The tritium breeding capacity of fusion blankets is a critical factor in achieving tritium self-sufficiency in fusion reactors. Current designs for tritium production in blankets are based on neutronics simulations, whose accuracy requires experimental validation. This study focuses on the experimental validation of the neutronic design reliability of the supercritical CO2-cooled lithium-lead (COOL) blanket developed for the China fusion engineering test reactor (CFETR). For this purpose, an experimental mock-up was designed and fabricated to replicate the key neutronics characteristics of COOL blanket. The mock-up was irradiated using D-T neutron generator and validated using multiple techniques: tritium production rate (TPR) online monitoring with a miniature back-to-back lithium glass scintillator detector, TPR integral measurement using Li2CO3 pellets analyzed by liquid scintillation counting (LSC), and neutron flux measurement with activation foils (Au, Zr). To enhance accuracy, corrections were applied for lithium-lead (PbLi) segregation based on element analysis and for neutron source intensity based on in-situ depth profiling of tritium in the tritide target. The results show excellent agreement between experiments and simulations, with calculation-to-experimental (C/E) value ranging from 0.96 to 1.11 for TPR measured by lithium-glass scintillator detectors, 0.90-1.09 for TPR by Li2CO3 pellets, and 0.84-1.13 for reaction rates measured by activation foils.

Ecological water replenishment (EWR) is vital for reversing coastal wetland degradation, yet its mechanistic effects on microbial nitrogen (N) removal-particularly via plant root-mediated processes-remain unclear. This study quantifies how EWR drives N removal in Phragmites australis wetlands of China's Yellow River Delta by analyzing rhizosphere soil properties, root exudates, enzymatic activities, functional genes (nirS, anammox 16S rRNA), and N-removal rates pre- and post-EWR. Our results showed that EWR reduced salinity while elevating NO3-N (72.3% increasing) and NH₄-N, enhancing denitrification (DNF, 1.54 ± 0.72 μmol·kg-1·h-1; 97.5% of total N removal) over anammox (AMX, 0.046 ± 0.02 μmol·kg-1·h-1). Critically, EWR upregulated nirS and AMX genes by reshaping root exudates: amino acids (AA) increased as carbon sources and microbial signals, whereas flavonoids and phenolics decreased, alleviating inhibitory to denitrifiers. Structural equation modeling confirmed that EWR controlled the release of root secretions by regulating the environmental factors, and thereby regulates the DNF and AMX process. Consequently, N-removal potential surged 1.3-fold (0.72 vs. 0.54 g N·m-3·d-1), purifying 1.86 × 103 t N monthly during EWR periods. We establish that EWR enhances coastal eutrophication control by optimizing root exudate-microbe interactions, providing root exudate profiles and nirS abundance as key ecological indicators for wetland restoration efficacy. This study demonstrated that EWR significantly enhanced the N removal function of wetlands by improving the water-salt environment, increasing substrate supply, and regulating root exudate composition, which EWR substantial practical significance for alleviating coastal eutrophication risks.

The measurement accuracy of tritium production rate in blanket neutronics is crucial for evaluating the tritium breeding performance of fusion reactors. Liquid scintillation counting (LSC) method, widely adopted for its high sensitivity and accuracy, with its measurement uncertainty primarily influenced by chemical processing procedures. This study presents general processing details and the calculation method for detection limits of low-content tritium (determined to be 1.70 Bq/L under this measurement conditions). We report the experimental results on the optimization of chemical processing techniques for lithium titanate (Li2TiO3) and lithium carbonate (Li2CO3) and their application result in WCCB and COOL blanket neutronics experiment. Experimental results demonstrates that for Li2TiO3 sample, extraction stability is positively correlated with sample activity, a minimum activity of 1.5 Bq is recommended to constrain the measurement uncertainty to below 5%. And for Li2CO3 sample, controlling the dissolution rate is critical to mitigate tritium escape for sample. The application in blanket neutronics experiments yielded calculation-to-experiment (C/E) ratios ranging from 0.97 to 1.09, with an overall measurement uncertainty controlled within 6%. These results demonstrate the effectiveness of the optimized protocols and provide a feasible technical approach to reduce uncertainty in LSC measurements.

