Heavy liquid metal natural circulation in a one-dimensional loop (original) (raw)
Liquid metals for nuclear applications
Nuclear applications of liquid metals concern waste transmuters and liquid metal cooled fast reactors of Generation IV. One section of this paper is devoted to a short review of the motivations for liquid metals as reactor coolant or spallation target material and to historic aspects. The next two sections are dedicated to the neutron and physical properties of liquid metals, with special emphasis on sodium, lead and lead–bismuth eutectic, their respective advantages and drawbacks as reactor coolants. The question of the structure of liquid metals in relation with the liquid metal coolant technology is briefly addressed. The last section concerns the compatibility of structural materials with sodium, lead and lead–bismuth eutectic, with attention being paid to the impurities control in the different cases. We conclude briefly.
Natural circulation in a liquid metal one-dimensional loop
Journal of Nuclear Materials, 2008
a r t i c l e i n f o a b s t r a c t A wide use of pure lead, as well as its alloys (such as lead-bismuth, lead-lithium), is foreseen in several nuclear-related fields: it is studied as coolant in critical and sub-critical nuclear reactors, as spallation target for neutron generation in several applications and for tritium generation in fusion systems. In this framework, a new facility named NAtural CIrculation Experiment (NACIE), has been designed at ENEA-Brasimone Research Centre. NACIE is a rectangular loop, made by stainless steel pipes. It consists mainly of a cold and hot leg and an expansion tank installed on the top of the loop. A fuel bundle simulator, made by three electrical heaters placed in a triangular lattice, is located in the lower part of the cold leg, while a tube in tube heat exchanger is installed in the upper part of the hot leg. The adopted secondary fluid is THT oil, while the foreseen primary fluid for the tests is lead-bismuth in eutectic composition (LBE). The aim of the facility is to carry out experimental tests of natural circulation and collect data on the heat transfer coefficient (HTC) for heavy liquid metal flowing through rod bundles. The paper is focused on the preliminary estimation of the LBE flow rate along the loop. An analytical methodology has been applied, solving the continuity, momentum and energy transport equations under appropriate hypothesis. Moreover numerical simulations have been performed. The FLUENT 6.2 CFD code has been utilized for the numerical simulations. The main results carried out from the pre-tests simulations are illustrated in the paper, and a comparison with the theoretical estimations is done.
Heavy liquid metal technologies development in Kalla
2006
The thermo-physical properties of Heavy Liquid Metals (Pb and Pb-Bi Eutectic) such as the low melting and high boiling temperatures, the chemical inertness in direct contact with typical reactor coolants, makes HLMs to relevant candidates as core coolant of critical and sub-critical nuclear systems. In addition the high neutron yield obtained by proton irradiation renders this material attractive for the development of neutron spallation sources. The practical use of HLM as core coolant and spallation material needs to be validated by experimental and computational activities. In this frame the KALLA (Karlsruhe Lead Laboratory) program, which consists of several stagnant and loop experiments, has been defined. Currently KALLA represents one of the most relevant infrastructures, which is in operation in Europe. The capabilities of KALLA make it possible to evaluate thermal-hydraulics parameters in complex geometries, to develop techniques for local and global quantities measurement, ...
In this paper detailed design of a liquid metal Lead-Bismuth-Eutectic (LBE) neutron spallation target for an experimental ADS reactor of ~30 MW with sub-criticality (k) of 0.975 is presented. The high energy beam consists of 650 MeV and 0.9 mA proton beam. The circulation of the liquid metal is based on gas lift method. Extensive numerical simulations have been carried out to optimise the target geometry, LBE/gas flow rate, beam parameters, neutron yield etc. This paper also includes time dependent two phase CFD analysis to study the effect of nitrogen gas flow rate on LBE flow rate, 3D thermal-hydraulic studies of liquid metal flow near the window and spallation region. The optimum asymmetric flow geometry at the bottom of the target to shift the stagnation zone to minimize the window temperature and estimation of thermo mechanical stress in the window has been carried out. In addition, spallation neutron generation and their energy spectrum, heat deposition distribution, spallation products and their activities have been estimated using high energy particle transport code FLUKA. (Energy: ~ 1 GeV and Current: few to tens of mA) interacts with the target, which is located in the core of a subcritical reactor and produces spallation neutrons (~ 10 19 n/s) that diffuse into and drive the reactor [6]. In this paper, detailed design of a heavy liquid metal neutron spallation target suitable for the proposed experimental MultiPurpose Research Reactor (MPRR) operating under ADS mode is presented. The experimental reactor is of ~30 MW (thermal) and will operate at k = 0.975. Various target configurations have been studied with different beam energies, top injection and bottom injection for different geometries. Based on this analysis, it is proposed to have LINAC with proton energy of 650 MeV and beam current of 0.9-1.0 mA for generating the required spallation neutrons [7]. The target will be located at the centre of the reactor in a vertical cylindrical diameter space of 240 mm. Heavy density liquid metal LBE (lead-bismuth-eutectic of 45% lead and 55% bismuth) will be used as spallation target. The schematic of the proposed Reactor is shown in Figure 1. Basic Spallation Target Loop The major components of the module are the window (the solid barrier through which the beam enters the target), spallation region above the window, riser pipe