Monte Carlo Program Research Articles

Research on the fabrication method of macroscopic cross section base on the Monte Carlo simulation

Recent studies related to Monte Carlo based homogenization have shown that we can use a one-step method to generate the macroscopic cross section database (MCSD) of each grid element of the reactor core. This paper presents a systematic study on the influence of energy groups and fuel rod groups on MCSD. The Monte Carlo method for generating multi-group MCSD is studied based on the Monte Carlo program OpenMC with ENDF-B-VII.1 continuous energy cross section library. Through Monte Carlo simulation of the whole model, a fine 69 groups MCSD of lattice level can be directly generated by a one-step method, without leakage correction, and compared with 2 and 8 groups MCSDs. Furthermore, a method is proposed to group the fuel rods in the model according to the symmetry and neutron energy spectrum similarity. OpenMOC was used to test the generated MCSDs. The effective multiplication factors and the power distribution were in good agreement between OpenMC and OpenMOC results. It demonstrates that the Monte Carlo method is feasible to generate the highly accurate multi-group MCSD by the one-step method of full model calculation and the fuel grouping method.

Optical analysis of a multi-aperture solar central receiver system for high-temperature concentrating solar applications.

A multi-aperture solar central receiver system is optically analyzed for increasing the net power to the receiver in a wide temperature range of 600-1800 K. A model system comprises a tower, a multi-aperture receiver with compound parabolic concentrators, and heliostat sub-fields. Optical modeling is performed using in-house developed Monte-Carlo ray-tracing programs. The heliostat sub-field geometrical configuration, the number of receiver apertures and optical properties of reflective surfaces are varied in the parametric study. Increasing the number of apertures from one to four increases the maximum net receiver power from 116 MW to 332 MW. The use of more than four apertures results in only limited further gain of the net receiver power but significantly decreases the overall optical efficiency and the solar-to-thermal efficiency. The optimal temperature for the maximized annual solar-to-exergy efficiency is found in the range of 1100-1200 K. This optimal temperature decreases slightly with an increasing number of apertures.

Mixed NNLO QCD\xd7electroweak corrections of mathcal{O} (Nf\u03b1s\u03b1) to single-W/Z production at the LHC

First results on the radiative corrections of order mathcal{O} (Nfαsα) are presented for the off-shell production of W or Z bosons at the LHC, where Nf is the number of fermion flavours. These corrections comprise all diagrams at mathcal{O} (αsα) with closed fermion loops, form a gauge-invariant part of the next-to-next-to-leading-order corrections of mixed QCD×electroweak type, and are the ones that concern the issue of mass renormalization of the W and Z resonances. The occurring irreducible two-loop diagrams, which involve only self-energy insertions, are calculated with current standard techniques, and explicit analytical results on the electroweak gauge-boson self-energies at mathcal{O} (αsα) are given. Moreover, the generalization of the complex-mass scheme for a gauge-invariant treatment of the W/Z resonances is described for the order mathcal{O} (αsα). While the corrections, which are implemented in the Monte Carlo program Rady, are negligible for observables that are dominated by resonant W/Z bosons, they affect invariant-mass distributions at the level of up to 2% for invariant masses of ≳ 500 GeV and are, thus, phenomenologically relevant. The impact on transverse-momentum distributions is similar, taking into account that leading-order predictions to those distributions underestimate the spectrum.

The Monte Carlo Program KKMC, for the Lepton or Quark Pair Production at LEP/SLC Energies—Updates of electroweak calculations

Since the {\tt KKMC} program was published for the first time over 20 years ago, it has gained popularity and was exploited in a broad spectrum of applications. The core part of the program itself did not change much. In contrast, some of the libraries have evolved substantially. The aim of this publication is to archive four versions, alternative to the one published 20 years ago versions of the electroweak libraries (or just parameter initialization versions), which were instrumental for the precision Standard Model calculation from the end of LEP era till now and for the sake of the future applications/comparisons for the future electron-positron colliders, in particular for the FCC-ee related studies. These electroweak libraries are useful for the hadron collider applications as well, for instance for {\tt KKMC-hh} or {\tt TauSpinner} projects.