To address the risk of flow non-uniformity in the Water-Cooled Ceramic Breeder (WCCB) blanket of the China Fusion Engineering Test Reactor (CFETR), three acrylic-based test sections were developed for flow visualization experiments: (1) 1:5 scaled outboard segment model featuring hydraulically equivalent pipes regulated by pinch valves, (2) first wall (FW) model with 39 U-shaped cooling channels, and (3) breeding zone (BZ) model comprising four groups of 29 cooling tubes each. A key contribution of this work is the development of the scaling strategy for outboard segment test section based on equal Euler number (Eu) and cooling water velocity matching, resolving scaling conflicts between the high-pressure/high-temperature prototype and the ambient-condition test section. Computational Fluid Dynamics (CFD) optimization showed that the maximum deviation in blanket module between the 1:5 scaled outboard segment, and the full-scale prototype is 6.1%. For FW test section, geometric optimizations—including inlet pipe downsizing and manifold wall thinning—reduced the maximum deviation in channel flow distribution to 0.51%, while the cooling water streamlines in the manifold closely matched those of the prototype. Mass flow rates in the cooling channels are measured using both Doppler-based ultrasonic flowmeters and Particle Image Velocimetry (PIV), enabling cross-validation and detailed characterization of the internal flow field. This test section design provides high-fidelity experimental support for the hydraulic optimization of the CFETR WCCB blanket.

The Water Cooled Ceramic Breeder (WCCB) blanket is one of candidate blankets for China Fusion Engineering and Test reactor (CFETR), which is responsible for tritium breeding, neutron shielding as well as energy removing for electricity generation. The Neutron Wall Loading (NWL) is the internal source that determines the blanket design, because it dominates the nuclear heat, which is further coupled with the cooling plates layout to decide the temperature field and inversely affect the Tritium Breeding Ratio (TBR). This paper tries to establish the mathematical models which can link the important parameters of NWL, nuclear heat, temperature as well as TBR. Finally, these models are integrated and programed as topology optimization model, in which the NWL is input and the radial layout can be automatically output. Furthermore, it is applied into the WCCB blanket design, and the results show that the optimal radial thickness covering the breeder zone should be theoretically the same as 0.68 m for each module at different poloidal location. Through these coupling analyses, we can have a deeply and accurately understanding of what exactly the optimal required radial thickness should be for the blanket design, which can realize higher performance of tritium breeding and heat removal. This topology optimization model lies that the blanket radial layout and thickness are internal-defined by the NWL, rather than external-defined by other fusion system. Although there are some simplifications during mathematical modelling, it could provide suitable engineering design guideline for blanket demands, especially for the radial thickness, to the interface group of CFETR, which is useful for the integration design with other systems, such as Vacuum Vessel (VV) and Toroidal Field Coil (TFC).

Seagrass carbon concentration mechanisms are modulated by seawater pH and salinity, yet their progressive regulation in photosynthetic inorganic carbon utilization pathways remain poorly characterized. This study novelly mathematically characterized first-order (pH change rate) and second-order (pH change acceleration) derivatives from pH-drift experiments in the intertidal seagrass Zostera japonica along China's coastline. The pH change-based method effectively highlights the dissolved inorganic carbon (DIC) utilization and biomass accumulation of seagrass, while pH change acceleration is sensitive to the progressive switch of DIC utilization pathways during Z. japonica photosynthesis. As pH increases, six significant regulations emerge that have ecophysiological significance: a. primary regulation via reaching the CO2 compensation point; b. extracellular carbonic anhydrase (exCA) activity dropping to negligible levels; c. diminished efficiency of proton pump-mediated extracellular acidification in supplying CO2; d. regulation via reaching the bicarbonate saturation point; e. regulation via reaching the bicarbonate compensation point; and f. regulation via enhanced respiratory CO2 into seawater temporarily stimulating photosynthesis as a feedback. We summarize a progressive and universal pH–salinity-driven regulation mode reflecting different combinations of DIC utilization pathways and their respective intensities. Specifically, seawater pH modulates the mode's fluctuating thresholds, while salinity governs the amplitude. Unexpectedly, elevated salinity serves as an effective stimulant for Z. japonica to maintain strong DIC utilization intensity in high pH (> 9.1) environments. Ocean acidification could increase pH change acceleration by 166%, enhancing carbon fixation, whereas artificial ocean alkalinity enhancement (Ca(OH)2 supplementation and olivine-seawater weathering) could reduce it by 165% and 105%, respectively, risking mortality of Z. japonica. Additionally, the salinity-dependent braking point (where acceleration drops to zero) serves as a critical threshold for seagrass photosynthesis and a new factor for transplantation-based restoration.

