A new model with Serpent for the first criticality benchmarks of the TRIGA Mark II reactor

We present a new model, developed with the Serpent Monte Carlo code, for neutronics simulation of the TRIGA Mark II reactor of Pavia (Italy). The complete 3D geometry of the reactor core is implemented with high accuracy and detail, exploiting all the available information about geometry and materials. The Serpent model of the reactor is validated in the fresh fuel configuration, through a benchmark analysis of the first criticality experiments and control rods calibrations. The accuracy of simulations in reproducing the reactivity difference between the low power (10 W) and full power (250 kW) reactor condition is also tested. Finally, a direct comparison between Serpent and MCNP simulations of the same reactor configurations is presented

Neurophthalmological conditions mimicking glaucomatous optic neuropathy: analysis of the most common causes of misdiagnosis

Background: To analyze the most common neurophthalmological conditions that may mimic glaucomatous optic neuropathy and to determine which most often lead to misdiagnosis when evaluated by a glaucoma specialist. Methods: We reviewed the charts of consecutive patients with optic neuropathies caused by neurophthalmological conditions screened in a single Eye Clinic within a period of 24 months. Within these enrolled patients, we selected the eyes whose fundoscopic appearance could resemble glaucoma based in pre-defined criteria (vertical cup-to-disc ratio >= 0.6, asymmetry of the cup-to-disc ratio >= 0.2 between eyes, presence of localized retinal nerve fiber layer and/or neuroretinal rim defects, and disc haemorrhages). Then, color fundus photographs and Humphrey Visual Field tests (HVF) of these eyes were mixed with tests from 21 consecutive glaucomatous patients (42 eyes with normal tension glaucoma). These images were mixed randomly and a masked glaucoma specialist was asked to distinguish if each set of exams was from a patient with glaucoma or with a neurophthalmologic condition. Results: Among the 101 eyes (68 patients) enrolled with neurophthalmological diseases, 16 (15.8%) were classified as conditions that could mimic glaucoma. The most common diagnoses were ischemic optic neuropathy (25%), compressive optic neuropathy (18.7%) and hereditary optic neuropathy (18.7%). Based on the analysis of fundus photographs and HVF tests, 25% of these were misdiagnosed as glaucoma (two ischemic optic neuropathies and two congenital optic disc anomalies). Conversely, 11.9% of the glaucomatous neuropathies were misdiagnosed as neurophthalmological disorders. Overall, the glaucoma specialist correctly diagnosed 84.5% of the eyes. Conclusions: Some neurophthalmological disorders can mimic glaucoma. In our study, isquemic and compressive optic neuropathies were the ones that most often did so. Almost one quarter of the eyes were misdiagnosed when evaluated by a glaucoma specialist, which can lead to inadequate management and influence the prognosis of these patients.Univ Fed Sao Paulo, Dept Ophthalmol, Sao Paulo, BrazilHosp Med Olhos, Glaucoma Unit, Sao Paulo, BrazilUniv Sao Paulo, Dept Ophthalmol, Sao Paulo, BrazilMayo Clin, Dept Ophthalmol, 4500 San Pablo Rd, Jacksonville, FL 32224 USAUniv Fed Sao Paulo, Dept Ophthalmol, Sao Paulo, BrazilWeb of Scienc

Neutron activation analysis of the 30Si content of highly enriched 28Si: proof of concept and estimation of the achievable uncertainty

We investigated the use of neutron activation to estimate the 30Si mole fraction of the ultra-pure silicon material highly enriched in 28Si for the measurement of the Avogadro constant. Specifically, we developed a relative method based on Instrumental Neutron Activation Analysis and using a natural-Si sample as a standard. To evaluate the achievable uncertainty, we irradiated a 6 g sample of a natural-Si material and modeled experimentally the signal that would be produced by a sample of the 28Si-enriched material of similar mass and subjected to the same measurement conditions. The extrapolation of the expected uncertainty from the experimental data indicates that a measurement of the 30Si mole fraction of the 28Si-enriched material might reach a 4% relative combined standard uncertainty