Neutronic and thermal-mechanical coupling analyses in a solid-state reactor using Monte Carlo and finite element methods

Improved computer capabilities and parallel algorithms have enabled high fidelity coupled analyses of classical nuclear power plant designs, which can also be applied to analyze the new heat pipe cooled reactor design. The neutronic/thermal coupling is a key part of multi-physics, high-fidelity reactor simulations. In a heat pipe cooled reactor, the solid-state core can reach temperatures over 1000 K which causes significant thermal expansion. The expansion then affects the neutronic and thermal conditions. Therefore, the mechanical conditions should also be carefully considered in the highly coupled solid-state system. The Monte Carlo program RMC and the commercial finite element program ANSYS Mechanical were used to develop coupled solutions of the neutronic (N), thermal (T), and mechanical (M) effects in a heat pipe cooled reactor with the ANSYS APDL interface used to link the two programs. The neutronic (N) and thermal–mechanical (T-M) coupled strategy was based on an iterative solution of the nonlinear governing equations. The method was used to study the reactivity changes occurring during startup of the MegaPower heat pipe cooled reactor. The most important effect of the temperature reactivity feedback during startup was the fuel temperature Doppler effect, while the monolith and reflector Doppler effects were much smaller. The radial expansion of the monolith and the reflector and the axial expansion of the fuel pellets have the most significant effects on the mechanical reactivity feedback. The results further show that the thermal–mechanical feedback in the solid-state reactor provides a negative reactivity feedback (-1500 pcm) and yet deteriorates the heat transfer due to the expansion. The peak fuel temperature increases 11 K when the thermal/mechanical feedback is considered. Therefore, the N/T-M coupling must be considered to produce conservative designs.

Development of virtual analogues of nuclear facilities in virtual reality

Using virtual reality technology - a modern trend. The nuclear industry is no exception. This article provides an overview of mathematical models used to create virtual analogue of critical assembly Godiva in virtual reality. Godiva - there is a simple example that allows to hone techniques for creating more complex virtual analogues of nuclear reactors and nuclear facilities. Mathematical models include stationary and dynamic ones. The stationary model is based on data from calculations carried out using Monte Carlo programs such as MCU, Serpent and Geant4. An approach is also described that makes it possible to calculate the reverse multiplication from the values of the effective multiplication factor for various states of the subcritical assembly. The dynamic model allows one to calculate the neutron-physical characteristics of the supercritical assembly during fast processes such as a neutron burst. In conclusion, there are other examples of virtual analogs created using similar approaches.

Photon Interaction Properties of Different Bones from Human Body Using MCNPX, WinXCom, XMuDat, and Auto-Zeff Programs

Abstract The human body consists of various bones with different elemental compositions and densities. The mass attenuation coefficients (μm), effective atomic and electronic cross sections (σa and σe), effective atomic numbers and electron densities (Zeff and Neff), and computed tomography (CT) numbers of the human body’s various bones have been determined for the main gamma rays of 67gallium, 153samarium, 99mtechnetium, 201thallium, 131iodine radionuclides and gamma rays from positron annihilation. To calculate these parameters, MCNPX code, WinXCom, and XMuDat computer programs and also the Auto-Zeff software and interpolation method have been used. The results of the MCNPX code were in good agreement with the WinXCom and XMuDat programs with differences of ≤4.42 %. It was found that the σa, σe, Zeff, and CT number parameters decrease as photon energy increases and the density of bone samples decreases. The μm and Neff values decrease with the increase in photon energy based on the results. Furthermore, they are approximately independent of the bone sample density. Of all the bone types, the σa, σe, Zeff, and CT number values of cortical bone are the greatest ones, while those of spongiosa are the lowest. Observed good agreement reveals that the chosen Monte Carlo code and computer programs could be useful to calculate the photon interaction characteristics of different bone types.

