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An integrated effort by the Versatile Test Reactor (VTR) Gas-Cooled Fast Reactor (GFR) Team to develop an experiment vehicle or extended-length test assembly for the VTR experiments is led by Idaho National Laboratory and supported by an industrial partner, General Atomics, and university partners, including Texas A&M University, University of Michigan, Oregon State University, University of Houston, and University of Idaho. The focus of the effort is to design a helium gas-cooled cartridge loop (GCL) to assist with the testing of fuels, materials, and instrumentation to further support development of advanced reactor systems. This study is divided into two parts. Part I provides the functional requirements and critical irradiation data needs for advancing gas-cooled fast reactor (GFR) technologies. The objective of Part I is to describe the overall preliminary conceptual design of the VTR helium cartridge loop, the design of a fission product venting system, thermal-hydraulic effects of flow direction, and gamma-heating generation in the cartridge. This paper, Part II, includes the measurement techniques being developed to measure the thermophysical properties of the different materials that make up the GCL, as well as the instrumentation and control system within the cartridge required for advancing GFR technologies. The purpose of Part II is to describe the functionality and efficacy of the measuring systems being developed to support the GCL. These systems include (a) a unique measurement platform that joins ion irradiation and a laser beam with an infrared camera and X-ray detection equipment developed and used to investigate more accurately and efficiently the influence of radiation and fission gases on the material properties under high temperatures; (b) a laser-induced breakdown spectroscopy to demonstrate its capability of monitoring possible fuel failure by detecting sub–part-per-million levels of xenon in the helium coolant stream, providing experimental data to better understand the interactions of fuel elements and coolant at high temperature, pressure, and fast neutron flux; (c) fiber-optic sensors with the ability to measure both the temperature demonstrated using a three-dimensional printed heat exchanger and, potentially, the strain in harsh environments; and (d) surface emissivity measurement test rigs to understand the effect of temperature, radiation, and surface finish on the silicon carbide cladding surface emissivity. Additional analyses and development, as well as integrated out-of-pile testing, are planned to demonstrate and validate the accuracy of the measuring systems and instrumentation in a more prototypic environment prior to their implementation into the VTR, Nuclear Science and Engineering, 196 (S1), ISSN:0029-5639, ISSN:1943-748X

An integrated effort by the Versatile Test Reactor (VTR) Gas-Cooled Fast Reactor (GFR) Team to develop an experiment vehicle or extended-length test assembly for the VTR experiments is led by the Idaho National Laboratory and supported by an industrial partner, General Atomics, and university partners, including Texas A&M University, University of Michigan, Oregon State University, University of Houston, and University of Idaho. The overall focus of the effort is to design a helium gas-cooled cartridge loop (GCL) to assist with the testing of fuels, materials, and instrumentation to further support development of advanced reactor systems. This study is divided into two parts. Part I provides the GCL functional requirements and critical irradiation data needs for advancing GFR technologies. Part II includes the measurement techniques developed to measure the thermophysical properties of the different materials in the GCL, as well as the functionality and efficacy of these instrumentation and control systems within the GCL. This paper, Part I, describes the overall preliminary conceptual design of the VTR helium cartridge loop, the design of a fission product venting system, the thermal-hydraulic effects of flow direction, and gamma-heating generation in the cartridge. This paper also describes a three-dimensional computational fluid dynamics study that was carried out to examine the effects of the helium flow direction in the GCL on its thermal-hydraulic characteristics, engineering feasibility, and in-VTR experiment design. Both steady-state operation and a transient scenario (pressurized loss of forced circulation) were analyzed for the upward and downward helium flow options in the test article section in the GCL to provide quantitative data for selection of the helium flow direction. Additional analyses and development, as well as integrated out-of-pile testing, are planned to demonstrate and verify the performance of the GCL prior to insertion into the VTR., Nuclear Science and Engineering, 196 (S1), ISSN:0029-5639, ISSN:1943-748X

