Sufficient Heat Removal Research Articles

Selection of EU-DEMO divertor operating conditions: water cooling thermal-hydraulic parameters and power exhaust capabilities

In the context of EUROfusion activities for the development of the DEMO reactor project, the divertor design is a major challenge. It must sustain very high heat, ion particle and neutron fluxes allowing, at the same time, the shielding of the vacuum vessel and the vacuum pumping for reducing the plasma pollution. The conceptual divertor design is based on the use of EUROFER97 for the divertor cassette body, while tungsten monoblocks bonded to CuCrZr pipes are used for plasma-facing targets. EUROFER97 was selected considering its reduced long-term activation and superior creep and swelling resistance under neutron irradiation. However, depending on the operating temperature under neutron irradiation, a pronounced shift of the Ductile to Brittle Transition Temperature (DBTT) is expected. At the same time, for the plasma-facing targets, the coolant temperature has to be identified such to allow sufficient heat removal capacity at the strike point. This study explores alternative cooling conditions for the divertor system that are able to ensure the fulfillment of functional and system requirements and to allow for divertor cassette body re-use during plant lifetime. The main aim is to identify the best water cooling thermal-hydraulic conditions avoiding material embrittlement (for EUROFER 97) and softening/hardening (for copper alloy pipes). At the same time, the goal is to reduce the inventories (enthalpy of the cooling circuit) and the radwaste at the end of divertor lifetime.

Load study and structural analysis for CFETR divertor OVT

China Fusion Engineering Test Reactor (CFETR) is an important device for studying fusion reactor engineering in China. The Outer Vertical Target (OVT) are high heat load components of the divertors and work in a strong electromagnetic field, so they need sufficient heat removal capability and structural strength. In addition, due to activation of neutrons on materials, the OVT also needs to meet the requirements of Remote Handling (RH) maintenance. CFETR puts forward the concept of hybrid divertor-blanket, which cancels the cassette and adopts a separate structure. The lower part of the divertor is occupied by the breeding blanket, and the divertor target is fixed on the breeding blanket, to improve the RH maintenance efficiency and Tritium Breeding Ratio (TBR). In previous work, the structural design and thermal-hydraulic analysis of the OVT were completed. In this paper, load study and structural analysis was carried out to verify the structural strength of the OVT under experimental test conditions (including liquid pressure, nitrogen baking), normal operation conditions (including the impact of thermal stress under thermal load, gravity, working pressure, etc.) and extreme event conditions (Vertical Displacement Event (VDE) or Major Disruption (MD) event, including the impact of thermal stress under thermal load, gravity, working pressure, electromagnetic load, etc.). The results show that the OVT meets the requirements of heat removal and strength, and effectively promote the processing and manufacturing of the prototype of the OVT.

Thermal Evaluation of a Short-Operating-Duty Dual-Lane Fault-Tolerant Actuator for Aerospace Applications

This paper presents design considerations for a short-operating-duty, fault-tolerant actuator for aerospace applications, with the research focus placed on thermal management. A fully enclosed and naturally ventilated permanent magnet (PM) synchronous machine with a dual-lane modular stator-winding topology is analysed. The aim is to assess alternative solutions for satisfying both sufficient heat removal and simple and robust machine construction design targets. The thermal management is particularly challenging because there are limited means for an effective heat removal from the machine body. Selected design choices impacting the machine's thermal behaviour, including alternative electrical insulation systems, winding impregnation quality, thermal contact interfaces and different winding and housing configurations are investigated. A three-dimensional (3D) transient finite element (FE) analysis has been carried out alongside an experiment informed low-order thermal network sensitivity evaluation. The theoretical body of work has been supplemented with thermal tests on an array of motorettes fabricated using alternative electrical insulation systems. The theoretical and experimental findings suggest that the winding impregnation quality has a dominant impact on the actuator's thermal behaviour, where both heat removal path (thermal resistance) and heat storage (thermal capacitance) need to be well balanced for the short-duty transient operation under a faulted condition.

