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The area of materials research has registered a phenomenal growth in the recent years, assiduously accepting and assimilating ideas, concepts and analytical as well as experimental methodologies and techniques form almost all scientific disciplines, thereby demonstrating its remarkably multidisciplinary and interdisciplinary character. The focus of the materials programme of this centre is to provide materials, processes and processing solutions to the emerging needs of evolving indigenous nuclear energy systems by proactive research and development on a continuing basis. The initial stage of our activities was formulated around three stage Indian nuclear power programme. In stage I, material issues related to in-core materials with emphasis on development of fabrication routes of zirconium alloys for structural application were addressed. Subsequently the thrust areas were development and characterization of mixed oxide fuel, advanced zirconium alloys, structural steels, superalloys, neutron absorber materials based on boron carbides and borides, and shape memory alloys. The research was useful for in-service performance evaluation, safety assessment, residual life estimation and life extension of nuclear reactors built during stage I i.e., PHWRs and BWRs. It also included developments which would permit rapid expansion of nuclear power initially through fast breeder reactor based on mixed oxide fuel and later based on metallic fuels. For the 3rd stage, multi-layer coatings, graphite coolant tube, BeO, refractory metals and alloys, heat-treated zirconium alloys are being developed for CHTR, ADSS and AHWR. The materials being developed for fusion programme are low Z and high Z material for plasma facing application, Cu-alloys for heat sink, austenitic steels, RAFMS and ODS for structurals and NbTi, Nb3Sn and Nb3Al superconductors, lithium titanate, lithium silicate breeders, and PbaBi coolant. A brief overview of the materials research activities currently being pursued at Bhabha Atomic Research Centre is presented in this article.

This study employs CFD software to numerically simulate accidents in a single-box CEFR fuel assembly, focusing on the impact of recirculation zones on flow instability within the domain during blockage incidents. The analysis explores how various factors affect the recirculation zone and its implications for system performance. The key findings are as follows: The size of the recirculation zone is positively correlated with both the area and thickness of the blockage. Larger blockage areas and thicknesses result in more extensive recirculation zones, which in turn have a greater impact on flow instability and a more significant variation in the maximum temperature within the domain. Furthermore, the size of the blockage significantly affects the time required for the entire domain to reach a steady state. The presence of a blockage disrupts the flow of sodium coolant, and as the blockage size increases, the time needed to achieve a steady state also increases. In severe scenarios, prolonged flow times can lead to localized boiling of the coolant.

This paper introduces a design method of an automatic control system for coolant circulation in the laboratory, which can use a “pneumatic pump + valve control” manual in place of “manual pressing + manual liquid filling + manual collection”. Then this paper analyzes the system principle and has carried out the application in a practical laboratory, which had solved the problems of low efficiency, environmental pollution, and waste of resources of the existing manual operation mode.

This contribution reports for the first time on the enhancement of the thermal conductivity of graphene grafted with Cu nanoparticles—ethylene glycol-based nanofluid (with a relatively low Cu volume concentration of about 0.3% & without any dispersant). This latter nanofluid engineered by Pulsed Laser Ablation in Liquid Solution (LLSI-PLAL) exhibited a significant thermal conductivity enhancement of 12.6% conjugated to a noteworthy time stability of at least 3 to 4 weeks without any additional dispersing agent of any sort. This latter time stability corroborates with Density Functional Theory as well as the Molecular Dynamic theoretical investigations. These latter showed that the binding affinity of Cu nanoparticles onto graphene nanosheets is far superior relative to those of Au or Ag nanoparticles onto graphene (bridge adsorption energies of -0.58, -0.24, and -0.5 eV for Cu, Ag & Au, respectively). Cost-wise, compared to previously validated Au-Graphene/EG and Ag-Graphene/EG, the reported Cu-Graphene/EG nanofluids would be more suitable for mass production in view of their cost-effectiveness, especially in mass technological applications, including but not limited to heat removal & cooling in data centers.

Small modular reactors (SMRs; i.e., nuclear reactors that produce < 300 MWelec each) have garnered attention because of claims of inherent safety features and reduced cost. However, remarkably few studies have analyzed the management and disposal of their nuclear waste streams. Here, we compare three distinct SMR designs to an 1,100-MWelec pressurized water reactor in terms of the energy-equivalent volume, (radio-)chemistry, decay heat, and fissile isotope composition of (notional) high-, intermediate-, and low-level waste streams. Results reveal that water-, molten salt–, and sodium-cooled SMR designs will increase the volume of nuclear waste in need of management and disposal by factors of 2 to 30. The excess waste volume is attributed to the use of neutron reflectors and/or of chemically reactive fuels and coolants in SMR designs. That said, volume is not the most important evaluation metric; rather, geologic repository performance is driven by the decay heat power and the (radio-)chemistry of spent nuclear fuel, for which SMRs provide no benefit. SMRs will not reduce the generation of geochemically mobile 129I, 99Tc, and 79Se fission products, which are important dose contributors for most repository designs. In addition, SMR spent fuel will contain relatively high concentrations of fissile nuclides, which will demand novel approaches to evaluating criticality during storage and disposal. Since waste stream properties are influenced by neutron leakage, a basic physical process that is enhanced in small reactor cores, SMRs will exacerbate the challenges of nuclear waste management and disposal.