Background/Aim. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global threat and a huge problem for our community. There are so many open questions. The aim of this study was to establish the frequency of gastrointestinal (GI) symptoms in hospitalized patients with infection caused by this virus (coronavirus disease-19 ?COVID-19), but also to compare if patients with GI symptoms have a higher computed tomography (CT) scan severity score of interstitial pneumonia (IP) compared to patients with COVID-19 without GI symptoms. Methods. Our database comprised 322 patients with COVID-19 who were divided into two groups, patients with and without GI symptoms. All information was taken from anamnestic data and patients? history, followed by statistical analysis. Results. Thorax CT scans of 206 patients (63.9%) were described as bilateral IP, of which 76 CT scans (36.9%) were described by radiologists as the peak of infection. Moreover, 130 patients (40.4%) had GI symptoms, and even 58 out of 130 patients (44.6%) reported GI symptoms as the first manifestation of COVID-19 infection. The most commonly reported one was the lack of appetite (73 patients or 56.15%). Furthermore, 65 (50%) patients reported diarrhea, 25 (19.2%) patients reported nausea and vomiting, and 9 (6.9%) patients reported abdominal pain. In addition, among patients with bilateral IP and GI tract symptoms, 31 (40.79%) of them did not have a higher CT scan severity score at the peak of the disease compared to the patients without GI symptoms (45 of them or 59.2%), (p = 0.704). Conclusion. GI symptoms often are the first manifestation of COVID-19. Therefore, every patient with newly formed digestive tract symptoms should be tested for COVID-19. On the other hand, GI symptoms do not indicate COVID-19 patients will have a severe form of IP.

Body temperature is an important indicator that may indicate the possibility of the existence of various pathological conditions and diseases. In the head and neck area, an infrared camera allows accurate temperature measurements of all regions of interest. The analysis of temperature characteristics of the region of interest of the head and neck in healthy subjects in terms of comparison of values in relation to the side of the face in the same person, and the comparison of values relative to the sex of the subjects is the topic of this research. These analyses are performed to create temperature maps of the face and determine physiological values. The research was conducted with the participation of 30 healthy people, 16 women and 14 men of different ages. Thermal imaging was performed in controlled conditions with infrared thermographic camera Varioscan 3021ST, while the software package IRBIS Professional 2.2 was used for thermogram analysis. Results show that the temperatures in female subjects at the submandibular region are significantly lower than in male subjects with an average temperature difference of 0.46?C, and the temperatures in female subjects at the supraorbital region are on average 0.5?C higher than in male subjects.

A method for reconstructing the direction of a fast neutron source using a segmented organic scintillator-based detector and deep learning model is proposed and analyzed. The model is based on recurrent neural network, which can be trained by a sequence of data obtained from an event recorded in the detector and suitably pre-processed. The performance of deep learning-based model is compared with the conventional double-scatter detection algorithm in reconstructing the direction of a fast neutron source. With the deep learning model, the uncertainty in source direction of 0.301 rad is achieved with 100 neutron detection events in a segmented cubic organic scintillator detector with a side length of 46 mm. To reconstruct the source direction with the same angular resolution as the double-scatter algorithm, the deep learning method requires 75% fewer events. Application of this method could augment the operation of segmented detectors operated in the neutron scatter camera configuration for applications such as special nuclear material detection., Comment: 15 pages. 9 figures. Preprint submitted to Elsevier August 2022

Opaque scintillators are designed to have a short scattering length such that scintillation photons are probabilistically confined to a small region of space about their origin. The benefit of this feature is that information on the interaction event topology can be recorded with greater fidelity than in traditional highly transparent media with sensors at large distances from the light production region. Opaque scintillator detectors rely on wavelength-shifting fibers to extract the scintillation light; however, the efficiency of light collection has not yet been directly measured in experiment. We measured the efficiency of light collection as a function of the optical parameters of an opaque liquid and the distance from the origin of the light to the fiber. We use the experimental data to validate a Monte Carlo model of light transport and collection and discuss a simple diffusion model that reproduces the results of Monte Carlo simulation with high fidelity. This combination of validated models has the potential for use in predictions of performance in various designs of future opaque scintillator detectors such as LiquidO., Comment: 25 pages, 15 figures