Design of the Cooling Water System for the EAST Lower Divertor

The new lower tungsten divertor is a crucial component to achieve the targets of long pulse and high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> H-mode operation of Experimental Advanced Superconducting Tokamak (EAST) device. The cooling water system (CWS) of lower divertor should have sufficient heat removal capability and be able to cope with pressure transients caused by the potential water hammer events, which makes the design challenging. In this study, the system process and details of main component are determined based on the design requirements. The thermal-hydraulic analysis model has been developed by Flowmaster (FLOWMASTER) to conduct the heat transfer analysis. Furthermore, the system water hammer transients under one pump trip condition have been analyzed. The results show that the flow distribution of each client is uniform, and the pressure and temperature of key points meet the design requirements. The maximum pressure fluctuation, 0.16 MPa, caused by the sudden closing of the check valve is within the acceptable range. The experiment data are in good agreement with the simulation values, which proves the correctness of the model and the feasibility of the design.

Modeling of Thermal Processes in a Technological System during Electromechanical Processing

The article presents mathematical models of thermal processes of combined methods of electromechanical processing, which are based on the heat conduction equations, which take into account thermophysical properties (thermal diffusivity, heat capacity, thermal conductivity and heat transfer), initial and boundary conditions, technological and other features of the studied processing methods. In view of the fact that electromechanical processing (EMT) is characterized by a process with a volumetric heat release zone, with sufficiently small dimensions and high intensity, it is assumed that the determination of temperature fields can be carried out using the superposition principle. In this case, the main factors affecting the amount of heat propagating into the contacting bodies are the intensity of heat removal, the thermophysical properties of the contacting bodies, and the speed of their relative movement. Dependences are proposed that allow one to describe the temperature fields in the volumes of parts subjected to thermal deformation during electromechanical processing, which have significant geometric parameters that ensure sufficient heat removal from the treated surfaces into the part. It has been established that in the case of processing parts of small dimensions, with insignificant heat removal, it becomes necessary to take into account the accumulation of heat, which will lead to a general increase in temperature in the technological system during processing, and a decrease in the efficiency of the hardening process. The derived mathematical dependencies in the form of heat conduction equations with the established restrictions make it possible to determine the parameters of thermal fields during electromechanical processing in the system “working tool” - “local microvolume of the surface layer”, while these presented mathematical relationships are presented in a linear formulation with thermophysical coefficients. It has been theoretically established and experimentally confirmed that in the process of processing the main factors affecting the amount of heat propagating into the contacting bodies are the intensity of heat removal, the thermophysical properties of the contacting bodies, and the speed of their relative movement. The performed experimental studies have confirmed the adequacy of the mathematical dependencies used to calculate the temperatures in the local microvolumes of the treated surface layer.

Heat Transfer Performance of Cu-Cr-Zr Tube with Swirl Insert Under Cyclic Thermal Loading in Monoblock Divertor

Development and optimization of the plasma-facing components for the fusion reactors ITER and DEMO are necessary for sufficient heat removal because of the high heat fluxes in these systems. In this work, we consider the heat transfer performance of the Cu-Cr-Zr alloy tube with a swirl (twisted tape) insert within a monoblock divertor experiencing cyclic thermal loading expected during ITER operating conditions. Thermal loading is examined up to 2000 cycles, leading to increased tube surface roughness and decreased tube thermal conductivity. A simplified model of thermal-hydraulic performance is used that accounts for forced convection in the swirled flow, conduction through the Cu-Cr-Zr tube, and tube fouling (surface roughness and thermal conductivity changes). From our work, it is found that the overall heat transfer rate of the tube is enhanced with increased thermal loading over a wide range of Reynolds numbers (i.e., flow rates). This is due to the increase of convective heat transfer from turbulence enhancement induced by increasing surface roughness. However, the increase in surface roughness also leads to an increase in pressure losses in the system, requiring increased pumping power to maintain flow rates. We consider the heat transfer rate at equivalent pumping power (quantified by the overall enhancement ratio) and find it has a complicated dependence on Reynolds number and the number of thermal loading cycles. In particular, we see that for a Reynolds number of 1 000 000, the overall enhancement ratio is decreased by up to 9% at 2000 loading cycles. Such a decrease could meaningfully impact the operations of ITER or DEMO, requiring additional pumping input to maintain sufficient heat removal. This suggests the need for further investigation of the thermal-hydraulic performance of plasma-facing components, including the full monoblock assembly, after many loading cycles.

