Abstract: Although cities are an important source of aerosol particles, aerosol number flux measurements over urban areas are scarce. These measurements are however important as they can allow us to identify the different sources/sinks of aerosol particles and quantify their emission contributions. Therefore, they can help us to understand the aerosol impacts on human health and climate, and to design effective mitigation strategies through the reduction of urban aerosol emissions. In this work we analyze the aerosol number concentrations and fluxes for particles with diameters larger than 2.5 nm measured by eddy covariance technique at an urban area (Granada city, Spain) from November 2016 to April 2018. This is the first study of particle number flux in an urban area in the Iberian Peninsula and is one of the few current studies that report long-term aerosol number flux measurements. The results suggest that, on average, Granada urban area acted as a net source for atmospheric aerosol particles with median particle number flux of 150 × 106 m−2 s−1. Downward negative fluxes were observed in only 12% of the analyzed data, and most of them were observed during high aerosol load conditions. Both aerosol number fluxes and concentrations were maximum in winter and 50% larger than those measured in summer due to the increased emissions from domestic heating, burning of residual agricultural waste in the agricultural area surrounding the site, as well as to the lower aerosol dilution effects during winter. The analysis of the seasonal diurnal variability of the aerosol number concentration revealed the significant impact of traffic emissions on aerosol population over Granada urban area in all seasons. It also shows the impact of domestic heating and agricultural waste burning emissions in winter as well as the influence of new particle formation processes in summer and spring seasons. Closer analysis by wind sector demonstrated that both aerosol concentrations and fluxes from urban sector (where high density of anthropogenic sources is located) were lower than those from rural sector (which includes agricultural area but also the main highway of the city). This evidences the strong impact of aerosol emissions from traffic circulating on the highway on aerosol population over our measurement site.

Palavras-Chave: urban areas; aerosols; concentration ratio; atmospheres; particles; eddy currents; data covariances

CASQUERO-VERA, J.A.; LYAMANI, H.; TITOS, G.; MOREIRA, G. de A.; BENAVENT-OLTRA, J.A.; CONTE, M.; CONTINI, D.; JARVI, L.; OLMO-REYES, F.J.; ALADOS-ARBOLEDAS, L. Aerosol number fluxes and concentrations over a southern European urban area. Atmospheric Environment, v. 269, p. 1-10, 2022. DOI: 10.1016/j.atmosenv.2021.118849. Disponível em: http://repositorio.ipen.br/handle/123456789/32956. Acesso em: $DATA.

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Abstract: In this work the reproducibility of the efficiency of different HPGe detectors was analyzed under a series of different conditions. The detectors studied were plugged either to a regular analogical amplifier or to a digital signal processing (DSP) device, to evaluate the possible differences between either setup. Detectors were inspected by performing a long series of sequential measurements with standard calibration sources and comparing the standard deviation of the number of counts per second in each series to the uncertainty of the individual measurements. Detectors were also subjected to distinct count rates, to verify the possible experimental issues associated with this parameter. The results allow a discussion on the stability of the detectors’ efficiencies over a few days, the possible dependence with the count rate, and the estimation of the uncertainty related to the efficiency variation.

Palavras-Chave: calibration standards; comparative evaluations; counting ratemeters; data covariances; efficiency; high-purity ge detectors; stability

ZAHN, G.S.; GENEZINI, F.A. Efficiency stability of HPGe detectors under distinct count rates. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-8, 2021. DOI: 10.15392/bjrs.v9i1A.1410. Disponível em: http://repositorio.ipen.br/handle/123456789/32110. Acesso em: $DATA.

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Abstract: In IPEN’s Neutron Activation Laboratory (LAN/IPEN), thin stainless steel sample holders are used for gamma spec-trometry in NAA measurements. This material is very practical, but its chemical composition may be troublesome, as it presents large amounts of elements with intermediate atomic number, with attenuation factors for low-energy gamma-rays that must not be neglected. In this study, count rates obtained using different sample holders were compared. To accomplish that, an Am-241 source, with 59-keV gamma emission, was used so that low-energy gamma attenuation differences can be determined. Moreover, in order to study the energy dependence of these differences, a Ho-166m source was also used. From these results, it was possible to analyze the experimental error associated to the variations between sample holders, with the aim of introducing an addictive term to the uncertainty analysis of comparative Neu-tron Activation Analysis results.

Palavras-Chave: neutron activation analysis; stainless steels; americium 241; holmium 166; counting rates; sample holders; data covariances; gamma spectroscopy; comparative evaluations; energy dependence; brazilian cnen

ZAHN, G.S.; TICIANELLI, R.B.; SAIKI, M.; GENEZINI, F.A. Evaluation of the uncertainty associated with sample holders in NAA measurements in LAN/IPEN. Brazilian Journal of Radiation Sciences, v. 7, n. 2A, p. 1-8, 2019. DOI: 10.15392/bjrs.v7i2A.676. Disponível em: http://repositorio.ipen.br/handle/123456789/29984. Acesso em: $DATA.

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Abstract: This paper aims to propose an easy and fast method of optimization of the gamma-ray spectrometry counting time in determining natural radionuclides (210Pb, 212Pb, 214Pb, 212Bi, 214Bi and 228Ac) in order to minimize uncertainties in the concentration. The samples were measured by gamma-ray spectrometry with a hyper-pure germanium detector Canberra, 25% relative efficiency, effective resolution of 1.9 keV on the 1332.5 keV 60Co with associated electronics and coupled to a microcomputer. Multichannel Maestro A65-I model was used for spectrum acquisition and peak net area determination, and WinnerGamma/Interwinner 6.01 software was used for gamma-ray spectra analysis and to calculate the concentrations and associated uncertainties. The counting times used were 86,000 s and 150,000 s.