There is significant motivation to develop and deploy novel nuclear reactor designs to deliver improved performance, safety, and economics for nuclear energy. In gas-cooled fast reactors that use helium as the primary coolant, the presence of xenon could indicate the onset of the fuel failure. We performed a feasibility study using single-pulse laser-induced breakdown spectroscopy to assess the sensitivity for trace xenon detection in a helium buffer of the pressure of 1.25 bar at room temperature. Under these experimental conditions, parametric optimization of recording parameters has ultimately led to the xenon detection limit of about 0.2 μmol mol−1 for 104 laser shots. The results show promise for the use of this technique for online monitoring of reactor fuel integrity, and motivate studies for the development of a compact measurement system that could be integrated with the reactor's primary helium-cooling loop.

We demonstrate the production of ultra-broadband long-wave infrared pulses spanning the 8–12 µm atmospheric window using chirped-pulse difference-frequency generation optimized by genetic algorithm.

We demonstrate that ultrafast laser filaments can excite chlorophyll fluorescence in green algae and show that it is a promising technique for remote detection of uranium exposure from the shape of the fluorescence time profile.

We present an ultrafast long-wave infrared (LWIR) source driven by a mid-infrared fluoride fiber laser. It is based on a mode-locked Er:ZBLAN fiber oscillator and a nonlinear amplifier operating at 48 MHz. The amplified soliton pulses at ∼2.9 µm are shifted to ∼4 µm via the soliton self-frequency shifting process in an InF3 fiber. LWIR pulses with an average power of 1.25-mW centered at 11 µm with a spectral bandwidth of ∼1.3 µm are produced through difference-frequency generation (DFG) of the amplified soliton and its frequency-shifted replica in a ZnGeP2 crystal. Soliton-effect fluoride fiber sources operating in the mid-infrared for driving DFG conversion to LWIR enable higher pulse energies than with near-infrared sources, while maintaining relative simplicity and compactness, relevant for spectroscopy and other applications in LWIR.

In order to model the fate and transport of particles following a nuclear explosion, there must first be an understanding of individual physical and chemical processes that affect particle formation. One interaction pertinent to fireball chemistry and resultant debris formation is that between uranium and oxygen. In this study, we use laser ablation of uranium metal in different concentrations of oxygen gas, either

We demonstrate a novel single-shot method to determine the detonation energy of laser-induced plasma and investigate its performance. This approach can be used in cases where there are significant shot-to-shot variations in ablation conditions, such as laser fluctuations, target inhomogeneity, or multiple filamentation with ultrashort pulses. The Sedov blast model is used to fit two time-delayed shadowgrams measured with a double-pulse laser. We find that the reconstruction of detonation parameters is insensitive to the choice of interpulse delay in double-pulse shadowgraphy. In contrast, the initial assumption of expansion dimensionality has a large impact on the reconstructed detonation energy. The method allows for a reduction in the uncertainties of blast wave energy measurements as a diagnostic technique employed in various laser ablation applications.

We demonstrate that atomically thin layered two-dimensional (2D) semiconductors are promising candidates for space electronics owing to their inherent and extraordinary resilience to radiation damage from energetic heavy charged particles. In particular, we found that ultrathin MoS2 nanosheets can easily withstand proton and helium irradiation with fluences as high as ∼1016 and ∼1015 ions/cm2, respectively, corresponding to hundreds or thousands of years of unshielded exposure to radiation in space. While radiation effects on 2D material-based field effect transistors have been reported in the recent past, none of these studies could isolate the impact of irradiation on standalone ultrathin 2D layers. By adopting a unique experimental approach that exploits the van der Waals epitaxy of 2D materials, we were able to differentiate the effects of radiation on the 2D semiconducting channel from that of the underlying dielectric substrate, semiconductor/substrate interface, and metal/semiconductor contact interface, revealing the ultimate potential of these 2D materials. Furthermore, we used a statistical approach to evaluate the effect of radiation damage on critical device and material parameters, including threshold voltage, subthreshold slope, and carrier mobility. The statistical approach lends additional credence to the general conclusions drawn from this study, overcoming a common drawback of methods applied in this area of research. Our findings do not only offer exciting prospects for the operation of modern electronics in space, but may also benefit electronics applications in high-altitude flights, military aircraft, satellites, nuclear reactors, particle accelerators, and other high-radiation environments. Additionally, they highlight the importance of evaluating the impact of damage to the substrate and surrounding materials on electrical characteristics during future radiation studies of 2D materials.