The Modeling of kinetic characteristics of subcritical assembly “Yalina” using SuperMC Monte Carlo code

Accelerator-driven systems (ADS) are considered to be promising for energy generation and transmutation of the long-live radiotoxic nuclides contained in spent nuclear fuel. The Yalina assembly has the same conceptual construction with a neutron generator coupled to a subcritical core. The major difference between ADS and Yalina experiments is that the neutron energy spectrum of the Yalina core is thermal. The simulation of the Yalina-Thermal experimental program was conducted via new neutron-physics code SuperMC developed by the FDS Team in China. SuperMC is a CAD-based Monte Carlo program for integrated simulation of nuclear systems by making use of hybrid Monte Carlo and deterministic methods and advanced computer technologies. The calculations were held with the use of the up to date nuclear data libraries ENDF/B-VII.1, ENDF/B-VIII, FENDL 3.0, JEFF 3.3, JENDL 4.0. The effective multiplication constant, keff, and the fraction of delayed neutrons, βeff, were calculated for the 285 fuel rod core configuration of the Yalina-Thermal subcritical assembly. Evaluation of the Yalina-Thermal experimental program using SuperMC code has been made for the first time in this work.

Monte Carlo Simulation and Experimental Validation for Radiation Protection with Multiple Complex Source Terms and Deep Penetration for a Radioactive Liquid Waste Cementation Facility

A new radioactive liquid waste cementation facility was under commissioning recently in the Institute of Nuclear and New Energy Technology of Tsinghua University, which is designed to simultaneously process multiple intermediate-level radioactive waste drums. Therefore, the multiple volume sources and the scattering effect becomes a key issue in its radiation protection. For this purpose, the Monte Carlo program FLUKA code and experimental measurement were both adopted. In the FLUKA simulation, five different scenarios were considered, i.e., one drum, two drums, four drums, six drums, and eight drums. For the multiple volume sources, the source subroutine code of FLUKA was rewritten to realize the sampling. The complex shielding also leads to a deep penetration problem; hence, the optimization algorithm and variance reduction techniques were adopted. During the measurement, two scenarios, outdoor and indoor, were carried out separately representing the dose field when only one drum is considered and when the scattering effect is considered. A comparison between the experiments and calculations shows very good agreement. From both of the Monte Carlo simulation and the experimental measurement, it can be drawn that, in the horizontal direction, with the increase of the drum number, the dose rate increases very little, while in the vertical direction, the increase of the dose rate is very obvious with the increase of the drum number. The complicated source term sampling methods, the optimization algorithm and variance reduction techniques, and the experimental verification can provide valuable references for the similar scattering problem in radiation protection and shielding design.

Quantum field theory motivated model for the Einstein, Podolsky, Rosen (EPR) experiment

Bell deduced the nature and form of “nonlocal hidden variables” that could yield the unusual pattern of responses in the paradoxical Bohm (B-EPR) version of the Einstein, Podolsky, Rosen (EPR) experiment. We consider that quantum field theory (QFT) allows for the existence of Bell’s hidden variables in the “dressing” of free electrons that may explain the EPR experimental results. Specifically, the dressing of free electrons can convey random vector information. Motivated by this, we use a random vector paradigm (RVP) to explore how well a Monte Carlo computer program compares with the experimental B-EPR statistics. In this algorithm, the random vector provides a unique fingerprint that allows these charged leptons to bear unique responses when their spin is read by Stern–Gerlach detectors. The program’s numerical results compare well with Bell’s experimental summary. This work offers the opportunity to consider that virtual particles play a role in understanding the origins of quantum mechanics (QM)’s unique entanglement and probabilistic behaviors.

Reducing the Breast Cancer Risk and Radiation Dose of Radiography for Scoliosis in Children: A Phantom Study.

