Showing papers in "Progress in nuclear energy in 2022"

Do renewable and nuclear energy enhance environmental quality in France? A new EKC approach with the load capacity factor

Abstract: In this study, we test the validity of the environmental Kuznets curve (EKC) hypothesis for France from 1977 to 2017. In this context, we analyze the effects of nuclear and renewable energy on the ecological footprint, carbon dioxide (CO2) emissions, and load capacity factor using co-integration and causality tests with Fourier transforms. In addition to the traditional indicators of environmental degradation, we make an important contribution to the literature by testing for the first time the impact of nuclear energy on the load capacity factor. The results of our empirical analysis suggest that there is no inverted U-shaped relationship between CO2 emissions and income, but rather the EKC hypothesis for the load capacity factor. While nuclear energy reduces CO2 emissions and increases the load capacity factor, in other words, improves environmental quality, renewable energy has no long-term impact on environmental conditions. The findings point to the importance of nuclear energy in green sustainability.

Revealing the nexus between nuclear energy and ecological footprint in STIRPAT model of advanced economies: Fresh evidence from novel CS-ARDL model

Abstract: In recent times, a rise in anthropogenic activities has increased the demand for water, energy, infrastructure, wood, and other natural resources, which causes the climate to change, land to erode, pollution to increase, and biodiversity to decrease. We aim to investigate the impact of nuclear energy and human capital on the ecological footprint in 12 advanced economies over the period 1980–2015. We have applied the novel Cross Sectionally Augmented Auto Regressive Distributive Lag (CS-ARDL) estimation technique that can handle the issue of Cross-Sectional Dependence (CSD) and also deal with the mixture I (0) and I (1) variables. The estimate of nuclear energy is negatively significant, confirming that the use of nuclear energy can protect the environment by preserving the water, land, and forest resources and reducing the carbon footprints. Similarly, the estimated coefficient of human capital is negative and significant, which confirms that human capital can reduce the ecological footprint in advanced economies. On the other side, electricity consumption is a factor that can spur economic activity and consequently the ecological footprints. Likewise, the increased economic activity in advanced economies also exhaust resources like water, land, and forests and consequently increase ecological footprints. The results suggest that nuclear energy can prove a panacea to the problems of energy security and environmental degradation; therefore, increasing nuclear energy production should be part and parcel of energy and environmental policies of all the countries around the globe.

Study of comprehensive shielding behaviors of chambersite deposit for neutron and gamma ray

Abstract: Comprehensive shielding behaviors of chambersite deposit in China for neutron and gamma ray were systematically analyzed for the first time. Monte-Carlo method simulation technique, American Evaluated Nuclear Data File (ENDF/B-VIII.0), XCOM program and Phy-X/PSD program were used to perform the analysis. Transmission against different neutron resources and cross section for neutrons, mass attenuation coefficient, half value thickness, effective atomic number and electron density for narrow beam gamma ray at 0.001–100000 MeV, and equivalent atomic number, G-P Fitting Parameters, exposure buildup factors and energy absorption buildup factors against wide beam gamma ray for penetration depths up to 40mfp at 0.015–15 MeV were obtained. Shielding performance of chambersite deposit is excellent for high energy and low energy neutrons because of Mn and B respectively, and better than SWX-210. Shielding ability for gamma ray dependent on the element with high-Z or higher content and is between steel-magnetite concrete and ilmenite concrete. The shielding performance for both thermal neutron and gamma ray of the prepared sample is better than SWX-201 and SWX-261. Thus chambersite deposit will be an excellent shielding raw material for both gamma ray and neutron, also combining it with hydrogen rich materials can improve its attenuation properties and expand its possible uses.

Identifying the strategic priorities of nuclear energy investments using hesitant 2-tuple interval-valued Pythagorean fuzzy DEMATEL

Abstract: This study aims to determine the strategic priorities for the nuclear energy investments in Turkey. In this context, nine different factors affecting nuclear energy projects are evaluated with the hesitant 2-tuple interval-valued Pythagorean fuzzy DEMATEL. Pythagorean fuzzy sets contribute significantly to the solution of uncertainty problem. Similarly, owing to the hesitant approach, it will be possible to manage the different opinions that may arise among experts more effectively. According to the results, factors related to security risk and technological infrastructure adequacy should be considered most in the nuclear energy investment decision. Important concern in this process is that Turkey does not have any experience in the process of building a nuclear power plant. Hence, there is a risk that the necessary security measures may not be taken in the new nuclear power plant planned to be established. Therefore, building nuclear power stations using uranium in Turkey does not seem very reasonable. Instead, Turkey should focus on the nuclear energy projects by using thorium. The main reason is that thorium element produces much less radioactive waste compared to uranium. Also, in the process of nuclear energy using thorium, no more neutrons emerge. Thus, the use of thorium eliminates the risk of explosion in nuclear power plants. In this context, Turkey should make investment in the proton accelerator technology. With the help of this issue, security risks can be minimized in these planned nuclear power plants.

