Nuclear power plants (NPPs) transfer electricity using off-site power systems. Wildfires can disrupt these systems and cause a loss of off-site power, which can impact the operation of NPPs. In South Korea, wildfire incidents in 2000 and 2022 interrupted the operation of off-site power systems, affecting the NPPs. Furthermore, rising temperatures due to climate change are increasing the frequency of wildfires. Therefore, NPPs are expected to become more vulnerable to wildfires. Wildfire hazard maps are necessary for analyzing the impact of wildfires on NPPs. This paper proposes a methodology for generating a wildfire hazard map via Monte Carlo simulation. The proposed methodology was applied to the vicinity of the Hanul NPP, and a wildfire hazard map was generated.
WANG Luyao1, ZHANG Fuhai1, GUO Yi2, CHAO Yilin3, LIU Xiangsong4, MENG Jin1, YUAN Hong5
Aiming at the abnormal low-frequency vibration of the three-bearing reactor coolant pump during the service period of the power station, the ANDRITZ reactor coolant pump was taken as the research object. Based on the calculation methods of fluid dynamics and rotor dynamics, the vibration characteristics of the reactor coolant pump shafting, the generation mechanism of half-frequency whirl of the reactor coolant pump, the key factors affecting the stability of water-lubricated bearings and their physical nature were explored. Then the water-film whirl problem of reactor coolant pump was studied. It is found that the nonlinear dynamic instability of water-lubricated bearing induces the half-frequency whirl phenomenon of reactor coolant pump. Under rated working conditions, the amplitude boundary of the nuclear pump shafting is double horn type, and the center point of the double horn is near the bearing area of the drive end of the motor. The vibration characteristics of the reactor coolant pump shafting in different coaxial segments are significantly different. The half-frequency whirl phenomenon mainly appears in the area near the coupling and the pump shaft side, while the upper shaft section of the motor is mainly power-frequency vibration, and the impeller side shaft section is mainly half-frequency vibration. The tangential force perpendicular to the rotation direction of the rotor is the key force leading to the water-film whirl problem, and the cross-stiffness coefficient and the average circumferential velocity ratio of the liquid film of the water-lubricated bearing are the key physical quantities affecting the tangential force. The research results are helpful to the optimal design of reactor coolant pump, fault diagnosis, and operation and maintenance management of power station.
The nuclear quadrupole collective states at low excitation energies are described in a novel, fully quantum mechanical and systematic manner as compared to traditional pictures initiated by Aage Bohr. The ellipsoidal shapes are shown to be triaxial in virtually all strongly deformed nuclei, in contrast to the Ansatz of axially symmetric shapes. The rotational bands of such triaxially deformed nuclei are described in a fully quantum mechanical way, i. e., without resorting to quantized free rotation of rigid body. The excitation energies within a rotational band, exhibiting the $J(J+1)$ dependence on angular momentum $J$, are shown to basically represent the change of binding energies due to nuclear forces. This differs from the interpretation á la Aage Bohr as rotational kinetic energies. The $K$ quantum numbers are shown to be practically conserved for triaxial ellipsoids, which turned out to be a real but positive surprise to many people in the field. The so-called $γ$ bands are shown to be $K$=2$^+$ rotations rather than $γ$-vibrations, leading to a nice description of the so-called $γγ$ 4$^+$ state as a $K$=4$^+$ rotation. Vibrational modes are also shown to emerge in this study. Thus, the whole picture of low-energy quadrupole collective motion of heavy nuclei has been renewed in a fully quantum mechanical fashion, which differs from the traditional picture but appears to be simpler and more natural.
