Heavy Water Research Articles

Assessment of heavy metal contentin water bodies of Zhytomyr Oblast

Assessment of heavy metal contentin water bodies of Zhytomyr Oblast

The effect of photodissociation of confined water on photoemission behaviors of monolayer MoS2

The effects of confined water on the photoluminescence of 2D MoS2 depending on the type of isotope, substrate, and surface termination were investigated. The monolayer MoS2 film showed quenched photoluminescence intensity when exposed to water, whereas it was not observed upon exposure to heavy water. This result is attributed to the overtone vibrational energy transfer between 2D MoS2 and water. Furthermore, the investigation of the photoluminescence in 2D MoS2 depending on the surface characteristics indicated that it can be controlled by the adsorbed water on the substrate. Real-time photoluminescence measurements revealed that the two types of adsorbed water affected the variation in the optical properties and that the orientation of the adsorbed water was also significant for reverting to the intrinsic 2D MoS2 by catalytic photodissociation process through exciton-to-vibronic transfer, facilitated in a confined space. Our results indicate that the substrate surface is crucial for controlling the adsorbed water formed during wet-transfer process. Therefore, this study is effective for applications that utilize large-scale two-dimensional materials.

Microglial lipid droplet accumulation in tauopathy brain is regulated by neuronal AMPK

The accumulation of lipid droplets (LDs) in aging and Alzheimer's disease brains is considered a pathological phenomenon with unresolved cellular and molecular mechanisms. Utilizing stimulated Raman scattering (SRS) microscopy, we observed significant in situ LD accumulation in microglia of tauopathy mouse brains. SRS imaging, combined with deuterium oxide (D2O) labeling, revealed heightened lipogenesis and impaired lipid turnover within LDs in tauopathy fly brains and human neurons derived from induced pluripotent stem cells (iPSCs). Transfer of unsaturated lipids from tauopathy iPSC neurons to microglia induced LD accumulation, oxidative stress, inflammation, and impaired phagocytosis. Neuronal AMP-activated protein kinase (AMPK) inhibits lipogenesis and promotes lipophagy in neurons, thereby reducing lipid flux to microglia. AMPK depletion in prodromal tauopathy mice increased LD accumulation, exacerbated pro-inflammatory microgliosis, and promoted neuropathology. Our findings provide direct evidence of native, aberrant LD accumulation in tauopathy brains and underscore the critical role of AMPK in regulating brain lipid homeostasis.

Ru@Co3O4@g-C3N4 as a novel adsorbent for enhanced copper and cadmium abolition

Elimination of heavy metals from contaminated water systems is of prime distress due to their capacity to prompt toxic impact on the flora and fauna. The usage of innovative nano-engineered materials predominantly opens up smart prospects for the treatment of persistent heavy metal adulterated water resources. This study presents an ultrasonic-assisted sol-gel production of Ru@Co3O4@g-C3N4 nanostructure that was utilized to remove Cu+2 and Cd+2 ions from aqueous solutions. The X-ray diffraction investigation revealed the development of RuO2, Co2O3 and g-C3N4 phases, and the relevant elemental composition was verified by the photoelectron spectroscopy and EDX. The dispersion of the metal oxides within the nitride sheets was evidenced by scanning and transmission electron microscopy. The initial metal ions concentration, pH, and contact time effects were investigated through batch experiments. The adsorption isotherm models matched the Langmuir isotherm well, whereas the kinetics model data perfectly fitted the pseudo-second-order model. The maximum adsorption capacities of Cu+2 and Cd+2 ions on the nanocomposite Ru@Co3O4@g-C3N4 were 696.9 and 564.5 mg/g, respectively. A mechanism based on a viable covalent type of bonding developed by the delocalized -conjugated electrons of the triazine ring and functional groups were efficiently involved in the metal ions anchoring and ultimate elimination. Thus, the suitability of the Ru@Co3O4@g-C3N4 nanocomposite for eradicating heavy metals, including Cu+2 and Cd+2, was established.