Nuclear energy: A pathway towards mitigation of global warming

Abstract: Global warming is the ongoing rise in the average temperature of Earth's climate system. Over the past 50 years, the average temperature has increased at the fastest rate in recorded history due to uncontrolled generation of greenhouse gases. Nuclear power is low carbon energy, and it is contributing on a large scale to a low carbon economy and a green energy grid. 442 nuclear power reactors are operating worldwide generating 393 GWe of electricity providing continuous and reliable low carbon power. Nuclear electricity accounts for 11% of total global electricity generation, and this amounts to a third of the low-carbon electricity produced in the world. New innovations are taking place which make nuclear power a more affordable and attractive energy option. These include advances in large reactors, emerging technologies such as advanced fuel and small modular reactors, engineering breakthroughs extending the operational lifetime of existing reactors, and new developments in materials and better waste management. Fast breeder reactor technology has become a commercial reality and it helps not only in generating electricity, but also in producing more fuel than it consumes, besides burning nuclear waste more efficiently compared to any of the existing commercial reactor technologies. The Sun's energy is generated by nuclear fusion. Mastering nuclear fusion technology can guarantee energy security in terms of clean, safe and affordable energy. Nuclear fusion, and plasma physics research of very complex nature are being carried out in many countries. Fusion reactions have been successfully demonstrated although for a fraction of a second and without demonstrating a net gain of electric power. The world's largest international fusion reactor facility called ITER is in an advanced stage of construction with the aim of demonstrating the scientific and technological success of fusion energy research for commercial production. Fusion fuel is plentiful and easily accessible. It is expected that fusion energy is the pathway towards energy security for thousands of years. Nuclear fission and fusion reactors do not emit greenhouse gases into the atmosphere and play a major role in mitigating climate change.

MHD effects on natural convection in a U-shaped enclosure filled with nanofluid-saturated porous media with two baffles

Abstract: The present work examines numerically the heat transfer and the buoyancy-driven flow within a U–shaped baffled enclosure filled with a nanofluid-saturated porous medium in the presence of an inclined magnetic field using a finite element scheme. The enclosure bottom wall is heated sinusoidally while the two baffles and the inner walls are maintained at a constant cold temperature. The rest walls of the enclosure are kept adiabatic. The parameters under investigation are Hartmann number ( Ha ), volume fraction (φ), Darcy number (Da), Rayleigh number (Ra), nanoparticles aspect ratio (AR), and the angle of applied magnetic field (γ). The results are crucial and illustrate that increasing the values of Ra, Da and the nanoparticles volume fraction enhances the heat transfer while the Hartmann number inversely affects the heat transfer augmentation. Moreover, the average Nusselt number (Nu ave ) increases by increasing the enclosure aspect ratio. For the geometry under consideration and for a better heat transfer rate , it is recommended to choose an AR = 0.6 at Ha = 0 with a 0.1 vol fraction.

Experimental and FLUKA evaluation on structure and optical properties and γ-radiation shielding capacity of bismuth borophosphate glasses

Abstract: For 662, 1173, 1275, and 1333 keV gamma-ray energy, photon transmissions, linear attenuation coefficients, half value layer, tenth value layer, and mean free path values of bismuth-borophosphate glasses were measured experimentally. Then, the measured findings were compared to the FLUKA code. The FLUKA code findings agreed well with the experimental results. Furthermore, the findings show that adding Bi 2 O 3 to the glass network improves the shielding properties. The current data reveal that when the Bi 2 O 3 content rises, so does the absorbance. Furthermore, the optical constants of the present gasses, such as optical band gap, phonon energy, and tails of localized states, were examined. Fourier transform infrared (FTIR) spectrometer was used to analyze the Fourier transform infrared (FTIR) spectra of our samples at room temperature in the 4000–400 cm −1 wavenumber range. From a shielding standpoint, bismuth-borophosphate glasses offer excellent gamma-ray shielding properties.

Enhancing the gamma-ray attenuation parameters of mixed bismuth/barium borosilicate glasses: Using an experimental method, Geant4 code and XCOM software