Experimental results from the 2022 tungsten (W)-coated Small Angle Slot (SAS-VW) divertor campaign at DIII-D coupled with interpretive 3DLIM modelling show opposing trends for core impurity content when compared to impurity deposition on far-Scrape Off Layer (SOL) Collector Probes (CPs) with increasing main ion density. SAS-VW is a closed, W-coated divertor designed to more easily facilitate divertor detachment while reducing impurity leakage. An experiment performed a series of upper-single-null L-mode discharges in each toroidal magnetic field (BT) direction, with increasing main ion density (line-averaged density = 3.15–4.35e19 m−3) that approaches and slightly exceeds the divertor detachment threshold. The results indicate: a) increased radial W transport with decreasing peak Te,tLP; and b) negligible change in W content in the far-SOL at the outer mid-plane with the onset of divertor detachment.Preliminary W deposition measurements using double-sided, graphite CPs inserted at the Midplane Materials Evaluation System (MiMES) reveal a 75% decrease over the density scan when operating in the unfavorable (ion B×∇B out of the divertor) BT direction. In contrast, soft X-ray (SXR) radiation from the same discharges is used as a proxy for W core contamination, showing core W content that increases by 77% with increasing line-averaged density. Similar L-mode discharges conducted in the favorable BT direction result in significantly less deposition on CPs.Using an interpretive modeling workflow following Zamperini 2022 [1] for assessing the transport of W sputtered from the SAS-VW divertor, the analysis suggests that W migration to the main chamber surfaces during the campaign may also contribute to far-SOL deposition.
Reactor core transient calculation is very important for the reactor safety analysis, in which the kernel is neutron kinetics calculation by simulating the variation of neutron density or thermal power over time. Compared with the point kinetics method, the time-space neutron kinetics calculation can provide accurate variation of neutron density in both space and time domain. But it consumes a lot of resources. It is necessary to develop a surrogate model that can quickly obtain the temporal and spatial variation information of neutron density or power with acceptable calculation accuracy. This paper uses the time-varying characteristics of power to construct a time function, parameterizes the time-varying characteristics which contains the information about the spatial change of power. Thereby, the amount of targets to predict in the space domain is compressed. A surrogate method using the machine learning is proposed in this paper. In the construction of a neural network, the input is processed by a convolutional layer, followed by a fully connected layer or a deconvolution layer. For the problem of time sequence disturbance, a structure combining convolutional neural network and recurrent neural network is used. It is verified in the tests of a series of 1D, 2D and 3D reactor models. The predicted values obtained using the constructed neural network models in these tests are in good agreement with the reference values, showing the powerful potential of the surrogate models.
This work aims to study the response function of a 2″×2″ NaI(Tl) scintillation detector using Monte Carlo simulations. A precise mathematical model of the NaI(Tl) scintillator was developed using both FLUKA and GAMOS Monte Carlo simulation software. The photon pulse height distributions of the NaI(Tl) without influence of its energy resolution, obtained with FLUKA and GAMOS codes, were converted into a real NaI(Tl) response function using the necessary conversion process. Spectral characteristics such as full-energy peak efficiency, energy resolution, peak-to-Compton ratio, and peak-to-total ratio were investigated by simulation at different gamma-ray energy obtained from 109Cd, 137Cs, 54Mn, 65Zn, and 60Co sources. The simulated spectra from the GAMOS code were consistent with those generated by the FLUKA code. Additionally, the comparison between simulated results and experimental data demonstrated good agreement. The validation of the computational models used for the NaI(Tl) detector in both FLUKA and GAMOS software was successfully achieved, confirming the accuracy of the simulations in replicating the detector's response.
Fuel (deuterium) removal by various helium (He) discharge cleanings under strong magnetic field are studied in EAST superconducting tokamak, including deuterium-to-helium changeover by main plasma operation, glow discharge cleaning (GDC), and ion cyclotron wall conditioning (ICWC). The study demonstrates that He-GDC works well in strong magnetic field, but the cleaning is poloidally located near the GDC anodes. Both He-GDC and He-ICWC are effective in removing deuterium under strong magnetic field. Moreover, deuterium-to-helium changeover by main plasma operation is highly effective in rapidly reducing the deuterium from the first wall surface. A comprehensive comparison of the three techniques shows that deuterium-to-helium changeover and He-GDC exhibit higher deuterium removal rate, and the pulse duration and duty cycle of He-ICWC should be optimized to improve the deuterium removal. These studies present a comprehensive investigation on fuel removal techniques in EAST tokamak, providing valuable insights into the optimization of tritium removal strategies for future fusion reactors.