Gas-phase oxidation of uranium (U), plume chemistry, and the corresponding impact on optical emission features of the U plasma are investigated. Plasmas were produced via nanosecond laser ablation of a natural U target in a chamber where U oxidation was controlled by varying the oxygen partial pressure in an argon cover gas. Monochromatic imaging of U atoms and monoxide (UO) molecules was performed using narrow bandpass optical filters. Results reveal the spatio-temporal evolution of atomic and molecular species in the plasma. U oxides are found to be formed further from the target (in comparison to U atoms), where lower temperatures favor molecular recombination. Segregation between the distribution of U atoms and UO species is observed at later times of plasma evolution, and is more apparent at lower oxygen partial pressures. At higher oxygen partial pressures, significant variation in plume morphology is noticed for UO species, which can be attributed to the higher oxide (UxOy) formation further from the target. The monochromatic images of U atoms and UO molecules and corresponding spectral features at various oxygen partial pressures presented here provide unique insight into gas-phase, high-temperature U oxidation and chemistry, with implications for a wide range of nuclear applications, from stand-off detection of radioisotopes to forensics and safeguards.

Various types of topological defects are produced during proton irradiation, which are crucial in functionalizing graphene, but the mechanisms of the defect generation process and the structure change are still elusive. Herein, we investigated the graphene defect generation probabilities and defect structures under proton irradiation using both ab initio and classical molecular dynamics simulations. As the proton energy increases from 0.1 keV to 100 keV, defect structures transition from single vacancy and Frenkel pairs to a rich variety of topological defects with the possibility of ejecting multiple atoms. We show that, relatively good agreement on defect generation probabilities can be reached between the two simulation approaches at a proton energy of 1 and 10 keV. However, at 0.1 keV, the single vacancy generation probability differs significantly in two methods due to the difference in the energy required to form single vacancy. Using the classical molecular dynamics simulation, we also studied the evolution of different types of defects and the dependence of their probabilities of occurrence on the proton energy and incident angle. The correlation between the impact positions and defect types allows for the convoluted relationship between the defect probabilities, geometric parameters, and proton energy to be elucidated. We show that the proton energy and incident angle can be used to effectively tune the generation probabilities of different types of defects. Our results provide insights into the controlled defect engineering through ion irradiation, which will be useful for the development of functionalized graphene and graphene electronics.

