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[en] Highlights: • A FEM model of the blanket and magnetic system was built. • Electromagnetic forces and moments of the typical blanket for ferromagnetic and non-ferromagnetic materials were computed and analyzed. • Maxwell forces and Lorentz forces were computed and compared. • Eddy current in the blanket was analyzed under MD condition. - Abstract: A Helium Cooled Solid Blanket (HCSB) for CFETR (Chinese Fusion Engineering Test Reactor) was designed by USTC. The structural and thermal-hydraulic analysis has been carried out, while electromagnetic analysis was not carefully researched. In this paper, a FEM (finite element method) model of the HCSB was developed and electromagnetic forces as well as moments was computed by a FEM software called MAXWELL integrated in ANSYS Workbench. In the geometrical model, flow channels and small connecting parts were neglected because of the extreme complication and the reasonable conservative assumption by neglecting these circumstantial details. As for electromagnetic (EM) analysis, Lorentz forces due to eddy currents caused by main disruption and Maxwell forces due to the magnetization of RAFM steel (i.e. EUROFER97) were computed. Since the unavailability of the details of the plasma in CFETR, when disruptions happen, the condition where a linear current quench of main disruption occurs was assumed. The maximum magnitude of the electromagnetic forces was 356.45 kN and the maximum value of the coupled electromagnetic moments was 1899.40 N m around the radial direction. It is feasible to couple electromagnetic analysis, structural analysis and thermal-hydraulic analysis in the future since MAXWELL has good channels to exchange data between different analytic parts.
[en] Highlights: • Through the calculation method of the model, it was found that the increase of the artificially determined startup inventory I0 causes significant increase of TBRreq and the increase of the achievable tritium breeding ratio TBRachiv leads to the decrease of the Im. • The increase of fueling efficiency and fractional burnup significantly contributes to the decrease of both Im and TBRreq, while the increase of the duty time and availability results in the decrease of TBRreq and the proportional increase of Im. • The outer tritium plant parameters of some subsystems that have relatively big tritium throughput have intense influence on either Im or TBRreq. - Abstract: In order to evaluate the tritium self-sufficiency of fusion plant, citing CFETR (Chinese Fusion Engineering Testing Reactor) as an example, a modified tritium fuel cycle model was developed. The calculation method of this model to obtain the minimum startup inventory I_m and its corresponding required minimum tritium breeding ratio TBR_r_e_q was first introduced. Then the model was utilized to analyze the influence on I_m and TBR_r_e_q by all tritium cycle parameters that were classified into two categories, namely, the tritium burning parameters and the outer tritium plant parameters. As for the tritium burning parameters, the increase of fueling efficiency and fractional burnup significantly contributes to the decrease of both I_m and TBR_r_e_q, while the increase of the duty time and availability results in the decrease of TBR_r_e_q and the proportional increase of I_m. As for the outer tritium plant parameters, it was found that the outer tritium plant parameters of some subsystems that have relatively big tritium throughput have intense influence on either I_m or TBR_r_e_q.
[en] In our precious study, a prediction model, which calculates the effective thermal conductivity k_e_f_f of mono-sized pebble beds, has been developed and validated. Based on this model, here the effects of these influencing factors such as pebble size, thermal radiation, contact area, filling gas, gas flow, gas pressure, etc. on the k_e_f_f of randomly packed fusion pebble beds are studied and analyzed. The pebble beds investigated include Li_4SiO_4, Li_2ZrO_3, Li_2TiO_3, Li_2O, Be and BeO pebble beds. In the current study, many important and meaningful conclusions are derived and some of them are similar to the existing research results. Particularly, some critters that under which conditions the effect of some influencing factors can be neglected or should be considered are also presented.
