Nuclear Model Research Articles

Carbonitriding reduction of TiO2 in the CH4-H2-N2 system: Reduction temperature effect and kinetics

Understanding reaction kinetics can provide valuable information for the design and optimization of a reaction process. In this study, the reduction degree and carbonitriding ratio of TiO2 in the CH4-H2-N2 system were investigated to understand the kinetics of carbonitriding reduction. The experimental results revealed the following important findings. The reduction degree of TiO2 increased significantly within the temperature range of 1000?C to 1200?C. At the same time, the duration of complete carbonitride time decreased with increasing temperature. However, it was found that excessively high temperatures (1200?C) had a detrimental effect on the degree of reduction. Consequently, the optimal reduction temperature was set at 1100?C, in order to achieve a balance between reduction degree and reaction time. The process of carbonitride reduction of TiO2 in the CH4-H2-N2 system corresponded to the unreacted nuclear model, where the process was mainly controlled by chemical reactions. A calculated apparent activation energy of 99.35 kJ/mol was obtained for the carbonitriding reduction process. The identification of the optimal reduction temperature and the dominant role of chemical reactions provide valuable insights for the design and optimization of carbonitriding processes with titanium compounds.

Application of reactor dosimetry techniques for source term validation in F-18 production with a medical cyclotron

Imaging techniques such as positron emission tomography need radionuclides that can be produced with cyclotrons. The involved nuclear reactions mostly produce neutron and gamma radiation, which must be shielded. In order to be able to determine the required thickness of the shielding for a newly bought medical cyclotron, corresponding radiation protection calculations were carried out. The necessary neutron source term was supplied by the manufacturer. To verify this source term, additional source terms were calculated with the MCNP6 and the FLUKA code packages. The results with the source, on base of code internal nuclear models, produced comparable results, but the neutron yield with the source supplied by the manufacturer turned out to be lower by a factor of about 5. To validate the results, experiments were carried out on an already existing cyclotron. Neutron fluence was measured with standard monitors which are used in reactor dosimetry. The experiments were performed during regular 18F production. Activities of the nuclides were measured by gamma spectroscopy and compared with the calculated activities.

Computation of Cross-sections by Effects of Theoretical Parameters Code for Production of 52Mn Radioisotope

Abstract: Theoretical calculations focusing on cross-section data results for the production of 52Mn from a natural chromium (natCr) target have been investigated for deuteron beams up to 35 MeV by using the EMPIRE 3.2.2 Malta nuclear model code. The optimization of theoretical calculations is important for the medical production routes of cross-section isotopes. In these computations, we tested different ATILNO parameters for the evaluation of cross-section data and improved techniques for the theoretical calculation of radioisotope 52Mn. The effects of these parameters were investigated, and the theoretical results were subsequently compared with each other, existing literature data, and the TENDL-2019 library. Keywords: EMPIRE code, Cross-section, Manganese-52, Radionuclide production, Positron emission tomography.

Approximation of BPS Skyrme model using modified Lagrangian Skyrmion

One of the nuclear atomic models represented by Skyrmion was the Skyrme model. This model was a modified nonlinear sigma model with a Skyrme field where the classical solution use generalized sixth order terms and potential terms. The binding energy that will be studied in the Skyrme SU(2) model is to generalize the second order nonlinear sigma model terms with sixth order derivative terms. The Lagrangian will be obtained for these two terms to find the BPS (Bogomolny Prasad Sommerfield) solution for the profile function numerically. The result of numerical calculation will be used to calculate static energy and rotational energy, where the characteristic of the nucleus can be observed from these two energies. Furthermore, the value of the coupling constant in the Lagrangian Skyrmion will be calculated from the static energy and rotational energy obtained previously. These values are expected to help in the application of Skyrme model for many research physics field.

Impact of the molecular resonances on the [formula omitted] fusion reaction rate

The properties of the low-energy C12+12C molecular resonances, which potentially enhance the fusion reaction rate at low temperatures, have been investigated by a full-microscopic nuclear model employing various nuclear energy density functionals. We show that some density functionals plausibly describe the observed high-spin C12+12C molecular resonances and predict many 0+ and 2+ resonances at low energies, which enhance the reaction rate. We also discuss how the uncertainty in the nuclear energy density functionals propagates to that of the reaction rate.

