Dominant Factor for the Occurrence of a Steam Explosion

2008 ◽  
Vol 273-276 ◽  
pp. 388-393
Author(s):  
B.T. Min ◽  
S.W. Hong ◽  
J.H. Kim ◽  
I.K. Park ◽  
H.D. Kim
Keyword(s):  
Steam Explosion ◽  
Nuclear Reactor ◽  
Cold Water ◽  
Hydrogen Reduction ◽  
Chemical Compounds ◽  
Hydrogen Gas ◽  
Dominant Factor ◽  
Small Particles ◽  
Debris Particles ◽  
Pure Zro2

For the study of a steam explosion phenomenon in a nuclear reactor, prototypic corium, a mixture of UO2 and ZrO2 was melted in a cold crucible by applying an induction heating technique. The molten corium was then poured into cold water. It was fragmented into very small particles, so called debris, which enables a very rapid heat transfer to the water. Some cases led to steam explosions by thermal expansion of the water. After the tests, all the debris particles were dried and classified by their size. From the analysis by using EPMA, it was shown that the particles generated by a steam explosion had fine and irregular forms. It is known that real corium (including UO2) hardly leads to a steam explosion, different from pure ZrO2 or metal. A reason for this was previously suggested in that the corium generated hydrogen gas during melt-water interaction, and it enclosed the melt drops to prevent a direct contact of the corium and water. In order to confirm this fact, the debris particles were analyzed with ICP-AES for their typical element contents, EPMA for the homogeneity of the solid solution, XRD for the chemical compounds, and TGA and hydrogen reduction analysis for the percentage of the debris oxidation and reduction. These analyses showed that hydrogen was not directly related to steam explosion. Meanwhile, the material characteristics of the corium compositions are newly suggested to be the most probable reason for the occurrence of a steam explosion so far.

Particle Size Characteristics of Molten Corium Quenched in Water

2008 ◽  
Author(s):  
B. T. Min ◽  
H. D. Kim ◽  
J. H. Kim ◽  
S. W. Hong ◽  
I. K. Park
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Steam Explosion ◽  
Eutectic Composition ◽  
Nuclear Reactor ◽  
Cold Water ◽  
Severe Accident ◽  
Test Facility ◽  
Water Steam ◽  
Explosive Composition

During a hypothetical severe accident in a nuclear reactor, a steam explosion might occur when molten corium interacts with water. The strength of a steam explosion affects the integrity of the containment of a nuclear reactor and is highly dependant on the characteristics of the melt-water-steam mixture. Since a break-up and fragmentation process during a pre-mixing are important mechanisms for a steam explosion behavior and affect the debris size distribution, the particle size characteristics of quenched corium have been investigated. For several years, series of experiments have been performed using prototypical corium in the TROI test facility with a high frequency induction heating using cold crucible technology. The molten corium was discharged into the cold water and the quenched debris particles were collected, sieved and examined for the effect of a size distribution on a steam explosion. The small corium droplets do not seem to contribute to a steam explosion owing to solidification at an early stage before the explosion but the large droplets contribute to it owing to their liquid state. It was also shown that single oxides and binary oxides with an eutectic composition (UO2/ZrO2 = 70/30 at weight percentage) led to steam explosions, but a binary oxide with a non-eutectic one did not. The mass mean diameters of the debris of the steam explosive composition was less than that of the non-steam explosive composition. Zirconia was the most energetic steam-explosive material in these tests, and an eutectic composition of corium also lead to a steam explosion, but a non-eutectic composition corium hardly led to a steam explosion. The particle sizes of the molten corium participating in a steam explosion were shown to be mainly 3–6 mm depending on the material and composition.

Bottom-driven upwelling generated by eastern intensification in closed and semi-closed basins with a sloping bottom

1999 ◽  
Vol 50 (7) ◽  
pp. 613 ◽  
Author(s):  
M. Herzfeld ◽  
M. Tomczak
Keyword(s):  
Numerical Model ◽  
Cold Water ◽  
Ekman Transport ◽  
Dominant Factor ◽  
Bottom Slope ◽  
Boundary Current ◽  
Bottom Stress ◽  
Eastern Side ◽  
Great Australian Bight ◽  
Sloping Bottom