[en] Highlights: • A 3D PISO-MHD was implemented on Kepler-class graphics processing units (GPUs) using CUDA technology. • A consistent and conservative scheme is used in the code which was validated by three basic benchmarks in a rectangular and round ducts. • Parallelized of CPU and GPU acceleration were compared relating to single core CPU in MHD problems and non-MHD problems. • Different preconditions for solving MHD solver were compared and the results showed that AMG method is better for calculations. - Abstract: The pressure-implicit with splitting of operators (PISO) magnetohydrodynamics MHD solver of the couple of Navier–Stokes equations and Maxwell equations was implemented on Kepler-class graphics processing units (GPUs) using the CUDA technology. The solver is developed on open source code OpenFOAM based on consistent and conservative scheme which is suitable for simulating MHD flow under strong magnetic field in fusion liquid metal blanket with structured or unstructured mesh. We verified the validity of the implementation on several standard cases including the benchmark I of Shercliff and Hunt's cases, benchmark II of fully developed circular pipe MHD flow cases and benchmark III of KIT experimental case. Computational performance of the GPU implementation was examined by comparing its double precision run times with those of essentially the same algorithms and meshes. The resulted showed that a GPU (GTX 770) can outperform a server-class 4-core, 8-thread CPU (Intel Core i7-4770k) by a factor of 2 at least.
[en] Highlights: • A detailed tritium cycle model of HCPB blanket for CFETR was developed. • Tritium concentrations and retentions inside HCPB blanket, tritium extraction rate and tritium losses of blanket were obtained. • Sensitivity analysis of parameters’ influence on tritium losses of blanket was performed. - Abstract: Based on the HCPB (Helium-Cooled Pebble Bed) blanket of CFETR (Chinese Fusion Engineering Testing Reactor), a more detailed tritium cycle model of HCPB blanket was developed by modeling the breeding parts inside the blanket separately. Utilizing the detailed model, tritium transport analysis of HCPB blanket was carried out. The outputs of the model were the tritium concentrations and tritium retentions at different positions, tritium extraction rate by TES (Tritium Extraction System) and by CPS (Coolant Purification System) and the tritium losses of blanket. In addition, sensitivity analysis of key parameters’ influence on tritium losses and tritium extraction rate by TES was performed. The tritium transport analysis provides valuable reference for the design of HCPB blanket.
[en] Hydrogen is considered as the most potential energy carrier in the near future and can be produced from fusion nuclear energy by several means. Water electrolysis can be served by fusion electrical energy, the steam reforming reaction and the thermochemical water-splitting process can be served by fusion thermal energy. The works about steam reforming with biomass waste and the thermochemical water-splitting with S-I cycle have been extensively investigated in the world. The radiation chemical process and plasma chemical process for hydrogen production also have been reported recently. The fusion energy can be improved by the development of high performance reactor. Some high temperature reactors based on SiCf/SiC composites have been developed, such as ARIES-AT, with high outlet temperature about 1100 C suitable for hydrogen thermal processes. But several issues for the SiCf/SiC composites including the uncertainty about behavior and performance at high temperature and under irradiation, the fabrication and joining technology have been addressed to limit the current development and application of high temperature blanket. RAFM steel remains presently the most promising structural material for breeding blanket with great technological maturity. An innovative high temperature liquid blanket concept is proposed based on RAFM steel as structural material and LiPb as tritium breeder. A special design is designated to obtain the high temperature LiPb about 1000 C far more higher than the RAFM temperature limit 550 C, that is, the multi-layer flow channel inserts (MFCIs) made of the refractory material are placed inside the LiPb flow channels. Low temperature LiPb flows into the channel, meanders through the MFCIs. The temperature of the LiPb is increased step by step, at last it is exported from the blanket at the high outlet temperature. The technology bases on the hydrogen production processes and the high temperature DEMO blanket development are reviewed and assessed in this paper at first. Then the conceptual design, performance analysis covering neutronics and thermal hydraulics, safety and environmental impact, etc. of the novel high temperature blanket, and the assessment of hydrogen efficiency based on S-I thermochemical cycle are given. R and D needs are specified in the end, especially to avoid the neutron activation contamination and tritium contamination for hydrogen. (orig.)
[en] Highlights: • One new method to couple the contact area with bed strain is developed. • The constant coefficient to correlate the effect of gas flow is determined. • This model is valid for various cases, and its advantages are showed obviously. - Abstract: A model is presented here to predict the effective thermal conductivity of porous medium packed with mono-sized spherical pebbles, and it is valid when pebbles’ size is far less than the characteristic length of porous medium just like the fusion pebble beds. In this model, the influences of parameters such as properties of pebble and gas materials, bed porosity, pebble size, gas flow, contact area, thermal radiation, contact resistance, etc. are all taken into account, and one method to couple the contact areas with bed strains is also developed and implemented preliminarily. Compared with available theoretical models, CFD numerical simulations and experimental data, this model is verified to be successful to forecast the bed effective thermal conductivity in various cases and its advantages are also showed obviously. Especially, the convection in pebble beds is focused on and a constant coefficient C to correlate the effect of gas flow is determined for the fully developed region of beds by numerical simulation, which is close to some experimental data.