Aiming at the short service life of an engine cooling water sleeve caused by uneven heating, the CFD model is established using STAR-CCM+ software, and the flow field simulation in the cooling water sleeve is completed. Based on this premise, the orthogonal test design method is employed to investigate the effects of cross-section size and allocation of cylinder holes in various areas of the cooling water sleeve on the uniformity of coolant velocity. The results show that the cylinder holes near the thermostat outlet have the most significant impact on the coolant velocity uniformity, followed closely by the cylinder holes near the coolant inlet and, finally, the cylinder holes near the EGR cooler outlet. Furthermore, it is observed that the uniformity of the velocity increases with the decrease of the cross-section areas of the cylinder holes located near the thermostat as well as the EGR coolant, with the increase of the cross-section areas of the cylinder holes near the inlet, which decreases firstly and then increases later. The study results hold substantial reference value for optimizing this engine’s cooling water sleeve structure.

Main results are presented of the trial tests of a closed loop with natural circulation (NC) of a light-water coolant under supercritical pressure (SCP), which is a part of the thermal engineering test facility at the site of the National Research Centre (NRC) Kurchatov Institute. Experimental data on a change in the distilled water heat transfer were obtained for an upward flow in a ∅6.0 × 1.5 mm stainless-steel tube with indirect electric heating at a specific heat load as high as 0.5 MW/m 2 and a mass velocity of up to 300 kg/(m 2 s) and also for a downward flow in a vertical tube bundle consisting of seven finned stainless-steel tubes with a size of ∅12.0 × 2.5 mm each in an upward natural convection air flow in the shell side. In addition, experimental data were obtained on the dynamics of heating of main equipment items in the loop circuit with natural convection of distilled water at supercritical pressure. These data were used to validate a code for calculation of the heater, cooler, and overall loop. The paper analyzes the features of the heating dynamics of the main equipment items in the closed loop with natural circulation of supercritical pressure water (SCW) as well as the specific of SCW heat transfer in four sections of the heater and cooler. In the experiments, the following main stages of SCW heating were experimentally revealed: heating of the pseudo-liquid, pseudo-phase change (pseudo-boiling), and heating of the pseudo-steam; in the cooler: cooling of the pseudo-steam, pseudo-phase change (pseudo-condensation), and cooling of the pseudo-liquid. The work was performed for substantiation of engineering and process solutions for a nonreactor loop of a supercritical pressure light water power reactor (VVER-SCP) under an order of AO Concern Rosenergoatom.

Coolant plays a critical role in maintaining thermal safety in nuclear power plants. A key concern is the coolant behavior in narrow gaps between core debris and the reactor pressure vessel wall, especially during severe accidents. Experimental studies related to in-vessel retention (IVR) and the thermal response in these narrow gaps remain essential for improving accident management strategies. In light water reactors (LWRs), counter-current flow limitation (CCFL) can occur when rising gas interacts with descending liquid in tight geometries, potentially impeding coolant penetration. This study aims to evaluate the impact of temperature variations on superficial velocities of gas and liquid in a semi-spherical narrow gap. Pressurized air is injected into water to simulate gas rise, with liquid penetration observed at gap widths of 1, 2, and 3 mm. The influence of coolant temperature is analyzed to determine its effect on the onset of CCFL. The results indicate that higher coolant temperatures increase gas generation, which significantly reduces or even obstructs the downward flow of liquid. By comparing superficial velocities under varying temperature conditions, this study offers insights into the mechanisms that drive CCFL in narrow gaps, thereby enhancing the understanding of thermal-hydraulic behavior during nuclear reactor emergencies.

The genesis of the conducted research was the intention to determine how the rheological properties of engine oil change upon the addition of a coolant. The aim of the study was to assess the effect of coolant addition to engine oil on its dynamic viscosity. The experiments were carried out for six different fresh engine oils and six of the same oils sampled during routine oil replacement after a vehicle mileage of 10,000 km. Two oils were selected from each of the three primary categories: synthetic, semi-synthetic, and mineral oils. Then, mixtures of engine oils with the addition of coolant were prepared at 0, 5, 10, 20, 30, 40 and 50% (v/v), respectively. The study involved measuring the dynamic viscosity of the samples at 1000 s−1, covering temperatures from 0 to 50 °C. The tests were conducted using a measurement setup equipped with a RHEOLABQC rotational rheometer manufactured by Anton Paar GmbH (Ostfildern, Germany). To investigate the temperature dependence of dynamic viscosity, a GRANT thermostatic bath was coupled with the rheometer. The studies demonstrated that dynamic viscosity strongly depends on temperature, as well as on the type and condition of the engine oil. At 0 °C, the dynamic viscosity of fresh oils ranged from approximately 500 to 700 mPa·s, whereas at 50 °C it decreased to approximately 100 mPa·s. The addition of 5% (v/v) coolant to engine oil resulted in only a slight change in dynamic viscosity. In contrast, a substantial decrease in dynamic viscosity was observed when 50% (v/v) coolant was added to the tested engine oils. The results indicate that coolant, which may enter the engine oil in the event of an engine failure, can significantly deteriorate the rheological properties of this lubricant.

The heat generation of electronic devices is increasing dramatically, which causes a serious bottleneck in the thermal management of electronics, and overheating will result in performance deterioration and even device damage. With the development of micro-machining technologies, the microchannel heat sink (MCHS) has become one of the best ways to remove the considerable amount of heat generated by high-power electronics. It has the advantages of large specific surface area, small size, coolant saving and high heat transfer coefficient. This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area. The heat transfer mechanisms and performances of different channel structures, coolants, channel materials and some other influencing factors are reviewed. Additionally, this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer. The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future. The studies on microchannel heat sinks for electronics cooling are reviewed comprehensively. The main research areas of interest for microchannel heat sinks are classified. The studies on both single-phase and phase-change flow cooling are reviewed. The characteristics, application conditions and shortcomings of microchannel heat sinks with different structures, working fluids, materials and some other influencing factors are introduced. The prospects for and development trends of microchannel heat sinks are revealed based on the overall review and analysis.