Full-spinal radiographs (FRs) are often the first choice of imaging modality in the investigation of scoliosis. However, FRs are strongly related to breast cancer occurrence due to multiple large-field radiographic examinations taken during childhood and adolescence, which may increase the risk for breast cancer in adulthood among women with scoliosis. The purpose of this study was to consider various technical parameters to reduce the patient radiation dose of FRs for scoliosis. To evaluate breast surface doses (BSDs) in FRs, radio photoluminescence dosimeters were placed in contact with a child phantom. Using the PC-based Monte Carlo (PMC) program for calculating patient doses in medical X-ray examinations, the breast organ dose (BOD) and the effective dose were calculated by performing Monte Carlo simulations using mathematical phantom models. The BSDs in the posteroanterior (PA) view were 0.15–0.34-fold those in the anteroposterior (AP) view. The effective dose in the PA view was 0.4–0.61-fold that in the AP view. BSD measurements were almost equivalent to the BODs obtained using PMC at all exposure settings. During FRs, the PA view without an anti-scatter grid significantly reduced the breast dose compared to the AP view with an anti-scatter grid.

QCD and electro-weak corrections to the production of Higgs+2 jets at the LHC

We present complete next-to-leading-order (NLO) QCD correction and electro-weak (EW) correction to the production cross section of Higgs–Boson in association with two hard quark jets by using Monte-Carlo numerical calculation program, HAWK, for various photon parton distribution functions at the Large Hadron Collider with center of mass energy 7, 8, 13, and 14 TeV without and with typical vector-Boson-fusion cuts on the tagging jets. In our calculation we include complete contribution from the full set of t-channel, u-channel and s-channel Feynman diagrams, and corresponding interferences as well as NLO QCD and EW corrections.

INVESTIGATIONS OF ELECTROWEAK SYMMETRY BREAKING MECHANISM FOR HIGGS BOSON DECAYS INTO FOUR FERMIONS

Models with extended Higgs boson sectors are of prime importance for investigating the mechanism of electroweak symmetry breaking for Higgs decays into four fermions and for Higgs-production in association with a vector bosons. In the framework of the Two-Higgs-Doublet Model using two scenarios obtained from the experimental measurements we presented next-to-leading-order results on the four-fermion decays of light CP-even Higgs boson, h → 4f. With the help of Monte Carlo program Prophecy 4f 3.0, we calculated the values Γ = ΓEW/(ΓEW + ΓSM) and Γ = ΓEW+QCD/(ΓEW+QCD + ΓSM) for Higgs boson decay channels H → νµµeνe, µµee, eeee. We didn’t find significant difference when accounting QCD corrections to EW processes in the decay modes of Higgs boson. Using computer programs Pythia 8.2 and FeynHiggs we calculated the following values: σ(V BH)BR(H → ZZ) and σ(V BF)BR(H → WW) for VBF production processes, σ(ggH)BR(H → WW) and σ(ggH)BR(H → ZZ) for gluon fusion production process at 13 and 14 TeV and found good agreement with experimental data.