A unique brick series based on Vietnamese clay was manufactured at 114.22 MPa pressure rate for γ-ray attenuation purposes, consisting of (x) metallic waste & (90%-x) red clay mineral & 10% (hardener mixed with epoxy resin), where (x) is equal to the values 0%, 20%, 40%, 50%, and 70%. The impacts of industrial metal waste ratio in the structure and radiation protective characteristics were evaluated experimentally. The increase in metallic waste doping concentrations from 0% to 70% was associated with an increase in the manufactured brick's density (ρ) from 2.103 to 2.256 g/cm3 while the fabricated samples' porosity (Φ) decreased from 11.7 to 1.0%, respectively. Together with a rise in fabricated brick's density and a decrease in their porosities, the manufactured bricks' γ-ray attenuation capacities improved. The measured linear attenuation coefficient (μ, cm−1) was improved by 30.8%, 22.1%, 21.6%, and 19.7%, at Eγ equal to the values respectively 0.662, 1.173, 1.252, and 1.332 MeV, when the metallic waste concentration increased from 0% to 70%, respectively. The study demonstrates that manufactured bricks exhibit superior radiation shielding properties, with radiation protection efficiencies of 88.4%, 90.0%, 91.7%, 92.1%, and 92.4% for bricks with industrial metal waste contents of 0%, 20%, 40%, 50%, and 70%, respectively, at γ-ray energy (Eγ) of 1.332 MeV.
BackgroundNegative ion sources driven by radio frequency (RF) waves have become the preferred solution for future neutral beam injection systems.PurposeThis study aims to monitor the plasma discharge state of each exciter of a high power RF negative ion source by developing a plasma luminescence monitoring system based on a photodiode is designed and constructed.MethodsThe intensity of plasma emission was closely related to the number of specific collisions, collision particle density, and collision particle energy. Therefore, the intensity of plasma emission was applied to monitoring plasma parameters qualitatively, and a photodiode-based multichannel plasma luminescence monitoring system was designed and implemented to monitor the plasma discharge state of each exciter of a high power RF negative ion source. Based on a reasonable collision radiation model, plasma parameters were quantitatively obtained by analyzing the intensity of plasma characteristic spectral lines, and the influence of the filtering magnetic field generated by plasma current on plasma emission signals as experimental tested.ResultsExperimental results this monitoring system demonstrate that the real-time intensity information of plasma emission from different positions is successfully collected, and subsequently presented and saved in the form of voltage signals for real-time monitoring and post-data processing by the host computer. The intensity of plasma emission has a good linearity with RF discharge power.ConclusionsThe plasma light monitoring system of this study can accurately and real-time measure the excitation, maintenance, and extinction processes of plasma in the RF exciter.
Neutron is an indirectly ionizing particle without charge, which is normally measured by detecting reaction products. Neutron detection system based on measuring gadolinium-converted gamma-rays is a good way to monitor the neutron because the representative prompt gamma-rays of gadolinium have low energies (79, 89, 182, and 199 keV). Low energy gamma-rays and their high attenuation coefficient on materials allow the simple design of a detector easier to manufacture. Thus, we designed a cadmium zinc telluride detector to investigate feasibility of simultaneous detection of gamma-rays and neutrons by using the Monte-Carlo simulation, which was divided into two parts; first was gamma-detection part and second was gamma- and neutron-simultaneous detection part. Consequently, we confirmed that simultaneous detection of gamma-rays and neutrons could be feasible and valid, although further research is needed for adoption on real detection.