Objective: To evaluate the nature and rate of sports injuries in medical students, as well as the risk factors at these events. Methods: All student-athletes (218) from a Medical School, integrated in at least one of the six team sport modalities (soccer, rugby, indoor soccer, handball, basketball, and volleyball) in 2017, were included. Injuries affecting their performance, regardless of time loss, were included. Athlete-exposure (A-E) was defined as one student-athlete participating in one practice or game. Results: Injury rates were significantly higher in junior medical students (1st - 3rd year) (7.58 per 1000 A-E, 95%CI = 6.11-9.06) than in senior medical students (4th - 6th year) (4.49 per 1000 A-E, 95%CI = 3.26-5.73) (p < 0.001). Multi-sports athletes had higher injury rates (10.69 per 1000 A-E, 95%CI = 8.22-13.17) than single-sport athletes (4.49 per 1000 A-E, 95%CI = 3.51-5.47) (p = 0.002). More than 60% of reported injuries occurred in the lower limbs and the mechanism that accounted for most injuries in games was player contact (51%); whereas in practice, it was non-contact (53%). Conclusion: Junior medical students present a higher injury rate than seniors. Medical students practicing more than one modality had a higher injury rate than those involved in just one sport modality. Level of Evidence IV, Cross-Sectional Study. RESUMO Objetivo: Avaliar a incidência e as características das lesões esportivas em alunos de medicina, assim como os fatores de risco envolvidos. Métodos: Todos os alunos (218) da Faculdade de Medicina da Universidade de São Paulo que integravam seis modalidades esportivas (futebol, rugby, futsal, handebol, basquete e vôlei) em 2017 foram incluídos. Foram incluídas as lesões que afetaram a performance, independente do tempo de afastamento. Uma exposição-atleta (E-A) foi definida como a participação de um aluno em um jogo ou treino. Resultados: A taxa de lesão foi maior em alunos do 1º ao 3º ano (7,58 por 1000 E-As 95% IC = 6,11-9,06) do que em alunos do 4º ao 6º ano (4,49 por 1000 E-As 95% IC = 3,26-5,73) (p < 0.001). Alunos praticantes de mais de uma modalidade apresentaram maior taxa de lesão (10,69 por 1000 E-As, 95% IC 8,22-13,17) do que alunos praticantes de apenas uma modalidade (4.49 por 1000 E-As, 95% IC 3,51-5,47) (p = 0.002). Mais de 60% das lesões ocorreram nos membros inferiores e o principal mecanismo em jogos foi contato com outro jogador (51%), e em treinos foi lesão sem contato (53%). Conclusão: Alunos do 1 ˚ ao 3 ˚ ano apresentaram maior taxa de lesão do que alunos do 4º ao 6º ano. Alunos praticantes de mais de uma modalidade apresentaram maior taxa de lesão do que alunos praticantes de apenas uma modalidade. Nível de Evidência IV, Estudo Transversal.

A 31-mJ, 9.6-ns, 2.73-µm parametric source is demonstrated, producing a supergaussian spatial profile with M2 = 2.8. The source is further sliced to 1-ns pulses, providing favorable characteristics for LWIR OPCPA pumping.

We demonstrate the production of broadband long-wave infrared pulses cen-tered near 10.3 μm using difference-frequency generation. An accompanying simulation shows that genetic algorithm optimization of chirp can significantly increase the spectral bandwidth.

Zettawatt Equivalent Ultrashort pulse laser System (ZEUS): The National Science Foundation’s mid-scale 3PW laser facility for exploration of relativistic plasmas, nonlinear quantum electrodynamics, and other extreme high-field phenomena is described.

We demonstrate a novel single-shot approach to determine the detonation energy of laser-induced plasmas. The method employs a double-pulse shadowgraphy scheme coupled with analysis of shock expansion rates using the Sedov blast model.

Photon active interrogation techniques offer improved detection of shielded special nuclear material (SNM). Shielded SNM detection is challenging due to limited passive emissions, especially by highly-enriched uranium. Photon active interrogation can improve detection capabilities because a high-energy photon beam can penetrate shielding materials and induce photonuclear reactions in SNM, greatly increasing radiation emissions. The University of Michigan is developing economical active interrogation techniques for homeland security applications using an off-the-shelf medical linear accelerator (linac) and economical detector technology. The linac produces a bremsstrahlung spectrum with a 9-MeV endpoint, which is sufficient to induce photonuclear reactions in actinides. To detect the neutrons produced in the photonuclear reactions with high confidence, detectors with robust gamma-rejection abilities must be employed. For this work, we use a commercial off-the-shelf (COTS) 4He scintillation detector developed by Arktis to detect photoneutrons during photon active interrogation of depleted uranium. 4He gas is inert, abundant, and has desirable gamma rejection capabilities. We first show measurements of isotopic photon sources, then several isotopic neutron sources in addition to two neutron generator experiments. Lastly, we show results from the photon active interrogation experiments.

We explored generation of high-energy nanosecond short pulses in the mid-IR wavelength range using 30–70-µm-core Er:ZBLAN fiber amplifiers. The highest energies achieved were ∼ 0.7 m J at 2.72 µm in 11.5-ns-long pulses, with the corresponding peak power of 60.3 kW, obtained with a 70-µm-diameter core fiber amplifier pumped at 976 nm and seeded by a K T i O A s O 4 -based optical parametric oscillator/optical parametric amplifier system. To the best of our knowledge, these pulse energies are the highest achieved to date from mid-IR fiber lasers at longer than 2-µm wavelengths with nanosecond pulses. The achieved highest pulse energies were limited by the surface damage of unprotected fiber output facets.