Palavras-Chave: actinium 228; bismuth 212; bismuth 214; cobalt 60; counting techniques; data covariances; gamma spectroscopy; high-purity ge detectors; lead 210; lead 212; lead 214; multi-channel analyzers; optimization

NISTI, M.B.; MADUAR, M.F.; SAUEIA, C.H.R.; CAVALCANTE, F.; MAZZILLI, B.P. Optimization of the gamma-ray spectrometry counting time based on uncertainties of radionuclides concentration in samples. Brazilian Journal of Radiation Sciences, v. 8, n. 2, p. 1-12, 2020. DOI: 10.15392/bjrs.v8i2.1197. Disponível em: http://repositorio.ipen.br/handle/123456789/31418. Acesso em: $DATA.

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Abstract: Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution to atmospheric chemistry and biogeochemical cycles. Tropical forests are the largest source of the dominant BVOC emissions (e.g. isoprene and monoterpenes). In this study, we report isoprene and total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using the eddy covariance (EC) method at the Tapajós National Forest (2.857∘ S, 54.959∘ W), a primary rainforest in eastern Amazonia. Measurements were carried out from 1 to 16 June 2014, during the wet-to-dry transition season. During the measurement period, the measured daytime (06:00–18:00 LT) average isoprene mixing ratios and fluxes were 1.15±0.60 ppb and 0.55±0.71 mg C m−2 h−1, respectively, whereas the measured daytime average total monoterpene mixing ratios and fluxes were 0.14±0.10 ppb and 0.20±0.25 mg C m−2 h−1, respectively. Midday (10:00–14:00 LT) average isoprene and total monoterpene mixing ratios were 1.70±0.49 and 0.24±0.05 ppb, respectively, whereas midday average isoprene and monoterpene fluxes were 1.24±0.68 and 0.46±0.22 mg C m−2 h−1, respectively. Isoprene and total monoterpene emissions in Tapajós were correlated with ambient temperature and solar radiation. Significant correlation with sensible heat flux, SHF (r2=0.77), was also observed. Measured isoprene and monoterpene fluxes were strongly correlated with each other (r2=0.93). The MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model could simulate most of the observed diurnal variations (r2=0.7 to 0.8) but declined a little later in the evening for both isoprene and total monoterpene fluxes. The results also demonstrate the importance of site-specific vegetation emission factors (EFs) for accurately simulating BVOC fluxes in regional and global BVOC emission models.

Palavras-Chave: organic compounds; volatility; atmospheres; data covariances; measuring instruments; atmospheric chemistry; large-eddy simulation; volatile matter; amazon river

SARKAR, CHINMOY; GUENTHER, ALEX B.; PARK, JEONG-HOO; SECO, ROGER; ALVES, ELIANE; BATALHA, SARAH; SANTANA, RAONI; KIM, SAEWUNG; SMITH, JAMES; TOTA, JULIO; VEGA, OSCAR. PTR-TOF-MS eddy covariance measurements of isoprene and monoterpene fluxes from an eastern Amazonian rainforest. Atmospheric Chemistry and Physics, v. 20, n. 12, p. 7179-7191, 2020. DOI: 10.5194/acp-20-7179-2020. Disponível em: http://repositorio.ipen.br/handle/123456789/31480. Acesso em: $DATA.

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Abstract: The safety of nuclear facilities has been a growing global concern, mainly after the Fukushima nuclear accident. Studies on nuclear research reactor accidents such as the Loss of Coolant Accident (LOCA), many times considered a design basis accident, are important for ensure the integrity of the plant. A LOCA may lead to the partial or complete uncovering of the fuel assemblies and it is necessary to assure the decay heat removal as a safety condition. This work aimed to perform, in a safe way, partial and complete uncovering experiments for an Instrumented Fuel Assembly (IFA), in order to measure and compare the actual fuel temperatures behavior for LOCA in similar conditions to research reactors. A test section for experimental simulation of Loss of Coolant Accident named STAR was designed and built. The IFA was irradiated in the IEA-R1 core and positioned in the STAR, which was totally immersed in the reactor pool. Thermocouples were installed in the IFA to measure the clad and fluid temperatures in several axial and radial positions. Experiments were carried out for five levels of uncovering of IFA, being one complete uncovering and four partial uncovering, in two different conditions of decay heat. It was observed that the cases of complete uncovering of the IFA were the most critical ones, that is, those cases presented higher clad temperatures when compared with partial uncovering cases, for the specific conditions of heat decay intensity and dissipation analyzed. The maximum temperatures reached in all experiments were quite below the fuel blister temperature, which is around 500 °C. The STAR has proven to be a safe and reliable experimental apparatus for conducting loss of coolant experiments.

Palavras-Chave: computer codes; computerized simulation; data covariances; fuel assemblies; loss of coolant; natural convection; r codes; radiosensitivity effects; reactor accident simulation; research reactors; sensitivity analysis

MAPRELIAN, EDUARDO; TORRES, WALMIR M.; BELCHIOR JUNIOR, ANTONIO; UMBEHAUN, PEDRO E.; BERRETTA, JOSE R.; SABUNDJIAN, GAIANE. Total and partial loss of coolant experiments in an instrumented fuel assembly of IEA-R1 research reactor. Nuclear Engineering and Design, v. 363, p. 1-11, 2020. DOI: 10.1016/j.nucengdes.2020.110610. Disponível em: http://repositorio.ipen.br/handle/123456789/31409. Acesso em: $DATA.

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