An improved path planning method, ASD-RRT*, is proposed to address the path planning problem in complex static radiation environments. First, the artificial potential field (APF) method is introduced to optimize the RRT* algorithm, guiding the RRT* tree nodes to shift away from the radiation sources. Next, a subregional dynamic probabilistic sampling strategy is employed, improving the goal-directedness of the path search process while considering the effects of radiation dose. Finally, the Douglas-Peucker algorithm is used to smooth the path. This study builds radiation fields using Geant4, simulates multiple radiation scenarios, and performs path planning using A*, PRM, APF-PRM, RRT*, and ASD-RRT* algorithms. The research results indicate that the ASD-RRT* algorithm performs better in navigating narrow regions and excels in complex radiation environments. It can find a safer path with the lowest cumulative dose within a reasonable time, providing a reference solution for path planning in radiation field environments.
The Korea Atomic Energy Research Institute (KAERI) is developing a novel Two-Region Arc Plasma Ion Source (TRAP) as a negative hydrogen (deuterium) ion source for a Neutral Beam Injection (NBI) system in a fusion tokamak. The TRAP ion source is based on a two-region configuration, comprising a high energy electron region that creates highly vibrationally excited molecules and a low electron temperature region that generates negative ions by attaching electrons to molecules. This configuration can be achieved by optimizing the filament position and magnetic cusp field. In order to optimize the TRAP configuration, the plasma parameters are investigated under various operating conditions, such as filament position, gas pressure, and arc power. Electron density and temperature are determined using Langmuir probe measurements. In this paper, the detailed experimental results are described and discussed.
A series of experiments were performed to produce a fuel source for a molten salt reactor (MSR) through pyroprocessing technology. A simulated LiCl–KCl–UCl3-NdCl3 salt system was prepared, and the U element was fully recovered using a liquid cadmium cathode (LCC) by applying a constant current. As a result, the salt was purified with an UCl3 concentration lower than 100 ppm. Subsequently, the U/RE ingot was prepared by melting U and RE metals in Y2O3 crucible at 1473 K as a surrogate for RE-rich ingot product from pyroprocessing. The produced ingot was sliced and used as a working electrode in LiCl–KCl–LaCl3 salt. Only RE elements were then anodically dissolved by applying potential at −1.7 V versus Ag/AgCl reference electrode. The RE-removed ingot product was used to produce UCl3 via the reaction with NH4Cl in a sealed reactor.
Seyed Abolfazl Ghasemi, Amir Moslehi, Samira Faghih
A parametric study of the average energy and scattering angle distribution of Bremsstrahlung x-ray photons generated in over-dense fuel were investigated using the Geant4 simulation toolkit in fast ignition concept. In our simulation, over-dense fuel with the mass ρc∼(300−1000)g.cm−3, and fast ignitor with the intensity I=(1021,1023)W.cm−2 and wavelength λ=(0.35,0.53)μm were considered in the presence of an external magnetic field with the strength Bext=(0−10)kT. Further, for the produced MeV electrons in pre-plasma, two types of energy distribution functions, i.e., exponential and quasi two-temperature, were considered. The simulation results show that by applying an external magnetic field strength Bext∼(1−2)kT, a smooth increase was observed in the x-ray photon average energy and a considerable increase in scattering angle and photon counts in over-dense plasma obtained, so that the peak values mostly obtained for Bext∼1kT. Meanwhile, between the two energy distribution functions for electrons, the optimal average energy and scattering angle values were obtained by considering the quasi-two-temperature energy distribution function and for the fast igniter intensity and wavelength, I=1021W.cm−2,λ=0.35μm respectively, and the fuel density ρc∼300g.cm−3. Finally, regarding to the obtained optimal average photon energy (i.e., Ebph<0.4MeV), which could be considered as minimum photon energy loss and maximum electron penetration toward the fuel, the minimum thickness of lead and concrete shields required to reduce the flux of photons to its one-tenth value were found to be 1.5 cm and 30.7 cm, respectively.