An improved beam splitting method for intensity modulated proton therapy

The pencil beam algorithm (PBA) has become the predominant dose calculation method in proton therapy, due to its high level of efficiency. However, density heterogeneity decreases the accuracy of PBA. To improve PBA’s accuracy, a beam splitting method is used to divide the original scanning beam into multiple thinner beamlets. Beam splitting should ensure that the beamlets’ summed fluence is as close to the original beam fluence as possible, while keeping the spatial variance of beamlets small, and minimizing the number of beamlets. In this work, the generalized differential evolution (GDE) algorithm is utilized for the optimal scheme. Under reasonable constraints for the radius and weight of beamlets, several schemes are optimized via the GDE algorithm. In order to achieve a trade-off between accuracy and calculation speed, three hexagon-based schemes, which split the original beam into 7, 13, and 19 beamlets, respectively, are proposed and compared with the scheme of Raystation 4.5. The fluence distribution calculated by the schemes with 13 beamlets and 19 beamlets are demonstrated to be more accurate than the Raystation scheme, which has 19 beamlets, with a maximum absolute difference between the summed beamlets fluence and the original beam fluence of 2.12%, and 0.93%, respectively. Furthermore, beam splitting schemes are implemented into a proton dose calculation algorithm based on the KylinRay-IMPT TPS. These schemes, based on the dose algorithm, are compared with the Monte Carlo program TOPAS 3.2 in slab geometry with lateral heterogeneity. The dose, calculated by the dose algorithm using a scheme of 13 beamlets, shows a good agreement with the dose from TOPAS. In addition, an abdominal geometry is used for further verification. Gamma analysis passing rates greater than 99.7% are observed, with a 2%/2 mm criterion. Thus, the accuracy and effectiveness of the improved beam splitting method are preliminarily verified.

Development of a Monte Carlo beam model for raster scanning proton beams and dosimetric comparison

Purpose To develop a Monte Carlo (MC) beam model for raster scanning proton beams for dose verification purposes. Methods and materials MC program FLUKA was used in the model. The nominal energy, momentum spread and beam angular distribution in the model were determined by matching the simulation profiles with the measured integral depth dose (IDD) and in air spot size. Dosimetric comparison was done by comparing the measured and simulated dose distributions. The 1 D dose profile of cubic Spread Out Bragg Peak (SOBP) plans, and the 2 D dose distribution of previously treated breast cancer patients’ clinical plans were measured by using Pinpoint chambers and 2 D array ionization chambers, respectively. Corresponding DICOM plan information was utilized for MC simulation. Results The MC results showed good agreement with measurements for the SOBP plans. The absolute comparison of the absorbed dose difference between the MC and the measurement was 0.93%±0.88%. For the patient plans, the overall passing rate of the gamma index analysis (γ-PR) between the MC simulation and measurement with the 2%-2 mm criteria was 97.78%, and only 1 case had a γ-PR less than 90%. With the 3%-3 mm criteria, γ-PR was never below 99% for all cases with and without the range shifter. Conclusions This work described a method for adapting a MC simulation model for a raster scanning proton beam. The good concordance between the simulations and measurements shows that the MC model is an accurate and reliable method. It has the potential to be used for patient specific quality assurance (PSQA) to reduce the beam time for the measurements in water.

LibMCXray: A Monte Carlo Simulator for Signal Analysis inside Dragonfly Software

Abstract:

Contrast optimization using triple energy window scatter correction method for In-111 SPECT imaging: A SIMIND Monte Carlo study

Introduction: Detection of scattered photons in photo-peak window degrades image contrast and quantitative accuracy of single-photon emission computed tomography (SPECT) imaging. Increases image contrast lead to significant improvement of image quality. The triple energy window (TEW) method, which has developed to eliminate the counts of scatter photons in measured counts, was applied to I-111 SPECT study and its effect was examined in a simulation study. Materials and method: The Siemens SYMBIA gamma camera equipped with a medium energy (ME) collimator was simulated by the Simulating Medical Imaging Nuclear Detectors (SIMIND) program. We used the SIMIND Monte Carlo program to generate the I-111 SPECT projection data of the Jaszczak phantom. The phantom consists of six spheres with different diameters (9.5, 12.7, 19.1, 15.9, 25.4, and 31.8 mm) which are used to evaluate the image contrast. Geometric, scatter and penetration fraction and also, point-spread functions (PSFs) and contrast curves were drawn and compared. Results: Results showed that 171keV photo-peak compared to 245keV gave the best results with a ME collimator when the TEW scatter correction method was applied. This can be explained by the large amount of collimator scatter and penetration from the photo-peak and by the collimator for 245 photo-peak window. Conclusion: With TEW scatter correction method, it is better to use a 171keV photo-peak window because of the better spatial resolution and image contrast.