An analysis on catalyst wettability design in strong exothermic reactions

It would be a great advantage to keep the catalyst interior completely dry while the catalyst external surface partially wetted for a three-phase catalytic reaction system in which the reaction is between two or among more gas reactants, while the liquid only acts an inert medium for heat removal. Through such a liquid–solid interface design, gas-phase reactions with high catalyst efficiency would occur, and reaction temperature can be controlled by liquid. Hydrodynamic experiments and simulations verified that this idea can be realized by lyophobic modification of the catalyst external surface. It shows although reducing the external wetting fraction to 0 is beneficial with respect to external mass transfer, it is deficient to heat transfer. In the case of highly exothermic reactions such as ethylene oxidation to ethylene oxide, partial wetting of the catalyst surface is essential, for both providing high mass transfer rate and sufficient reaction heat removal capacity.

Hydraulic assessment of cooling circuit for CFETR W/Cu divertor

Divertor, whose main functions are to sustain extremely high heat load and to exhaust impurity, is a key component in fusion reactor. CFETR divertor is currently under engineering design and technical validation phase. In this study, a cooling circuit design is proposed to obtain sufficient heat removal capability for CFETR divertor. The cooling circuit consists of two main modules which are outer target module and inner target module. Considering the complexity of the parallel cooling circuit concept, hydraulic characteristics is assessed and optimized for enough heat transfer capability and critical heat flux margin. Assessment of the hydraulic characteristics for the cooling circuit is performed by investigating flow velocity and local pressure on channels’ cross-sections. Uniform flow velocity of 10 m/s and acceptable critical heat flux margin higher than 1.4 in PFU coolants channels are obtained after optimization meeting the design requirements of the divertor.

The role of cell geometry when selecting tab or surface cooling to minimise cell degradation

Thermal management of lithium ion batteries is critical to maintain cells at their optimum temperature and balance performance with degradation. Previous work has shown tab cooling to be better for performance and lifetime, but only if sufficient heat removal can be achieved, which depends in part on cell geometry. In this paper, a large form-factor pouch cell is shown to suffer from faster degradation when tab-cooled although still benefitting from higher useable energy. This paper introduces the ratio of surface-to-tab cell cooling coefficient, CCC ratio , as a qualitative measure to assess a cell’s suitability for tab cooling. For low CCC ratio cells, tab cooling results in more useable energy and lower degradation rates than surface cooling. However, the large pouch cell used in this study has a high CCC ratio , indicating that it is difficult to remove sufficient heat through tab cooling. At beginning of life, tab cooling allows access to more usable energy in the cell, but the rate of high temperature-induced degradation is greater, compared to the surface cooled cell. As a result, the useable energy from the tab cooled cell diminishes more rapidly, and after a certain cycle count, the useable energy from the surface cooled cell is superior. The optimum cooling approach will therefore be dependent on the desired lifetime of the system. This research should be of particular interest to cell and battery pack designers. • Thermal management approach (tab or surface cooling) is dependent on cell geometry. • The cell cooling coefficient (CCC) can be used to evaluate which approach is preferred. • Cells that give slower degradation through surface cooling still provide more energy when tab cooling. • The choice of tab or surface cooling depends on the target lifetime required.

Fluid Flow in Microchannel Heat Sinks for various Flow Configurations in Tapered Manifold Arrangements

Micro channels face several types of thermal engineering challenges from different levels of heat generation. The reduction of the available surface area for sufficient heat removal becomes mandatory. If the working temperature of the component becomes very high in the absence of the sufficient heat removal, leads to a critical failure. So working fluid and flow configuration plays an important role. In the present work, CFD analysis of flow on U, P, S type micro channels heat sinks with tapered manifold arrangements is presented. At Reynolds number 705-1410 and with different heat inputs, the P type flow configuration is better than U-type and then followed by S-type flow configuration.

