Lower Port Research Articles

Characterizing Flow Dynamics in a Two-dimensional Flow Cell: Developing Methodologies for Enhanced Subsurface Contaminant Remediation Research

This study used a two-dimensional (2-D) flow cell apparatus (25 cm × 25 cm × 1 cm) to characterize water flow and contaminant transport in porous media. The primary objective was to enhance the understanding of flow dynamics and contaminant behavior in controlled 2-D environments, which is crucial for optimizing the application of remediation technologies to treat contaminants in saturated and unsaturated soil conditions. The 2-D cell was designed with transparent walls to simulate subsurface conditions using medium grained sand, allowing for precise control and observation of fluid movement under saturated and quasi-saturated (trapped air) conditions. Visualization techniques and flow measurement tools were employed to capture detailed data on flow patterns, velocities, and dispersion characteristics. Analysis of breakthrough curves for salt tracer tests using electrical conductivity measurements, alongside varying flow rates, flow fractions, and port configurations, provided significant insights into fluid behavior and contaminant transport. The study also explored the effects of varying salt concentrations (and solution densities) on flow dynamics, contributing to a better understanding of the role of contaminant concentration in contaminant plume development and remediation processes. Visual analysis using dyed contaminant complemented the quantitative data, offering real-time observations of flow patterns and contaminant distribution. A custom-built apparatus was used to control the hydraulic head of multiple outlet ports to sample water from different depths. The experiments demonstrated that gravity plays a crucial role in solute (salt) breakthrough, with lower ports showing earlier breakthrough. Flow fields formed vertically, from bottom-to-top, and horizontally, from inlet-to-outlet, with lower portions advancing sooner. However, multi-port configurations, especially involving five ports, disrupted the sequential breakthrough order, possibly due to convection in the clear well that formed the outlet boundary of the flow cell. These findings will support research students in conducting similar experiments with flow and transport that varies with depth, with future insights for professionals in developing and optimizing remediation strategies related to subsurface contaminant flow. Special thanks are extended to Liam Price, Julia-Barnes James, and Brooke Belfall who were helpful during the research and the experimentation process.

Nonreciprocal polarized transmission via bound states in the continuum.

We realize the observation of near-unity nonreciprocal polarized transmission via the bound states in the continuum (BICs) in a double-layer grating structure. By introducing out-of-plane perturbations and topological defects that break the mirror symmetry between the upper and lower layers, the far-field polarization states in momentum space are inverted vertically and horizontally, showing mirrored polarization characteristics for incident channels from different upper and lower ports. During the process of introducing mirror perturbations in the upper and lower layers, a π/2 phase inversion occurs in the Г-M direction, making chirality possible. Utilizing this bidirectionally tunable nonreciprocal spatiotemporal phase transition enables multiple modulations of polarization states and opens up more possibilities for asymmetric light manipulation in chiral optical effects.

Design of a diamond-based in-vessel soft x-ray detector for the SPARC tokamak.

The in-vessel silicon diode arrays that are used for soft x-ray detection in many tokamaks are sensitive to neutron damage, making them unsuitable for burning plasma devices such as SPARC. In such a device, the silicon diodes would need to be placed far from the plasma-limiting their field of view-or an alternative detector could be used. Here, we present the design of a camera containing an array of chemical vapor deposition single-crystal diamonds, which will be placed in the upper and lower port plugs of the SPARC tokamak with a large enough view of the poloidal cross section to enable tomographic inversion. The camera design presented here is optimized to provide a wide field of view of the poloidal cross section. Simulated plasma conditions are used to estimate the x-ray signal that this detector array will receive and to fine-tune the camera placement within the tokamak.

Assessment of Metal Foil Pump Configurations for EU-DEMO

It is a challenging but key task to reduce the tritium inventory in EU-DEMO to levels that are acceptable for a nuclear regulator. As solution to this issue, a smart fuel cycle architecture is proposed based on the concept of Direct Internal Recycling (DIR), in which the Metal Foil Pump (MFP) will play an important role to separate the unburnt hydrogen isotopes coming from the divertor by exploiting the superpermeation phenomenon. In this study, we will present the assessment of the performance of the lower port of EU-DEMO after the integration of the MFP. For the first time, a thorough comparison of three different MFP (parallel long tubes, sandwich and halo) designs is performed regarding conductance for helium molecules, the pumping speed and the separation factor for deuterium molecules under different physical and geometric parameters. All simulations were carried out in supercomputer Marconi-Fusion with our in-house Test Particle Monte Carlo (TPMC) simulation code ProVac3D because the code had been parallelized with high efficiency. These results are essential for the development of a suitable MFP design in the vacuum-pumping train of EU-DEMO.