Medical physics. Medical radiology. Nuclear medicine, Nuclear engineering. Atomic power
WANG Jinshun, CHEN Ronghua, ZHU Xinyang, TIAN Jiahao, TIAN Wenxi, QIU Suizheng, SU Guanghui
Against the backdrop of China's ambitious three-step nuclear energy development strategy, encompassing pressurized water reactors (PWR), fast reactors (FR), and fusion reactors (FNR), the purpose of this study is to meet the pivotal need for a specialized sub-channel analysis code tailored to the unique thermal-hydraulic characteristics of liquid metal fast reactors (LMFRs). Building upon the foundational SACOS sub-channel code, the approach involves the seamless integration of LMFR-specific models. These include the wire-wrapped model, turbulent crossflow model, and liquid metal convective heat exchange model. The utilization of advanced computational techniques, such as the SIMPLE algorithm and staggered grid methodology, ensures the completion of accurate sub-channel calculations, establishing SACOS-LMR as a robust code for thermal-hydraulic safety analysis in LMFRs. Validation of the SACOS-LMR code was conducted through a sodium transient experiment involving 37-pin bundles at the Karlsruhe Institute of Technology. The results not only demonstrate a commendable alignment between computed parameters (e.g. temperature distribution, pressure drop) and experimental values but also confirm the code's precision in transient analysis for LMFRs. Applying the validated SACOS-LMR code, an in-depth thermal-hydraulic safety analysis of the European Lead-cooled Fast Reactor (ALFRED) core was conducted. The calculated results are not only reasonable but also exhibit consistency with comparable codes, affirming SACOS-LMR's applicability for LMFR core design and thermal-hydraulic analysis. In conclusion, this research represents a significant step forward in the development of LMFR technology. SACOS-LMR, with its validated capability in both steady-state and transient analysis, stands as a sophisticated and reliable sub-channel analysis tool. It not only supports LMFR core design but also contributes to the broader global pursuit of sustainable and clean energy solutions in the nuclear energy landscape.
The neutron-induced cross sections are of great significance for the design of nuclear devices and advanced reactors for the nuclear energy production. At CSNS Back-n white neutron source, new measurements of the fission cross sections and total cross sections are performed with two sets of Day-one spectrometers based on the multi-cell fast fission ionization chamber (FIC). The neutron-induced 236,238U fission cross sections relative to 235U from the fission threshold energy to 200 MeV were measured by using the TOF method and the Fast Ionization Chamber Spectrometer for Fission Cross Section Measurement (FIXM) in the single/double bunch mode of Back-n. The experimental uncertainties are analyzed in detail, and the results from the two modes are consistent. The measured 236,238U/235U fission cross section ratios are compared with previous experiments and evaluations. The 236,238U(n,f) cross sections are obtained based on the standard 235U fission cross section. The neutron total cross sections of carbon and aluminum in the energy region from 1 eV to 20 MeV have been measured by using the TOF method and transmission method based on the Neutron Total Cross Section Spectrometer (NTOX) in the double bunch mode. The total cross section results after unfolding are in good agreement with the previous measurements as well as the broadening of the ENDF/B-Ⅷ.0 evaluation with Gaussian function within the experimental uncertainty. The present results provide the experimental data for further measurements, relevant evaluations and the design of nuclear system.
BackgroundSolid oxide cell (SOC) is the core converter for hydrogen production by high temperature electrolysis of water vapor and hydrogen fuel utilization.PurposeThis study aims to develope two kinds of aqueous casting pastes of NiO-YSZ with different components for the batch preparation of SOC without the usage of a large number of organic solvents.MethodsA 10 cm×10 cm large-scale full-scale cell was prepared by screen printing the hydrogen electrode functional layer, electrolyte layer, barrier layer and oxygen electrode layer with NiO-YSZ support film at one time casting of about 450 μm. The effect of dispersant on the microstructure of hydrogen electrode support and the stability of the pastes were analyzed by scanning electron microscope (SEM). The performance of the SOCs were tested by I-V curve and electrochemical impedance.ResultsBased on the optimized NiO-YSZ supports, the prepared planar SOCs delivers a peak power density of 0.36 W·cm-2 at 750 ℃. The electrolysis current density of SOC can reach -0.68 A·cm-2 at 1.30 V in solid oxide electrolysis cell (SOEC) model.ConclusionsThe performances of the aqueous-based SOCs can be considered highly remarkable, thus supporting the success in scaling the fabrication of SOCs using more environ-mentally friendly processes than conventional ones.