Performance evaluation of decay heat removal systems of Fluoride-salt-cooled High-temperature Reactor (FHR)

The Fluoride-salt-cooled High-temperature Reactor (FHR) is one of the Generation IV nuclear reactor concepts being investigated mainly in the U.S. and China. Liquid salt with high boiling point of over 1400 °C is used as a coolant and its baseline fuel is the graphite-matrix coated-particle fuel developed for high-temperature gas-cooled reactors. To establish advanced safety systems in FHR, passive decay heat removal system which utilizes fluid’s natural circulation is considered. Three systems are proposed: Direct Reactor Air Cooling System (DRACS), Reactor Vessel Air Cooling System (RVACS), and Silo Cooling System (SCS). Although these three safety systems were previously developed for other types of reactors, their heat removal performances need to be evaluated for the FHR plant. The current study provides evaluation of decay heat removal systems of FHR during thermal-hydraulic transient. In addition, FHR’s grace period to start the reactor cooling was determined under the condition where no operable heat removal systems are available. The current study shows that FHR’s decay heat removal systems possess sufficient heat removal capability to avoid catastrophic accidents. The construction of Fluoride-salt-cooled High-temperature Test Reactor (FHTR) is currently being planned and its development is a key step to realize the commercialization in near future. This study provides performance evaluation of decay heat systems for FHTR under thermal-hydraulic transient, and also suggests the adequate operation procedure suitable for FHTR to avoid a severe accident.

Temperature Distribution in the “Material-Coating” Interface from a Fast-Moving Heat Emission Source for Electromagnetic Surfacing

During simulation of the surfacing process, it is proposed to present the heat emission source in the form of the system of instantaneous point sources flickering for some time; and the period between flashes tends to zero. The final results of the temperature distribution are determined by summing the solitary impacts according to the proposed computational pattern. The obtained characteristics and analytical curves allow presenting, at a first approximation, the value and intensity of the temperature fields in the working zone during the electromagnetic surfacing of the large size blanks with sufficient heat removal from the restored surface. The proposed method may be applied for repair and modernization of the railway vehicles elements.

Development of an Open Loop Test Facility for HWRR fuel assembly irradiation experiments in Tehran Research Reactor

Test of nuclear material and fuels under neutron irradiation is one of the major applications of research reactors. HWRR is a newly fabricated domestic rod-type fuel assembly that is planned to be tested in Tehran Research Reactor (TRR). This paper presents neutronic and thermal-hydraulic safety evaluation of HWRR irradiation in TRR core. The comparisons of neutronic safety parameters of TRR core before and after HWRR loading are also provided. CFD thermal-hydraulic analysis of HWRR cooling channel reveals the necessity of increasing the coolant flow rate to satisfy safety limits. In this regard, a special setup called Open Loop Test Facility (OLTF) is developed to make possible irradiation experiments under safe and controlled condition inside TRR core. The OLTF provides a solution to overcome the main challenge of irradiating rod-type fuels inside TRR core at high thermal powers and neutron fluxes by providing sufficient heat removal capacity. OLTF uses reactor pool water as coolant source and injects a controllable flow into HWRR loaded channel through a pipe which is connected to the desired position in the core grid plate. OLTF can control various process parameters of the fuel test experiment such as coolant velocity and flow rate and it also measures important parameters of under irradiation fuel including inlet pressure, pressure drop, coolant and clad temperatures of the test fuel. An experiment is performed to evaluate hydraulic influences of OLTF exploitation on TRR fuel assemblies flow and its results are presented.