Abstract: In this paper, we scrutinize the availability of borosilicate glassy systems doped with mixed heavy metals as radiation shielding attenuators; for this purpose, a glass system [20SiO 2 + 54B 2 O 3 +1NiO + xBi 2 O 3 + (25-x) BaO], x = 5, 10, 15, 20 and 25 mol.%] was prepared using melt quenching procedures. The optical transmittance of the glassy specimens was measured in the ultraviolet–visible range to study the influence of bismuth oxide on the transparency. The density and molar volume of the prepared glasses were increased from 3.31 to 4.51 g/cm 3 and from 31.47 to 36.96 cm³/mole, respectively, as the concentration of Bi 2 O 3 increased from 5 to 25 mol%. Moreover, the radiation shielding parameters, such as the mass and linear attenuation coefficients, the total atomic and electronic cross-sections, the effective atomic number, the effective electron density, and the half value layer and tenth value layer of these glasses were experimentally obtained at gamma-ray energies of 0.662, 1.173 and 1.332 MeV. We compared the measured linear attenuation coefficients with those simulated via Geant4 code and computed by XCOM software to ensure the accuracy in the experimental data. For all the current glasses, we found that the maximum linear attenuation coefficient occurred at 0.662 MeV and lied within the range of 0.246–0.365 cm −1 . We also found that the values of both the linear and mass attenuation coefficients increased as Bi 2 O 3 concentration was increased. Additionally, we found that the half value layer for the prepared glasses was smaller for the low energy (0.662 MeV) than the other energies, which confirmed that thin glass samples can shield from low energy photons . In terms of the tenth value layer, we report that the glass sample that contains 25 mol% of Bi 2 O 3 had the smallest TVL. According to the obtained results, it can be stated that the borosilicate glasses doped with mixed heavy metals (BaO and Bi 2 O 3 ) appeared to be transparent to the visible range and have good gamma-ray shielding features.

Gamma radiation shielding performance of CuxAg(1-x)-alloys: Experimental, theoretical and simulation results

Abstract: Different types of photon shielding parameters such as total mass attenuation coefficient (μ/ρ), linear attenuation coefficients (μ), half value layers (HVL), mean free paths (MFP), effective atomic numbers (ZEff), energy absorption build-up factors (EABF), exposure build-up factors (EBF) and kerma relative to air were investigated for the fabricated Cu–Ag based alloys. The considered parameters were measured through gamma spectrometer equipped with HPGe detector in order to obtain the experimental attenuation coefficients and other related parameters at various photon energy in the energy range 59.5–1332.5 keV. The measured μ/ρ values were confirmed with WinXCOM database results. FLUKA and GEANT4 simulation codes were used to examine the compatibility of the experimental and WinXCOM database results with these simulation codes. The exposure buildup factors of the alloy samples were estimated with help of Geometric Progression fitting formula over photon energy 0.015–15 MeV up to 40 mfp penetration depth. The results revealed that the exhibited effectiveness of Cu0.2Ag0.8 alloys against high energetic photon radiations had a good performance than that of alternative absorbers such conventional concretes, glasses and some alloys. The results of the present survey can be quite useful for possible applications of such materials, especially in nuclear laboratory and reactor core design for preference of effective photon shielding materials.

Numerical investigation of heat-transfer enhancement in helically coiled spiral grooved tube heat exchanger

Abstract: Passive enhanced heat transfer technology considerably influences helically coiled tube (HCT) heat exchangers (HEs), which are typically used in nuclear power plants . Numerical investigations were performed to study the effects of various grooving methods and depths on the heat transfer characteristics of HCT HEs. The results revealed that grooving on the plain tube could enhance the comprehensive heat transfer performance and simultaneously increase the pressure drop of the fluid. The performance evaluation criterion ( PEC ) value of the helically coiled spiral grooved tube (HCSGT) HEs was 25% higher than the helically coiled plain tube (HCPT) HEs, whereas the PEC value of a helically coiled parallel grooved tube (HCPGT) HEs was 20% better than that of the HCPT HEs. Furthermore, the HCSGT HEs exhibited superior heat transfer enhancement ability. A comparison of the influences of various grooving depths on the heat transfer enhancement of HCSGT HEs revealed that the increase in the groove depth first increased the Nusselt number ( Nu ) and friction factor ( f ), followed by a subsequent decrease. The PEC value of the HCSGT HEs with 0.5 mm groove depth was observed to be maximal. Thus, grooved treatment can effectively improve the comprehensive heat transfer capacity of HEs. • This paper provides the simulation data of heat transfer performance of helically coiled grooved tube heat exchanger (HE). • Study the effect of different grooving methods and grooving depth on heat transfer performance of HE. • Compared with helically coiled plain tube HE, grooved treatment can effectively improve the heat transfer capacity of the HE.

Control automation in the heat-up mode of a nuclear power plant using reinforcement learning

Abstract: Next-generation nuclear instrumentation and control technology is aimed at higher levels of automation and lower operation burden. In recent years, studies have been conducted to contribute to the operation of power plants using artificial intelligence technology. This paper proposes an automatic control method for plant heat-up mode using deep reinforcement-learning technology as a basic study for plant automation. First, the existing compact nuclear simulator (CNS) is expanded to enable reinforcement learning, and key elements for reinforcement learning are designed to be suitable for the heat-up mode. A deep neural-network structure and a CNS deep reinforcement-learning mechanism are then presented for automatic control. The experimental results demonstrate that deep reinforcement-learning has the potential to perform automatic control operation.