Cold water is observed in the eastern Great Australian Bight, and the presence of this water is inconsistent with that expected from surface Ekman-induced upwelling resulting from the imposed windfield. A numerical model is employed to investigate this situation under idealized conditions, from which the bottom slope has been identified as the most dominant factor contributing towards the presence of the cold water. A boundary current generated on the eastern side of the idealized bight is attributed to eastern intensification of a predominantly Stommel type, induced by the topographical gradient. It is proposed that the cold water observed at the eastern boundary is the result of upwelling driven by a bottom Ekman-transport convergence in this region, which is in turn the result of a large bottom stress curl maintained by the eastern intensification.

scholarly journals CFD Code Validation against Stratified Air-Water Flow Experimental Data

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
F. Terzuoli ◽  
M. C. Galassi ◽  
D. Mazzini ◽  
F. D'Auria
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Water Flow ◽  
Nuclear Reactor ◽  
Cold Water ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Two Phase ◽  
Code Validation

Pressurized thermal shock (PTS) modelling has been identified as one of the most important industrial needs related to nuclear reactor safety. A severe PTS scenario limiting the reactor pressure vessel (RPV) lifetime is the cold water emergency core cooling (ECC) injection into the cold leg during a loss of coolant accident (LOCA). Since it represents a big challenge for numerical simulations, this scenario was selected within the European Platform for Nuclear Reactor Simulations (NURESIM) Integrated Project as a reference two-phase problem for computational fluid dynamics (CFDs) code validation. This paper presents a CFD analysis of a stratified air-water flow experimental investigation performed at the Institut de Mécanique des Fluides de Toulouse in 1985, which shares some common physical features with the ECC injection in PWR cold leg. Numerical simulations have been carried out with two commercial codes (Fluent and Ansys CFX), and a research code (NEPTUNE CFD). The aim of this work, carried out at the University of Pisa within the NURESIM IP, is to validate the free surface flow model implemented in the codes against experimental data, and to perform code-to-code benchmarking. Obtained results suggest the relevance of three-dimensional effects and stress the importance of a suitable interface drag modelling.

Steam Explosion Experiments Using Nuclear Reactor Materials in the TROI Facilities

2008 ◽  
Vol 29 (8) ◽  
pp. 748-756 ◽  
Author(s):  
Jong-Hwan Kim ◽  
Ik-Kyu Park ◽  
Seong-Wan Hong ◽  
Beong-Tae Min ◽  
Seong-Ho Hong ◽  
...  
Keyword(s):  
Steam Explosion ◽  
Nuclear Reactor ◽  
Reactor Materials

Critical Two-Phase Flow in Pipes for Subcooled Stagnation States With a Cavity Flooding Incipient Flashing Model

1990 ◽  
Vol 112 (4) ◽  
pp. 1032-1040 ◽  
Author(s):  
S. Y. Lee ◽  
V. E. Schrock
Keyword(s):  
Nuclear Reactor ◽  
Safety Evaluation ◽  
Phase Region ◽  
Dominant Factor ◽  
Critical Flow ◽  
Primary System ◽  
Transient Heating ◽  
Two Phase ◽  
Flow Process ◽  
Sequence Of Events

Analysis of loss of coolant accident (LOCA) scenarios in nuclear reactor safety evaluation depends on knowledge of many complex phenomena. A primary phenomenon controlling the sequence of events, by determining the residual coolant mass inventory within the primary system, is the critical flow process. Critical flow of a flashing liquid is complicated by marked departure from thermal equilibrium. Several complex models have been proposed to represent the non-equilibrium effects, including six-equation two-fluid models. Amos and Schrock (1983) developed a model based on the premise that the two-phase region is homogeneous and that thermal nonequilibrium is the dominant factor causing the departure from the homogeneous equilibrium idealization. Flashing inception was represented by a modification of the Alamgir-Lienhard (1981) pressure undershoot. Exponential relaxation of the metastable liquid was formulated as suggested by Bauer et al. (1976) and the critical flow criterion used the sound speed formulation of Kroeger (1976). Lee and Schrock (1988) extended the Amos-Schrock work by developing an improved correlation for the pressure undershoot correction factor in terms of Reynolds number and subcooling Jakob number. Improvements were also made in the relaxation constant and in the application of Kroeger’s formulation. In the present paper a new cavity flooding model is used for the evaluation of pressure undershoot at flashing inception. This model is similar to the one developed by Fabic (1964) for the evaluation of liquid superheat required for boiling on a surface subjected to transient heating. The model contains an experimentally deduced factor, which is correlated against stagnation subcooling using the experimental data of Amos and Schrock (1983, 1984), Jeandey et al. (1981), and the Marviken tests (Anon., 1979). The model was then tested against seven additional data sets and shown to be very accurate in predicted mass flux (standard deviation of 10.9 percent for all data). The cavity flooding model is thought to represent the true physics more correctly than does the earlier model, which had its origin in molecular fluctuation theory.