The 25 MeV wastewater treatment electron linear accelerator uses a 15 MW klystron as the microwave power source, which provides a microwave power no less than 13 MW at the entrance of the traveling wave tube, and accelerates the electron beam to 25 MeV/5 kW in a traveling wave tube with length of 76 cm. The operating frequency of the accelerator is 2 856 MHz in the Sband. The traveling wave tube adopts a diskloaded waveguide structure, which is simple and stable. To ensure that the beam can reach sufficient energy and power, the traveling wave tube is composed of a variable phase velocity bunching section, a constant phase velocity bunching section, and a light velocity section. The physical design of the traveling wave tube was introduced in detail. Using SUPERFISH, a two-dimensional cavity model was established, effective shunt impedance, attenuation constant, cavity wall loss, and other key parameters were calculated, and the traveling wave tube field distribution was obtained based on the power loss. Using numerical calculation methods, the phase oscillation equation and the beam envelope equation were solved, the capture efficiency of longitudinal motion is about 50% and the beam energy spread is about 72% with optimizing the length of the constant phase velocity bunching section. The solenoid magnetic field that was calculated by the SUPERFISH software was substituted, and magnetic field distribution to make the beam envelope smaller than the beam aperture of the accelerating tube was optimized. Finally, the design was verified with PARMELA. When 10 000 particles are injected, 6 106 particles can be accelerated to the exit of the acceleration tube, that is, the capture efficiency is about 61%. Good consistency is obtained. Then, the threedimensional RF structure model was established. The accelerating cavity model in the simulation software was calculated using the principle of the probe method. The coupler model was calculated by using three frequency methods, and the coupling degree was optimized by adjusting the size of the coupling port and the inner diameter of the cavity. The field distribution of traveling wave tube was analyzed by timedomain method, and cavity inner diameter was adjusted to optimize field distribution. The simulation field distribution is consistent with the beam dynamics design. Voltage standing wave ratio of operating frequency is 101, and bandwidth of accelerator tube is 2 MHz. The design of 2.5 MeV traveling wave accelerator tube is completed, providing a reference for its research and development.
Thermal helium beam diagnostics using the line ratio spectroscopy method are widely used to infer temperature and density in fusion-relevant edge plasmas. These diagnostics consist of an observational system which measures emitted line radiation from either intrinsic or injected helium plasma impurities. These spectral features are then compared to the output of a collisional-radiative model to infer plasma parameters (Te, ne) from the observed helium radiation. In order to investigate the systematic uncertainties of such a diagnostic, we present the results of a Bayesian treatment of a helium collisional-radiative model (Schmitz et al., 2008) using synthetic data modeled after an existing system on the plasma experiment Wendelstein 7-X (Barbui et al. 2016). From this study, we present a new method for comprehensively combining measurement uncertainties with underlying atomic rate parameter uncertainties in the inference of plasma parameters. Finally, we also demonstrate the utility of this Bayesian approach in targeting sensitivities within the model, allowing determination of high-priority atomic data for future refinement and comparison between differing atomic models.
