bluuebunny/crossref_metadata_2025 huggingface dataset:
SENSITIVITY ANALYSIS OF STAINLESS STEEL REFLECTOR FOR VR-1 TRAINING REACTOR
Authors: Frybort Jan , Sklenka Lubomir , Fejt Filip , Suk Pavel , Frybortova Lenka
Published: February 2021

Pressurized water reactors are typically surrounded in the radial direction by neutron reflectors made from stainless steel and water. These reflectors decrease neutron leakage and provide protection of pressure vessel from fast neutrons damaging its integrity. Such a radial reflector influences multiplication factor of the core and distribution of neutron flux and fission power inside the core. All these effects can be analyzed by full-core simulations using macroscopic constants. Methodology for generation of the macroscopic constants for non-fuel regions will be tested for new stainless steel reflectors at the VR-1 reactor. Rods from SS 304l material will be used for construction of radial reflectors for the VR-1 reactor. They will be design to generate sufficient measurable response in selected core characteristics. The study is focused on core power distribution and reactivity worth of absorbing rods in a VR-1 reactor core. The core typically consists of about 20 IRT-4M fuel assemblies and seven absorbing rods UR-70. Replacing water surrounding the core by several reflector assemblies containing stainless steel will influence leakage and distribution of neutrons inside the core. The current analysis deals with local effects and employs the sensitivity study to discover the nature of reflectors’ impact on the reactor core. These effects were studied even for several past VR-1 reactor core configurations. All calculations were carried out in Serpent2 Monte-Carlo code with various evaluated libraries: ENDF/B-VII.1, ENDF/B-VIII.0, and JEFF-3.3 data.
EVALUATION OF APPROXIMATIONS IN REACTOR PULSE
Authors: Vavtar Ingrid , Snoj Luka
Published: February 2021

An evaluation of validity of theoretical pulse models (Fuchs-Hansen and Nordheim-Fuchs model) in reactor pulse modelling was performed by developing so called Improved Pulse Model. The effect of each of the five assumptions on the most important pulse physical parameters, maximal power, total released energy and full width at half maximum was studied. In the Improved Pulse Model the assumptions are disposed out with the improvements, where to account the delayed neutrons the six point kinetic equations are solved, the temperature dependences of the temperature reactivity coefficient of fuel and specific heat are taken into account, also the final ejected time of transient control rod from reactor core, whose value of reactivity varies in height and the heat dissipation from the fuel are considered. It is found that the theoretical models predict a higher maximum power, lower total released energy and full width at half maximum than the Improved Pulse Model.
NEW SCRAM EXPERIMENTAL DEVICE AT TRAINING REACTOR VR-1
Authors: Novak Ondrej , Sklenka Lubomir
Published: February 2021

The paper deals with design of new SCRAM experimental device at Training reactor VR-1. Crucial works cowers the detector development, transient calculations and principal design of the device. Conceptual design will be prepared in 2019–2020. This paper presents current work status.
HIGHLY LOCALIZED AZIMUTHAL MEASUREMENTS IN THE CROCUS REACTOR TOWARDS THE VALIDATION OF HIGH-FIDELITY NEUTRONICS CODES
Authors: Vitullo Fanny , Lamirand Vincent , Frajtag Pavel , Perret Gregory , Pautz Andreas
Published: February 2021

Highly localized in-core measurements are necessary for the validation of neutron transport calculations with high spatial resolution. In the present work, a miniature neutron detector developed at EPFL in collaboration with PSI was used to carry out a set of thermal neutrons counting measurements in the zero-power CROCUS reactor core within a spatial range in order of mm. The miniature detector, positioned close to the core reflector, shows a gradient of +(4.29 ± 0.10)% in the count rate profile in the radial direction within 1.3 cm, with higher values pointing towards the core reflector because of the higher share of neutrons in the thermal range. On the contrary, in a control rod guide tube the count rate gradient is -(4.37 ± 0.10)% and it is directed towards the core center. The measured values are compared with the azimuthal trend of the normalized 6Li reaction rate calculated with an iterative three-steps method performed with the Monte Carlo code Serpent 2. These measurements proved the feasibility of resolving spatial effects in the mm-range and they represent a basis for further investigating highly spatially-resolved phenomena in the CROCUS core.
MEASUREMENT OF 182,184,186W (N, N’ γ) CROSS SECTIONS AND WHAT WE CAN LEARN FROM IT
Authors: Henning Greg , Bacquias Antoine , Borcea Catalin , Boromiza Mariam , Capote Roberto , Dessagne Philippe , Drohé Jean-Claude , Dupuis Marc , Hilaire Stephane , Kawano Toshihiko , Kerveno Maëlle , Negret Alexandru , Nyman Markus , Olacel Adina , Plompen Arjan , Romain Pascal , Rudolf Gérard , Scholtes Pol
Published: February 2021

Today’s development of nuclear installations rely on numerical simulation for which the main input are evaluated nuclear data. Inelastic neutron scattering (n, xn) is a reaction of importance because it modifies the neutron population, the neutron energy distribution and may create new isotopes. The study of this reaction on tungsten isotopes is interesting because it is a common structural material. Additionally, tungsten isotopes are a good testing field for theories. The IPHC group started an experimental program with the GRAPhEME setup installed at the neutron beam facility GELINA to measure (n, xn γ) reaction cross sections using prompt gamma spectroscopy and neutron energy determination by time-of-flight. The obtained experimental data provide constraints on nuclear reaction mechanisms models for 182,184,186W. Indeed, to reproduce correctly the experimental (n, n’ γ) cross-sections, the reaction codes must include accurate models of the reaction mechanism, nuclear de-excitation process and use correct nuclear structure information.
MEASUREMENT, EVALUATION AND VALIDATION OF MOLYBDENUM CROSS SECTIONS
Authors: Duhamel Isabelle , Leclaire Nicolas , Leal Luiz , Kimura Atsushi , Nakamura Shoji
Published: February 2021