Design and simulation of neutron radiography system for an aqueous homogeneous solution reactor

AHR reactors are known for the production of radiopharmaceuticals. The ARGUS reactor is one of the most famous of these reactors, which has been designed originally for radioisotopes production. The ARGUS reactor produces a suitable neutron flux that can be used for other applications such as neutron radiography (NR). Here, a NR system is designed step by step using the Monte Carlo method. The length of the collimator, divergence angle, diameter of the aperture, and thermal column dimension are designed. The designed aperture and thermal column are selected from boron carbide and heavy water, respectively. The depth of the thermal column is changed until the ratio of thermal neutrons to total neutrons (TNC) reached above 90%. The hole inside the thermal column is designed and internal lining is done. The inner lining is made of cadmium and had a thickness of 1 mm, and the space between the inner and outer lining is filled with lead. To reduce the gamma dose to acceptable values, the position of the collimator is changed instead of using a gamma filter. By changing the depth of the hole and creating the convergence angle to the hole, the flux of thermal neutrons will be 1.8E+6 n.cm−2s−1 that satisfy the IAEA suggested values for NR. Then, the uniformity of the radiation field of the neutron flux output from the collimator is obtained. At the end, images of SI and BPI standards are recorded. The good quality and contrast of these images showed the acceptable design of the NR system for the ARGUS reactor.

Neutronic Analysis of the Conceptual Molten Uranium Breeder Reactor Using MCNP and SCALE Tools

The Molten Uranium Breeder Reactor (MUBR) is a radically new reactor concept with a mixed-energy spectrum. MUBR is fueled with molten uranium metal in large-diameter fuel tubes and is cooled by circulating molten uranium fuel through a heat exchanger. The reactor has heavy water as moderator, and the reactivity of the reactor is primarily controlled by the voiding effect of the moderator through an innovative control cavity structure design. Because the MUBR design is vastly different from most existing fission reactors, neutronics analysis must be performed for many different combinations of design parameters to identify viable and optimum design configurations. To facilitate the neutronics analysis, a proprietary program called MUBR6gen is being developed to provide a pipeline tool to expedite the process. MUBR6gen employs two well-established neutronics codes, i.e., MCNP and SCALE, to perform standard neutronics calculations for MUBR by automating input preparation and output processing. In addition, MUBR6gen ensures consistency of the MCNP and SCALE inputs and compares the outputs of the two codes to warrant the simulation results. Augmented with MUBR6gen, standard neutronics analysis was carried out on a small-scale MUBR design, which serves as a model problem in the paper. The neutronics performance characteristics of the model reactor were obtained and discussed in a code-to-code pattern. An overall very good agreement between the results of the two neutronics codes was established. Based on the success of the model problem analysis, further neutronics analysis using MUBR6gen was extended for a set of MUBR variant designs. Meaningful and promising fuel cycle analysis results for the 10 different designs were achieved and discussed. These results are used to identify the best MUBR candidates in terms of fuel lifetime and utilization efficiency for future applications.

Comparing Coupled Multiphysics Simulations of Pump-Driven Transients for a Pressurized Heavy Water Reactor

Comparison of results for global responses predicted by different multiphysics simulations of benchmark problems may fail to reveal potentially significant local modeling issues. An examination of code interactions in coupled simulations can provide more information, which may help identify potential modeling issues that went unnoticed during verification (and validation) of the individual codes, or may call into question approximations otherwise deemed reasonable at the individual code level. We illustrate this challenge for the case of coupled neutronics/thermal-hydraulic transient simulations using one of the problems and contributed results documented in International Atomic Energy Agency TECDOC-1994. This recently published report documents the specifications of four numerical multiphysics pressurized heavy water reactor (PHWR) transient challenge problems and the results contributed by 10 participants. Our work is based on the pump rundown problem, where TECDOC-1994 suggests that differences in modeling and methods employed in thermal-hydraulics may be the dominant factor in the observed differences. We performed a more detailed assessment with two different multiphysics coupled computational frameworks using NESTLE-C/ARIANT and PUMA/RELAP-5. We also studied a pump seizure transient, a more challenging variant of the pump rundown transient. Several aspects were investigated: comparisons of standalone results, sensitivity to gap modeling, selection of boundary conditions at the pressurizer, and an examination of correlations used in ARIANT and RELAP-5. Our assessment goes beyond the results for global parameters and dives into details of predictions at the channel level. This paper briefly describes the PHWR pump rundown transient problem and a pump seizure variant, the computational methods employed, and the areas investigated, and discusses some selected results.