Proposal of Application of a Simple Analysis Code DYMOS for Accident Analyses of Molten Salt Reactors

The Molten Salt Reactor (MSR) possesses unique characteristics, including the circulation of liquid fuel salt in-core and ex-core, and the absence of cladding tubes of fuel rods. To perform safety analyses for accidents and transients, the selection of appropriate models is crucial. Proposed models vary from the coupling of a three-dimensional (3-D) nuclear reactor model and a detailed thermal/hydraulic (T/H) model to a simple point reactor model coupled with a lumped parameter model of the T/H system. The authors have been investigating the development of a simple and accurate model that can be utilized during the design stage and licensing evaluation, while also providing transparency, which means that models can be easily understandable by experts and reproduced in licensing evaluation. Given the distinctive features of the MSR, the peak heat flux or fuel cladding peak temperature is not a requirement. Instead, the most decisive parameter for safety evaluations is the fuel salt temperature in the fuel salt boundary. As demonstrated in this paper, the outlet of the MSR core consistently displays the highest temperature.Based on the afore-mentioned prospects for both nuclear and T/H systems, the authors have developed a simple safety and transient analysis code for MSR (DYMOS). The DYMOS code has been verified for MSRE experiments, as described in this paper. However, the previous verification was limited to small experimental MSRs, and there is a lack of verification for large reactor systems. This paper shows that the DYMOS code is applicable to these larger reactors. In other words, the main objective of this article is not to claim the originality of the model of DYMOS code, but to propose applicability of such simple code to large reactor systems.

A new nuclear magnetic resonance-based permeability model based on two pore structure characterization methods for complex pore structure rocks: Permeability assessment in Nanpu Sag, China

The nuclear magnetic resonance (NMR) estimate of permeability is a fundamental method that has numerous applications in reservoir engineering and petrophysics. To improve the accuracy of the NMR-based permeability model, many variables are introduced into NMR-based permeability prediction models due to geometric complexity and pore structure heterogeneity. In this paper, two pore structure characterization methods are investigated based on the Kozeny-Carman model and equivalent component model. Furthermore, an NMR-based permeability model accounting for the effect of pore structure is developed based on the analysis of the relationship between two pore structure parameters, and it is applied to practically predict permeability. Results indicate that the new model-calculated permeability has good agreement with experimental data; moreover, the adaptability of the new NMR-based permeability prediction model is highly improved through reducing undetermined variables, and key parameters can be measured directly using NMR. The new model provides a valuable scientific resource and assists in the evaluation of hydrocarbon-bearing reservoirs with complex pore structure, such as tight sandstone, shale, and carbonate rock.

The Roles of IL-18 in a Realistic Partial Body Irradiation with 5% Bone Marrow Sparing (PBI/BM5) Model.

IL-18 has been shown to play important roles in response to total body irradiation. However, homogenous total body irradiation is not a realistic model to reflect the radiation exposure in a real nuclear event. To further study the roles of IL-18 in a real nuclear scenario, we developed a mouse partial body irradiation with 5% bone marrow sparing (PBI/BM5) model to mimic the inhomogeneous radiation exposure. We established the dose response curves of PBI/BM5 using different radiation doses ranging from 12 to 16 Gy. Using the PBI/BM5 model, we showed that IL-18 knockout mice were significantly more radiation resistant than the wild-type mice at 14.73 Gy. We further studied the hematopoietic changes using a complete blood count, bone marrow colony-forming assays, and serum cytokine assays on the mice exposed to PBI/BM5 with IL-18BP treatment and wild-type/IL-18 knockout mice. In conclusion, our data suggest that IL-18 plays important roles in mouse survival in a realistic nuclear exposure model, potentially through the IL-18/IFNγ pathway.

Deuteron Optical Model Calculations for Elastic and Inelastic Reactions on 14N, 16O, 27Al Target Nuclei

Nuclear reaction cross sections have a key role in nuclear radioisotope production research. It is also an important part of applied fields such as energy production and experimental nuclear studies. It has been the subject of theoretical studies such as elucidating the nuclear structure and preparing and testing nuclear reaction models. It has become a very useful tool, especially for determining nuclear optical model parameters. In this study differential cross sections were calculated for elastic and inelastic scattering of 14-15 MeV energy range deuterons from 14N, 16O and 27Al. Calculation were carried out with TALYS 1.96/2.0 nuclear reaction code. Calculations include determining the deuteron optical model that match the experimental data. The values calculated with theoretical models were compared with experimental data obtained from the literature. While such studies are important for testing nuclear reaction models, they are also important for encouraging the preparation of nuclear reaction codes.