Available nuclear data for molybdenum included in the nuclear data libraries are not of sufficient quality for reactor physics or criticality safety issues and indeed information about uncertainties and covariance is either missing or leaves much to be desired. Therefore, IRSN and JAEA performed experimental measurements on molybdenum at the J-PARC (Japan Proton Accelerator Research Complex) facility in Japan. The aim was to measure capture cross section and transmission of natural molybdenum at the ANNRI (Accurate Neutron-Nucleus Reaction measurement Instrument) in the MLF (Material Life and science Facility) of J-PARC. The measurements were performed on metallic natural molybdenum samples with various thicknesses. A NaI detector, placed at a flight-path length of about 28 m, was used for capture measurements and a Li-glass detector (flight-path length of about 28.7 m) for transmission measurements. Following the data reduction process, the measured data are being analyzed and evaluated to produce more accurate cross sections and associated uncertainties.
VALIDATION OF THERMAL SCATTERING LAWS FOR LIGHT WATER AT ELEVATED TEMPERATURES WITH DIFFUSION EXPERIMENTS
Authors: Holmes Jesse C. , Zerkle Michael L. , Hawari Ayman I.
Published: February 2021

Light water is the most important neutron moderator in many reactor applications. Thermal neutron scattering kernels for H bound in H2O are represented by ENDF-format thermal scattering laws (TSLs) evaluated at discrete temperatures T. Nuclear data evaluations are conventionally validated utilizing a combination of critical benchmarks and experimental cross section data. Existing public critical benchmarks may be inadequate for testing water TSLs over the full range of T of interest in reactor applications, and experimental thermal scattering cross section data for water is sparse at elevated T. In this work, MC21 is used to simulate the decay of the equilibrium thermal neutron flux in light-water spheres of several radii. The fundamental-mode time eigenvalue α is calculated at 22 °C and 227 °C (at saturation pressure) for each sphere using three different H-H2O TSLs. Fitting α to a polynomial function of geometric buckling allows calculation of the thermal neutron diffusion length L. Extrapolation lengths are treated as a function of the transport mean free path and geometry. Experimental L data from 25 publications at 49 temperatures (from 10 °C to 295 °C), computed by several different time-dependent and space-dependent decay methods, is used to develop an empirical fit of L vs. T. The MC21-calculated L for the TSLs tested are within ±1% of the predicted values at 22 °C and 227 °C. This validation approach, which may be repeated at arbitrary T, constitutes an integral benchmark specific to and characterizing the detailed physics of the thermal scattering kernel applied.
DIAGNOSIS OF THE UNRESOLVED DOMAIN TREATMENT IN MONTE CARLO TRANSPORT CALCULATIONS THROUGH THE IDENTIFICATION AND MODELLING OF CRITICALITY SAFETY EXPERIMENTS
Authors: García-Herranz N. , Rodríguez J. , Jiménez-Carrascosa A. , Cabellos O.
Published: February 2021

Monte Carlo neutron transport codes can be used for high-fidelity predictions of the performance of nuclear systems. However, validation against experiments is required in order to establish the credibility in the results and identify the inaccuracies due to the used calculation scheme and associated databases. The International Handbook of Evaluated Criticality Safety Benchmark Experiments (ICSBEP) contains criticality safety benchmarks derived from experiments that have been performed at various nuclear critical facilities around the world and are very valuable for validation purposes.

The main objective of this work is the identification and modelling of experimental benchmarks included at ICSBEP in support of the validation of Monte Carlo neutron transport calculations when applied to fast systems, and in particular, KENO-VI and associated AMPX-formatted continuous-energy libraries from SCALE package. In such systems, the predicted k-eff values can be very sensitive to the treatment of nuclear data in the Unresolved Resonance Region (URR). Consequently, benchmarks with intermediate and fast spectra are identified and modelled with KENO-VI. Then, calculated results with and without probability tables in the URR are compared with each other in order to identify the most sensitive configurations to the URR. As a result of the proposed study, recommendations are given about the benchmarks that should be modelled and analysed to qualify the processed continuous-energy libraries before their use in Monte Carlo transport codes for practical fast reactor applications.
NEUTRON EMISSION MEASUREMENTS OF PWR SPENT FUEL SEGMENTS AND PRELIMINARY VALIDATION OF DEPLETION CALCULATIONS
Authors: Perret G. , Rochman D. , Vasiliev A. , Ferroukhi H.
Published: February 2021