Code validation of a scaled-down DRACS model in RELAP5/SCDAPSIM/MOD 4.0

Direct Reactor Auxiliary Cooling System (DRACS) is a passive safety system proposed for Fluoride-salt-cooled High-temperature Reactors (FHRs). Benchmark study of decay heat removal capability of DRACS by natural circulation is critical for FHR safety analysis. Two scaled-down test facilities, a low-temperature DRACS test facility (LTDF) and a high-temperature DRACS test facility (HTDF), were designed following a scaling analysis and constructed to investigate thermal performance and heat removal capability of the DRACS. The LTDF uses water as a surrogate coolant for both the primary and DRACS loops. Two transient scenarios were carried out in the LTDF, namely, DRACS startup and primary coolant pump trip. In both of the scenarios, the experimental results demonstrate sufficient heat removal capabilities of the DRACS with natural circulations established in the system. These two scenarios were simulated using RELAP5/SCDASIM/MOD4.0 code and the code simulation results show good agreement with the LTDF experimental data. For the HTDF, molten salts FLiNaK and KF-ZrF4 are used respectively as the primary coolant and DRACS coolant. Thermodynamic and transport properties of FLiNaK and KF-ZrF4 were implemented into RELAP5/SCDAPSIM/MOD 4.0. Simulations of transient scenarios in the HTDF were also performed and the code results will be compared with the HTDF experimental data once available.

Preliminary assessment on safety performance of updated HCCB blanket module for CFETR

As one candidate tritium breeding blanket concept for CFETR, a conceptual structure design of helium cooled ceramic breeder (HCCB) blanket was proposed. After the engineering design of CFETR HCCB blanket as well as its associated ancillary systems, a safety assessment on two postulated accident scenarios were carried out for the prediction of the potential consequences. Each scenario was modeled and computed by RELAP5 code. The transient accidents analysis was performed based on the steady state results. The comparison of thermal-hydraulic parameters computed by RELAP5 and ANSYS CFX code was to verify the accuracy of the RELAP5 modeling. Results involving a number of parameters investigated indicate good agreement for better integrity of FW and BU design under the two assumed accident scenarios and infer sufficient heat removal capability of the analyzed blanket module under postulated accidents.

Design, Fabrication, and Performance of an Optimized Flow Reactor with Parallel Micropacked Beds

Herein, we build on the results of our previous studies and describe the design and fabrication of a hybrid glass/silicon flow reactor with 32 parallel packed beds using an eight-inch wafer process. Increasing throughput of the exothermic reaction requires sufficient heat removal for maintaining reasonable productivity as well as for safe operation. In this work, a glass/silicon combination was chosen as reactor materials. We predicted the heat dissipation effect of the bonding of a silicon substrate to the glass microreactor, which was validated by the reaction experiment monitored by IR thermography. The reactor withstood pressures of up to 13 MPa, which ensures safe reactor operation in spite of the brittleness of materials (silicon and glass) used. It was designed to serve for the direct synthesis of hydrogen peroxide (10 wt %) with 0.5 kg/h productivity per single reactor, and its parallel operation was demonstrated. Here we can show that the reactor is well suited for the safe and efficient operatio...

24 - Impact of Gene Mutations on Response to Lenalidomide and OS in Lower-Risk Non-Del(5Q) MDS Patients Ineligible/Refractory to Erythropoiesis-Stimulating Agents (ESAS)

As one candidate tritium breeding blanket concept for CFETR, a conceptual structure design of helium cooled ceramic breeder (HCCB) blanket was proposed. After the engineering design of CFETR HCCB blanket as well as its associated ancillary systems, a safety assessment on two postulated accident scenarios were carried out for the prediction of the potential consequences. Each scenario was modeled and computed by RELAP5 code. The transient accidents analysis was performed based on the steady state results. The comparison of thermal-hydraulic parameters computed by RELAP5 and ANSYS CFX code was to verify the accuracy of the RELAP5 modeling. Results involving a number of parameters investigated indicate good agreement for better integrity of FW and BU design under the two assumed accident scenarios and infer sufficient heat removal capability of the analyzed blanket module under postulated accidents.

Preliminary accident analysis of Loss of Off-Site Power and In-Box LOCA for the CFETR helium cooled solid breeder blanket

As one of three candidate tritium breeding blanket concepts for Chinese Fusion Engineering Test Reactor (CFETR), a conceptual structure of helium cooled solid breeder (HCSB) blanket was recently proposed. In this paper, the preliminary thermal-hydraulic and safety analyses of the typical outboard equatorial blanket module (No.12) have been carried out using RELAP5/Mod3.4 code. Two design basis accidents are investigated based on the steady-state initialization, including Loss of Off-Site Power and In-Box Loss of Coolant Accident (LOCA). The differences between circulator coast down and circulator rotor locked under Loss of Off-Site Power are compared. Regarding the In-Box LOCA, the influences of different break sizes and locations are thoroughly analyzed based on a relatively accurate modeling method of the heat structures in sub-modules. The analysis results show that the blanket and the combined helium cooling system (HCS) are designed with sufficient decay heat removal capability for both accidents, which can preliminarily verify the feasibility of the conceptual design. The research work can also provide an important reference for parameter optimization of the blanket and its HCS in the next stage.