Sources of the active substances in microwave catalytic redox processes induced by iron-based carbon materials: The key role of B doping

Organic and heavy metal water pollutants is an urgent environmental problem to be solved. Herein, a B-doped iron-based carbon material (FC-B) was synthesized and used in a microwave field for the degradation of sulfamethoxazole (SMX) and the reduction of Cr(VI). Under a low power of microwave irradiation (240 W), FC-B rapidly degraded SMX (99.8 %, 12 min) and reduced Cr(VI) (100.0 %, 14 min) without adding any oxidizing and reducing agents. SEM, XRD, XPS, and FTIR verified the successful synthesis of FC-B. And the “temperature visualization test” verified the existence of “hot spots”. The presence of O2− in the MW/FC-B system but not in the MW/FC system was verified by quenching experiments, electron paramagnetic resonance (EPR) experiments and nitro blue tetrazolium chloride (NBT) quantitative experiments, and then the conversion of microwave-generated electrons (e−) to O2− was elaborated using N2 blowing experiments, temperature-programmed desorption of O2 (O2-TPD), density functional theory (DFT) calculations and electrochemical tests. Subsequently, cycling experiments showed that FC-B has good reusability. Finally, the practical application of the MW/FC-B system was verified with antibiotic-containing farm wastewater. This study not only proposed a new technology for water pollution treatment, but also provided a pioneering explanation of the production of oxidizing substances in microwave-induced catalytic reactions.

Improving Pb(II) Removal via Ascorbic Acid-Enhanced Red Mud Adsorption: Kinetics and Isotherm Analysis

This study explored the efficacy of red mud, an aluminum production by-product, as an adsorbent for Pb(II) ion removal from contaminated water and assessed the adsorption isothermal model and kinetics. Red mud, characterized by its richness in oxide minerals with reactive surfaces, has potential for heavy metal adsorption, but its capacity for larger ions like Pb(II) is limited. This research aimed to enhance red mud’s adsorption properties through modification with ascorbic acid. The modification process involved heating a mixture of red mud and ascorbic acid to its boiling point, followed by the formation of adsorbent beads using red mud and Na-alginate mixture dropped into a 2 % CaCl2 solution at −2 °C. The beads were tested over varying durations ranging from 30 to 210 min. The results indicated that ascorbic acid modification led to the transformation of minerals in red mud, improving its pore diameter, pore volume, and specific surface area of the adsorbent. The modified and unmodified red mud adhered to both Langmuir and Freundlich isotherms, with R² values converging to one, and displayed pseudo-second-order kinetics. Notably, the introduction of ascorbic acid augments the adsorption efficacy of red mud for Pb(II) ions from 84.8 % to a compelling 99.3 %. This underscores the augmented capability of ascorbic acid-modified red mud, highlighting its prospective applicability as a potent adsorbent in the remediation of heavy metal-contaminated water. HIGHLIGHTS Innovative Use of Red Mud: Explored the potential of red mud, a by-product of aluminum production, as an adsorbent for removing Pb(II) ions from contaminated water Ascorbic Acid Modification: Developed a novel modification process using ascorbic acid, including heating the red mud and ascorbic acid, enhancing the adsorption properties of red mud as pore diameter, pore volume, and specific surface area of the adsorbent Adsorption Isotherms and Kinetics: Conducted a comprehensive assessment of adsorption isothermal models and kinetics, with modified and unmodified red mud adhering to Langmuir and Freundlich isotherms and displaying pseudo-second-order kinetics Enhanced Adsorption Efficacy: the adsorption effectiveness is enhanced from 84.8 to 99.3 %, emphasizing its potential applicability for Pb(II) GRAPHICAL ABSTRACT

Imaging the Ion-Molecule Reaction Dynamics of O- + CD4.