In this paper, modal effective mass for asymmetric fluid-structure interaction system is defined and equations for its calculation is derived. To establish consistency, modal effective mass in symmetric structure only system is briefly reviewed, followed by a definition of the modal effective mass in asymmetric system. The equations for calculating modal effective mass in asymmetric system are derived by utilizing the properties of left and right eigenvectors. To simplify the equations, the assumption is made that the mass matrix is only affected by the fluid. The simplified equation is then compared to the equation already used in ANSYS. Finally, the validity of the modal effective mass definition and derivation in this paper is demonstrated through a simple example.
Agriculture has a good stake in the world’s GDP. In many countries, agriculture and allied sectors have a good stake in national GDP. This paper covers details related to livestock since 1960s. The workforce has managed livestock for many decades. The workforce increases as the number of animals increases; it is an energy, time-consuming, and economically costly approach. Apart from it, there is no assurance about animal welfare in case of diseases, breeding, and feed intake issues. In the 21st century of digitalization, technology has a key role in improving overall monitoring, controlling, and processing in livestock management. This paper has gone thoroughly into the manual and automated livestock farm management, aiming welfare of animals, livestock products, consumers’ benefit, and sustainable environmental approaches.
The effect of thermal annealing on defect recovery of in-core neutron-irradiated 4HSiC was investigated. Au/SiC Schottky diodes were manufactured using a 4HSiC epitaxial wafer that was neutron-irradiated at the HANARO research reactor. The electrical characteristics of their epitaxial layers were analyzed under various conditions, including different neutron fluences (1.3 × 1017 and 2.7 × 1017 neutrons/cm2) and annealing times (up to 2 h at 1700 °C). Capacity–voltage measurements showed high carrier compensation in the neutron-irradiated samples and a recovery tendency that increased with annealing time. The carrier density could be recovered up to 77% of the bare sample. Deep-level-transient spectroscopy revealed intrinsic defects of 4HSiC with energy levels 0.47 and 0.68 eV below the conduction-band edge, which were significantly increased by in-core neutron irradiation. A previously unknown defect with a high electron-capture cross-section was discovered at 0.36 eV below the conduction-band edge. All defect concentrations decreased with 1700 °C annealing; the decrease was faster when the defect level was shallow.
Douglas Beck, Joseph Carlson, Zohreh Davoudi
et al.
In preparation for the 2023 NSAC Long Range Plan (LRP), members of the Nuclear Science community gathered to discuss the current state of, and plans for further leveraging opportunities in, QIST in NP research at the Quantum Information Science for U.S. Nuclear Physics Long Range Planning workshop, held in Santa Fe, New Mexico on January 31 - February 1, 2023. The workshop included 45 in-person participants and 53 remote attendees. The outcome of the workshop identified strategic plans and requirements for the next 5-10 years to advance quantum sensing and quantum simulations within NP, and to develop a diverse quantum-ready workforce. The plans include resolutions endorsed by the participants to address the compelling scientific opportunities at the intersections of NP and QIST. These endorsements are aligned with similar affirmations by the LRP Computational Nuclear Physics and AI/ML Workshop, the Nuclear Structure, Reactions, and Astrophysics LRP Town Hall, and the Fundamental Symmetries, Neutrons, and Neutrinos LRP Town Hall communities.