Understanding dissolved organic nitrogen (DON) transformation is critical for estuarine nitrogen dynamics, yet microbial contribution and mechanism remain poorly constrained under high terrestrial input. This study reveals that DON in Pearl River Estuary (PRE) exhibits non-conservative mixing jointly regulated by terrestrial inputs, autochthonous production and microbial processes. By integrating field observations, model simulations, and incubation experiments, this study identifies the mid-salinity mixing zone (10-25 PSU) as a transformation hotspot. Based on dark in vitro incubations, the microbial transformation rate was approximately 0.67 ± 0.23 μmol L-1 h-1. This process accounted for 77-87% of the total potential DON pool (defined as the sum of measured concentration and transformed DON) in mixing zone. Molecular analysis indicates that while physical dilution primarily drives the decline in bulk aromaticity (AImod, DBE), microbial processing qualitatively reshapes the DON pool. Specifically, microbial metabolism promotes the relative accumulation of recalcitrant lignin-like compounds by selectively consuming labile components. Microbial metabolism (particularly Candidate_Actinomarina) is the core driver of DON transformation. FAPROTAX analysis suggests a functional transition from methyl-oxidation-associated N transformations (heterotrophic nitrification and denitrification) to sulfur-oxidation-associated N transformations underlies the DON molecular variations along the salinity gradient. Terrestrial input accelerates biochemical reactions such as demethylation and deamination through the priming effect. Furthermore, mineralization of labile terrestrial DON potentially supplies key substrates that are closely linked to N2O production. These findings highlight the pivotal role of microbial transformation in regulating DON fate, providing new insights into estuarine nitrogen cycling under strong terrestrial inputs.

In this paper, we present a solid-type PbxLiy blanket and related R&D activities. This blanket concept is designed to enhance the Technical Readiness Level (TRL) by addressing risks identified in both current solid and liquid blanket designs. It employs PbxLiy with a high melting point as both neutron multiplier and tritium breeder, configured in the form of pebble beds within the solid blanket. This approach leverages mature tritium extraction technologies already developed for solid blankets, while eliminating the need for expensive beryllium. At this stage, a conceptual design of the blanket has been developed to verify its compliance with neutronics and thermal-hydraulics performance requirements. Additionally, initial fabrication of this material has been attempted, and preliminary characterizations, including density, chemical reactivity with water, and composition, have been conducted. The results confirm that the dominate composition is the PbxLiy alloy with high melting point. i.e. Li4Pb, Li3Pb, Li5Pb2 and Li10Pb3. However, there is still some purely lithium and PbxLiy at lower melting point 481.9 degrees C. Therefore, we need to improve the manufacturing methods to make it much more purely with high melting point, e.g. Pb28Li72 at 650 degrees C. In the following, we will find new way to make the element Pb/Li mixing much more uniformly, and cool them instantly during the mixing to make the solid-type PbxLiy more purely.

This study explores the application of the Reactor Monte Carlo (RMC) code in fusion neutronics, demonstrating its capabilities in various areas of fusion reactor analysis. We developed the MCNP-to-RMC conversion tool (M2R) to facilitate the transition from MCNP to RMC format, validated by converting the ITER C-model and CFETR model. The study further investigates the use of RMC for global flux distribution calculations in the CFETR model, employing a density reduction method for weight window generation, showcasing RMC’s variance reduction and neutron transport capabilities in complex fusion reactor geometries. Additionally, the Tritium Breeding Ratio (TBR) for the CFETR blanket was calculated and compared with OpenMC, showing excellent agreement. The study also assessed RMC’s CAD-based transport capabilities using the Paramak to model a half-tokamak design, with simulations performed in both RMC and OpenMC, showing consistent results. Overall, the findings validate RMC as a reliable tool for fusion neutronics simulations, demonstrating its capability to handle complex reactor models, neutron transport, and key parameter calculations.