Shutdown dose rates in-cryostat outside the EU-DEMO vacuum vessel

Future fusion reactors using deuterium–tritium fuel will exhibit high fluences of high-energy neutrons inside and around the reactor vacuum vessel (VV). As well as causing material damage, fusion neutrons will activate materials, the decay of which leads to radiation fields in and around the reactor after shutdown. Gamma-ray emission from activated materials is a particular radiological hazard during periods of reactor shutdown. This must be accounted for in the design of the reactor shielding to ensure that risks are reduced as low as reasonably achievable.Recent neutronics work has evaluated the shutdown dose rates (SDDRs) in the EU DEMOnstration power plant (DEMO) around the ports and throughout the cryostat, incorporating prospective shielding improvements to the VV and ports. Prior to the proposed shielding design improvements, calculations for the model including the helium-cooled pebble bed (HCPB) blanket showed that radiation leakage through the blanket and VV leads to biological-equivalent SDDRs (following 12 days’ decay) above 103μSv/h throughout the cryostat, ignoring additional contribution from radiation streaming through the port openings. Inclusion of the proposed VV changes reduces this dose rate to below 100 μSv/h. The work finds an approximate order-of-magnitude reduction in SDDR throughout the cryostat when all proposed shielding improvements are applied, leading to dose rates in the cryostat in the range of hundreds to thousands of μSv/h for the full model. The work shows that to further reduce dose rates inside the cryostat, improving the shielding performance of the ports is required, with particular emphasis on the lower port and the equatorial electron–cyclotron launcher which currently dominate the dose rates.

Locking Mechanism of Diagnostic Rack in ITER Lower Port #02

The development of the Locking Mechanism (LM) for the Diagnostic Rack, to be placed in the Lower Port of the ITER Vacuum Vessel, has been underway. This paper proposes a new type of LM due to the feasibility issues in positioning repeatability and Remote Handling (RH) compatibility encountered with previous types. Each LM type was compared based on its ability to generate the largest possible reaction force with the smallest preload, which is necessary for the LM to maintain contact with interface structures. We confirmed that the new LM type could generate the greatest reaction force among the three types, with the smallest preload and assumed attributes of superior repeatability and simpler RH operation.

River logistics amid war and post-war recovery in Ukraine: current situation and prospects .

River logistics amid war and post-war recovery in Ukraine: current situation and prospects .

Completion of design and manufacturing of the iter vacuum vessel lower port extension

The ITER is an international project that aims to demonstrate fusion power generation through scientific and engineering research. Most of the major components consisting of the Tokamak machine have been under manufacturing and/or achieved completion of manufacturing with verification of functional tests to be installed as a part of Tokamak. Korean Domestic Agency completed manufacturing of the first ITER VV lower port extension, with the implementation of major technical resolutions, and the rest of units are under fabrication in 2022. There were several technical considerations when conducting the first-of-a-kind design and manufacturing of the ITER VV port component, which will respect the RCC-MR, the essential safety and radioprotection requirements of the French Regulation ESPN. This study explains these technical problems and the solutions established during fabrication.

Full-scale installation trial of ITER's in-vessel and marshalling area loom prototypes

The in-vessel components of the ITER Diagnostics are located all over the inner shell of the Vacuum Vessel, in the Ports and on the Divertor Cassettes as well. The electrical transmission lines which transmit the signals from the sensors across the vacuum boundaries are Mineral Insulated Cables. These cables will be arranged into looms, which will be fixed to the vacuum vessel with different kinds of attachments.The ITER tokamak is at a stage where manufacturing and testing of each component are becoming more and more important. For this reason, to allow IO to assess feasibility, gain experience and obtain feedback with respect to the suitability of the current designs regarding handling and installation of in-vessel signal cables and loom components, GEMS Engineering has carried out a series of installation trials on full-scale mockups of in-vessel and divertor looms, upper and lower port marshalling area looms. Beside of installation trials, the scope of the work also covered the manufacturing and testing of cable clamps and clips for in-vessel and divertor looms and marshalling areas.This paper outlines the results of the manufacturing of prototypes and assembly trials of the above-mentioned components.