scholarly journals On the nature and combinations of a newly discovered vegetable acid; with observations on the malic acid, and suggestions on the state in which acids may have previously existed in vegetables

1833 ◽  
Vol 2 ◽  
pp. 22-23
Keyword(s):  
Sulphuric Acid ◽  
Malic Acid ◽  
Cold Water ◽  
Sorbic Acid ◽  
The State ◽  
Hydrogen Gas ◽  
Sorbus Aucuparia ◽  
Ripe Fruit ◽  
A Current ◽  
Sulphuretted Hydrogen

The acid here noticed by the author being obtained in greatest quantity from the fruit of the Sorbus aucuparia , is denominated by him sorbic acid, in order to distinguish it from other known vegetable acids. To prepare it, he presses the ripe fruit, previously bruised, in a linen bag, and thereby obtains nearly half its weight of juice. With this juice he mixes a solution of acetate of lead, and obtains a precipitate of sorbate of lead, which requires to be frequently washed with cold water. The purified powder is then boiled in a large quantity of water, which dissolves a part as a super-sorbate, leaving undissolved a sub-sorbate. The liquor being filtered and suffered to cool, deposits brilliant crystals of purified sorbate of lead. To the crystals thus obtained he adds a quantity of dilute sulphuric acid, sufficient to separate nearly the whole of the lead; and having then separated the remainder by a current of sulphuretted hydrogen gas, he obtains the acid in a state of purity.

In-Vessel Corium Behavior and Steam Explosion Risks: A Review of Experimental Approaches

2017 ◽  
Author(s):  
Pei Shen ◽  
Wenzhong Zhou
Keyword(s):  
Heat Transfer ◽  
Steam Explosion ◽  
Large Scale ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Reactor Vessel ◽  
Radioactive Material ◽  
Severe Accident ◽  
Reactor Accident ◽  
Experimental Approaches

Although no one would like to see, a severe nuclear reactor accident may result in reactor core melting, the fuel melt dropping into water in the reactor vessel, and then interacting with coolant into steam explosion. Steam explosion is a result of very rapid and intense heat transfer and violent interaction between the high temperature melt and low temperature coolant. The timescale for heat transfer is shorter than that for pressure relief, resulting in the formation of shock waves and/or the production of missiles at a later time during the expansion of coolant steam explosion. Steam explosion may endanger the reactor vessel and surrounding structures. During a severe reactor accident scenario, steam explosion is an important risk, even though its probability to occur is pretty low, since it could lead to large releases of radioactive material, and destroy the containment integrity. This study provides a comprehensive review of vapor explosion experiments, especially the most recent ones. In this review, fist, small to intermediate scale experiments related to premixing, triggering and propagation stages are reviewed and summarized in tables. Then the intermediate to large scale experiments using prototypic melt are reviewed and summarized. The recent OECD/SERENA2 project including KROTOS and TROI facilities’ work is also discussed. The studies on steam explosion are vital for reactor severe accident management, and will lead to improved reactor safety.

scholarly journals Effects of Bonding Treatment and Ball Milling on W-20 wt.% Cu Composite Powder for Injection Molding

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1897
Author(s):  
Mingliang Ouyang ◽  
Cuiping Wang ◽  
Huayu Zhang ◽  
Xingjun Liu
Keyword(s):  
Injection Molding ◽  
Ball Milling ◽  
Composite Powder ◽  
Hydrogen Gas ◽  
Powder Injection ◽  
Small Particles ◽  
Tap Density ◽  
Large Particles ◽  
Dimension Precision ◽  
Powder Characteristics