Interaction between forced and natural convection in a thin cylindrical fluid layer at low Prandtl number

Motivated by nuclear safety issues, we study the heat transfers in a thin cylindrical fluid layer with imposed fluxes at the bottom and top surfaces (not necessarily equal) and a fixed temperature on the sides. We combine direct numerical simulations and a theoretical approach to derive scaling laws for the mean temperature and for the temperature difference between the top and bottom of the system. We find two asymptotic scaling laws depending on the flux ratio between the upper and lower boundaries. The first one is controlled by heat transfer to the side, for which we recover scaling laws characteristic of natural convection (Batchelor, Q. Appl. Maths, vol. 12, 1954, pp. 209–233). The second one is driven by vertical heat transfers analogous to Rayleigh–Bénard convection (Grossmann & Lohse, J. Fluid Mech., vol. 407, 2000, pp. 27–56). We show that the system is inherently inhomogeneous, and that the heat transfer results from a superposition of both asymptotic regimes. Keeping in mind nuclear safety models, we also derive a one-dimensional model of the radial temperature profile based on a detailed analysis of the flow structure, hence providing a way to relate this profile to the imposed boundary conditions.

Effects of correlations in uncertainties of total cross section and elastic angular distribution for a deep penetration of 14-MeV neutrons in Cu

ABSTRACT Uncertainty in neutron reaction rates after penetrating a thick copper benchmark assembly was estimated based on two different kinds of Total Monte Carlo methods under random sampling methodology. Five hundred random nuclear data files were generated for 63Cu by Bayesian Monte Carlo method by perturbing the underlying nuclear model parameters. In the first method, these files were used directly to generate processed libraries, preserving all the correlations among different physical quantities. In the second method, the random files generated in the first method were used, but the angular distributions of elastic scattering were kept fixed to those of the non-perturbed nominal one. It was found that the two methods have the same neutron reaction rate after 608 mm penetration of copper. However, the uncertainty of the first method was smaller than that of the second method. It shows that the correlation between angular distribution of elastic scattering at 0 degrees and total cross section, which stems from Wick’s inequality, affects uncertainty of the calculated neutron reaction rate. It could be concluded that the uncertainty obtained by using the covariance files given in the ENDF-6 format may not give correct results for the uncertainty of neutron penetration calculations.

Recent radiation protection activities related to nuclear facilities on the Iberian Peninsula

Part of the radiation protection in Spain and Portugal is focused on the protection of workers, public and environment due to the influence of nuclear facilities present in their territory (Spanish case) or nearby. Radiation protection is in a process of continuous improvement, with the participation of nuclear facilities, companies and researchers in numerous research projects funded in Spain by the Nuclear Safety Council or other international organizations. This article presents some of the projects in which Spanish working groups have participated. In addition, specific examples of activities related to radiation protection and environmental radiological monitoring carried out in Spain in recent years are shown. Among them are: the development of methods of analysis of environmental samples in case of emergency, real-time monitoring networks for measuring radiation, environmental dosimetry in the environment of nuclear facilities, programs and models of radiation dispersion in case of accident, and the treatment and management of radioactive waste for its clearance.

Fast neutron induced reaction cross sections on natural manganese and tantalum

The cross sections for the 55Mn(n,2n)54Mn, 181Ta(n,2n)180gTa, and 181Ta(n,p)181Hf reactions were measured to be 705.1 ± 26.1 mb at 14.0 MeV, 1362.7 ± 87.2 mb at 13.6 MeV, and 2.31 ± 0.09 mb at 13.6 MeV, respectively, by using an off-line γ-ray spectroscopic technique. The neutrons were produced via the 3H(d,n)4He reaction. The monitor reactions 27Al(n,α)24Na and 93Nb(n,2n)92mNb were used for neutron flux determination. The results from the present work were compared with those of the literature and the evaluated data from ENDF/B-VIII.0, JEFF-3.3, JENDL-5, CENDL-3.2, and BROND-3.1 libraries. Besides, the cross sections were also estimated with the TALYS-1.96 nuclear model code using different level density models for a better description of the present work and literature data. The present experimental results were found to be in good agreement with most of the available literature data and with the evaluated data.

