Calculation of the Neutron Parameters for Accelerator-Driven Subcritical Reactors

In this paper, the accelerator-driven subcritical reactor (ADSR) is simulated based on structure of the TRIGA-Mark II reactor. A proton beam is accelerated and interacts on the lead target. Two cases of using lead are considered here: firstly, solid lead is referred to as spallation neutron target and water as the coolant; secondly, molten lead is considered both as a target and as a coolant. The proton beam in the energy range from 115 MeV to 2000 MeV interacts with the lead to create neutrons. The neutron parameters as neutron yield Yn/p, neutron multiplication factor k, the radial and axial distributions of the neutron flux in the core have been calculated by using MCNPX program. The results show that the neutron yield increases as the energies of the proton beam increases. When using the lead target, the differences between the neutron yield are from 4.2% to 14.2% depending on the energies of the proton beam. The proportion of uranium in the mixtures should be around 24% to produce an effective neutron multiplier factor greater than 0.9. The neutron fluxes are much higher than the same calculations for the TRIGA-Mark II reactor model using tungsten target and light water coolant.

Comparative of blanket reactor design in assuring of tritium self-sufficiency

The comparison of four blanket modules in DEMO made up the optimization material having a reasonable requirement as blanket material in this study. Either neutron flux distribution in blanket material or material endurance under neutron irradiation, from four modules, the WCLL has a high tolerance neutron distribution and the best neutron irradiation endurance. Furthermore, many suggestions closed to the statement to use the benefits of water coolant and lithium lead (compose Li-6) as a material component in the blanket.

Actual problems of the thermal hydraulic reliability ensuring of prospective nuclear reactors with supercritical parameters

There is a significant lack of reliable information on the physical characteristics of thermohydraulic processes in emergency heat transfer modes when cooling the surface of fuel rods with light water coolant with supercritical thermodynamic parameters, in particular, on the physics of heat transfer processes and hydromechanics in the critical area. It is shown that in these conditions there is physical uncertainty about the causes of deteriorating heat transfer, which limits the possibility of creating effective calculation techniques for reliable determination of the upper limit of safe forcing of the heat transfer process in the core. At present, the vast majority of theoretical and experimental studies of thermohydraulic processes in the near-critical area have been performed only for the socalled “normal” heat transfer, which corresponds to the heat removal conditions with mixed turbulent convection of superheated to “gas” state of light water coolant in its inertial mode. Attention is paid to the possible appearance of macromolecular ensembles on this surface in the form of pseudo-vapor formations, which are capable of causing an emergency mode of pseudo-film boiling. On the basis of the given experimental data of various authors existence of rather deep physical analogy between processes of heat exchange in supercritical thermodynamic system and unheated boiling at subcritical parameters of the heat carrier is proved. Existence of the pseudo-boiling process in the conditions of supercritical thermodynamic parameters makes it impossible to use in the thermohydraulic calculation the empirical dependences for “hot” gas for the range of active zones operational parameters.

Problems of abnormal dynamics of thermal hydraulic processes in prospective reactors with supercritical parameters of light water coolant

A complex of scientific and technical problems directly related to the priority of ensuring the operational safety and reliability of the cores of promising power nuclear reactors with supercritical thermodynamic parameters of a light-water coolant is systematized. The problems of implementation of effective heat removal from the surface of fuel elements and ensuring reliable calculation of thermal and hydrodynamic processes in turbulent flows of a supercritical coolant are considered. The main attention in the consideration of thermohydraulic processes in the near-critical region is paid to the conditionality of the physical nature of these processes by the regularities of transformation of the thermophysical properties of the coolant with changes in its temperature. It is noted that these phenomena have not been sufficiently studied and that modern designers of nuclear reactors with supercritical parameters practically do not have physically substantiated adequate ideas about the physical nature of an emergency mode of deteriorated heat transfer, which can arise unpredictably on the surface of a fuel element even if it is continuously cooled by a coolant with supercritical parameters. It is only known that the main physical sign of the occurrence of this emergency mode is a significant deterioration in heat transfer, which becomes abnormally low, but the physical reasons for such a dangerous anomaly are currently unknown. Based on the analysis of the molecular kinetics data of the near-wall coolant layer, it was proposed to consider such facts of an emergency decrease in the heat transfer intensity due to the appearance of an unknown pseudo-film boiling regime on the fuel element surface. In this context, it is shown that under the conditions under study, macromolecular assemblies in the form of pseudo-vapor formations can appear on the heat exchange surface, as a result of which the heat transfer on the fuel element surface is disturbed. Using experimental data, it is shown that there is a rather deep physical analogy between heat transfer in a supercritical thermodynamic system and the subcooled boiling process at subcritical parameters of the coolant. The dynamics of changes in the characteristics of the experimental spectra of acoustic emission of pseudo-boiling with a sequential increase in the thermal load is analyzed and it is shown that these phenomena can, in principle, be used in promising systems for diagnostic monitoring of reactors with supercritical parameters for early detection of the initial phases of pseudo-boiling and prompt prevention of the occurrence of emergency modes of deteriorated heat transfer

