Improvement of Gas Entrainment Prediction Method —Introduction of Surface Tension Effect—
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A gas entrainment (GE) prediction method has been developed to establish design criteria for the largescale sodium-cooled fast reactor (JSFR) systems. The prototype of the GE prediction method was already confirmed to give reasonable gas core lengths by simple calculation procedures. However, for simplification, the surface tension effects were neglected. In this paper, the evaluation accuracy of gas core lengths is improved by introducing the surface tension effects into the prototype GE prediction method. First, the mechanical balance between gravitational, centrifugal, and surface tension forces is considered. Then, the shape of a gas core tip is approximated by a quadratic function. Finally, using the approximated gas core shape, the authors determine the gas core length satisfying the mechanical balance. This improved GE prediction method is validated by analyzing the gas core lengths observed in simple experiments. Results show that the analytical gas core lengths calculated by the improved GE prediction method become shorter in comparison to the prototype GE prediction method, and are in good agreement with the experimental data. In addition, the experimental data under different temperature and surfactant concentration conditions are reproduced by the improved GE prediction method.Keywords:
Sodium-cooled fast reactor
Entrainment (biomusicology)
Neutron Transport
Burnup
Sodium-cooled fast reactor
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In the case of a severe accident in a core resulting from unprotected loss of flow (ULOF) or unprotected transient overpower, damage can propagate from subassembly to subassembly and produce a whole-core–scale molten pool. Because the core is not in its most reactive configuration, a massive collapse of the molten material could result in a rapid supercritical condition with release of a large amount of energy. However, timely and sufficient fuel relocation outside the core by dedicated means could prevent any risk of recriticality and accident escalation. Based on a reference 1500-MW(electric) sodium-cooled fast reactor design, this paper describes the main results obtained in evaluating the recriticality potential of the European Sodium Fast Reactor (ESFR) core and conditions for its elimination during a ULOF-type transient. This study has been carried out in the frame of the Collaborative Project on European Sodium Fast Reactor of the 7th Framework Programme Euratom. The numerical analyses carried out in the present work allow one to estimate the amount of fuel mass that has to be removed from the core in order to maintain it in subcritical conditions, preventing the formation of a critical pool. Requirements for successful application of this approach, in terms of the negative reactivity insertion rate by fuel relocation and timing of discharge from the core, are derived.
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Scram
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Sodium-cooled fast reactor
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A fast reactor is one of recommended candidates of Generation IV nuclear energy systems, which would meet wide requirements such as sustainability, safety and economics for nuclear energy development. To be the China’s first fast reactor, China Experimental Fast Reactor (CEFR) typical technical options are following: 65 MW thermal power and 20 MW electric power, three circuits of sodium-sodium-water, integrated pool type structure for the primary circuit. To establish modular simulation system for sodium fast reactor, the code which simulated the thermal-hydraulic behavior of primary circuit was developed. The physical models include reactor core, reactor vessel cooling channel, pumps, protection vessel, intermediate heat exchangers, ionization chamber cooling channel, cold sodium pool, hot sodium pool, inlet plenum, and pipes, etc. The code could compute coolant pressures, flow rates, and temperatures in the primary circuit. This module was designed for analysis of a wide range of transients. Although based on CEFR, it can treat an arbitrary arrangement of components.
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This paper compares the performance and characteristics of two innovative sodium-cooled fast reactors (iSFRs) with different fuel types. One is loaded only with low-enriched uranium fuel and the other one is loaded with spent nuclear fuels. The iSFR is designed based on the Korean prototype Gen-IV sodium-cooled fast reactor in order to enhance the safety and economics through innovative core designs. The iSFR core is also equipped with two new and unique passive safety devices called floating absorber for safety at transient and static absorber feedback equipment to improve the safety performance of iSFR and particularly to address the positive coolant void reactivity coefficients. In this work, several important parameters such as core reactivity, kinetics parameters, reactivity feedback coefficients, power profiles, and fuel composition changes have been analyzed by using the McCARD Monte Carlo code. The sub-channel code MATRA-LMR is used to perform the thermal-hydraulics analysis. The balance of reactivity method has also been utilized to investigate the self-controllability of the two iSFR cores. Copyright © 2016 John Wiley & Sons, Ltd.
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Enriched uranium
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An innovative sodium cooled fast reactor has been investigated as part of the fast reactor cycle technology development project. In the reactor, a compact reactor vessel (R/V) with increased sodium flow velocity was designed to reduce the construction cost. One of the thermal hydraulic problems in this design is gas entrainment at the free surface in the R/V. In most of past studies, water experiments were performed to investigate the gas entrainment in the reactor. It is necessary to evaluate an influence of fluid physical property on the gas entrainment phenomena. In this study, sodium experiments were carried out to clarify the onset criteria of the gas entrainment due to a free surface vortex. Water experiments using a test section in which geometry is the same as that in the sodium tests were also performed. The gas entrainment in water slightly tended to take place in comparison with that in sodium under low velocity conditions. Overall, the onset condition map on the lateral and downward flow velocities in the sodium and water experiments were in good agreement.
Entrainment (biomusicology)
Sodium-cooled fast reactor
Air entrainment
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Among Generation IV reactors, the sodium-cooled fast reactor (SFR) is attracting attention as a system having great potential for commercial use. Gas entrainment is a thermal-hydraulic issue related to the safety problem of the reactor core in the SFR. Typically, a dipped plate or baffles are installed under the free surface to suppress gas entrainment. However, these approaches can cause gas entrainment in other locations and require many trial-and-error and verifications. In this study, a new strategy using magnetohydrodynamics to suppress gas entrainment in the SFR is proposed. In a counter-flow model, a judgment criterion of gas entrainment occurrence was developed for both water and liquid metal. Moreover, the gas entrainment can be completely suppressed by applying a magnetic field.
Entrainment (biomusicology)
Sodium-cooled fast reactor
Baffle
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Sodium-cooled fast reactor
Transient (computer programming)
Thermal hydraulics
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AbstractSodium-cooled mixed-oxide core design studies are performed with a target burnup of 150 GWd/t and possible measures against the recriticality issues in core disruptive accidents. Four types of core are compared from the viewpoints of core performance and reliability. Results show that all the types of core satisfy the target and that a homogeneous core with an axial blanket partial elimination subassembly is the superior concept, although experimental demonstration is required of molten fuel motion for mitigation of recriticality following fuel melting and loss of fuel pin integrity.
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An innovative sodium cooled fast reactor has been investigated as part of the fast reactor cycle technology development (FaCT) project. In the reactor, a compact reactor vessel (R/V) with increased sodium flow velocity was designed to reduce the construction cost. One of the thermal hydraulic problems in this design is gas entrainment at the free surface in the R/V. In most of past studies, water experiments were performed to investigate the gas entrainment in the reactor. It is necessary to evaluate an influence of fluid physical property on the gas entrainment phenomena. In this study, sodium experiments were carried out to clarify the onset criteria of the gas entrainment due to a free surface vortex. Water experiments using a test section in which geometry is the same as that in the sodium tests were also performed. The gas entrainment in water slightly tended to take place in comparison with that in sodium under low velocity conditions. Overall onset condition map on lateral and downward flow velocities in the sodium and water experiments were in good agreement.
Entrainment (biomusicology)
Sodium-cooled fast reactor
Air entrainment
Cite
Citations (2)