Gamma and neutrons shielding using innovative fiber reinforced concrete

Abstract: Concrete is a worldwide structural material. However, extensive research was applied for ductile alternatives due to their poor ductility. Recently, engineered cementitious composite (ECC) was used in several structural applications due to its superior elasticity. ECC comprises cement, pozzolanic material, fine aggregate, water, chemical admixtures, and mono or hybrid fibers by up to 2% by volume fraction. In this research work, mechanical properties and adequacy of ECC to resist gamma radiation and neutrons emission penetrability were experimentally investigated. Furthermore, the effect of partial replacement of traditional fine aggregate with nano-silica on the aforementioned characteristics was explored. Different ECC mixtures were prepared with variant compositions and thickness for gamma and neutron penetration tests. It was observed that the flowability of ECC was generally increased with increasing the percentage replacement of nano-silica. Also, ECC's compressive and tensile strength enhancement can partially replace conventional sand with nano-silica. Furthermore, a well-noticed gamma and neutrons attenuation of up to 63% and 37% were achieved, respectively.

Gradient descent-particle swarm optimization based deep neural network predictive control of pressurized water reactor power

Abstract: A pressurized water reactor (PWR) is an integrated system of various interdependent subsystems that show highly nonlinear behavior, and each component is prone to uncertainties and malfunctions that initiate potential accidents. In contrast, PWR needs to be continuously monitored for stable and safe operation over a service time. In this study, a gradient descent-particle swarm optimization hybrid algorithm-based deep neural network (GD-PSO-based DNN) approach is proposed to monitor the PWR core power and outlet temperature. The Gaussian noise is introduced to the input signal, and the PWR core stability conditions are examined by using Lyapunov analysis. The simulation results verified under different conditions, in which the proposed control approach tracks the reference inputs successfully and enhances the stability as compared with the sliding mode control, linear quadratic regulator, and proportional-integral-derivative methods. The controller is validated by using the data from RELAP5 system codes, and the performance is examined using the mean square error, integral square error, integral absolute error, integral time square error, and integral time absolute error criterion functions. This study gives the benefit to apply the GD-PSO-based DNN control method for other nuclear engineering fields for system identification, prediction, and control.

Deep learning for safety assessment of nuclear power reactors: Reliability, explainability, and research opportunities

Abstract: Deep learning algorithms provide plausible benefits for efficient prediction and analysis of nuclear reactor safety phenomena. However, research works that discuss the critical challenges with deep learning models from the reactor safety perspective are limited. This article presents the state-of-the-art in deep learning application in nuclear reactor safety analysis, and the inherent limitations in deep learning models. In addition, critical issues such as deep learning model explainability, sensitivity and uncertainty constraints, model reliability, and trustworthiness are discussed from the nuclear safety perspective, and robust solutions to the identified issues are also presented. As a major contribution, a deep feedforward neural network is developed as a surrogate model to predict turbulent eddy viscosity in Reynolds-averaged Navier–Stokes (RANS) simulation. Further, the deep feedforward neural network performance is compared with the conventional Spalart Allmaras closure model in the RANS turbulence closure simulation. In addition, the Shapely Additive Explanation (SHAP) and the local interpretable model-agnostic explanations (LIME) APIs are introduced to explain the deep feedforward neural network predictions. Finally, exciting research opportunities to optimize deep learning-based reactor safety analysis are presented.

Applying analytic hierarchy process to industrial process design in a Nuclear Renewable Hybrid Energy System

Abstract: Nuclear Renewable Hybrid Energy Systems (NRHESs) co-locate a nuclear power plant with a renewable power generation source, such as solar or wind, with an industrial process(es), and can include a battery for energy storage and a fossil fuel power plant. By co-locating these various components, the nuclear-generated power can be directed to the industrial process when demand is low or renewable generation is high, as well as toward meeting grid demand when needed. This paper will apply the risk assessment and management technique of the fuzzy Analytical Hierarchy Process (AHP) to an NRHES. The goal is to develop a method of evaluating industrial components in preliminary NRHES design. Criteria selected in this study within which each process is assessed are profitability, flexible operation, and safety. Based on this, the fuzzy AHP approach determined desalination to be the strongest candidate based on system definition and related assumptions. Additional studies can be undertaken using this approach for more in depth analysis of NRHES design. With no NRHESs currently deployed, fuzzy AHP can offer a useful decision-making tool.

Numerical investigation of the flow and heat transfer of Al2O3/water nanofluid in a tube equipped with stationary and self-rotating twisted tapes

Abstract: In this study, the rotating twisted tape and its effect on fluid flow and heat transfer as well as Performance Evaluation Criterion (PEC) in a tube under constant heat flux is investigated. The twisted tapes are examined in two rotating and stationary cases, namely four geometric cases of Plain Tube (PT), tube equipped with Stationary Twisted Tape (STT), tube equipped with Rotating Twisted Tape- Clockwise (RTT-C) and the tube is equipped with Rotating Twisted Tape-Counterclockwise (RTT-CC). The used nanofluid is Al 2 O 3 /water nanofluid in volume fraction of nanoparticles 0, 1, 2, and 3% and is considered as Newtonian, and two-phase mixture method is used to simulate the nanofluid. The flow regime in this study is laminar and the Reynolds numbers are 250, 500, 750, 1000, and heat flux of 5000 W/m 2 is applied to the wall of the tube. The height of the twisted tape is 90% of the height of the channel and they act as thermal insulation and are only responsible for creating the secondary flow. The results show that increasing the Reynolds number increases Nu ave and increases the pumping power, and by using nanoparticles and changing the volume fraction of nanoparticles from 0 to 3%, heat transfer, pumping power, and pressure drop are increased.