W-20 wt.% Cu pseudo-alloys were produced via powder injection molding (PIM) with powders prepared thermochemically. Bonding treatment and ball milling (BTBM) were used, and the effects of BTBM on the characteristics of the powders, rheological properties of the feedstock, shrinkage and properties of the sintered samples were studied. The morphology of the powder changed from extremely agglomerated small particles to pebble-shaped smooth large particles which were composed of several small particles combined tightly. The tap density increased from 3.25 g/cm3 to 7.22 g/cm3, and the specific surface area decreased from 0.86 m2/g to 0.45 m2/g. The critical powder loading of the feedstock increased from 45 vol.% to 56 vol.% due to the change in powder characteristics, thereby improving densification and dimension precision. For the PIM samples sintered at 1290 °C for 120 min in a hydrogen gas, the oversizing factor decreased from 1.297 to 1.216, and the dimension fluctuation ratio decreased from ±0.61% to ±0.33%. At the same time, the relative density increased from 97.8% to 98.6%, the thermal conductivity increased from 218 W/(m·K) to 233 W/(m·K), and the average coefficients of thermal expansion were roughly similar, within the range of 8.43–8.52 × 10−6/K.

Electrochemical degradation of pentachlorophenol on a palladium modified gas-diffusion electrode

2009 ◽  
Vol 59 (9) ◽  
pp. 1759-1767 ◽  
Author(s):  
H. Wang ◽  
J. L. Wang
Keyword(s):  
Removal Efficiency ◽  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Hydrogen Reduction ◽  
Amorphous Structure ◽  
Gas Diffusion ◽  
Gas Diffusion Electrode ◽  
Hydrogen Gas ◽  
Electrochemical Degradation ◽  
X Ray

Pd/C catalyst was prepared by a hydrogen reduction method and used for making a Pd/C gas-diffusion electrode. It was fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). In the catalyst, Pd particles with an average size of 4.0 nm were highly dispersed in the activated carbon with an amorphous structure; Pd content on the surface of the Pd/C catalyst reached 1.3 at% (atomic concentration). The Pd/C gas-diffusion electrode was then used as the cathode to investigate the electrochemical degradation of pentachlorophenol (PCP) in a diaphragm electrolysis device, feeding firstly with hydrogen gas then with air, compared with the carbon/polytetrafluoroethylene (C/PTFE) gas-diffusion cathode. The Pd/C gas-diffusion cathode can not only reductively dechlorinate PCP by feeding hydrogen gas, but also accelerate the two-electron reduction of O2 to hydrogen peroxide (H2O2) by feeding air. Therefore, both the removal efficiency and the dechlorination degree of PCP exceeded 80% after 100 min, and the average removal efficiency of PCP in terms of total organic carbon (TOC) was more than 75% after 200 min by using Pd/C gas-diffusion cathode, which was better than that of the C/PTFE gas-diffusion cathode. Phenol was identified as the dechorination product using high-performance liquid chromatography (HPLC).

scholarly journals EXTRACTION OF ZINC SULFATE THAT UTILIZES IN THE MANUFACTURING OF FOOD SUPPLEMENTS BY USAGE (ZN-C) BATTERIES WASTES

2021 ◽  
Vol 25 (5) ◽  
pp. 67-74
Author(s):  
Mohammed A. Ahmed ◽  
Keyword(s):  
Zinc Sulfate ◽  
Chemical Compounds ◽  
Food Supplement ◽  
Hydrogen Gas ◽  
Sulfate Heptahydrate ◽  
Xrd Pattern ◽  
Take Back ◽  
Selective Corrosion ◽  
Essential Chemical ◽  
Dry Cell

Spent zinc-carbon (dry cell) batteries have negative environmental effects. It is necessary to save the environment from them and take back the mineral values from these batteries. Many engineering materials were contained in the spent batteries. A large amount of anode zinc (zinc casing) was occupied in spent batteries, therefore; it must be recovered on the form of a useful and essential chemical compounds that can be used in daily life. It is found from the chemical composition an anode zinc (zinc casing), it was over 99 percent perspicuous with a very small percentage of traces metals in it. Zinc sulfate was known as a significant food supplement for humans, animals and plants. It can be made by investing the selective corrosion resulted from the chemical reaction between zinc metal and diluted sulfuric acid. Thus, the zinc sulfate heptahydrate was produced. Zinc sulfate heptahydrate resulted from corrosion reactions was tested by XRD and it was found similar to standard patterns. The XRD pattern of zinc sulfate heptahydrate shows four major peaks happened at (2ϴ). The most intense peak for zinc sulfate heptahydrate happened at 27.5°. In addition, to hydrogen gas was produced as a by-product of that reaction.

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