Assessing neutron emission of LWR spent fuel is necessary for the back-end of the fuel cycle, such as the dimensioning of transport and storage casks of spent fuel. Although core and depletion codes can calculate the isotopic composition of the discharged fuel and therefore infer its neutron source, accurate measured neutron emission values remain rare mainly because of the difficulty to prepare, handle and characterize spent fuel. Measured neutron emission values are, however, extremely relevant to code validation, as neutrons emitted by LWR spent fuel mainly originates from spontaneous fissions of minor actinides (e.g., 242Cm, 244Cm and 252Cf) that are produced only after a large number of neutron captures in the reactor core. This paper reports on neutron emission measurements of selected LWR-PROTEUS spent fuel samples and their comparisons with a core and depletion calculation chains based on CASMO-5, SIMULATE-3 and the SNF codes. The measured LWR-PROTEUS samples are comprised of 11 samples irradiated in a Swiss PWR. The samples are UO2 or MOX and have discharge burn-ups ranging from 20 to 120 GWd/t. We measured the 40-cm long samples in a hot-cell of the Paul Scherrer Institut using a measurement station made of polyethylene and a BF3 detector. We repeated the measurements several times and in different conditions to ensure the accuracy and reproducibility of the results. We derived ratios of neutron rates emitted by the different samples and absolute neutron emission rates by comparison with a reference 252Cf source, which we re-calibrated for this exercise. The experimental uncertainty (1σ) on the absolute neutron emission varies from 3% to 4%. We compared a subset of the measured values to the calculation predictions and showed an agreement within less than 7% for all but one sample.
PARTICLE DEPOSITION STUDY IN A HORIZONTAL SQUARE CHANNEL USING HIGH-RESOLUTION IMAGING
Authors: Orea D. , Chavez R. , Nguyen D.T. , Vaghetto R. , Anand N. K. , Hassan Y. A. , Sabharwall P.
Published: February 2021

The ongoing research at Texas A&M University (TAMU) aims to develop and implement measurement techniques to quantify fission product transport and related phenomena in a Gas-Cooled Fast Reactor (GCFR). This study summarizes the experimental measurements performed in a Proof-of-Concept Facility (PCF) to understand particle transport under various Reynolds numbers. Using high-resolution high-magnification optical measurement techniques, surrogate particle deposition was measured on the bottom wall surface of the PCF. The particle deposition over time was observed to decrease as the Reynolds number increased. In addition, the particle spatial distributions increased approaching the side wall of the PCF. This state-of-the art optical technique allows for the non-intrusive measurements of micron-sized particles near the wall surface.
ZERO POWER CRITICALITY BENCHMARK EVALUATION OF THE MSRE IN WIMS
Authors: Constable Charlie , Lindley Ben , Parks Geoff
Published: February 2021

This paper discusses work done to benchmark the deterministic code WIMS [1] against the Monte Carlo code Serpent [2] and experiment. Comparison is made against the Molten Salt Reactor Experiment at Oak Ridge National Laboratory as well as a Serpent model produced at the University of California, Berkeley. Producing a model for an MSR is possible thanks to the development of the next version of WIMS, WIMS11. The structure of the WIMS model built is discussed, and the final predicted criticality value for the MSR is given. This compares favourably with the Serpent model; however, both codes predict values considerably different to those expected. Potential reasons for this are suggested. However, it is concluded that WIMS has successfully been benchmarked against the current state of the art. This provides confirmation that this is a valid approach for molten salt reactor research analysis.
NUCLEAR DATA V&V ANALYSIS FOR FUSION APPLICATIONS: INTEGRAL BENCHMARKS AND DECAY DATA
Authors: Vilkhivskaya Olga , Gilbert Mark
Published: February 2021

A reliable estimation of the operational parameters is one of the primary concerns in the design of magnetic fusion devices such as ITER and DEMO. Methods of diagnostics and control over the critical plasma parameters determining its stability and efficiency rely on the high-energy neutron field monitoring. Extreme operational environment, such as high-energy neutron flux, electromagnetic radiation, and high temperatures might reduce the performance of the detector systems. Therefore, research and development activities in detector prototyping are carried out to address this problem. To predict the performance of the detector materials, simulations using the latest releases of the nuclear data libraries as input for the inventory codes are carried out. This paper describes the latest validation and verification (V&V) benchmark exercise for FISPACT-II & TENDL-2017 based on the fusion decay heat measurements performed at the Japanese FNS facility for the materials in the diagnostic components for the radiation measurements. The breakdown of decay-heat contributions from individual radionuclides have been employed to interpret the simulated results, benchmark the data against the experimental measurements, and revise the neutron-induced reactions cross-section and decay data for the associated radionuclides for the upcoming release of the TENDL-2019 nuclear data library.
NEUTRONIC MODELLING OF THE FFTF CONTROL ROD WORTH MEASUREMENTS WITH DIFFUSION CODES
Authors: Nikitin E. , Fridman E. , Mikityuk K. , Radman S. , Fiorina C.
Published: February 2021

This paper presents an assessment of three deterministic core simulators with the focus on the neutronic performance in steady-state calculations of small Sodium cooled Fast Reactor cores. The selected codes are DYN3D, PARCS and the novel multi-physics solver GeN-Foam. By using these codes, the multi-group diffusion solutions are obtained for the selected twenty control rod worth measurements performed during the isothermal physics tests of the Fast Flux Test Facility (FFTF). The identical set of homogenized few-group cross sections applied in the calculations is generated with the Serpent Monte Carlo code. The numerical results are compared with each other as well as with the measured values. The obtained numerical results, such as the multiplication factors and control rod worth values, are in good agreement as compared to the experimental data. Furthermore, a comparison of the radial power distributions is presented between DYN3D, PARCS and GeN-Foam. Ultimately, the power distributions are compared to the full core Serpent solution, demonstrating an adequate performance of the selected deterministic tools. In overall, this study presents a verification and validation of the neutronic solvers applied by DYN3D, PARCS and GeN-Foam to steady-state calculations of SFR cores.
MPACT VERIFICATION WITH MAGNOX REACTOR NEUTRONICS PROGRESSION PROBLEMS
Authors: Luciano Nicholas P. , Ade Brian J. , Kim Kang Seog , Conant Andrew J.
Published: February 2021