LI Changyuan;XIA Xiaobin;CAI Jun;ZHANG Zhihong;WANG Jianhua;QIAN Zhicheng;CHEN Defeng;XIE Guiying
LiF-BeF2-ZrF4-UF4 and LiF-BeF2 have been employed as fuel salt and coolant in liquid fueled molten salt reactor, respectively. A heat exchanger containing both fuel salt and cooling salt is placed inside the reactor vessel to dissipate the heat produced by the reactor. A molten salttoair heat exchanger outside the reactor vessel is used to cool the molten salt, and a molten salt pump is used to drive the circulation of the entire circuit of coolant system. As of the molten salt, LiF-BeF2 coolant, flows through the molten salt heat exchanger located inside the reactor vessel, nuclides in the coolant are activated by 19F(n, α)16N, 19F(n, γ)20F, and 19F(n, p)19O reactions with neutrons in the reactor core, and thus radionuclides such as 16N, 20F and 19O are produced. These radionuclides have radiation impact on the surrounding environment and equipment if they enter the rooms where equipment for molten salt coolant circuit locate. According to the flow process and distribution law of the cooling salt, theoretical calculation formulas to calculate the amount of radionuclide were given. Using theoretical formulas, calculated radioactivities of the three most important radionuclides 16N, 20F and 19O per unit volume of cooling salt are 9.05×106, 8.33×106 and 2.69×105 Bq/cm3 at the outlet of the molten salt heat exchanger, while the radioactivities of the three radionuclides at the same location calculated by ORIGENS program are 8.98×106, 8.58×106 and 2.76×105 Bq/cm3, respectively. The results calculated by the formulas are in good agreement with the data of the ORIGENS program, and the maximum relative deviation between the results of the two methods is 292%, indicating that applying the derived formulas to carry out cooling salt activation analysis is reasonable and feasible. These radionuclides, 16N, 20F and 19O, produced in the cooling salt of molten salt reactor release highenergy gamma rays as they decay. The total gamma emissivities of the cooling salt in equipment and pipelines located in the cooling salt storage tank room, in the molten salt-to-air heat exchanger room and in the cooling salt pump room are 8.71×1011, 9.51×1011 and 1.93×1012 s-1, respectively, and the most radioactive area is in the cooling salt pump room. The maximum absorbed dose rate at the location of the cooling salt auxiliary equipment is 45.7 mGy/h without shielding, which cannot meet the requirement of the radiation dose, and which should be less than 50 Gy for the entire life of the equipment (300 full power days). By setting a 30 cm thick concrete shielding wall between the cooling salt auxiliary equipment and the cooling salt pump, the absorbed dose rate at the location of the auxiliary equipment can be reduced to less than 7 mGy/h, thereby the radiation protection requirements for the cooling salt auxiliary equipment can be met.
H. B. Cokrokusumo, I. Hariyati, L. E. Lubis
et al.
In this study, an in-house residual encoder-decoder convolutional neural network (RED-CNN)-based algorithm was composed and trained using images of cylindrical polymethyl-methacrylate (PMMA) phantom with a diameter of 26 cm at different simulated noise levels. The model was tested on 21 × 26 cm elliptical PMMA computed tomography (CT) phantom images with simulated noise to evaluate its denoising capability using signal to noise ratio (SNR), comparative peak signal-to-noise ratio (cPSNR), structural similarity (SSIM) index, modulation transfer function frequencies (MTF 10 %) and noise power spectra (NPS) values as parameters. Evaluation of a possible decrease of image quality was also performed by testing the model using homogenous water phantom and wire phantom images acquired using different mAs values. Results show that the model was able to consistently increase SNR, cPSNR, SSIM values, and decrease the integral noise power spectra (NPS). However, the noise level on either training or testing data affects the model’s final denoising performance. The lower noise level on testing data images tends to result in over-smoothed images, as indicated by the shift of the NPS curves. In contrast, higher simulated noise level tends to result in less satisfactory denoising performance, as indicated by lower SNR, cPSNR, and SSIM values. Meanwhile, the higher noise level on training data images tends to produce denoised images with reduced sharpness, as indicated by the decrease of the MTF 10 % values. Further studies are required to better understand the character of RED-CNN for CT noise suppression regarding the optimum parameters for best results.
Flow boiling is widely encountered in many industrial fields such as the steam generator in nuclear reactors. Nowadays, a lot of studies are focused on the bubble dynamics parameters due to the close relationship between the heat transfer and bubble behaviors. Bubble departure frequency is one of the important bubble dynamic parameters which reflects the bubble cycle in time and thus directly influences the bubble evaporation heat. In order to improve the predicting accuracy of bubble departure frequency and thus improve the accuracy of heat transfer calculation under flow boiling, the affecting factors of bubble departure frequency firstly through 13 groups of flow boiling independent experiments of water (506 experimental data points) were analyzed in this paper. It is found that bubble departure frequency decreases with the increasing of liquid subcooling, while it increases with the increasing of channel size, mass flux, wall superheating and pressure in which the effect of channel size is often ignored by many researchers. Then the accuracy of five existing prediction models was evaluated. The results show that none of them have high prediction accuracy in all experimental data points. Cole model and Zuber model both perform badly and have the absolute errors of 163.2% and 218.2% respectively and the relative errors of 134.2% and 205.1% respectively, because they only consider the effect of physical properties and thus they are more suitable for pool boiling. Brooks model and Basu model both overestimate the results with the absolute errors of 280.2% and 102.1% respectively and the relative errors of 2352% and 37.1% respectively. The reason lies in that these two models are developed through their own experiment data and thus have limited application ranges. Chen model performs relatively better with the absolute error of 64.8%, but it largely underestimates the results with the relative error of -52.3% for the reason that this model is developed based on the pool boiling experiments of methane and ignored the effects of mass flux and liquid subcooling. Besides, the results show that most predicting models perform badly when the channel size is small which confirm the significant influence of channel size. Therefore, in this paper, a new prediction model was developed with higher predicting accuracy through dimensionless analysis which consideres the effects of channel size, physical properties, wall superheating and mass flux. This new model has the mean absolute error of 39.2% and mean relative error of -14.3% with the application ranges of bubble Reynold number 28-2 303, Bond number 1-9.272 and Jakob number 0.004-0.049.