European DEMO divertor target: Operational requirements and material-design interface

Recently, an integrated program of conceptual design activities for the European DEMO reactor was launched in the framework of the EUROfusion Consortium, where reliable power handling capability was identified as one of the most critical scientific as well as technological challenges for a DEMO reactor. The divertor is the key in-vessel plasma-facing component being in charge of power exhaust and removal of impurity particles. The DEMO divertor target will have to withstand extreme thermal loads where the local peak heat flux is expected to reach up to 20 MW/m2 during slow transient events in DEMO. To assure sufficient heat removal capability of the divertor target against normal and transient operational scenarios under expected cumulative neutron dose of up to 13 dpa is one of the fundamental engineering challenges imposed on target design. To develop the design of the DEMO divertor and related technologies, an R&D work package ‘Divertor’ has been set up in this consortium. The subproject ‘Target Development’ is devoted to the development of the conceptual design and the core technologies of the plasma-facing target. Devising and implementing novel structural heat sink materials (e.g. W/Cu composites) to advanced target design concepts is one of the major objectives of this subproject. In this paper, the underlying design requirements imposed by the envisaged power exhaust goal and the prominent material-design interface issues are discussed. In addition, the candidate design concepts being currently considered are presented together with the related material issues. Finally, the first results achieved so far are presented.

Electrochemical and Thermal Contributions to Ultra-Deep AAO Growth: Aspect Ratio >104

Self-ordered anodic aluminum oxide (AAO) nanopores is the focus of intense research for many diverse fields including photocatalysts, electrochemical energy storage, thermoelectrics, and optics. Furthermore, the self-ordering of densely packed pores serves as an ideal template for 1-D nanostructure fabrication. Currently, hard anodization has achieved the highest growth rates (50 – 100 μm h-1) to >1000 aspect ratio1, but no further research has been presented on extended depth regimes. Technical and economic success of many of these technologies, is dependent on fast fabrication of ultra-high aspect ratio (>104) AAO arrays. We present here the high-speed growth of AAO pores with ultra-high aspect ratios achieved by balancing the thermal and electrochemical physics of pore ordering during initiation and extended steady-state growth rate. Effective management of reaction and joule heating is paramount to achieving self-ordering and preventing thermal failure of AAO during pore initiation. Traditionally, slow ramp rate (1 v/s), low concentration (~0.05M), and low electrolyte temperature (~0°C) conditions have been used to prevent initial thermal failure of potentiostatic anodizations at the cost of well-defined pore ordering. However, recent studies have shown that thermal control of the working electrode is much more effective than chilling the electrolyte2. The effect of direct potential application with sufficient heat removal by electrode cooling is discussed. Furthermore the effect of temperature was studied to optimize the rate of hard anodization at steady-state. During steady-state, isothermal anodization rate decays exponentially as a function of time making the rate infeasible to economical production of deep arrays. Electrode temperature step experiments were conducted and its effect on steady-state anodization rate is discussed. Long-term, isothermal anodizations exhibit a radial distribution of pore lengths with pore lengths decreasing with increasing radial dimension, resembling a cone structure. This effect is unfavorable as it suggests a non-ideal distribution of current thus complicating the geometry of the array. Forced ideal current distribution and its effect on extended depth anodizations is discussed. Additional technical hurdles and the results of these tests will be presented. 1. Lee, W., et al., Fast Fabrication of Long-Range Ordered Porous Alumina Membranes by Hard Anodization. Nature Materials 2006, 5 (9), 741. 2. Aerts, T., et al., Control of the Electrode Temperature for Electrochemical Studies: A New Approach Illustrated on Porous Anodizing of Aluminium. Electrochemistry Communications 2009, 11 (12), 2292.