A review of VOF methods for simulating bubble dynamics

Abstract: The bubbly flow is encountered in many industrial processes. Numerical efforts dedicated to the explanation of the bubbly flow physics have never been overemphasized. Based on the computational fluid dynamics (CFD) technique, the volume of fluid (VOF) method has been adopted to predict flow phenomena in nuclear reactors. For the VOF method, a volume fraction transport equation is solved simultaneously with a set of continuity and momentum equations throughout the computational domain. The VOF method is relatively reliable but could produce inaccurate interface curvatures due to the shortage of the volume fraction step function in smoothening discontinuous quantities near the interface. In view of this, the present study summarizes recent development of the VOF method. The strategies coupling the VOF method and other specific methods are discussed. A comprehensive explanation of numerically obtained bubble behaviors such as detachment, rising, deformation, and coalescence is provided. Applications of the VOF method in describing various bubble characteristics are reviewed. Available data shows that simulations of bubble dynamics and interfacial behaviors still call for irrefutable clarifications. Furthermore, this study serves as a benchmark resource for selecting an appropriate VOF method in related research.

Numerical study on the boiling heat transfer and critical heat flux in a simplified fuel assembly with 2×2 helical cruciform rods

Abstract: The helical cruciform fuel was potential to upgrade the core power density while maintaining the safety margin of a reactor. However, the detailed analysis on the boiling phenomena was inadequate. In this paper, the flow boiling and critical heat flux in a fuel assembly with 2 × 2 helical fuel rods were predicted based on the Eulerian two-fluid framework and auxiliary models for interphase exchanges. The averaged and localized distributions for velocity, temperature, vapor fraction and heat flux were obtained. The four-petalled helical structure introduced significant differences in the flow and heat transfer characteristics compared with traditional cylinder rod bundle. The cross flow intensity was high due to the continuous mixing effects of blades. The azimuthal heat flux distribution was nonuniform, with the maximum to average heat flux ratio larger than 2. The vapor phase crowded at the elbow of the rods, that is, the location of maximum heat flux. The averaged heat flux of helical fuel assembly at critical condition was very close to that of cylinder rod bundle; however, the critical linear heat flux of helical fuel assembly was about 31% higher than cylindrical one, which can upgrade the core power limitation significantly.

Radiation shielding performances of Na2SiO3 based low-cost micro and nano composites for diagnostic imaging

Abstract: The present study deals with determining the gamma-ray shielding parameters of the micro (μ)- Bi2O3, μ−WO3, nano (n)-Bi2O3, and n-WO3 reinforced Na2SiO3 (sodium metasilicate) composites experimentally and theoretically. The study has aimed to compare the size of reinforcing particles on the gamma-ray shielding ability of very low-cost and non-toxic Na2SiO3. In this context, the gamma-ray shielding performances of the samples containing different weight percentages of μ-Bi2O3, μ-WO3, n-Bi2O3, and n-WO3 particles have been evaluated by employing mass attenuation coefficient, half-value layer, and mean free path. The related parameters have been measured experimentally and also calculated by WinXCom. It has been revealed that Na2SiO3 composites having micro and nano-structured Bi2O3 and WO3 particles show good radiation shielding for 81 keV photons. In this respect, among all composites, the Na2SiO3/30% μ-WO3 sample has a promising potential to shield the ionizing radiation utilized in diagnostic imaging such as mammography, conventional X-ray machine, etc.

Synthesis and characterization of Barium ferrite nano-particles for X-ray/gamma radiation shielding and display applications

Abstract: In the present communication, BaFe2O4 (BFO) nanoparticles were synthesized by solution combustion method using urea as a fuel and calcined at 500 °C for 3 h. To know the phase purity, functional group, surface morphology, structural analysis and energy band gap, the synthesized sample was characterized by using the techniques such as powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Fourier transmission infrared spectroscopy (FTIR) and UV–Visible spectrophotometer. The Bragg’s reflection of PXRD confirms the formation of orthorhombic spinel crystal structure with space group Cmc21(36). In addition to orthorhombic phase, additional PXRD peaks corresponding to monoclinic phase of BFO were also observed. Wood and Tauc’s relation was used to calculate direct energy band gap and was found to be 5.2 eV. Photoluminescence studies (λex = 350 nm), CIE and CCT values revealed that the present BFO nanomaterial could meet the needs of illumination devices. In addition, X-ray/gamma ray shielding properties of BFO nanoparticles in the energy range 0.081–1.332 MeV have been measured using NaI (Tl) detector and PC based multi channel analyser (MCA). The measured shielding parameters are compared with the standard theoretical values. It is found that above 356 keV energy of gamma ray, the measured shielding parameters agrees well with the theory, whereas, slight deviation is observed below 356 keV. This deviation may be mainly attributed to the particle size of the target medium. Furthermore, an accurate theory is necessary to explain the interaction of X-ray/gamma with the nano size atoms. The present work opens new window to use this facile, economical, efficient, low temperature method to synthesize nanomaterials for X-ray/gamma ray shielding purpose as well as the display device applications.