Object-Oriented Modeling and simulation of a TRIGA reactor plant with Dymola

This work presents the modeling and simulation of a TRIGA-Mark II pool-type reactor with Zirchonium-Hydryde and Uranium fuel immersed in light water, with Modelica object-oriented language, in Dymola simulation environment. The model encompasses the integrated plant system including the reactor pool and cooling circuits. The reactor pool plays a fundamental role in the system dynamics, through a thermal feedback effect on the reactor core neutronics. The pool model is tested against three experimental transients: simulation results are in good accordance with experimental data and provide useful information about the inertial effect of the water inventory on the reactor cooling

Development of a Nitridation Gas-Surface Boundary Condition for High-Fidelity Hypersonic Simulations

Gas-surface interaction phenomena have a strong impact on the heat flux experienced by atmospheric entry bodies in the hypersonic regime. Numerically, they can be expressed as a boundary condition to be imposed to the Navier-Stokes equations to achieve predictive engineering simulations. The mass and energy conservation can be abstracted in a thin layer containing both the solid and the gas phases. Such a balance was implemented in the open source MUTATION++ library. It is convenient to easily plug verified models in any type of CFD solver to model the response of material surfaces. We have extended the library to accommodate a state-of-the-art nitridation and nitrogen recombination mechanisms derived from beam experiments. MUTATION++ was coupled to US3D, a high-fidelity finite-volume flow solver, to simulate an experimental campaign conducted in the VKI Plasmatron facility. The experiment consists in applying a subsonic high-enthalpy nitrogen flow over an axi-symmetric ablative material sample. The simulation results on the stagnation line were compared to those obtained using a one-dimensional solver. Both results showed good agreement, verifying the implementation of the boundary condition. The computational model predicts a lower mass blowing rate than the experimental value. The catalytic behaviour of the mechanism, in agreement with the beam experiment predictions, induces higher heat flux values than those expected for the testing conditions of the Plasmatron facility

Cryoconite as a temporary sink for anthropogenic species stored in glaciers

Cryoconite, the typical sediment found on the surface of glaciers, is mainly known in relation to its role in glacial microbiology and in altering the glacier albedo. But if these aspects are relatively well addressed, the same cannot be said about the geochemical properties of cryoconite and the possible interactions with glacial and peri-glacial environment. Current glacier retreat is responsible for the secondary emission of species deposited in high-altitude regions in the last decades. The role played by cryoconite in relation to such novel geochemical fluxes is largely unknown. Few and scarce observations suggest that it could interact with these processes, accumulating specific substances, but why, how and to what extent remain open questions. Through a multi-disciplinary approach we tried to shed lights. Results reveal that the peculiar composition of cryoconite is responsible for an extreme accumulation capability of this sediment, in particular for some, specific, anthropogenic substances

Avaliação de ruído ambiental da região central da cidade de Uberaba – MG

Noise pollution occur a sound exceeds the normal hearing limit.  The World Health Organization (WHO) said that noise pollution is the second largest pollution cause, being considered a worldwide public health problem, as it affects the population physical and mental health. Today, it is one polltution sources that more affect the health human  due to excessive noise generated by different sources. Because to the  health problems  noise pollution, the study objective  was to evaluate some points in the Uberaba - MG central region  to quantify the existing sound intensity levels and  verify if the noise levels are above the noise levels permitted,  cause impacts humans negative effects.  Sound pressure level measurements were performed according to NBR 10.151 / 2019 in 5  zones Uberaba central region and for each zone 4 points measurement were made. The measurement was performed every 1 minute, totaling 10 minutes. The sound pressure level values, the equivalent sound pressure level was obtained, which corresponds to the average noise of each location and this value was compared with the noise pollution standards. The results obtained were above those established by standards and may cause damage to the population health that is subjected to this pollution. Thus, better city urban planning city and the incorporation of control measures and sound attenuation are necessary for the community well-being. Key words: Noise. Noise Pollution; Health Damage.A poluição sonora ocorre quando um som ultrapassa o limite auditivo normal. Segundo a Organização Mundial de Saúde (OMS) a poluição sonora é a segunda maior causa de poluição, sendo considerada um problema de saúde pública mundial, pois afeta a saúde física e mental da população. É uma das fontes de poluição que mais geram incômodos atualmente em decorrência dos excessivos ruídos gerados por diferentes fontes. Devido aos diversos problemas de saúde acarretados pela poluição sonora o objetivo do estudo foi avaliar alguns pontos da região central de Uberaba – MG a fim de quantificar os níveis de intensidade sonora existentes e verificar se os níveis de ruído encontram-se acima do permitido causando efeitos negativos nos seres humanos. Foram realizadas medições de nível de pressão sonora de acordo com a NBR 10.151/2019 em 5 zonas da região central de Uberaba e em cada zona foram realizados 4 pontos de medição. Para cada ponto, a medição foi realizada de 1 em 1 minuto, totalizando 10 minutos. A partir dos valores de níveis de pressão sonora foi obtido o nível de pressão sonora equivalente que corresponde à média do ruído de cada local e este valor foi comparado com as normas referentes a poluição sonora. Os resultados obtidos ficaram acima dos estabelecidos por normas podendo acarretar danos à saúde da população que está submetida a esta poluição. Desta forma é necessário um melhor planejamento urbano da cidade e a incorporação de medidas de controle e de atenuação sonora para o bem-estar da comunidade. Palavras-chave: Ruídos. Poluição sonora. Danos à saúde