While neutral reactions involved in methane oxidation have been intensively studied, much less information is known about the reaction dynamics of the oxygen radical anion with methane. Here, we study the scattering dynamics of this anion-molecule reaction using crossed-beam velocity map imaging with deuterated methane. Differential scattering cross sections for the deuterium abstraction channel have been determined at relative collision energies between 0.2 and 1.5 eV and ab initio calculations of the important stationary points along the reaction pathway have been performed. At lower collision energies, direct backscattering and indirect complex-mediated reaction dynamics are observed, whereas at higher energies, sideways deuterium stripping dominates the reaction. Above 0.7 eV collision energy, a suppressed cross section is observed at low product ion velocities, which is likely caused by the endoergic pathway of combined deuteron/deuterium transfer, forming heavy water. The measured product internal energy is attributed mainly to the low-lying deformation and out-of-plane bending vibrations of the methyl radical product. The results are compared with a previous crossed-beam result for the reaction of oxygen anions with nondeuterated ̧methane and with the related neutral-neutral reactions, showing similar dynamics and qualitative agreement.

Synthesis of new analogs of N-substituted(benzoylamino)-1,2,3,6-tetrahydropyridines

Abstract The tetrahydropyridine (THP) moiety is notably present in synthetic and natural products, playing a cardinal role in the food, cosmetic, and pharmaceutical industries. The THP structure is an instrumental constituent and is widely found in alkaloids that have therapeutic properties against inflammation, cancer, the nervous system, and bacterial infections. The use of THPs has gained traction, so it is imperative to increase the structural database through the synthesis of THP derivatives. The focus of this study is to make structural modifications to the benzene ring portion of the lead compound while keeping the pyridine ring constant. Eleven novel THP analogs were synthesized using a four-step synthetic approach involving partial reduction of N-substituted ylides into 1,2,3,6-THPs. The results illustrate that 11 THPs were successfully synthesized in low to moderate yields. Flash chromatography was utilized for purification. Proton nuclear magnetic resonance, deuterium oxide exchange, carbon nuclear magnetic resonance, infrared spectroscopy, and CHN elemental analysis were utilized to characterize the THP analogs. This study aids in contributing knowledge to the THP database.

The Application of Laser-Scanning 3D Model Reconstruction Technology for Visualizing a Decommissioning Model of the Heavy Water Research Reactor

Currently, over 100 nuclear power units globally have been in operation for more than 40 years. Hindered by the limitations of computer technology at the time, these nuclear facilities lack detailed electronic drawings. Activities such as equipment replacement and process circuit system modifications during operation result in discrepancies between paper drawings and actual conditions. Given the complexity and irreversibility of nuclear facility decommissioning activities, virtual simulation technology is often employed before the decommissioning process begins to assist in designing and validating decommissioning plans. Consequently, the creation of high-precision 3D models is crucial for subsequent decommissioning designs. Through innovatively utilizing laser-scanning 3D model reconstruction technology in the reconstruction of the model of China’s first heavy water research reactor undergoing decommissioning, this paper provides an overview of the process of laser-scanning 3D model reconstruction and its application in reconstructing the heavy water research reactor model. Using a 3D laser scanner, four decommissioning areas of the heavy water research reactor, including the reactor building, secondary water pump room, ventilation center, and low-level radioactive wastewater storage tank area, were subjected to 3D laser scanning. The acquired point cloud data from 572 scanning stations were processed using point cloud processing software for denoising, stitching, and triangulation. The triangulated model was then imported into modeling software for 3D reconstruction, ultimately establishing a digitalized model of the heavy water research reactor suitable for subsequent decommissioning simulation and design.

PCMI Uncertainty and Sensitivity Analysis of Es-Salam Reactor Fuel Rods During Steady-State Operations