Experimental investigation of aluminum fins on relative thermal performance of sintered copper wicked and grooved heat pipes

Abstract: Heat pipes are one of the most modern thermal devices used for high heat flux applications like fuel engines and thermal boilers to hydrogen storage tanks etc. Various kinds of thermal performance enhancement techniques have been employed to increase heat transfer through these pipes. For this purpose, manufacturing of a finned heat pipe is one of the famous techniques which maximizes heat transfer and increases operating range of heat pipes too. This study compiles the experimental results; 1) of installing Aluminum fins on the condenser section of heat pipes, 2) and a comparison between finned and finless distilled water based sintered wicked as well as grooved heat pipes, by keeping all other parameters same. The distribution of surface temperatures, thermal conductivity and thermal resistance is considered for comparison purposes. It is clearly observed that power surface temperature has an inverse relationship with the evaporator thermal resistance that is; if the power surface temperatures increases then the evaporator thermal resistance decreases. Also, installation of fins is more significant in sintered heat pipes as compared to grooved heat pipes. Due to installation of fins, there is an increase in the operating range which was observed 47% for sintered heat pipes and 30.1% for grooved heat pipes, when compared at 20 W. It has also been noted that the thermal conductivity of sintered heat pipes increased up to 73.2% due to the installation of fins and unexpectedly decreased up to 58.8% in case of grooved heat pipes. Thermal resistance of finned sintered heat pipes was 42% lower than finless type, and surprisingly it has increased up to 1.43 times in grooved heat pipes. Finally, a through comparison of finless sintered and grooved heat pipes results that finless grooved heat pipe shows the best performance and up to a 4.7% lower evaporator surface temperature was observed.

Explicit modeling of pebble temperature in the porous-media model for pebble-bed reactors

Abstract: In this study, a multiscale model has been developed to include an explicit pebble-temperature model nested in the porous-media model for pebble-bed reactor applications. The multiscale solid-phase energy balance model, including the pebble surface energy balance equation and an explicit modeling of pebble temperature, can predict the macroscopic (pebble bed) and microscopic (pebble) temperature distributions under both steady-state and transient conditions. The proposed multiscale model is solved in a fully coupled manner using the Newton-Krylov method, and therefore iterations between the macroscopic (pebble-bed-scale) and microscopic (pebble-scale) model are avoided. Extensive code verifications, validation, and demonstrations have been performed for this newly developed model. By explicitly modeling pebble temperatures, this new model addresses a major deficiency of the basic porous-media model, which assumes homogeneous solid-phase temperature and is not appropriate for pebble-bed reactor design and safety analyses.

Radiation shielding performance for local granites

Abstract: This study has been devoted to investigate the radiation shielding performance of some najran granite samples. In this investigation, experiments are carried out in order to depict the radiation shielding properties of local granites considering the influence from existing some oxide elements. Different types of granite samples were examined and computed for gamma shielding parameters such as linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), half value layer (HVL), tenth value length (TVL), and mean free bath (MFP). The transmission of gamma rays has been measured by using NaI (Tl) detector. The Total atomic and total electronic cross sections for these samples have been investigated. The radiation shielding capabilities of granite samples were experimentally tested at 59.5, 661.6, 1173, and 1332 keV. It is clear that, the granite samples had a considerable attenuating effectiveness at low energies. Furthermore, the experimental LAC values were found to be consistent with those obtained theoretically using the XCOM program. The chemical composition of the samples has been investigated using EDX (energy dispersive spectroscopy). The computed data was compared to the experimental findings. Results of irradiation of granite samples with gamma rays and the attenuation characteristics, along with the chemical analysis of the granite samples are also addressed and thoroughly discussed.