Liquid Cooling Utilizing a Hybrid Microchannel/Multi-Jet Heat Sink: A Component Level Study of Commercial Product

The miniaturization of microelectronic devices and an increasing demand for faster computing results in high heat flux applications. By adopting direct liquid cooling, the high heat flux and high-power demands can be met. In this paper, thermo-hydraulic performance of a commercial hybrid micro-channel/multi-jet heat sink with water coolant was analyzed in detail. The copper microchannel heat sink with 3 mm fin height, fin thickness of 0.1 mm and channel width of 0.1 mm was used for removing heat flux from the chip surface area of 1″ × 1″(6.45 cm2). Water coolant was directed to microchannel fins by multiple slot jets, continuously providing impingement flow. A three-dimensional numerical simulation using commercial software 6sigmaET is carried out and validated with experimental results. The effects of the coolant inlet temperature and flow rate on the thermo-hydraulic performance was studied. CFD simulation was performed at inlet temperature of 29 °C, 36 °C, 50 °C and 60 °C. Flow rate was varied from 0.7 LPM to 3 LPM. Geometry optimization was performed, considering process of cutting the microchannel into pin fins. It was observed that the thermal resistance of pin-fins/multi-jet heat sink was reduced by 29.4 % as compared to original microchannel/multi-jet heat sink and without changing pressure drop significantly. In this specific heat sink design, the combination of multiple jets and pin fins leads to improvement of thermal performance as compared to micro-channel/multi-jet combination.

CPS Based Liquid Metal Divertor Target for EU-DEMO

Power exhaust is a key mission in the roadmap to the realization of a future fusion reactor. Among the different solutions, the use of liquid metals as plasma facing materials are of interest due to their potential increased lifetime. Several liquid metal limiters have been successfully tested in the Frascati Tokamak Upgrade over the last 10 years. Liquid materials such as lithium and tin have been investigated using capillary porous systems (CPSs), and their impact on plasma performance has been explored. From such experience, a liquid metal divertor (LMD) concept design, CPS-based, is here proposed. Tin has been preferred as plasma facing material. The proposed LMD would operate, in low evaporative regime, with matching heat exhausting capabilities to those of the baseline ITER-like divertor. Continuous refilling of the CPS is guaranteed with a reservoir at the back of the unit, where the metal is kept liquid through a gas heating circuit. The study has been carried out using ANSYS and the thermal results will be shown. All the design choices are compatible with the current materials and the constraints adopted for the DEMO W divertor. Using such configuration, thermal loads up to 20 MW/m2 are exhausted while keeping the surface temperature below 1250 °C. The design foresees values of pressure, temperature and flow rate of the water coolant in the same range expected for the W DEMO divertor, thus facilitating the integration of such solution in the current cassette design. Technological and practical aspects are addressed, i.e. tin corrosion and CPS wettability. Possible solutions to prevent tin corrosion, and its compatibility with structural materials, will be outlined.

Investigation the Cooling Performance of Vehicle Engines Using Radiator with Nano-Fluid as a Coolant

In the cooling system of the automobile engine, the water which is used as a coolant is evaporated due to high engine temperature, so it needs to add some additives to the coolant water but they dont give high performance compared to adding some of Nano-particles. This work investigated the heat transfer characteristics with Nano-fluid used in a radiator as vehicle engines coolant. The Nano-particles are introduced to a conventional coolantin certain concentrations resulted in, enhancing the ability to transfer heat, lowering the energy cost and theenvironmental impact. The performance enhancement caused reduction of the radiator and the vehicle frontal areathat lowered the coefficient of drag consequently reduced the fuel consumption. Two types of Nano-particles; metal(Cu) and metal oxide (CuO) are used with different concentrations (1%, 2% and 4%) in conventional coolant asa base fluid. Cooling of vehicle engine using radiator operated with different working fluids as water, coolant and modified coolant with Nano-particles are investigated. The conventional coolant with Nano Cu 2% had lowest exit temperature from the radiator and highest amount of heat rejection, so it can be used as industrial Nano-coolant.