Tritium permeation into the Primary Heat Transfer System (PHTS) of DEMO and ITER reactors is one of the challenging issues to be solved in order to demonstrate the feasibility of nuclear fusion power plants construction. Several technologies were investigated as antipermeation and corrosion barriers to reduce the tritium permeation flux from the breeder into the PHTS. Within this frame, alumina coating manufactured by Pulsed Laser Deposition (PLD) and Atomic Layer Deposition (ALD) are two of the main candidates for the Water Cooled Lithium Lead (WCLL) Breeder Blanket (BB). In order to validate the performance of the coatings on relevant WCLL BB geometries, a mock-up was designed and will be characterized in an experimental facility operating with flowing lithium-lead, called TRIEX-II. The present work aims to illustrate the preliminary engineering design of a WCLL BB mock-up in order to deeply investigate permeation of hydrogen isotopes through PHTS water pipes. The permeation tests are planned in the temperature range between 330 and 500 °C, with hydrogen and deuterium partial pressure in the range of 1–1000 Pa. The hydrogen isotopes transport analysis carried out for the design and integration of the mock-up in TRIEX-II facility is also shown.
The rapid rise in the application of novel treatment techniques, such as intensity-modulated radiotherapy (IMRT), motivated us to survey the status of Korea's radiation safety management and the shielding designs of facilities employing medical linear accelerators (LINACs). To this end, a questionnaire was used to collect information on LINAC facilities and treatments, workload, shielding design, shielding management, and path of obtaining shielding information. Out of 100 domestic institutions, 52 responded to the survey. Approximately 70% of the institutions utilized IMRT for more than 60% of their cases, and an IMRT factor of 5 was adopted by 75% of these institutions. Over 80% of the institutions accounted for the applied time-averaged dose rate per week and instantaneous dose equivalent rates in their shielding designs. Approximately 45% of the institutions obtained important shielding information via a radiation shielding design company and the NCRP-151 report. Overall, most facilities were shown to follow the standards recommended by the relevant international agencies. However, the requirement to establish standardized shielding design information and clarify ambiguous paths for information acquisition was also highlighted. Therefore, the study's results can be used as a foundation for establishing a safety control system and for creating adequate shielding designs.
In this paper, we attempt to reproduce the results obtained by Sovacool et al. in their recent paper that focuses on the differences in carbon emissions reduction between countries pursuing renewable electricity versus nuclear power. We have found several flaws in the models and the statistical analysis performed theirein, notably the correlations performed between the fractions of renewable power and of nuclear power and greenhouse gas emissions per capita and the lack of consideration for natural bias between the variables examined.
According to Monte Carlo calculations of spatial distributions of photon energy in Lead from point isotropic and plane mon-directional monoenergetic sources with energies of 10-50 MeV, define the attenuation coefficient of air Kerma and the dose buildup factors are determined for the studied material. The calculations take into account the contribution of fluorescence, annihilation radiation, and bremsstrahlung radiation. The independence of the Buildup Factors and attenuation coefficient from the angular distribution of the source radiation and the weak dependence of the attenuation coefficient on its energy in the range of 30-50 MeV are shown. Corrections for barrier protection were determined and their independence from the thickness of the shielding material and the photon energy of the source was noted. The obtained information makes it possible to reduce errors in the results of calculations of the thickness for anti-radiation protection of electronic accelerators at high energies, using the developed engineering methods of calculation. The obtained information can also be used in calculations of protection against bremsstrahlung radiation of electronic accelerators by engineering methods.
This paper introduces a new model for highly accurate distribution voltage solutions, coined as a parameterized linear power flow model. The proffered model is grounded on a physical model of linear power flow equations, and uses learning-aided parameterization to increase the fidelity of voltage solutions over a wide range of operating points. To this end, the closed-form analytic solution of the parameterization approach is obtained via a Gaussian Process using a deliberately small input sample and without the need for recomputation. The resulting "self-adjusting" parameter is system-specific and controls how accurate the proposed power flow equations are according to loading conditions. Under a certain value of the resulting parameter, the proposed model can fully recover the linearized formulation of a specialized branch flow model for radial distribution systems, the so-called simplified DistFlow model. Numerical examples are provided to illustrate the effectiveness of the proposed model as well as the improvement in solution accuracy for voltage magnitudes over the simplified DistFlow model and several other linear power flow models, at multiple loading levels. Simulations were carried out on six small- and medium-sized test systems.