A Discontinuous Galerkin Finite Element Method based axial SN for the 2D/1D transport method

Abstract: The 2D/1D transport method is a prominent solver for the 3D Boltzmann equation due to its strong geometric capability. To pursue high accuracy, the discrete ordinate (SN) method for transport equation is a straightforward choice as the axial 1D solver instead of the traditional nodal expansion method (NEM) for diffusion equation . In practice, the axial SN solver is usually combined with the transverse leakage splitting method to deal with the negative source issue, which strongly affects the convergence of the 2D/1D method. However, transverse leakage splitting breaks the consistency of scalar fluxes between the 2D MOC and 1D SN equations. To solve this problem, a discontinuous Galerkin finite element method (DGFEM) for axial SN together with an improved 2D/1D transport approach is proposed in the present study to ensure that the scalar flux from the 1D axial solver is the same as that from the 2D solver. The accuracy, consistency and computational efficiency of the new scheme are evaluated using various well-known numerical problems, including heterogeneous assembly problem, KUCA benchmark, and C5G5-3D benchmark.

Design of passive residual heat removal systems and application of two-phase thermosyphons: A review

Abstract: We conducted a review on the application of two-phase thermosyphons in passive residual heat removal systems (PRHRs). Thermal management to handle the heat of decay in nuclear power plants is crucial for maintaining the integrity of the reactor core. Nuclear power plants are equipped with decay heat removal systems under normal and accident conditions. These systems are generally known as residual heat removal systems. The technology of decay heat removal that relies on electric power, known as an active system, will become ineffective when there is a total loss of electrical power for an extended period (e.g., extended station blackout (SBO)), such as the accident at the Fukushima Daiichi Nuclear Power Plant. To deal with SBO accidents, the design of Generation III+ and small- and medium-size nuclear power plants already includes PRHR systems, which is designed to function for at least 72 h without operator intervention. On the other hand, the use of two-phase thermosyphons as part of thermal management in nuclear power plants is also increasing. This review aims to determine the current status and challenges of the PRHR system design and the application of two-phase thermosyphons in PRHR design. The tools and models used for analyzing PRHR designs are also included in this review. Therefore, a review of thermal-hydraulic performance PRHR that uses the two-phase thermosyphon has been prepared based on simulation and experimental approaches found in the literature. This review focuses on the design and analysis of PRHR systems for light water reactors (LWR) and the usage of two-phase thermosyphon as cooling devices for nuclear-spent pools and non-transient cooling for both LWR and non-LWR reactors. We highlight the PRHR system design and the application of two-phase thermosyphons in PRHR design. As major contributions, different configurations of long-term cooling of PRHRs are discussed. It has been found that to extend the working life of PRHR beyond 72 h, several researchers have proposed new designs with unlimited cooling capabilities. One of the proposed technologies to support PRHR systems of this type is the sub-atmospheric two-phase thermosyphon. It has also found that RELAP5 is the most frequently used PRHR system design analysis tool. This paper, as a whole, acts as a current reference for researchers and lays the groundwork for future research in the use of two-phase thermosyphon for long-term decay heat removal systems. • Passive residual hear removal systems (PRHRs) are to increase the safety of nuclear power plants (NPPs). • Currently, PRHRs are generally designed to function passively for 3 days. • Heat Pipes and two-phase thermosypons are studied as passive cooling in the NPPs. • Two-phase thermosyphons are capable to extend the PRHR's operation for indefinite. • Thermal hydraulic system codes are widely used for PRHR performance analysis.

Conceptual design and thermal-hydraulic analysis of a megawatt-level lead-bismuth cooling reactor for deep-sea exploration

Abstract: A new conceptual design of a mega-power nuclear reactor (MPNR) for applications in deep-sea exploration was developed. A solid core cooled by the natural circulation of a lead-bismuth eutectic (LBE) reactor was designed with a thermal power of 1 MW. It consists of 126 coolant channels, which are holes surrounded by highly enriched fuel of UO2 dispersed in titanium-zirconium-molybdenum (TZM) alloy. A control rod at the center of the fuel and six control drums around the block are made of boron carbide to control the reactivity of the reactor. The core and heat exchangers are arranged horizontally to reduce the volume of the entire system. Compared with traditional deep-submersible reactors used at sea, the MPNR is highly compact, has a high-power output and simple structure, and ensures safety under ocean conditions. The neutronic and thermal-hydraulic design characteristics of the MPNR were calculated and assessed. The temperature reactivity and void fraction reactivity coefficients of the MPNR are negative values to ensure that the reactor has negative feedback characteristics. The thermal-hydraulic analysis of the MPNR design was carried out using the computational fluid dynamics program STAR-CCM+, in which field functions were added to the program to realize the inclined, rolling, and heaving motions of the reactor. The numerical simulations showed that under stationary conditions, the MPNR could establish natural circulation with a mass flow rate of 93.32 kg/s. At an inclination angle of ±30°, the natural circulation mass flow rates are 88.6 kg/s and 87.5 kg/s, respectively. Under rolling and heaving conditions, the mass flow rate fluctuated periodically, and the maximum temperature of the core changed within 10 K.