Nuclear safety relies heavily on the quality of the results of numerical simulation codes. Among the various components of the simulation of the installation are the pellet-cladding mechanical interaction (PCMI), and the peak cladding temperature (PCT). Although the correlations describing the physical, mechanical, chemical, and thermal phenomena that occur in nuclear installations have reached a high level of quality, there remain uncertainties on the final results due to uncertainties in the input parameters which cannot be eliminated. A realistic estimate of these uncertainties is necessary to evaluate the reliability of the simulation results. When the best-estimate approach plus uncertainty (BEPU) is employed in the design of a nuclear installation, design-basis accidents are studied more realistically. This method must be used even in the design of research reactors because they are at the origin of any development of nuclear technology. We propose through this study an uncertainty and sensitivity analysis of PCMI and PCT of a heavy water nuclear research reactor fuel rod. To determine the input parameters that influence PCMI and PCT, we utilize the FEMAXI-6 code. The thermodynamic table of the FEMAXI-6 code is adapted to the case of heavy water. Two system codes are used for uncertainty and sensitivity analysis: RELAP5 and PARET. The study confirmed that in the event of a shortage of heavy water, light water can be injected in its place to remove decay heat from the core and shut down the reactor safely. The safety margin between the PCT and the saturation temperature is reduced from about 10°C in the conservative approach to less than 1°C by the BEPU approach.

The far infrared absorption spectrum of D216O, D217O, and D218O: Experimental line positions, empirical energy levels and recommended line lists

The far infrared absorption spectra of D216O, D217O, and D218O are analyzed with improved accuracy and sensitivity in the 50–720 cm−1 range corresponding to the rotational band. Four room-temperature absorption spectra of highly deuterated water vapor were recorded at the SOLEIL synchrotron by high-resolution Fourier transform spectroscopy. Line centers are reported with a typical accuracy of 5 × 10−5 cm−1 for well isolated lines. The combined line list of about 9700 water lines was assigned to about 10 400 transitions of the nine stable water isotopologues (H2XO, HDXO, D2XO, with X = 16, 17, and 18). A total of 2885 transitions of eight bands involving the first five vibrational states were assigned to D216O. Among them, 2057 are newly reported. The obtained set of transition frequencies was merged with literature data to generate a new set of empirical energy levels for the first five vibrational states of D216O. A total of 1089 transitions of the (000)–(000) and (010)–(010) bands were measured for D217O. They were merged with literature sources to derive 724 empirical term values of seven vibrational states, up to 8088 cm−1. 348 D217O levels are newly determined. A set of 1150 transitions belonging to the (000)–(000) and (010)–(010) bands was measured for D218O. 3451 empirical energies of rotation–vibration levels up to 9222 cm−1 were retrieved using our observations and literature sources. The extension and accuracy of the derived empirical energy levels allow us to recommend new line lists with empirically corrected line positions for D216O, D217O, and D218O.

Deuterium enrichment by proton exchange membrane water electrolysis with electrolyte circulation

Hydrogen isotopes will be new energy sources in nuclear fusion. In this study, a batch system for producing heavy water was developed in which pure water with deuterium (D) was circulated during proton exchange membrane water electrolysis. Deuterium was enriched by up to 94.7 at.% from 51.1 at.%. The D components of water and gas were analyzed during electrolysis. The relationship between the concentration of D (CD) and the electrolytic consumption ratio (R) was evaluated. This relationship was simulated using a mass balance model. From the gas analysis, the separation factor α was calculated. It was found that α depended on the ratio among H2O, HDO, and D2O to maintain the equilibrium state of the chemical exchange reaction.

The Effects of Mine Waste and Rain Water on the Structure of Bacteria Community of Paddy Soils

ABSTRACT Heavy metal contamination of soil has become one of the most important environmental problems worldwide. Heavy metals can affect growth and lead to changes in microbial community composition, which could influence the growth of crops in the soil. In this study, we conducted an experiment to investigate the distribution profile of heavy metals and bacterial communities in soil with the effects of slag and/or water on the top of the soil. Extra heavy metals, acting as selective pressure, led to the loss of sensitive taxa, with tolerant or less sensitive taxa being more abundant in the community. The results showed that the addition of slag on the top of soils did not change the diversity of bacteria but influenced the relative abundance of indigenous members in the community. Water addition, however, improved the homogeneity of the environment vertically in the soil, which consequently led to a lower variation in the bacterial community. This study mimicked the scenario of tailings and abandoned mines in nature, and aimed to study the effects of mines on the soil microbial community with the influence of precipitation on the distribution of heavy metals in the soil. With the effect of precipitation, the transportation of heavy metals in the slag may influence the local bacterial community and subsequently undermine the quality of soil for agriculture. These observations provide evidence of the effects of heavy metals on the soil around abandoned mines without any treatment. Mining causes both heavy metal and water pollution, which may lead to the accumulation of heavy metals in plants and agricultural production. Therefore, it is necessary to take care of tailings with proper procedures instead of exposing them to nature.