The supercritical carbon dioxide (S-CO _2 ) cOoled Lithium-Lead (COOL) blanket is under development for China Fusion Engineering Test Reactor (CFETR). As a key component of the blanket, the first wall (FW) is subjected to high heat flux and plasma sputtering, requiring the simultaneous satisfaction of stringent thermal and structural requirements. To reduce the prohibitive computational cost of high-fidelity simulations when exploring vast design spaces, a thermo-mechanical coupled surrogate model is developed, which integrates the FW geometry, heat loads and boundary conditions as parametric inputs. By combining thermal balance theory, empirical correlations and 1D/2D hybrid analytical heat conduction model, the surrogate model enables the rapid prediction of key thermal-hydraulic responses, including coolant outlet temperature, pressure drop and temperature distribution of reduced activation ferritic martensitic steel. Based on the temperature distribution, the corresponding stress quantities are evaluated using generalized Hooke’s law, beam theory and plate theory. To improve the consistency of thermo-mechanical stress prediction, FEM-derived stress linearization results are further used to correct the analytical stress quantities, leading to a corrected thermo-mechanical surrogate model. Through consistency assessment against CFD/FEM simulations and FEM-based correction, the corrected surrogate model shows improved agreement with numerical results while retaining sub-second computational performance, making it suitable for rapid pre-design screening within the investigated parameter range. On this basis, a multi-objective optimization framework employing the Non-dominated Sorting Genetic Algorithm II (NSGA-II) for FW design is established. Taking the equatorial unit #3 of COOL blanket as an example, the framework is applied to optimize the coolant channel geometry and mass flow rate, with the objectives of maximizing outlet temperature and minimizing the flow-resistance power loss associated with the FW pressure drop to improve the thermal-to-electric conversion efficiency under multi-physics constraints. The optimization result is a nonlinear Pareto–Front curve describing the trade-off between these competing objectives. Two representative solutions on the curve are selected for detailed comparison with the baseline design: one design maintains a similar outlet temperature while reducing flow-resistance power loss by 22.67%, whereas the other maintains comparable flow-resistance power loss but increases the outlet temperature by 8.31 °C. Moreover, all solutions between these two points on the Pareto–Front outperform the baseline design in both objectives. Overall, the proposed surrogate-based optimization framework demonstrates its capability to efficiently identify high-performance designs via balancing competing objectives and provides a flexible and systematic tool for thermo-mechanical pre-design screening and optimization of the CFETR COOL blanket FW.

Within the framework of the Comprehensive Research Facility for Fusion Technology (CRAFT) Program of China, the China LIthium-lead Magnetohydrodynamics Blanket expERiment (CLIMBER) facility is currently being constructed. The facility is designed to systematically investigate the intrinsic mechanisms of the MagnetoHydroDynamics (MHD) effect through a series of experiments, thereby providing experimental evidence and theoretical support for optimizing the design of the supercritical carbon dioxide (s-CO2) cOoled Lithium-Lead (COOL) blanket. In this paper, the thermal hydraulic system analysis is performed for CLIMBER facility using the modified RELAP5/MOD3.3. Firstly, the component-level simulations are performed using both ANSYS-CFX and RELAP5. The accuracy of the modified RELAP5 code in heat transfer calculations is evaluated, and necessary corrections are applied to the pressure loss based on the CFX results. Subsequently, the verified RELAP5 component models are integrated into the system model, which comprises of the PbLi, thermal oil, and water systems, to conduct system-level analysis. Various operating conditions required for the experiments are simulated by adjusting critical parameters such as valve openings, pump flow rates, and electric heating power. Temperature, pressure, and flow rate at different nodes are obtained, and the maximum pressure drop of each system is calculated. The results not only confirm the feasibility of the loop design, but also provide essential guidance and data support for future experimental implementation and the formulation of operational control strategies.