GeN-ROM—An OpenFOAM®-based multiphysics reduced-order modeling framework for the analysis of Molten Salt Reactors

Abstract: This work presents a projection-based multiphysics Model Order Reduction (MOR) framework for the analysis of nuclear systems and its application to parametric simulations of Molten Salt Reactors (MSR). The framework, named GeN-ROM, is developed using OpenFOAM® and employs a Proper Orthogonal Decomposition aided Reduced-Basis technique (POD-RB). It can be used to reduce steady-state and transient multiphysics problems involving parametric fluid dynamics, heat exchange, and neutronics phenomena. For the treatment of structural elements in the hydraulic systems, a porous medium approach has been adopted. The reduction process is data-driven and snapshot information is extracted via POD to learn the solution manifold and to build global spatial basis functions. At the data collection phase, GeN-ROM makes use of the solvers available in GeN-Foam, a similarly OpenFOAM®-based multiphysics framework developed for the analysis of nuclear reactors. The global bases are used both to approximate the solution fields and to project the full-order equations onto lower-dimensional subspaces, thus considerably reducing the number of unknowns in a numerical system. This reduction leads to significant computational speedups, which is ideal for multi-query applications such as uncertainty quantification or design optimization. The developed tool has been tested using a 2D multiphysics model of the Molten Salt Fast Reactor (MSFR) with steady-state and transient scenarios, with speedups on the order of 10 − 1 0 5 .

Inert-matrix fuel for transmutation: Selected mid- and long-term effects on reprocessing, fuel fabrication and inventory sent to final disposal

Abstract: Partitioning and transmutation (P&T) fuel cycles provide a technical approach to ease the problem of radioactive waste disposal. Some of the partitioned components of the waste stream are irradiated while others can be used for energy production or are sent to final storage. Minor actinides are planned to be irradiated in a fast spectrum nuclear facility to transmute them into stable or short-lived isotopes. As minor actinides have negative effects on reactor dynamics, subcritical, accelerator-driven systems are proposed to increase their fraction in the fuel. An example is the MYRRHA research reactor to be built in Mol, Belgium. This reactor is modeled for depletion calculations. The behavior of special fuel elements that mirror fuel composition as envisioned for large scale transmutation facilities, namely inert-matrix fuels with an increased minor actinide content, are investigated within this reactor environment. It turns out that gamma dose rates, activity and residual heat from the spent fuel elements present significant challenges for implementing a P&T program. Spent inert-matrix fuel element show significantly higher levels than spent fuel elements from fast reactors. This requires long cooling periods and poses unprecedented challenges to reprocessing technology. The problem is amplified by the fact that it is generally agreed upon that due to low transmutation efficiencies several transmutation steps would be necessary. Looking at the radiotoxicity index, the efforts suggested to reduce the minor actinide content in a final repository are justified. The long-term safety case of deep geological repositories, however, implies that certain long-lived fission products are more relevant. The build-up of some of these radionuclides is investigated for two hypothetical German P&T scenarios. Naturally, the amount of fission products increases with continued irradiation. But namely the fraction of Cs-135 increases over-proportionally when inert-matrix fuel rich on minor actinides is used.

Radioactive decontamination of metal surfaces using peelable films made from chitosan gels and chitosan/magnetite nanoparticle composites

Abstract: In this work, we explored the feasibility of using peelable films from chitosan gels and chitosan/magnetite nanoparticle (NPs–Fe3O4) composites to deal with radioactive contamination on metallic surfaces. We formulated four chitosan-based gels, one without NPs–Fe3O4 and three with NPs–Fe3O4: one using commercial nanoparticles and the other two synthesized by applying the chemical reduction method at 25 °C and 94 °C. The decontamination capacity of these gels was evaluated on steel stainless and aluminum, clean and corroded, and on weathered iron test pieces. The films of chitosan-based gels were characterized by infrared spectroscopy. The radioactive decontamination process from metal surfaces was most efficient on clean surfaces. The decontamination factors were independent of the presence of NPs–Fe3O4 in the chitosan-based gel applied to the metal surface and depended on the type of radioisotope deposited on the metal. Gels formulated with 2.8% w/v chitosan in 1 M acetic acid with and without NPs–Fe3O4 (333 μg/mL) were applied to a non-compactable waste contaminated with uranium, which obtained removal efficiencies of 85%.

Gels, coatings and foams for radioactive surface decontamination: State of the art and challenges for the nuclear industry

Abstract: The decontamination of solid surfaces is an important process in nuclear decommissioning, but also during regular maintenance operations in active nuclear facilities. The outcomes of these operations are highly variable, depending among others on the nature of the substrate, the type of contamination, and the amount and nature of the secondary waste generated. A wide range of decontamination technologies have therefore been developed, based on mechanical (cutting, abrasion, etc.), laser (ablation, stripping) or chemical (washing, wiping) processes. The focus of this review is on liquids that can form gels, strippable coatings, and foams that can effectively remove contamination for surfaces relevant to the nuclear industry. Its aim is particularly to highlight the importance of the formulation step and guide the future development of gels and foams for nuclear decontamination. Recent innovative formulations are presented along with new perspectives and challenges for these technologies.