MPACT is a state-of-the-art core simulator designed to perform high-fidelity analysis using whole-core, three-dimensional, pin-resolved neutron transport calculations on modern parallel computing hardware. MPACT was originally developed to model light water reactors, and its capabilities are being extended to simulate gas-cooled, graphite-moderated cores such as Magnox reactors. To verify MPACT’s performance in this new application, the code is being formally benchmarked using representative problems. Progression problems are a series of example models that increase in complexity designed to test a code’s performance. The progression problems include both beginning-of-cycle and depletion calculations. Reference solutions for each progression problem have been generated using Serpent 2, a continuous-energy Monte Carlo reactor physics burnup calculation code. Using the neutron multiplication eigenvalue ke_ as a metric, MPACT’s performance is assessed on each of the progression problems. Initial results showed that MPACT’s multigroup cross section libraries, originally developed for pressurized water reactor problems, were not sufficient to accurately solve Magnox problems. MPACT’s improved performance on the progression problems is demonstrated using this new optimized cross section library.
OPTIMIZATION OF LOAD-FOLLOW OPERATIONS OF A 1300MW PRESSURIZED WATER REACTOR USING EVOLUTIONNARY ALGORITHMS
Authors: Drouet V. , Do J.-M. , Verel S.
Published: February 2021

Because of the increase of intermittent renewable energies, load follow operations for French PWR will be crucial in the years to come. The goal of this study is to make realistic changes to the plant operations in order to optimize load-following without disrupting the plant. 6 discrete parameters were considered among the overlaps, speeds and maneuvering bands of the control rods. A simulator oriented model of the pressurized reactor based on APOLLO3® is used. It includes 3D neutronics calculations with point kinetics and a 0D model of the secondary system. The operating mode (G mode) was modeled, to account for the human operator of the power plant. Two objectives were considered so as to both minimize the volume of effluents generated during the transient, and maximize the core axial stability. The reaction of the power plant to a load follow transient varies greatly during the operating cycle, because of fuel depletion effects. Therefore, 4 burnup points are considered and the objectives are computed for each point and then reduced to two “whole cycle” objectives. A biobjective massively parallel asynchronous master worker evolutionary algorithm based on AMS-MOEA/D was implemented. It is a highly exploratory algorithm, suitable for black-box problems with an important computing time. The analysis of the performances of this algorithm shows that it is able to find a diversified Pareto front, with solutions that greatly improve the load follow operations for all burnup points compared to the standard control rod parameters.
DEVELOPMENT OF FUEL CHARACTERIZATION TOOL BASED ON LIBRARY INTERPOLATION
Authors: Malec J , Ambrožič K , Kromar M
Published: February 2021

The feasibility of using Origen+ARP code for depletion and decay calculations for Krško NPP was tested by performing depletion and decay calculations using interpolated libraries and comparing the results to the ones calculated from non-interpolated libraries in order to evaluated the number of libraries needed in order to interpolate fuel properties with sufficient precision for any realistic burnup scenario. For Krško NPP fuel, using three interpolation libraries with different decay heat parameters was enough to bring the approximation error bellow 0:5 % when comparing fuel decay heat through the decay interval.
COSI7: THE NEW CEA REFERENCE ELECTRO-NUCLEAR SIMULATION TOOL
Authors: Krivtchik G.
Published: February 2021

Nuclear fuel cycle scenario studies are used as a prospective analysis tool in order to provide stakeholders with decision aid. Nuclear fuel cycle simulation tools model the deployment of reactor fleets, the mass flows in the fuel cycle, and track the nuclear materials. The CEA has been developing for more than 30 years the nuclear fuel cycle tool COSI. The latest version, COSI7, was designed in order to model dynamic systems of ever-increasing complexity with improved user experience. The new developments include functionalities designed to improve the user experience as well as new physical models and post-processing capabilities. COSI7 supersedes COSI6 as the CEA reference nuclear fuel cycle simulation code starting January 2020.
CONSOLIDATION OF REACTOR PHYSICS EDUCATION – THE KHALIFA UNIVERSITY STUDENT FIELD TRIPS CASE STUDY
Authors: Alameri Saeed A. , Alrwashdeh Mohammad , Beeley Philip , Kim Myung-Hyun , Unlu Kenan
Published: February 2021

In 2010, the Department of Nuclear Engineering at Khalifa University of Science and Technology (NUCE) established the MSc degree in Nuclear Engineering. This program was established to support the United Arab Emirates (UAE) emerging civil nuclear energy program and produce graduate engineers capable of supporting the safe construction, operation, maintenance and eventual decommissioning of the UAE nuclear reactors. In order to enhance and consolidate classroom teaching, an overseas “Field Trip” module was integrated into the MSc curriculum in order to provide practical exercises, demonstrations and site visits. With respect to the consolidation of reactor physics teaching in particular, the field trips over the past 9 years have utilized mainly the AGN Zero Power reactor at Kyung Hee University (2012-2015) and the Breazeale TRIGA reactor at Penn State University (2017-2018). In both cases students gained “hands-on” supervised experience in classical reactor experiments, shielding measurements, health physics and radiological protection control, and radioanalytical measurement methods, such as neutron activation analysis. At Penn State University, the experiments were extended to surveillance measurements, taking advantage of the facilities specialized modules in nuclear security.