Mammal-bearing Pleistocene deposits, Vranić, southwestern Pannonian Basin System

Vranić site is a sand quarry that is located on the southern foothills of Papuk Mountain. From bottom to top of the succession, three sedimentary units have been recognized as: Unit 1 containing massive sand with scattered gravel-sized clasts, marl cobbles and boulders, and abundant marine mammal and fish fossils; Unit 2 consisting of sand intercalated with silt, clay and gravel, which may be horizontally bedded; and Unit 3, which is an erosionally-based lenticular matrix to clast-supported structureless gravel. The basal part of Unit 1 shows numerous reworked skeletal remains of Miocene marine mammals. Cosmogenic radionuclides constrain the age of burial of Unit 1 to 895 ± 211 ka, while the source area of Unit 1 had a quick denudation.The massive sands deposited on the slopes of Papuk Mountain were vulnerable to erosion due to the absence of clay. Heavy rainfall or water from snow melting created flash floods that infiltrated the sands, thereby causing slope destabilization and deformation. This process led to slumps that were transformed into a sandy debris flow. This sediment was probably deposited during the interglacial marine isotope age (MIS) 21 period when the scarce vegetation and a warmer climate favored the melting of permafrost ice and consequently triggered slope movements during MIS 22. The reworked skeletal material sampled at the Vranić site comprises fossilized fish along with mammal bones and teeth. Thus, the Vranić site represents an important site for cetacean fossil remains and serves as an important data source for marine life in the Central Paratethys.

Local polarization redistribution in ZnmIn2S3+m for the enhancing synergetic piezo-photocatalytic overall water splitting

Piezo-photocatalytic water (deuterium oxide) decomposition is a promising strategy for realizing renewable energy, but the manipulation of the polar center remains a big challenge. This study uses a simple low-temperature hydrothermal process to successfully manufacture ZnmIn2Sm+3 (m = 1–3) (ZnIn2S4, Zn2In2S5 and Zn3In2S6). Incorporating both experimental and theoretical analyses, the structural contraction and local polarization of the Zn-S bond in Zn2In2S5 enhance the piezoelectric response and surface charge accumulation, which facilitate charge transfer and reduce the activation energy of water. Remarkably, Zn2In2S5 exhibits excellent piezoelectric photocatalytic total water splitting performance (H2/O2: 4284.72/1967.00 μmol g-1h−1), which is 1.77 times that of photocatalytic performance. Moreover, a significant enhancement in D2O splitting performance can be obtained for the optimized Zn2In2S5. Our work offers valuable insights into the disclosure of local polarization in catalysts for enhancing piezo-photocatalytic overall water splitting.

Analysis of ferroelectric properties of ALD-Hf0.5Zr0.5O2 thin films according to oxygen sources

Ferroelectric Hf0.5Zr0.5O2 (HZO) thin films are mostly deposited with a thickness of less than 10 nm by an atomic layer deposition (ALD) process. Since the oxygen source used in the ALD process affects the residues in the deposited HZO films, the choice of oxygen source can be one of the important factors to improve ferroelectricity. From this point of view, the ferroelectric properties of 10-nm-thick ALD-HZO films according to the oxygen source (O3, H2O, and D2O) were comprehensively analyzed in this study. Heavy water (deuterium water, D2O) was used as a tracer to pinpoint the origin of hydrogen that could be derived from unreacted metal precursors or unreacted hydroxyl groups. As a result, it was revealed that the decrease in ferroelectric polarization and increase in leakage current observed in the H2O- and D2O-based HZO capacitors compared to the O3-based HZO capacitor were due to the oxygen source. These results highlight the importance of using O3 as a hydrogen-free oxygen source in the ALD process to achieve better ferroelectricity.

EXPERIMENTAL RESEARCH CONCERNING WATERSIDE CORROSION OF FUEL CLADDING IN CANDU REACTOR

EXPERIMENTAL RESEARCH CONCERNING WATERSIDE CORROSION OF FUEL CLADDING IN CANDU REACTOR