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New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. A time projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document} mixtures with a CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CH}_{4}$$\\end{document} content between 2.8 and 5.0%, and so far up to 4 bar absolute with Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} (90-10). The charge gain of the OROC was measured with signals induced by an 55Fe\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{55}\ ext {Fe}$$\\end{document} source. The largest gain achieved at 4.2 bar was (29±1)·103\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(29\\pm 1)\\cdot 10^{3}$$\\end{document} in Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document} with 4.0% CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CH}_{4}$$\\end{document} with an anode voltage of 2975V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2975}\\,\\hbox {V}$$\\end{document}. In Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} with 10% CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CO}_{2}$$\\end{document} at 4 barA, a gain of (4.2±0.1)·103\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(4.2\\pm 0.1)\\cdot 10^{3}$$\\end{document} was observed with anode voltage 2975V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2975}\\,\\hbox {V}$$\\end{document}. We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} with 10% CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CO}_{2}$$\\end{document} (10,000 in Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document} with ∼4%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim \\!{4}{\\%}$$\\end{document}CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CH}_{4}$$\\end{document}) may be achieved with anode voltage of 4.6kV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${4.6}\\,\\hbox {kV}$$\\end{document} (∼3.6kV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim \\!{3.6}\\,\\hbox {kV}$$\\end{document}).

Global comparison between experimentally measured isomeric yield ratios and nuclear model calculations

The level density steers transition probabilities between different states in the decay and de-excitation of excited nuclei. Reliable level density modelling is, therefore, key in describing, e.g., de-excitation of fission fragments, with implications on neutron and gamma-rays multiplicities, and also manifested in the population of isomeric states. We test six currently used level density models and the spin distribution in the level density by comparing calculations with measured isomeric yield ratios. The model calculations are performed with the TALYS code and experimental data for nuclear reactions populating spin isomers are retrieved from the EXFOR database. On average, calculations are in agreement with measured data. However, we find that the population of the high-spin state in an isomeric pair is clearly favoured in all of the six studied level density models. Further studies are then performed on the three used phenomenological level density models, to investigate the significance of their effect. We find that a significant reduction of the spin width distribution improves the agreement between calculated and experimentally observed isomeric yield ratios. This result is independent of the incident particle in the nuclear reaction. The needed reduction of the spin width distribution to comply with empirical data has, e.g., implications for studies in angular momentum generation in fission using isomeric yield rations, calculations of anti-neutrino spectra from nuclear reactors, as well as neutron and gamma-ray multiplicities in nuclear reactor calculations.

New 5-Substituted SN38 Derivatives: A Stability Study and Interaction with Model Nicked DNA by NMR and Molecular Modeling Methods.

The new 5-substituted SN-38 derivatives, 5(R)-(N-pyrrolidinyl)methyl-7-ethyl-10-hydroxycamptothecin (1) and its diastereomer 5(S) (2), were investigated using a combination of nuclear magnetic resonance (NMR) spectroscopy and molecular modeling methods. The chemical stability, configuration stability, and propensity to aggregate as a function of concentration were determined using 1H NMR. The calculated self-association constants (Ka) were found to be 6.4 mM-1 and 2.9 mM-1 for 1 and 2, respectively. The NMR experiments were performed to elucidate the interaction of each diastereomer with a nicked decamer duplex, referred to as 3. The calculated binding constants were determined to be 76 mM-1 and 150 mM-1 for the 1-3 and 2-3 complexes, respectively. NMR studies revealed that the interaction between 1 or 2 and the nicked decamer duplex occurred at the site of the DNA strand break. To complement these findings, molecular modeling methods and calculation protocols were employed to establish the interaction mode and binding constants and to generate molecular models of the DNA/ligand complexes.

Effect of process variables on leaching behavior and kinetics of silver element from waste photovoltaic modules

In order to achieve efficient leaching of silver, in waste photovoltaic panels, the leaching process using nitric acid was investigated. The effects of nitric acid concentration, leaching time, solid–liquid ratio, and leaching temperature on the silver leaching rate were examined. The response surface method was used to establish an experimental model for analyzing and optimizing the leaching experiment. The results showed that the nitric acid concentration had the most significant effect on the leaching rate. The leaching rate of 98.02% was achieved under the following optimal leaching conditions: a nitric acid concentration of 18%, a leaching time of 32 min, a solid–liquid ratio of 1:30, and a leaching temperature of 60 °C. According to the shrinkage nuclear model, the leaching kinetics of silver using nitric acid followed a chemical reaction-controlled process with an apparent activation energy of 42.26 kJ/mol. Scanning electron microscopy–energy-dispersive x-ray spectrometry results of minerals before and after leaching confirmed the efficient recovery of silver in waste photovoltaic cells.