This paper provides details of the arrangements made for the field trips and the learning outcomes these practical arrangements helped to satisfy meeting the overall degree outcomes. The case study will also illustrate where a nuclear energy newcomer State can take advantage of international collaborations without the need to invest in a national research reactor.
UNCERTAINTY ANALYSIS OF SUB-EXERCISES IN UAM-SFR BENCHMARK WITH THE MCS CODE
Authors: Jo Yunki , Dos Vutheam , Mai Nhan Nguyen Trong , Lee Hyunsuk , Lee Deokjung
Published: February 2021

Uncertainty analysis in Modelling (UAM) for Design, Operation and Safety Analysis of Sodium-cooled Fast Reactors (SFRs) has been formed by OECD/NEA to assess the effect of nuclear data uncertainties on parameters of interest in SFR analysis. In this paper, sub-exercises of a medium 1000 MWth metallic core (MET-1000) and a large 3600 MWth oxide core (MOX-3600) are tested by a Monte Carlo code MCS to perform uncertainty analysis. Classical perturbation theory and generalized perturbation theory are used to calculate sensitivity coefficients. Uncertainty is calculated by multiplying the sensitivity coefficients and relative covariance matrix from ENDF/B-VII.1 library.
DETECTING NUCLEAR MATERIALS IN URBAN ENVIRONMENTS USING MOBILE SENSOR NETWORKS
Authors: Flanagan R. , Brandt LJ , Deinert MR , Osborne AG
Published: February 2021

Radiation detectors installed at major ports of entry are a key component of the overall strategy to protect countries from nuclear terrorism. While the goal of deploying these systems is to intercept special nuclear material as it enters the country, no detector system is fool proof. Mobile, distributed sensors have been proposed to detect nuclear materials in transit should portal monitors fail to prevent their entry in the first place. In large metropolitan areas a mobile distributed sensor network could be deployed using vehicle platforms such as taxis, Ubers and Lyfts which are already connected to communications infrastructure. However, the potential geographic coverage that could be achieved using a network of sensors mounted on commercial passenger vehicles has not been established. Here we evaluate how a mobile sensor network could perform in New York City using a combination of radiation transport and Geographic Information Systems. The Geographic Information System QGIS is used in conjunction with OpenStreetMap data to isolate roads and construct a grid over the streets. Vehicle paths are built using pickup and drop off data from Uber, and data from the New York State Department of Transportation.
ESTIMATION OF THE GENERATION OF 13C AND 14C IN THE REACTOR GRAPHITE USING MCNP6 MODELLING, ISOTOPE RATIO MASS SPECTROMETRY AND 14C MEASUREMENT TECHNIQUE
Authors: Plukienė R. , Lagzdina E. , Garankin J. , Garbaras A. , Gudelis A. , Germanas D. , Plukis A. , Remeikis V.
Published: February 2021

Characterization of irradiated graphite in terms of 14C activity is crucial for the optimization of treatment technology: geological disposal, landfill storage, recycling, etc. The main contributor to 14C generation in the RBMK reactor graphite is 14N(n, p)14C reaction. The generation of carbon isotopes 13C and 14C in the virgin RBMK graphite samples irradiated at the LVR-15 research reactor (Research Centre Řež, Ltd.) were investigated in order to obtain the impurity concentration level of 14N. Afterwards the modeling of graphite activation in the RBMK-1500 reactor was performed by computer code MCNP6 using obtained 14N impurity concentrations and new nuclear data libraries. The irradiation parameters – neutron fluence have been checked by method based on coupling of stable isotope ratio mass spectrometry and computer modelling. The activity of 14C in the different constructions of irradiated graphite of the RBMK-1500 reactor has been measured by the β spectrometry technique (LSC) and has been compared with the simulated one. Obtained results have indicated the importance of 14C production from 14N in the RBMK-1500 reactor and in the LVR-15 neutron spectrum. Measured 14C specific activity values in the samples varied from 130-700 kBq/g in the RBMK-1500 irradiated samples and from 3-12.5 Bq/g in the LVR-15 irradiated graphite samples. This corresponds to 15±4 - 80±10 ppm impurity of 14N in various graphite samples of RBMK reactor.
VALIDATION OF SERPENT FOR FUSION NEUTRONICS ANALYSIS AT JET
Authors: Žohar Andrej , Štancar Žiga , Batistoni Paola , Conroy Sean , Snoj Luka , Lengar Igor ,   JET contributors
Published: February 2021

Fusion neutronics analysis before and after experiments at JET is traditionally performed using Monte Carlo particle transport code Monte Carlo N-Particle. For redundancy and diversity reasons there is a need of an additional Monte Carlo code, such as Serpent 2, capable of fusion neutronics analysis. In order to validate the Serpent code for fusion applications a detailed model of JET was used. Neutron fluxes and reaction rates were calculated and compared for positions outside the tokamak vacuum vessel, in the vacuum vessel above the plasma and next to a limiter inside the vacuum vessel. For all detector positions with DD and DT neutron sources the difference between neutron fluxes calculated with both Monte Carlo codes were within 2σ statistical uncertainty and for most positions (more than 90 % of all studied positions) even within 1σ uncertainty. Fusion neutronics analysis in the JET tokamak with Serpent took on average 10 % longer but this can be improved by changing the threshold value for determination of the transport method used. With the work presented in this paper the Serpent Monte Carlo code was validated to be a viable alternative to MCNP for fusion neutronics analysis for the JET tokamak.
Étude du comportement de l’interface sable-pieu sous chargement axial monotone et cyclique à l’échelle granulaire
Authors: Doreau-Malioche Jeanne , Combe Gaël , Viggiani Gioacchino
Published: February 2021