Locking Mechanism of Diagnostic Rack in Iter Lower Port #02

Locking Mechanism of Diagnostic Rack in Iter Lower Port #02

Investigation of the Effect of Puncture Order and Position on the Difficulty of Lower and Middle Abdominal Port Placement.

Port placements at the mid-abdomen (mainstay of robotic surgery [Rob]) appear to be difficult compared to that at lower abdomen (mainstay of conventional laparoscopy [Con-Lap]). We hypothesized that the reason for this may be the difference in port puncture places. We examined how the differences between the place and puncture order of ports affected Con-Lap cases with ports mainly placed in the lower abdomen and Rob cases with ports mainly placed in the middle abdomen. The trocar time was measured from the time when the puncture position and skin incision were determined and initiated, respectively, to the time when the port was punctured and fixed and used as the indicator of difficulty. In the Con-Lap group analysis, the trocar time of the left lower port was longer (right lower: 77 s, middle lower: 117.5 s, and left lower: 138 s, P < 0.0001). In the Rob group analysis, the trocar time of the left most port was significantly longer (right-most: 89.0 s, right-middle: 92.5 s, left-middle: 121.0 s, and left-most: 197.0 s; P < 0.0001). In addition, the total trocar time was significantly longer in the first puncture at the right-middle port in the Rob group (right-most first: 8.4 min, right-middle first: 12.4 min, and left-middle first: 8.5 min, P = 0.0063). In the mid-abdomen port placement, mainstay of Rob cases, the puncture order, and port site have a significant impact on the difficulty of the procedure. It is preferable to avoid initially puncturing the right-middle port in case of the Rob.

Nuclear Analyses of ITER Diagnostics Lower Ports

The present work is devoted to the nuclear analyses of International Thermonuclear Experimental Reactor (ITER) diagnostics lower ports (LPs) with the aim to select an optimal shielding layout considering various requirements, such as shielding performance, reduced and simplified remote handling (RH) operations, standardization across all LPs, and cost-effective solutions. The LP configuration with back rack, RH shield, and front rack with stainless-steel (SS) ribs for all diagnostic LP ports is the most advantageous option to address these requirements.

Characterization of dust produced during the 2021 first campaign in EAST tokamak

• The dust collected from 2021 first experimental campaign in EAST was characterized and analyzed. • By using the diagnostic observation window, dust was collected during the campaign for several times. The local dust production rate decreases as the plasma operation goes. • Ferromagnetic dust with the shape of strips, flakes, irregular blocks and spheroids has been found in EAST. Dust has been collected and characterized by various methods during the 2021 first experimental campaign in EAST tokamak. It was found that the weight of the in-vessel dust collected at the mid-plane port varied from about 265 mg to about 966 mg. And the dust appeared mainly in the shape of spheroids, flakes, stripes and irregular-shaped particles with the sizes ranging from micrometers to several millimeters. The dust consisted of different elements, which was from the wall-conditioning, erosion of plasma-facing materials (PFMs) as well as the flaking of deposits. The dust collected from the lower port K contained different elements from those collected from the in-vessel port K, with more Fe in the lower port and more Li in the vacuum vessel. The ferromagnetic dust with different shape has been found, and different shape has different O content and size. By using the diagnostic observation window, dust was firstly collected during the campaign and the local dust production rate is calculated, which is found to decrease as the plasma operation goes.

Electromagnetic Analysis of CFETR Vacuum Vessel During Plasma Vertical Displacement Event

The vacuum vessel (VV) of the China Fusion Engineering Test Reactor (CFETR) performs many functions, but its main function is to provide a high-quality, ultra-high-vacuum environment for plasma operation. The electromagnetic load acts on the VV and its ports during a plasma vertical displacement event (VDE). This paper adopts a new simulation method of the plasma current during transient electromagnetic analysis. The distribution of the electromagnetic load on the VV shells, the upper ports, the equatorial ports, and the lower ports is entirely displayed. The structural stress under the electromagnetic load during a VDE was obtained by electromagnetic-structural coupling. According to the structural analysis, the results indicate that the VV can meet the structural strength and stiffness requirement.