along with mixer for gas injection, annular down comer along with heat exchanger, cover gas region which also acts as a gravity based passive gas separator. The schematic of the target module and various subsystems are shown in Figure 2. Instead of mechanical pump or electromagnetic pump, the circulation of the liquid metal is achieved by the gas lift method [8]. This enhances the reliability of the system. In addition, an outer water cooled jacket will be provided around the target module to act as a safety jacket in case of LBE window failure [9]. The window is a very important component of the loop. Typically it is a hemispherical in shape, having a thickness of ~1.5 mm at the outlet and ~3 mm at the edges. One of the candidates for the proposed window material that will be tested in this facility is T91 steel [10]. The incident proton beam deposits 409 kW of heat (as estimated by FLUKA code presented later) in the target and 4.1 kW in the window for the above beam. An additional heat of 370 kW is deposited due to gamma radiation from the reactor. The liquid metal is circulated to extract the heat deposited by the beam in the window and in the liquid metal itself. The circulation of the liquid metal is achieved in the loop as follows. In the mixer, located below the riser pipe, nitrogen (or argon or helium) gas is injected. This gives rise to two-phase mixture in the riser pipe and consequently leads to a density difference between the riser and downcomer pipes. This causes circulation of liquid metal in the loop. The riser height is designed in such a way that required flow rate of liquid metal is achieved. Both the phases enter the separator located at the top of the loop. Gas is separated here and taken to a gas outlet pipeline. The liquid metal flows down through the downcomer (annular pipe). At the top of the downcomer and below the separator, a heat-exchanger is located which extracts the heat from the liquid metal. At the bottom of the downcomer, where the liquid metal enters spallation region, there is a cut at slanted angle to break the flow symmetry [11]. This is to shift the stagnation zone at the bottom and provide convective heat transfer, where proton beam deposits bulk of the heat. Through
Bellows-type accumulators for liquid metal loops of space reactor power systems
AIP-CP-813, Space Technology and Applications International Forum (STAIF-2006), Albuquerque NM, 2006
In many space nuclear power systems, the primary and/or secondary loops use liquid metal working fluids, and require accumulators to accommodate the change in the liquid metal volume and maintain sufficient subcooling to avoid boiling. This paper developed redundant and light-weight bellows-type accumulators with and without a mechanical spring, and compared the operating condition and mass of the accumulators for different types of liquid metal working fluids and operating temperatures: potassium, NaK-78, sodium and lithium loops of a total capacity of 50 liters and nominal operating temperatures of 840 K, 860 K, 950 K and 1340 K, respectively. The effects of using a mechanical spring and different structural materials on the design, operation and mass of the accumulators are also investigated. The structure materials considered include SS-316, Hastelloy-X, C-103 and Mo-14Re. The accumulator without a mechanical spring weighs 23 kg and 40 kg for a coolant subcooling of 50 K and 100 K, respectively, following a loss of the fill gas. The addition of a mechanical spring comes with a mass penalty, in favor of higher redundancy and maintaining a higher liquid metal subcooling.
Reactor Divertor Designs Based on Liquid Metal Concepts
2016
The use of liquid metals as plasma facing components in Fusion devices was proposed as early as 1970 for a field reversed concept and inertial fusion reactors. The idea was extensively developed during the APEX Project, in the turn of the century, and it is the subject at present of the biannual International Symposium on Lithium Applications (ISLA), whose fourth edition took place in Granada, Spain at the end of September 2015. While liquid metal flowing concepts were specially addressed in the USA research projects, the idea of embedding the metal in a Capillary Porous System (CPS) was put forwards by the Russian teams in the 90’s, thus opening the possibility of static concepts. Since then, many ideas and accompanying experimental tests in fusion devices and laboratories have been produced, involving a large fraction of the countries within the International Fusion Community. Within the EuroFusion Road map, these activities are encompassed into the Working Programs of the PFC and...
Annals of Nuclear Energy, 2014
The concept of supercritical natural circulation loop (SCNCL) is an important inclusion in Generation-IV nuclear reactors. Use of supercritical fluids promises a simplified design, along with higher thermal efficiency for heat transport systems. Characteristics of such loops are markedly different from its singlephase and two-phase counterparts, while carrying quite a few similarities with both as well. Therefore significant number of research studies is carried out on SCNCL in the present millennium and current work presents a state-of-the-art summary of all associated observations. Most of the reported studies are theoretical in nature, with only a limited number of experimental works being reported. A number of indigenous computation codes were developed, while use of commercial software can also be found. Thermal-hydraulic and heat transfer aspects are discussed in details, showing the gradual growth of knowledge and comprehending the influence of various geometric and operating variables on steadystate profile. Water and carbon dioxide are identified as the only fluids considered for analysis both numerically and experimentally. Both time-domain and frequency-domain approach of stability analysis are discussed meticulously. Available experimental works are described, with exhaustive discussion on the novelty of the concerned facility and major observations. Finally a few topics are earmarked as the possible guidelines for future research.