De nombreuses études expérimentales sont conduites pour analyser quantitativement la cinématique et l’écrasement des grains à l’interface sable-pieu sous chargement axial. Néanmoins, les résultats sont obtenus soit post-mortem, soit en déformations planes, et principalement pendant l’installation du pieu. L’article présente une approche innovante associant la tomographie à rayons X et l’analyse d’images en 3D et permettant d’extraire des informations à l’échelle granulaire, pendant le chargement monotone et cyclique du pieu. Les tests sont réalisés sur un pieu instrumenté installé par fonçage monotone dans un échantillon dense de sable. Après son installation, le pieu est soumis à un grand nombre de cycles axiaux contrôlés en déplacement à contrainte radiale constante. Ces essais sont conduits dans une mini-chambre de calibration qui permet d’acquérir des tomographies à rayons X à haute résolution après différentes étapes de chargement. La réponse macroscopique de l’interface montre une évolution du frottement à l’interface pendant les cycles en deux phases, avec une augmentation non négligeable de la résistance de frottement dans la seconde phase. Pour ces deux phases, la mesure de la cinématique révèle un comportement du sable différent associé à une densification importante à l’interface. D’abord, le sol se contracte radialement dans une zone de 4 D50d’épaisseur. Ensuite, les grains de sable se déplacent difficilement et la densité à l’interface atteint un seuil pour lequel le frottement sur le pieu augmente de manière significative.
Modélisation sous macrogravité d’une paroi clouée respectant le phasage de construction
Authors: de Sauvage Jean , Tfayli Fatima , Dubreucq Thierry , Rajot Jean-Pierre
Published: February 2021

Développé en France dans les années 1970, le clouage des sols est une technique de stabilisation des talus réalisés par déblai. Des inclusions subhorizontales assurent la stabilité de l’ouvrage par frottement avec le sol. Les réflexions engagées à l’occasion de la révision en cours de la norme NF P 94-270, sur le dimensionnement des massifs en sol renforcé, ont souligné le manque de connaissances quant aux efforts au parement, notamment sur l’influence du phasage de construction sur ces efforts. Afin de mener une étude paramétrique pour répondre à ces questions, des modèles réduits de paroi clouée ont été réalisés et instrumentés, puis centrifugés à l’Université Gustave Eiffel, campus de Nantes. Un protocole expérimental spécifique a été utilisé pour réaliser l’excavation en vol. Les évolutions des efforts le long des clous ont été mesurées à l’aide de fibres optiques équipées de réseaux de Bragg. Enfin, les déplacements du massif ont été observés à l’aide d’une technique d’imagerie appelée GeoPIV, les modèles centrifugés étant réalisés dans un caisson à face latérale transparente. L’élancement du massif cloué, (rapport entre hauteur du mur et longueur des clous) a une forte influence sur le comportement de l’ouvrage et en particulier sur la répartition des efforts au parement. La technique de GeoPIV a permis en outre de décrire les mécanismes de rupture des différents soutènements par clouage testés dans cette étude.
International cooperation: A brief history We’ve experienced
Authors: Ji Wu , Qingjiang Bai , Yongjian Xu
Published: February 2021

The solar-terrestrial space is of considerable significance for human activities. Since the first artificial satellite Sputnik 1 was launched in 1957, more knowledge about the dynamic conditions of the space environment has been acquired. With growing dependence on modern technology – both in space and on the ground, the vulnerability of the modern society and its infrastructure to space weather has increased dramatically. To better understand, forecast and reduce the adverse effects of space weather, science programs on space weather always prioritize the measurement or acquisition of the data from different locations of the geo-space, such as in magnetopause, polar cusps, and the magnetic tail. For the ground observations, it is necessary to locate the instruments in different longitudes and latitudes. For a single country, it is impossible to cover all these observation points. Therefore, international cooperation is very much needed. The paper reviews some of the international space weather observation programs we have experienced at the system design level. It may provide lessons learned for the community that may enable such kind of cooperative programs in the future.
Surgical Aspects in Gene Therapy for Inherited Retinal Diseases
Authors: Fischer M. Dominik , Bartz-Schmidt Karl Ulrich , Dimopoulos Spyridon , Herrmann Philipp , Gerhardt Maximilian , Holz Frank G. , Priglinger Siegfried
Published: February 2021

Inherited retinal dystrophies (IRD) have been studied since their recognition by Franz Donders and Albrecht von Graefe. It nevertheless took 100 years for a causal therapy to take shape in the form of gene therapy: The approval of Voretigen Neparvovec (VN) for the treatment of hereditary retinal dystrophies due to RPE65 mutations was thus a significant milestone – for the era of personalised medicine in general and ophthalmology in particular. The clinical management around gene therapy applications is complex and requires the cooperation of various experts as a multidisciplinary team. This article describes the requirements, challenges, approaches, and open questions regarding the surgical aspects of gene therapy for retinal dystrophies. The first part outlines the standard surgical treatment. Based on this standard, alternative approaches are indicated for each individual step and their value discussed. Knowledge gaps are defined and in the outlook we speculate
on future developments.
Predicting the Relapse of Hyperthyroidism in Treated Graves’ Disease with Orbitopathy by Serial Measurements of TSH-Receptor Autoantibodies
Authors: Stöhr Mareile , Oeverhaus Michael , Lytton Simon D. , Horstmann Mareike , Zwanziger Denise , Möller Lars , Stark Achim , Führer-Sakel Dagmar , Bechrakis Nikolaos , Berchner-Pfannschmidt Utta , Banga J. Paul , Philipp Svenja , Eckstein Anja
Published: February 2021

