edge research, where we explored a wide range of compositions of cathode materials for Na-ion batteries by first-principles calculations using workflow chains developed within the AiiDA framework. We trained crystal graph convolutional neural networks and geometric crystal graph neural networks, and we demonstrate the ability of the machine learning algorithms to predict the formation energy of the candidate materials as calculated by the density functional theory. This materials discovery approach is disruptive and significantly faster than traditional physics-based computational methods
Photoproduction of K+K- Pairs in Ultraperipheral Collisions
No full textK+K- pairs may be produced in photonuclear collisions, either from the decays of photoproduced φ(1020) mesons or directly as nonresonant K+K- pairs. Measurements of K+K- photoproduction probe the couplings between the φ(1020) and charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction of K+K- pairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of direct K+K- production. There is significant K+K- production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1<MKK<1.4 GeV/c2 above the φ(1020) resonance, for rapidity |yKK|<0.8 and pT,KK<0.1 GeV/c, the measured coherent photoproduction cross section is dσ/dy=3.37±0.61(stat)±0.15(syst) mb. The center-of-mass energy per nucleon of the photon-nucleus (Pb) system WγPb,n ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for φ(1020) photoproduction alone. The mass spectrum is fit to a cocktail consisting of φ(1020) decays, direct K+K- photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct K+K- photoproduction are presented
Indagine geomagnetica e metrologica in Antartide con la bussola solare elettro-ottica brevettata da ENEA
Get PDFUna bussola solare elettro-ottica di elevata precisione, progettata e sviluppata presso il Centro Ricerche ENEA di Frascati, è stata usata per misure di orientamento presso l'Osservatorio polare della Stazione Concordia, in Antartide. La bussola solare (brevetto ENEA) è compatta, automatica, e for-nisce una risposta in pochi secondi. È in grado di misurare la direzione geografica del Polo Nord con una deviazione standard di 0,01 gradi. Le sue prestazioni sono paragonabili a quelle dei costosi si-stemi GPS e giroscopi, senza gli inconvenienti di lunghi tempi di misura, dipendenza del risultato dalla latitudine, e costi elevati. La bussola ENEA è stata usata durante la campagna antartica estiva del dicembre 2017 condotta dall'INGV, allo scopo di misurare la presunta deriva della banchisa antartica su cui si trova la base Concordia, che era stata evidenziata da diverse misurazioni tramite GPS differenziale. I risultati delle misure con la bussola solare ENEA mostrano che tale deriva non c’è stata. Questo falso allarme ha permesso di capire che alle latitudini elevate i risultati delle misure di orientamento effettuate con la bussola solare sono molto più affidabili di quelli ottenuti con i sen-sori GPS
Holistic Assessment for Social Housing Retrofitting: Integrating Seismic, Energy, and Social Aspects in the REHOUSE Project
Get PDFThere are many existing buildings for which seismic rehabilitation interventions are required, especially in earthquake-prone areas like Italy. At the same time, the huge energy cost increase in Europe highlights the need for sustainable techniques that are able to increase the energy efficiency of buildings. These issues are even more significant for weak social groups living in social housing buildings, often in poor and vulnerable conditions. In order to address the solution regarding building renovations from the social, structural, and energy efficiency perspectives, in the framework of the Horizon Europe REHOUSE (Renovation packagEs for HOlistic improvement of EU’s bUildingS Efficiency, maximizing RES generation and cost-effectiveness) Project, this paper proposes an integrated methodology of building assessment that was tested on a social housing building in Margherita di Savoia, a small town of Apulia Region, Italy. In addition to the structural and energy aspects, the social one is particularly important since the building is located in the “Capitanata Area”, considered to be one of the most socially vulnerable areas in Italy. For this reason, an assessment methodology must consider reducing the overall impact of the assessment activities while explaining to tenants the purpose of the assessment and future renovation actions, maintaining the accuracy of the assessment results. Therefore, this study outlines an assessment methodology, demonstrated through its application to the case study building, that integrates the structural, energy, and social aspects, showing that the tenants’ involvement is also crucial for the technical evaluations. The final result is a low-impact approach for the building knowledge gathering needed to start a deep renovation intervention in social housing
Observation of alpha-particles in recent D-T experiments on JET
Get PDFThe fusion reaction between deuterium and tritium, D(T,n)4 He is the main source of energy in future thermonuclear reactors. Alpha-particles (4 He-ions) born with an average energy of 3.5 MeV transferring energy to the thermal plasma during their slowing down, should provide the self-sustained D-T plasma burn. The adequate confinement of α-particles is essential to provide efficient heating of the bulk plasma and steady burning of a reactor plasma. That is why the fusion-born α-particle studies have been a priority task in the second D-T experiments (DTE2) on the Joint European Torus (JET) to understand the main mechanisms of their slowing down, redistribution and losses and to develop optimal plasma scenarios. JET with Be-wall and W-divertor, enhanced auxiliary heating systems and improved energetic-particle diagnostic capabilities, producing significant population of α-particles, provided the possibility for comprehensive studying of the α-particle behaviour. Selected results of the confined and lost α-particle measurements, evidence of α-particle self-heating and assessments of the fusion performance are presented in this paper giving an opportunity for further modelling and extrapolation to the International Thermonuclear Experimental Reactor and burning plasma reactors