Passive detection of special nuclear material (SNM) is challenging due to its inherently low rate of spontaneous emission of penetrating radiation, the relative ease of shielding, and the fluctuating and frequently overwhelming background. Active interrogation, the use of external radiation to increase the emission rate of characteristic radiation from SNM, has long been considered to be a promising method to overcome those challenges. Current active-interrogation systems that incorporate radiography tend to use bremsstrahlung beams, which can deliver high radiation doses. Low-energy ion-driven nuclear reactions that produce multiple monoenergetic photons may be used as an alternative. The ${}^{12}\mathrm{C}(\mathrm{p},{\mathrm{p}}^{\ensuremath{'}}{)}^{12}\mathrm{C}$ reaction is one such reaction that could produce large yields of highly penetrating 4.4- and 15.1-MeV gamma rays. This reaction does not directly produce neutrons below the approximately 19.7 MeV threshold, and the 15.1-MeV gamma-ray line is well matched to the photofission cross section of ${}^{235}\mathrm{U}$ and ${}^{238}\mathrm{U}$. We report the measurements of thick-target gamma-ray yields at 4.4 and 15.1 MeV from the ${}^{12}\mathrm{C}(\mathrm{p},{\mathrm{p}}^{\ensuremath{'}}{)}^{12}\mathrm{C}$ reaction at proton energies of 19.5, 25, and 30 MeV. Measurements are made with two $3$-in. EJ-309 cylindrical liquid scintillation detectors and thermoluminescent dosimeters placed at ${0}^{\ensuremath{\circ}}$ and ${90}^{\ensuremath{\circ}}$, with an additional $1.5$-in. $\mathrm{Na}\mathrm{I}$($\mathrm{Tl}$) cylindrical scintillation detector at ${0}^{\ensuremath{\circ}}$. We estimate the highest yields of the 4.4- and 15.1-MeV gamma rays of $1.65\ifmmode\times\else\texttimes\fi{}{10}^{10}$ and $4.47\ifmmode\times\else\texttimes\fi{}{10}^{8}\phantom{\rule{0.2em}{0ex}}{\mathrm{sr}}^{\ensuremath{-}1}$ $\ensuremath{\mu}{\mathrm{C}}^{\ensuremath{-}1}$ at a proton energy of 30 MeV, respectively. The yields in all experimental configurations are greater than in a comparable deuteron-driven reaction that produces the same gamma-ray energies---${}^{11}\mathrm{B}(\mathrm{d},\mathrm{n}\ensuremath{\gamma}{)}^{12}\mathrm{C}$. However, a significant increase of the neutron radiation dose accompanies the proton energy increase from 19.5 to 30 MeV.

Production of ultrafast coherent radiation in the long-wave infrared range is of significant interest to both fundamental science and applications. We discuss the design and preliminary validation of a method to produce high-power ultrashort long-wave infrared pulses using optical parametric chirped-pulse amplification.

In 1930, Wolfgang Pauli proposed that conservation of energy and momentum in beta decay required the existence of a new particle: the neutrino. Since then experimental methods have matured to the point that neutrino detection now has an important practical application, namely, enhancing nuclear security. In this Colloquium the challenges and advances in the field of neutrino detection and their use in national security are discussed.

Building on past support, NSF has funded the Zetawatt Equivalent Ultrashort pulse laser System (ZEUS), a mid-scale 3PW multi-beam user facility, to explore nonlinear quantum electrodynamics, relativistic plasmas, and other phenomena in High-Field Science.

Small-signal parametric gain at 10.6 pm in GaSe crystal pumped at 2.75 pm is experimentally demonstrated. Simulation predicts that nanosecond optical parametric chirped-pulse amplification in GaSe supports sub-three-cycle pulses.

We examine the utility of beam shaping for femtosecond filament-induced breakdown spectroscopy at long range. Diffraction-resistant and self-healing Bessel and Airy beams offer the advantage of longitudinally extended working zones.