Implementation and strategies to ensure adequate coordination within a Urology Department during the COVID-19 pandemic

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WARP: a double phase Argon programme for Dark Matter detection

WARP (Wimp ARgon Programme) is a double phase Argon detector for Dark Matter detection under construction at Laboratori Nazionali del Gran Sasso. We present recent results obtained operating deep underground a prototype detector with sensitive mass 2.3 litres. 1. WARP: a double phase argon detector for Dark Matter detection. A double phase Argon detector offers unique sensitivity for the search of dark matter in the form of WIMPs: such detector has the highest discrimination of background events in favour of potential WIMP interactions, which are expected to produce low energy Ar recoils with typical energies of a few tens keV. The basic concept of the detector is the measurement of both the scintillation and the ionization produced by particle interactions inside a liquid argon sensitive volume. Two simultaneous criteria can be applied to select Ar recoils eventually produced by WIMPs: i) Prompt scintillation versus ionization. The prompt scintillation light produced by a particle interacting in the liquid argon phase is detected by PMs. The ionization electrons are extracted from the liquid into the gas and accelerated by an appropriate electric field to produce a proportional (high gain), secondary light pulse seen by the same PMs. The pulse ratio S2/S1 of secondary light S2 (from drift time-delayed ionization) over prompt scintillation light S1 is strongly dependent from columnar recombination of the ionising tracks: therefore nuclear recoils produce typical signals with pulse ratio S2/S1 about 60 times lower than electrons. ii) Pulse shape discrimination of primary scintillation: the primary light is emitted with two components with very large difference in decay times (fast 7 ns, and slow 1.8 μs). The relative amount of the slow component strongly depends from the interacting particle, being around 0.7 for electrons and. 0.1 for heavy charged paricles. The WARP liquid argon detector under construction has a sensitive volume of 100 liters. The goal scintillation yield is of the order of 1 collected photoelectron per keV and the detection threshold for the WIMPs 30 keV. A detailed description of the 100 liters detector can be find in reference [1]. 1 INFN and Dept. of Physics University of Pavia: P. Benetti, E. Calligarich, M. Cambiaghi, C. De Vecchi, R. Dolfini, L. Grandi, A. Menegolli, C. Montanari, M. Prata, A. Rappoldi, G.L. Raselli, M. Roncadelli, M. Rossella, C. Rubbia (Spokesperson), C. Vignoli. INFN and Dept. of Physics University of Napoli "Federico II": F. Carbonara, A.G. Cocco, G. Fiorillo, G. Mangano, R. Santorelli. INFN Laboratori Nazionali del Gran Sasso and University of L'Aquila: F. Cavanna, N. Ferrari, O. Palamara,. L. Pandola. Princeton University, Physics Department: F. Calaprice, C. Galbiati, Y. Zhao. Institute of Nuclear Physics, Krakow : A. Szelc. Figure 1. Energy spectrum observed with the WARP 2.3 liters prototype in the LNGS underground laboratory inside a 10 cm thick Pb shielding. The overlapped red histogram is the expected (montecarlo-simulated) background by interactions of environmental gamma rays. The residual events below 650 keV are produced by Ar and Kr contaminations inside the liquid Argon. Figure 2. Residual energy spectrum after subtraction of the estimated background from environmental gamma rays. The residual spectrum (upper blue curve) is perfectly fitted by the sum of the beta spectra of Ar (green curve, end-point 565 keV, rate 1.1 Bq/litre) and Kr (red curve, end-point 687 keV, rate 0.5 Bq/litre). The vertical scale is expressed in counts/sec/keV. 2. The WARP 2.3 liters prototype detector In order to perfect the detection method, a 2.3 liters prototype detector is in operation at Laboratori Nazionali del Gran Sasso since February 2005. The detector has been equipped, in subsequent phases, with 2'' and 3'' PMs made of low background materials for an onsite detailed study of the backgrounds. The structure is a down-scaled version of the 100 liters detector, with field-shaping electrodes and gas to liquid extraction and acceleration grids. The chamber is filled with ultra-purified argon in order to allow for long drift times of free electrons. Purity is maintained stable by means of continuous argon recirculation. 