Climate change with the impact of drought stress has become a major environmental problem for rice (Oryza sativa L.). The use of gamma ray radiation at a dose of 300 Gy is one way to develop drought tolerant rice varieties with little change to the characteristics of the Towuti variety. However, research is still needed to determine its resistance to drought stress. This study aims to identify characters for selection, genotype selection, and determine the response of Towuti mutant rice to drought stress conditions.The characters that can be used to select rice genotypes under drought stress conditions are plant height, number of leaves, number of tillers, and SPAD chlorophyll value. The Towuti mutant has the best tolerance to drought stress compared to other genotypes. Tolerance to drought stress in the Towuti mutant is not caused by the stay-green gene.
Helium cooled solid breeder blanket as an important blanket candidate of the Tokamak fusion reactor uses ceramic pebble bed for tritium breeding. Considering the poor effective thermal conductivity of the ceramic breeder pebble bed, thin structure of tritium breeder pebble bed is usually adopted in the blanket design. The container wall has a great influence on the thin pebble bed packing structure, especially for the assembly of mono-sized particles, and thin pebble bed will appear anisotropic effective thermal conductivity phenomenon. In this paper, thin ceramic pebble beds composed of 1 mm diameter Li4SiO4 particles are generated by the EDEM 2.7. The effective thermal conductivity of different thickness pebble beds in the three-dimensional directions are analyzed by three-dimensional thermal network method. It is observed that thin Li4SiO4 pebble bed showing anisotropic effective thermal conductivity under the practical design size. Normally, the effective thermal conductivity along the bed vertical direction is higher than the horizontal direction due to the gravity effect. As the thickness increases from 10 mm to 40 mm, the effective thermal conductivity of the pebble bed gradually increases.
This study systematically compared two hybrid deterministic/Monte Carlo transport codes, ADVANTG/MCNP and MAVRIC, in solving a difficult shielding problem for a real-world spent fuel storage cask. Both hybrid codes were developed based on the consistent adjoint driven importance sampling (CADIS) methodology but with different implementations. The dose rate distributions on the cask surface were of primary interest and their predicted results were compared with each other and with a straightforward MCNP calculation as a baseline case. Forward-Weighted CADIS was applied for optimization toward uniform statistical uncertainties for all tallies on the cask surface. Both ADVANTG/MCNP and MAVRIC achieved substantial improvements in overall computational efficiencies, especially for gamma-ray transport. Compared with the continuous-energy ADVANTG/MCNP calculations, the coarse-group MAVRIC calculations underestimated the neutron dose rates on the cask's side surface by an approximate factor of two and slightly overestimated the dose rates on the cask's top and side surfaces for fuel gamma and hardware gamma sources because of the impact of multigroup approximation. The fine-group MAVRIC calculations improved to a certain extent and the addition of continuous-energy treatment to the Monte Carlo code in the latest MAVRIC sequence greatly reduced these discrepancies. For the two continuous-energy calculations of ADVANTG/MCNP and MAVRIC, a remaining difference of approximately 30% between the neutron dose rates on the cask's side surface resulted from inconsistent use of thermal scattering treatment of hydrogen in concrete. Keywords: hybrid deterministic/Monte Carlo transport code, CADIS methodology, Spent nuclear fuel, Storage cask, Dose rate distribution