The decomposition of recalcitrant organic matter (ROM) in seagrass litter plays a crucial role in mediating blue carbon magnitude. However, the mechanisms underlying ROM decomposition in seagrass litter under eutrophication, driven by anthropogenic pressures, remain poorly understood. Here, we investigated the effects of eutrophication on the decomposition of two types of seagrass litter (leaf and sheath) through laboratory experiments adding nitrogen and macroalgae. We found that macroalgae addition inhibited ROM breakdown in leaves and sheaths. Nitrogen addition enhanced ROM decomposition in leaves by 4% while suppressing it in sheaths compared to the treatments without nitrogen addition. Additionally, the combined addition of nitrogen and macroalgae led to a more substantial loss of sheath ROM (35-39%) compared with macroalgae alone. The opposite response of ROM breakdown in leaf and sheath under nitrogen addition were co-regulated by litter quality and bacteria taxa (i.e., Flavobacteriales, Actinomarinales, and Phycisphaerales). In the presence of macroalgae, fungi, including Lecythophora luteoviridis, Tyrannosorus hystrioides, and Pseudeurotium_ovale, were found to play a significant role in the decomposition of leaf ROM, but not in sheath decomposition. These findings highlight the negative effects of eutrophication on litter ROM sequestration and the important role that litter quality and microbe play.

Short-term marine heatwaves, driven by global climate change, frequently occur in coastal areas and increasingly threaten seagrass meadows by raising temperatures, which impair their ecological functions. Lignocellulose, a key component of plant cell walls, is crucial for maintaining plant morphology and resilience. However, empirical evidence on the response of seagrass lignocellulose to short-term marine heatwaves is limited. This gap hampers understanding of seagrass cell wall adaptation and their roles in blue carbon storage, disturbance resistance, and biodegradation defense. To address this gap, a 10-day laboratory simulation was conducted, featuring a control group at 26 °C and an experimental group at 35 °C. The study examined the impact of temperature on the different organic matter types (lignocellulose and non-structural carbohydrates) and the growth rate changes of the tropical seagrass Thalassia hemprichii. We found that high temperatures converted starch stored in rhizome tissues into soluble sugars, which was associated with a significant decrease in leaf growth and belowground biomass. This suggests that the energy stored in the form of starch was mobilized to meet the plant's metabolic demands in response to heat stress, but at the cost of overall growth. While the lignocellulose exhibited slightly lower values at higher temperatures compared to the control treatment, the difference was not significant. This may be due to the response of lignocellulose lagging, or the high contents of non-structural carbohydrates in seagrass providing sufficient energy to buffer short-term marine heatwaves. These results indicated that the lignocellulose may be more resilient to short-term warming events.

The breeding blanket is a critical component of magnetic confinement fusion reactors. The reliability, availability, maintainability, and inspectability (RAMI) of the blanket has been recognized as a major challenge on the pathway to commercial fusion demonstration reactors. However, the absence of blanket failure modes and failure rate data under fusion environment has significantly impeded progress in blanket RAMI research. To address this critical knowledge gap, the present investigation focuses on the dominant failure mechanism induced by pulsed operational loading-specifically fatigue failure, and proposes a novel probabilistic framework to predict lifetime and assess reliability for fusion blankets. The framework incorporates three key elements: (1) structural material damage prediction model grounded in the degradation mechanisms, (2) operational loading spectra characterization, and (3) blanket lifetime prediction and reliability assessment. The framework enables probabilistic evaluation of fatigue lifetime while generating essential reliability metrics, including failure rates and mean time between failures. Validated through application to the Water-Cooled Ceramic Breeder blanket design for the Chinese Fusion Engineering Testing Reactor, the proposed framework demonstrates the potential to overcome existing data limitations in blanket RAMI research, offering substantial support for the blanket design optimization.