2.1.1. Study of the β and γ detector backgrounds. The overall background of the 2.3 litres prototype installed underground inside a 10 cm thick Pb shielding has been carefully measured and identified. The total trigger rate above a threshold of 30 keV is about 5 Hz. From a detailed study of the energy spectrum shape (Figure 1) it is shown that about 2 Hz are produced by gamma ray interactions from radioactivity of materials surrounding the sensitive volume; the remaining 3 Hz are produced by the β decays of Kr and Ar dissolved in the liquid argon. In particular, the specific activity of Ar was found to be 1.1 ± 0.4 Bq/litre of liquid Argon, in very good agreement with ref. [2]. We notice that no particular care in the selection of materials was adopted, since in this test phase the background itself helps in the identification of the rejection power. Most of the backgrounds will be strongly reduced in the 100 litres setup. Figure 3. R-like events recorded with the 2.3 liters chamber during 13.4 days of live time in june 2005. The plot shows the primary signal energy (in keV) along the drift time, expressed in μs. The fiducial volume is defined by drift times between 10 and 35 microseconds. Figure 4. Energy distribution of R-like events inside the cathode (upper plot), and inside the fiducial volume (lower plot). The red histogram in the lower plot is the result of a simulation of the expected signal from environmental neutrons in the underground area. 2.1.2. Analysis of Recoil-like events. Data recorded during 13.4 days of live time in a run done in june 2005 have been analyzed looking for recoil-like events by applying the two selection criteria described in section 1. About 6.5 millions events have been processed. The spatial and energy distribution of the 580 selected R-like events (see Figure 3) suggests the following origin for the signals: i) R-like events in the cathode region are mostly induced by decays of Rn daughters. Rn is introduced in the chamber during the filling together with the Ar: being electrically neutral it is uniformly distributed inside the chamber. Daughter nuclei, produced into an ionized state, are drifted to the cathode by the electric field, where they stick. Subsequent decays may end up: (a) with the heavy ion entering the cathode and the α or β travelling in the LAr; (b) with the heavy ion travelling in the LAr and producing the observed R-like signal. The two peaks observed in the energy spectrum (Figure 4, upper plot) are coherently explained by the nuclear recoils from α decays Po Pb (ER=110 keV) and Po Bi (ER=144 keV), assuming a light yield of 0.7 photoelectrons/keV. ii) R-like events inside the fiducial volume are induced by environmental neutrons. Both the event rate and the shape of the energy spectrum (Figure 4, lower plot) are compatible with the expected interactions induced by environmental neutrons inside the underground area (represented by the red histogram). The WARP 2.3 liters chamber in operation at LNGS proofs that the double discrimination technique is effective for separation of recoil events. The first results of the 2.3 liters test (with no neutron shielding) show that the observed background is understood, and that recoil-like signals are compatible with the expected neutron background in the underground area. References [1] WARP proposal, available online at http://warp.pv.infn.it/proposal.pdf [2] H.H. Loosli and H. Oeschger, Earth and Plan. Sci. Lett. 7 (1969) 6