Numerical Analysis of Electron Beam Welding Deformation for the Vacuum Vessel Lower Port Stub of 316L Stainless Steel

The China Fusion Engineering Test Reactor vacuum vessel has strict tolerances requirements and a large number of fully penetrated joints in the manufacturing and assembly processes. As the most complicated component of vacuum vessel, port stubs have stricter tolerance requirements, to guarantee the high assembly accuracy with the vacuum vessel. Due to the small deformation of electron beam welding, this method is adopted for the welding of port stub. However, welding deformation cannot be avoided, thus it is necessary to carry out finite element analysis to analyze and control the welding deformation of the port stub. In this paper, based on thermo-elastic–plastic theory, the double ellipsoid and cone-shaped hybrid heat source can accurately outline the electron beam weld pool contour of the 316L stainless steel with 50 mm thickness, which is further verified by the welding process experiment. The above hybrid heat source is applied to analyze the welding deformation of the lower port stub, and according to the deformation simulation results, the welding fixture is designed to reduce the welding deformation. The welding deformation analysis can effectively provide theoretical data support and practical guidance for the actual electron beam welding process of port stub.

Coordinated design of the cartridge-type blanket and the ceramic pebble divertor for the helical reactor FFHR-b3

The cartridge-type blanket for the helical reactor has been updated and named the CARDISTRY-B3. Together with this, the ceramic pebble ergodic limiter/divertor system named the REVOLVER-D3 has been adopted in the design. There was a difficulty in fabricating the blanket cartridges due to the first wall shape with three-dimensional surface. This difficulty has been removed by introducing the slit first wall, where the first wall surface is formed by alternately stacking solid metal plates and porous plates made of metal or ceramic. The liquid metal flowing inside the blanket cartridge oozes out through the porous plates and forms the surface flow covering the first wall. Solid target plates for the helical divertor has been omitted, because the divertor region is already covered and protected by the liquid metal surface flow. The liquid metal freely falls inside the blanket cartridges by the gravity force and then exhausted to the pool set on the lower port. The ceramic pebbles, which are dropped to the inboard-side ergodic layer to form the flowing limiter divertor, also flow into the liquid metal pool. The pebbles and liquid metal are individually elevated again by screw conveyers. Since the free surface of the liquid metal is exposed to the plasma, the vapor pressure of the working liquid metal should be low enough. Ternary or quadruple alloys, which include Li, Sn, Pb (or Bi), and Er, have been selected as the candidates of the functional liquid metal for the CARDISTRY-B3 that satisfies the requirements of low vapor pressure, low density, low melting point, and high tritium breeding ratio. In this study, the coordinated design of CARDISTRY-B3 and REVOLVER-D3 for the FFHR-b3 is presented. The FFHR-b3 is one of the design options that aims at demonstration of 100 MW net electricity with two times larger devise size than LHD.

Structural analysis of the diagnostic rack locking in ITER lower port #8

ITER (International Thermonuclear Experimental Reactor) is a nuclear fusion research and engineering project. It is supposed to be the first fusion device to test the integrated technologies, materials and operational regimes necessary for the commercial production of fusion-based electricity. Front (explored in this paper) and Back diagnostic racks are used as supporting structures of the so-called ITER Divertor Thomson Scattering (DTS) Diagnostic System that is created to measure plasma characteristics. They will be attached to the lower port walls (ITER ports are used to locate diagnostic equipment and its supporting structures) through the so-called Divertor Rails. The developed design of the Front (Diagnostic) Rack locking (e.g. Rack attachment to the rails mechanism) was analyzed in this research to be consistent with thermal stresses, electromagnetic and seismic loads taking into account some specific assembly and maintenance loads including preloading under installation. The analysis of the rack locking design's resistance to the mentioned loads should prove correspondence of the suggested common rack design with the structure integrity criterions. Construction strength under the most severe loading scenario was estimated in this research and appropriate conclusions were made. It was found out that the stress criterion was not fully satisfied, so a new rack locking design concept was proposed. Its main details are also described at the end of this article.