Seagrasses growing in different eutrophic states in carbonate and terrigenous sediments may exhibit contrasting sulfide intrusion and responses; however, limited information is available. In this study, sulfide intrusion in the tropical typical seagrass Thalassia hemprichii along a eutrophication gradient in carbonate and terrigenous sediments on Hainan Island, South China Sea, was investigated using combined elements, stable isotopes, and photobiology. The sediment porewater sulfide concentration increased with rising nutrient levels, with porewater sulfide as 223.92 ± 25.34 μmol/L when the dissolved inorganic nitrogen concentration was 10.83 ± 0.60 μmol/L and the dissolved inorganic phosphate concentration was 0.39 ± 0.01 μmol/L. The nutrient input significantly enhanced sulfide intrusion in seagrass, resulting in reduced δ34S values in roots from 12.78 ± 1.16 to 2.69 ± 0.46 ‰, with leaf δ15N as the greatest explanatory factor. In addition, sulfide intrusion inhibited photosynthesis more strongly in seagrass growing in carbonate sediments than in terrigenous sediments because of the low iron content in carbonate sediments (almost 50 % of the iron content in terrigenous sediments), reducing rETRmax and Ek by 43.08 % and 36.42 %, respectively. Therefore, the synergistic effects of nutrient input, sulfide concentration, sediment substrate, and iron content affected the sulfide intrusion in seagrass.

Landslides are a common type of geological hazard. When a landslide collides with a water body, it can generate secondary waves, the destructive potential of which may exceed that of the landslide itself, highlighting the necessity for research on landslide-generated tsunamis. This catastrophic disaster represents a typical fluid-solid coupling process, and the interactions among the two phases significantly complicate the study of this issue. This research proposes an innovative approach to efficiently and effectively simulate this disaster using multi-layer nested grids and a flexible selection of various governing equations. The method couples the progressive landslide model (Ls-Rapid), developed by the International Consortium on Landslides, with the Cornell Multi-grid Coupled Tsunami Model; data conversion between the two models was implemented in Fortran. The effectiveness of this method at different computational scales was validated through case studies of the Gongjiafang landslide in the Three Gorges Reservoir area in 2008 and the 1946 Aleutian tsunami. The simulated results align well with field survey data, demonstrating the promising application prospects of this method in predicting and mitigating landslide-generated tsunamis.

The Vacuum Vessel (VV), as the first confinement barrier of the Chinese Fusion Engineering Test Reactor (CFETR) must guarantee its integrity once the In Vacuum Vessel Loss of Coolant Accident (In-VV LOCA) happens. Enough experimental verifications are inevitable. And the data from the experimental facility should be convincing with an acceptable cost. In the present research, scaling criteria are identified for the In-VV LOCA, which can provide the direction for the design scheme of the experimental facility. The experimental facility employs the same working fluid and the equal thermal operation conditions. The volume scaling factor of 1/1000 for the VV with a toroidal structure adopted in the experimental facility is selected. The similarities of the flow at the break, flash and the flow resistance are prioritized. Through the computational simulation for the experimental facility, it has been demonstrated that the thermal hydraulic responses could be reappeared in the experimental facility within an acceptable range of distortions.

This study investigates the dynamic behavior of mixed pebble beds used in the Water-Cooled Ceramic Breeder (WCCB) blanket under vertical vibration. An experimental platform, including a transparent chamber, force- loading component, and gas supply system, was employed to simulate the vibration dynamic behavior of relevant mixed pebble beds. The Particle Tracking Velocimetry (PTV) was utilized to capture the particle's position and movement. In unitary pebble beds, the relative static states, vibration heaping, nonlinear velocity in the convection state, and face-centered cubic packing occur as the vibration parameters and particle size change. In the binary pebble beds, the experimental results show that vibration parameters, spatial confinement, and loading pressure significantly impact particle behavior. Higher vibration acceleration leads to the segregation of binary pebble beds due to the Brazil Nut Effect. The study reveals that the segregation threshold for binary pebble beds is a vibration acceleration (Gamma) of 1.0, and complete segregation occurs at Gamma = 1.5. The percolation mechanism predominates in this range and the convection mechanism starts to impact when acceleration Gamma exceeds 2. Conversely, confined spaces and loading pressures suppress segregation, maintaining the mixed state of binary pebble beds. These findings are essential for comprehending the segregation mechanisms and provide solutions for controlling vibration-induced segregation.