Parton-shower effects in Higgs production via vector-boson fusion

We present a systematic investigation of parton-shower and matching uncertainties of perturbative origin for Higgs-boson production via vector-boson fusion. To this end we employ different generators at next-to-leading order QCD accuracy matched with shower Monte Carlo programs, PYTHIA8, and HERWIG7, and a next-to-next-to-leading order QCD calculation. We thoroughly analyse the intrinsic sources of uncertainty within each generator, and then compare predictions among the different tools using the respective recommended setups. Within typical vector-boson fusion cuts, the resulting uncertainties on observables that are accurate to next-to-leading order are at the 10% level for rates and even smaller for shapes. For observables sensitive to extra radiation effects uncertainties of about 20% are found. We furthermore show how a specific recoil scheme is needed when PYTHIA8 is employed, in order not to encounter unphysical enhancements for these observables. We conclude that for vector-boson fusion processes an assessment of the uncertainties associated with simulation at next-to-leading order matched to parton showers based only on the variation of renormalisation, factorisation and shower scales systematically underestimates their true size.

Dose-Area Product-to-Effective Dose Conversion Coefficients for Pelvic Radiography Using a Monte Carlo Program.

OBJECTIVE. The purpose of this study was to determine dose-area product-to-effective dose (DAP/E) conversion coefficients for a five-view pelvic radiograph series. DAP/E conversion coefficients may be used for radiation dose optimization when designing institutional protocols for pelvic trauma evaluation. MATERIALS AND METHODS. We conducted a retrospective record review of 25 patients at a level 1 trauma center who had sustained pelvic fractures and required a five-view pelvic radiograph series during workup. E values given in International Commission on Radiological Protection Publication 103 were simulated with a PC-based Monte Carlo program in conjunction with anthropomorphic phantoms adjusted on the basis of patient height and weight. Inputs included tube voltage (in kV), tube filtration (in millimeters of aluminum), anode angle, x-ray beam collimation, geometric distances, and angle of projection for each radiograph in the series. An incident polychromatic x-ray spectrum was generated and matched to the corresponding DAP values of each radiograph, and regression analysis was performed for the DAP/E conversion coefficients. RESULTS.E was strongly correlated with DAP independent from body mass index, with a mean global DAP/E conversion coefficient of 0.0125 mSv/dGy · cm2 for all radiographs (R2 = 0.95). Mean DAP/E conversion coefficients were 0.0133, 0.0110, 0.0143, 0.0113, and 0.0101 mSv/dGy · cm2 for anteroposterior, inlet, outlet, Judet left, and Judet right views, respectively (all R2 ≥ 0.94). CONCLUSION. DAP/E conversion coefficients are provided for a five-view pelvic radiograph series to allow reliable estimation of E. Measurement of cumulative E may affirm protocol design changes for the management of pelvic trauma.

Effects of environment variation of glycerol smoke particles on the persistence of linear and circular polarization.

Environment variation is an important factor affecting the polarization propagation through the smoke. In this paper, we investigate the effects of the relative humidity and optical thickness on polarization transmission character, as well as the persistence of the linear and circular polarization of artificial smoke particles with simulations and experiments. We develop an environment modulation system to control the environment variation and measure the transmission degree of polarization (DOP). Correspondingly, by building the relation between the smoke filling time and optical thickness, as well as between the relative humidity and particle size and refractive index, we utilize the Monte Carlo program to track photon scattering process through varying the radius, refractive index and optical thickness. Both the simulation and the experimental results show that the DOP of both linear and circular polarizations are constantly decreased with the increasing of the optical thickness. However, at the same optical thickness, both the linear and circular polarization's persistence benefits with the increasing of the relative humidity. Moreover, circular polarization persists better than linear polarization in the larger optical thickness and the higher humidity environment under the wavelength of 532 nm. These works can verify the persistence of circular polarization and broaden the application range of polarized lights in a variable artificial smoke environment.