The influence of Monte Carlo radiation transport codes and hadron physics models on stray neutron dose estimations in proton therapy: An extended intercomparison

PurposeSelecting a Monte Carlo (MC) radiation transport code and nuclear physics model affects the simulation of secondary neutron fluence energy spectra and the estimation of the neutron dose equivalent in proton therapy. This study compares the MC codes FLUKA, MCNPX and GEANT4 from previous work with two additional MC codes, TOPAS (with either the Binary Intra-nuclear Cascade (BIC) or the Bertini intra-nuclear cascade model (Bert)) and PHITS (with either the Intra-Nuclear Cascade of Liege (INCL) or the Bert model), to facilitate a more comprehensive comparison. Material and methodsSecondary neutron fluence energy spectra were scored at different locations inside a water phantom, exposed to a 10 × 10 cm2 parallel mono-energetic proton beam with energies of 110 MeV, 150 MeV, 180 MeV and 210 MeV. The neutron dose equivalent was estimated by applying fluence-to-dose equivalent conversion coefficients. ResultsDiscrepancies between MC codes and physics models reach 90 % for the total neutron fluence. Differences are most pronounced in the forward direction of the beam due to a notable presence of high-energy neutrons and the higher uncertainty on the neutron cross-section data for these neutrons. Nuclear model selection within PHITS (INCL or Bert) and TOPAS (BIC or Bert) shows a worse agreement for the Bert model than for the other MC codes and nuclear models. The discrepancies in the neutron spectrum simulations propagate into differences in the estimated neutron dose equivalents. They are more prominent for distal positions (up to a factor of 3) than for lateral positions (up to a factor of 2) and decrease at higher proton energies. ConclusionsThis study shows considerable differences in the out-of-field neutron fluence energy spectra calculated by different MC codes and nuclear physics models. Differences in the neutron dose equivalent reach a factor of 3. The discrepancies are most apparent in distal positions and at lower proton energies.

Least-squares analysis of the moments of the charge distribution in the mean-field models

Abstract The nth moment, $R^{(n)}_c$, of the charge distribution is composed of not only the m(≤ n)th moments, $R^{(m)}_p$, of the point proton distribution, but also the m(≤ (n − 2))th ones, $R^{(m)}_n$, of the point neutron distribution. The experimental value of $R^{(n)}_c(R^{(n)}_{c,{\rm exp}})$ observed through electromagnetic interaction makes it possible to investigate the point proton and neutron distributions together on the same basis. In order to estimate $R^{(m)}_\tau (\tau =p,n)$ from $R^{(n)}_{c,{\rm exp}}$, however, nuclear models are required. The structure of the least-squares analysis (LSA) between $R^{(n)}_c$ and $R^{(m)}_\tau$ is investigated within the mean-field framework. The LSA reveals constraints inherent in the model framework through the least-squares lines (LSL) and determines the value of $R^{(m)}_\tau$ of $R^{(n)}_{c,{\rm exp}}$ uniquely as a result of the sum rule with respect to the coefficients of the LSL equations. The n-dependence of the values of $R^{(m)}_\tau$ in the LSA is examined numerically by using the moments calculated up to n = 6 for 40Ca, 48Ca, and 208Pb.

Comparison of machine learning models on breast cancer risk prediction challenge

Breast cancer is a malignant tumor that poses a serious risk to women's life and wellbeing. To make matters worse, this cancer is less symptomatic in its early stages. It is not easily diagnosed through traditional means. The topic of this essay is to investigate machine learning for the determination of breast cancer.. The methods based on machine learning are as followed: automated nuclear section segmentation model, BCRecommender System, DNNs, and computer-aided diagnosis model (CADM). The methods studied are all based on the BreCaHad dataset and use a comparative metric.To measure the performance of each model, the accuracy, F1-score, specificity, and precision are used. The result shows that the approaches based on machine learning work well in diagnosing breast carcinoma, with high accuracy. Most of them have a percentage over 90% in accuracy and some of them are even higher than 95%. However, some of the models work poorly, such as layer 1 of BCRecommender with 61.06% accuracy and EfficientNetB0 with 72.96%. With every aspect taken into consideration, computer-aided diagnosis (CADM: Using combined features of HOG, WPD, ResNet as well as PCA + SVM) has the greatest advantage in diagnosing BC.