[en] Highlights: • MHD flows in ducts of different wall thickness compared with wall uniform. • Study of velocity, pressure distribution in ducts MHD flows with single pass of helium cooling channels. • Comparison of three types of dual helium cooling channels and acquisition of an option for minimum pressure drop. • A single short duct MHD flow in blanket without FCI has been simulated for pressure gradient analysis. - Abstract: The concept of dual coolant liquid metal (LM) blanket has been proposed in different countries to demonstrate the technical feasibility of DEMO reactor. In the system, helium gas and PbLi eutectic, separated by structure grid, are used to cool main structure materials and to be self-cooled, respectively. The non-uniform wall thickness of structure materials gives rise to wall non-homogeneous conductance ratio. It will lead to electric current distribution changes, resulting in significant changes in the velocity distribution and pressure drop of magnetohydrodynamic (MHD) flows. In order to investigate the effect of helium channels on MHD flows, different methods of numerical simulations cases are carried out including the cases of different wall thicknesses, single pass of helium cooling channels, and three types of dual helium cooling channels. The results showed that helium tubes are able to affect the velocity distribution in the boundary layer by forming wave sharp which transfers from Hartmann boundary layer to the core area. In addition, the potential profile and pressure drop in the cases have been compared to these in the case of walls without cooling channel, and the pressure gradient of a simplified single short duct MHD flow in blanket shows small waver along the central axis in the helium channel position.
[en] Highlights: • A T/H analysis code for small modular natural circulation LFRs was developed. • A validation case from Argonne National Laboratory (ANL) was carried out. • The T/H design and analysis of a small natural circulation LFR was presented. - Abstract: Small modular natural circulation lead or lead-alloy cooled fast reactor (LFR) is one of the potential candidates for passive cooling SMR development. In a pump-forced reactor, the coolant mass flow rate is determined by the pump power, while in a small modular natural circulation LFR, the coolant mass flow rate is determined from the balance between the driving force (due to density difference between hot and cold sides) and the resistance force (due to pressure drop in the system). For this reason, the effects of the core coolant channel geometry on the thermal-hydraulics performance in a small modular natural circulation LFR is more sensitive than that in a pump-forced reactor. This problem is not considered in existing thermal-hydraulics analysis codes, which are developed for pump-forced reactors originally. In this paper, a thermal-hydraulics analysis code for small modular natural circulation LFRs was developed, which is based on the mathematical models for natural circulation reactors originally. A validation case from Argonne National Laboratory (ANL) was chosen and calculated by using this code and the results agree fairly well with the ANL’s ones. As a typical application case, the thermal-hydraulics design and core coolant channel geometry effect analysis of a 10 MW natural circulation LFR was carried out
[en] In fusion liquid metal blanket, sudden expansions and sudden contractions are very common geometries. Changing of the cross-section causes 3-D magnetohydrodynamic (MHD) effects, which will affect the flow pattern, current distribution and pressure drop. In this paper the numerical code based on OpenFOAM platform developed by University of Science and Technology of China was used to investigate and optimize the sudden expansion pipe. The code has been validated by the recommended benchmark cases including Shercliff, Hunt, ALEX experiments (rectangular duct and round pipe) and KIT experiment cases. The obtained numerical results agreed well with those of all the benchmark cases. Previous and valuable analytical and experimental works have been done by L. Buhler, et. el. Based on these works, in the present paper, further investigation of different expansion lengths between the upstream pipe and downstream pipe at high Hartmann number and Reynolds number were conducted. Besides, different expansion ratios with a specific expansion length were conducted. The numerical results showed that with the increasing of expansion length, the 3D MHD effects gradually weakened. Especially, the 3D pressure drop decreases with the increasing of expansion length. Whereas, the expansion ratio factor shows no obvious influences on the total MHD pressure drop but greatly influence the local pressure distribution. These numerical simulations can be used to evaluate the MHD flow inside the expansion and contraction pipes.