The aim of this study was to investigate the potential of the new TSH-receptor antibody (TRAb) assays to predict remission or relapse of hyperthyroidism in patients with Graves’ disease (GD) and Graves’ orbitopathy (GO). TRAbs were measured retrospectively in sera from a cohort of GD patients with GO (n=117; remission n=38 and relapse n=79–Essen GO biobank) with automated binding immunoassays: TRAb Elecsys (Cobas Roche) and TRAb bridge assay (IMMULITE, Siemens), and the TSAb (thyroid stimulating Ab) cell-based bioassay (Thyretain, Quidel Corp.). To identify relapse risk/remission of hyperthyroidism patients were followed up at least 10 months after the end of antithyroid drug therapy (ATD) therapy. ROC plot analysis was performed to calculate cut-off levels of TRAb and TSAb for prediction of relapse and remission of hyperthyroidism. Cut-off serum levels are provided for timepoints around 3, 6, 10, and 15 months after the beginning of ATD. Repeated measurements of TRAb increase the rate of relapses predictions to 60% (Elecsys), 70% (IMMULITE), and 55% (Thyretain). Patients with remission have consistently TRAb levels below the cut off for relapse in repeated measurements. The cell-based bioassay was the most sensitive – and continued to be positive during follow up [at 15 months: 90% vs. 70% (IMMULITE) and 65% (Elecsys)]. Identification of relapsing hyperthyroidism is possible with automated immunoassays and cell-based bioassay especially with serial TRAb measurements during the course of ATD therapy. Patient who need eye surgery may profit from an early decision towards definitive treatment.
Custom-Made Pyrene Photocatalyst-Promoted Desulfonylation of Arylethenyl Sulfones Using Green-Light-Emitting Diodes
Authors: Orita Akihiro , Watanabe Hikaru , Nakajima Kazuki , Ekuni Kento , Edagawa Ryota , Akagi Yuta , Okuda Yasuhiro , Wakamatsu Kan
Published: February 2021

The Sonogashira coupling of 1,3,6,8-tetrabromopyrene with 4-[(–)-β-citronellyloxy]phenylethyne was employed to synthesize 1,3,6,8-tetra[4-(citronellyloxy)phenylethynyl]pyrene. The pyrene derivative catalyzed the reductive desulfonylation of ethenyl sulfones via visible-light irradiation (514 nm green light-emitting diodes) in the presence of i-Pr2NEt. The β-citronellyloxy groups provided the sufficient solubility to the highly π-expanded pyrene catalyst, and their polar oxygen functionalities enabled the easy separation of the catalyst from the products via column chromatography.
The Accuracy of Direct Targeting Using Fusion of MR and CT Imaging for Deep Brain Stimulation of the Subthalamic Nucleus in Patients with Parkinson's Disease
Authors: Almahariq Fadi , Sedmak Goran , Vuletić Vladimira , Dlaka Domagoj , Orešković Darko , Marčinković Petar , Raguž Marina , Chudy Darko
Published: February 2021

Introduction In 33 consecutive patients with Parkinson's disease (PD) undergoing awake deep brain stimulation (DBS) without microelectrode recording (MER), we assessed and validated the precision and accuracy of direct targeting of the subthalamic nucleus (STN) using preoperative magnetic resonance imaging (MRI) and stereotactic computed tomography (CT) image fusion combined with immediate postoperative stereotactic CT and postoperative MRI, and we report on the side effects and clinical results up to 6 months' follow-up.

Materials and Methods Preoperative nonstereotactic MRI and stereotactic CT images were merged and used for planning the trajectory and final lead position. Immediate postoperative stereotactic CT and postoperative nonstereotactic MRI provided the validation of the final electrode position. Changes in the Unified Parkinson's Disease Rating Scale III (UPDRS III) scores and the levodopa equivalent daily doses (LEDD) and appearance of adverse side effects were assessed.

Results The mean Euclidian distance (ED) error between the planned position and the final position of the lead in the left STN was 1.69 ± 0.82 mm and that in the right STN was 2.12 ± 1.00. The individual differences between planned and final position in each of the three coordinates were less than 2 mm. The UPDRS III scores improved by 75% and LEDD decreased by 45%. Few patients experienced complications, such as postoperative infection (n = 1), or unwanted side effects, such as emotional instability (n = 1).

Conclusion Our results confirm that direct targeting of an STN on stereotactic CT merged with MRI could be a valid method for placement the DBS electrode. The magnitude of our targeting error is comparable with the reported errors when using MER and other direct targeting approaches.
Design of a hexagonal air-coupled capacitive micromachined ultrasonic transducer for air parametric array
Authors: Zhang Xiaoli , Zhang Hui , Li Dachao
Published: February 2021

An air parametric array can generate a highly directional beam of audible sound in air, which has a wide range of applications in targeted audio delivery. Capacitive micromachined ultrasonic transducer (CMUTs) have great potential for air-coupled applications, mainly because of their low acoustic impedance. In this study, an air-coupled CMUT array is designed as an air parametric array. A hexagonal array is proposed to improve the directivity of the sound generated. A finite element model of the CMUT is established in COMSOL software to facilitate the choice of appropriate structural parameters of the CMUT cell. The CMUT array is then fabricated by a wafer bonding process with high consistency. The performances of the CMUT are tested to verify the accuracy of the finite element analysis. By optimizing the component parameters of the bias-T circuit used for driving the CMUT, DC and AC voltages can be effectively applied to the top and bottom electrodes of the CMUT to provide efficient ultrasound transmission. Finally, the prepared hexagonal array is successfully used to conduct preliminary experiments on its application as an air parametric array.
Rigorous results for the electrical conductivity due to electron–phonon scattering
Authors: Amarel J. , Belitz D. , Kirkpatrick T. R.
Published: February 2021