POSTOPERATIVE PORT-SITE PAIN AFTER GALL BLADDER RETRIEVAL FROM EPIGASTRIC VS UMBILICAL PORT IN LAPAROSCOPIC CHOLECYSTECTOMY: A RANDOMIZED CONTROLLED TRIAL

Objective: To determine whether gall bladder (GB) retrieval from umbilical port is associated with more pain at port site as compared to GB retrieval from epigastric port in adult patients undergoing four port elective laparoscopic cholecystectomy at a tertiary care hospital. Methods: Adult patients, who were undergoing elective laparoscopic cholecystectomy during a six-month period in 2010 at our institute, were randomized to either group A (n = 60, GB retrieval through epigastric port) or group B (n = 60, GB retrieval through umbilical port). VAS for pain was assessed by a registered nurse at 1, 6, 12, 24 and 36 h after surgery. Results: The VAS for pain at umbilical port was less than epigastric port at 1, 6, 12, 24 and 36 h after surgery (5.9 ±1.1 vs. 4.1± 1.5, 4.6± 0.94 vs. 3.5± 1.05, 3.9± 0.85 vs. 2.4± 0.79, 3.05± 0.87 vs. 2.15± 0.87, respectively) and the difference was statistically significant (p-value &lt; 0.001). Multiple linear regression was done for port site pain at 24 h and the VAS at umblical port was less than epigastric port with VAS difference of 0.9 after adjusting for age, sex, duration of surgery and additional analgesia use (r 2 =0.253, p-value &lt; 0.001). Conclusion: Gall bladder retrieval from umbilical port is associated with lower port site pain than GB retrieval from epigastric port in patients undergoing elective laparoscopic cholecystectomy. We recommend umbilical port for gall bladder retrieval.

Experimental study on the stability and flame characteristics of LPG flames in O2/N2 and O2/CO2 environment

The current energy crisis and the escalating concern over pollution level necessitate the development of various low emission and clean technologies for efficient utilization of fossil fuels. These technologies offer the benefits of using fossil fuels continuously without harming the environment. Oxy fuel combustion technology is one of the promising low emission combustion technologies having an additional advantage of being a better retrofit option compared to other clean technologies. In the present study, the stability and flame characteristics of LPG flame in a tubular burner has been investigated with oxygen as the oxidizing gas and nitrogen or carbon dioxide as the balance gas. The experiments were conducted to study the effect of primary aeration and the effect of balance gas on the stability and flame characteristics of air and oxy flames. The experimental results from the preliminary experiments show that the flame height decreases with increase in primary aeration for both air and oxy cases and the premixed blue zone increases with primary aeration. The flames observed for oxy cases are dull and weak at all equivalence ratio (or primary aeration). The measured axial flame temperature indicated that the temperature of oxy flames is lower than that of the air flames for the same primary aeration. The data obtained from the stability tests show that the oxy flames can withstand relatively lower port velocity than its air counterpart. Therefore, the stable operating range of the given burner design is lower when CO2 is used as the balance gas. These differences in the stability and flame characteristics is attributed to the difference in the thermo physical properties like molar heat capacity, mass diffusivity and thermal conductivity of the balance gas CO2 and N2.

Subsidy or minimum requirement? Regulation of port adaptation investment under disaster ambiguity

This paper models two commonly adopted regulatory polices (the minimum requirement regulation vs. subsidy) on port adaptation investment to mitigate the damage caused by climate change-related disasters. The ambiguity of the disaster occurrence probability and the decision makers’ attitudes towards risk are explicitly modelled. It is found, under the minimum requirement regulation, ports balance the option of increasing their adaptation vs. reducing their economic activities. In comparison, subsidies promote adaptation without introducing any incentive for ports to reduce outputs, but they can be less efficient than minimum requirement regulations in addressing market failures, such as that caused by a spill-over externality. The ambiguity of disasters changes the optimal designs of minimum requirement regulation and subsidy policy but does not change their relative ranking qualitatively. Decision makers’ risk attitudes also play important roles. Higher degrees of pessimism (more risk aversion) lead to lower port outputs but can also increase the level of port adaptation to achieve full insurance against disaster loss. Higher degrees of pessimism also make the government more conservative to intervene in the ports’ adaptation and thus less likely to impose the two regulatory policies. Our analysis also explains why it is justified for the government to withhold intervention under ambiguity, and also shows that the ambiguity does not necessarily bring worse expected social welfare.