We present a rigorous solution of the Boltzmann equation for the electron–phonon scattering problem in three spatial dimensions in the limit of low temperatures. The different temperature scaling of the various scattering rates turns the temperature into a control parameter that is not available in classical kinetic theory and allows for a rigorous proof of Bloch’s T5 law. The relation between the Boltzmann equation and the Kubo formula is also discussed, as well as implications for the scattering of electrons by excitations other than phonons.
Combination anti-coronavirus therapies based on nonlinear mathematical models
Authors: González J. A. , Akhtar Z. , Andrews D. , Jimenez S. , Maldonado L. , Oceguera-Becerra T. , Rondón I. , Sotolongo-Costa O.
Published: February 2021

Using nonlinear mathematical models and experimental data from laboratory and clinical studies, we have designed new combination therapies against COVID-19.
Ellipsometric study of the electronic behaviors of titanium-vanadium dioxide (TixV1−xO2) films for 0 ≤ x ≤ 1 during semiconductive-to-metallic phase transition
Authors: Kakiuchida Hiroshi , Okada Masahisa , Yamada Yasusei , Tazawa Masato
Published: February 2021

Titanium-vanadium dioxide or TixV1−xO2 films for 0 ≤ x ≤ 1 were examined using ellipsometry, and their optical constants (n and k) at visible and near-infrared wavelengths were determined at temperatures (T) below, at, and above the semiconductive-to-metallic phase transition (SMT) temperature (TSM). Ellipsometric analysis was performed for each x at each T using a wavelength dispersion model, i.e., a combination of Lorentz oscillators and a Drude free electron model. The ellipsometric analyses provided information on the electronic band transition caused by the SMT and the influence of cationic replacement (Ti↔V) on the SMT. The results revealed that when x ≤ 0.05, close to the SMT, the energy gap of the interband transition O2p→V3d varied from ≈3.5 eV to ≈3.1 eV, and the quantity of electrons in the interband transition decreased by half. In addition, the energy gap monotonically increased to 4.2 eV when x was increased to 1. Moreover, the energy gap of the split V3d intraband transition varied from ≈1.4 eV to zero, and the quantity of electrons in the intraband transition increased by a factor of four. Furthermore, when x ≥ 0.2, close to the SMT, the energy gap of the intraband transition varied from ≈1.4 eV to a constant positive value, with the generation of a small number of conductive electrons, depending on x.
Domain-wall photovoltaic effect in Fe-doped BaTiO3 single crystals
Authors: Noguchi Yuji , Inoue Ryotaro , Matsuo Hiroki
Published: February 2021

A single crystal of Fe (0.3%)-doped BaTiO3 was grown by a top-seeded solution growth method, and the photovoltaic (PV) properties (at 3.1 eV) in a multi-domain state with a 90° domain structure are investigated. We show that the overall behavior can be well understood by an analytical expression of the domain wall (DW)-PV effect superimposed on the bulk-PV effect. The fitting of photocurrents as a function of light polarization reveals that the offset component of the DW-PV effect is much larger than that of the bulk-PV effect, even though the volume fraction of the DW region is extremely small. A local electric field in the DW region is estimated to be several hundred kV cm−1, which is three orders of magnitude higher than the effective field inside the domains.
Plume particle energy analysis of an ionic liquid electrospray ion source with high emission density
Authors: Ma C. , Ryan C.
Published: February 2021

A retarding potential analyzer was used to characterize the energy distribution of the plume particles from an electrospray source. The electrospray device uses an ionic liquid, operates at bipolar and relatively high voltages from ±1800 to ±3500V, and demonstrated ionic emissions with a relatively high emission density of more than ±30μA per emission tip. Electrostatic simulations were used to study the effects of electric field distortion near the grids in the retarding potential analyzer, and a correction factor of 93% was used to regulate the deceleration voltage in the energy analysis, from which the voltage losses between the applied voltage of the electrospray source and the actual acceleration voltage of the charged particles were calculated, demonstrating non-kinetic efficiency from 85.8% at −2100 V to 79.6% at 2600 V. The plume particle energy analysis shows evidence of fragmentation of heavier particles, mostly from dimer ions to monomer ions, and the detailed energy analysis was used to estimate the position where the fragmentation occurs. The results suggest that about 45%–55% of the particle fragmentation occurred in the field-free region and 20%–30% occurred in the acceleration region with an intense electric field, with the rest of the plume containing unfragmented ions.
Consensus on simplicial complexes: Results on stability and synchronization
Authors: DeVille Lee
Published: February 2021

We consider a nonlinear flow on simplicial complexes related to the simplicial Laplacian and show that it is a generalization of various consensus and synchronization models commonly studied on networks. In particular, our model allows us to formulate flows on simplices of any dimension so that it includes edge flows, triangle flows, etc. We show that the system can be represented as the gradient flow of an energy functional and use this to deduce the stability of various steady states of the model. Finally, we demonstrate that our model contains higher-dimensional analogs of structures seen in related network models.