Melt jet-breakup and fragmentation phenomena in nuclear reactors: A review of experimental works and solidification effects

Iwasawa, Yuzuru; Abe, Yutaka

doi:10.1016/j.pnucene.2018.05.009

Cited by 37 publications

(8 citation statements)

References 92 publications

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“…The jet breakup length, the distance from free surface to the breakup point, is an important parameter to evaluate whether molten corium will directly come in contact with the lower plenum of the pressure vessel before it sufficiently breaks up. Parameters in physical units Once the length is longer than the water depth, the pressure vessel is likely to be melted through by the molten corium, which might cause the radioactive material leakage (Iwasawa and Abe 2018). In the melt jet breakup experiments, the jet breakup length usually can hardly be measured directly from the observation because the jet column is covered by lots of fragments similar to those in Figure 2, while with the simulations in the current study, the jet breakup length can be easily extracted from the middle cross-sectional density contours as shown in Figure 4, where Case 4 and Case 10 are presented.…”

Section: Jet Breakup Lengthmentioning

confidence: 99%

“…The design of the in-vessel retention (IVR) strategy requires the full understanding of the physical phenomena related to FCIs, especially the corium jet breakup process which will significantly affect the formation of the debris bed and the subsequent in-vessel cooling. The corium jet breakup behavior in water has been extensively studied with real core material experiments, simulant material experiments, and various simulations (Spencer et al, 1994;Burger et al, 1995;Dinh et al, 1999;Huhtiniemi et al, 1999;Abe et al, 2006;Thakre et al, 2015;Zhou et al, 2017;Iwasawa and Abe 2018;Saito et al, 2018;Shen et al, 2018;Cheng et al, 2019;Cheng et al, 2020;Cheng et al, 2021a;Cheng et al, 2021b). To the best of authors' knowledge, in almost all of the previous studies, the jet cross-section shapes are naturally assumed to be circular, which is actually not always the case.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study on the Effect of Jet Cross Section Shape on the Corium Jet Breakup Behavior With Lattice Boltzmann Method

Cheng¹,

Cheng²,

Wang

2022

Front. Energy Res.

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In a core meltdown accident in light water reactors, molten corium may drop into the lower plenum of the pressure vessel and interact with water, which is called fuel–coolant interaction (FCI). The behavior of the corium jet breakup in water during FCIs is important for the in-vessel retention strategy and has been extensively studied. While in previous studies, the jet cross-section shapes are naturally assumed to be circular, which is actually not always the case, in this study, the breakup processes of the corium jets with four different elliptical cross-section shapes and three different penetration velocities are simulated with color-gradient lattice Boltzmann method. The effect of the cross-section shape on the hydrodynamic breakup behavior of the corium jet is analyzed in detail. It is found that the effect of the cross-section shape on the jet penetration depth is very limited. With the increase in the aspect ratio under the same penetration velocity, the jet breakup length decreases gradually. In general, the dimensionless corium surface area increases with the increase in the aspect ratio for the jets under the same penetration velocity.

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Section: Jet Breakup Lengthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Study on the Effect of Jet Cross Section Shape on the Corium Jet Breakup Behavior With Lattice Boltzmann Method

Cheng¹,

Cheng²,

Wang

2022

Front. Energy Res.

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“…From this point of view, a number of experimental research studies have been conducted on the FCI related to an SFR to figure out the fragmentation characteristics over the past decades (Iwasawa and Abe, 2018). Some researchers used molten fuel materials (U/UO 2 ) in pursuit of a realistic core condition.…”

Section: Introductionmentioning

confidence: 99%

An improved multiphase SPH algorithm with kernel gradient correction for modelling fuel–coolant interaction

Wang

Zhang²,

Wu³

2023

Front. Energy Res.

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Fuel–coolant interaction (FCI) has a pivotal role in the development of core disruptive accident in a sodium-cooled fast reactor. The drastic deformation of multiphase interface in the FCI is hard to deal with in the traditional grid method. In this paper, an improved multiphase smoothed particle hydrodynamics (SPH) algorithm corrected with the kernel gradient correction (KGC) technique is presented for multiphase flow with a large density ratio and complex interfacial behaviors. The density discontinuity across the multiphase interface is described with the use of special volume, which only depends on the position information of adjacent particles. This multiphase SPH algorithm, which is troubled by an unstable and mixed-interface problem under a large density ratio, is significantly improved with the KGC technique. The accuracy and robustness of the improved method are demonstrated in the numerical simulations of the deformation of a square droplet, Rayleigh–Taylor instability, and bubble rising in water. The verified corrected multiphase SPH is applied to simulate the hydrodynamic behaviors of the general FCI and the interaction between fuels coated with stainless steel film and coolant. Boundary layer stripping, Rayleigh–Taylor instability, and Kelvin–Helmholtz instability are observed as important mechanisms of hydraulic fracturing. The fragments’ distribution and the influence of stainless steel film are analyzed. The existence of a stainless steel film has been shown to inhibit breakage.

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“…Usually, in practice, a situation arises when a jet of a high-temperature melt is poured into a vessel with water, water begins to boil on the surface of the jet, and a vapor film is formed that separates the melt and water. Due to the development of Kelvin -Helmholtz instabilities on the "melt -steam" and "steam -water" interfaces, the jet breaks up and a mixture of water and melt droplets surrounded by vapor films is formed [4]. The vapor film reduces the heat transfer from the melt to the water, so such a mixture can exist for several seconds until the melt drops reach the bottom of the vessel.…”

Section: Introductionmentioning

confidence: 99%

Calculation of stationary thermal detonation wave in the multiphase system “water drops, surrounded by steam films, in continuous molten lead”

Melikhov,

Saleh

2023

E3S Web Conf.

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A mathematical model of a thermal detonation wave in a multiphase system “water droplets in vapor shells located in a high-temperature heavy metal melt”, which can form after a rupture of the heat exchange tube of steam generator of a fast neutron reactor with a liquid lead or lead-bismuth coolant, is proposed. The model is based on the equations of the mechanics of multiphase systems. Interphase heat transfer and friction are described by well-known correlations validated on numerous experimental data. The key mechanism of thermal detonation wave propagation is the fragmentation of water droplets in the shock wave front. Fragmentation is carried out due to the difference in the velocities of drops and melt, which occurs on the shock wave due to the difference in their densities. The propagation velocity of a thermal detonation wave is determined by calculation of the Hugoniot adiabat. The parameters on the leading shock wave are calculated from relations expressing the laws of conservation of mass, momentum, and energy of a multiphase mixture. The calculated pressure distribution behind the shock wave has a maximum near the shock wave plane. The calculation results revealed that the thermal equilibrium of the phases is achieved much later than their velocity equilibrium.

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Melt jet-breakup and fragmentation phenomena in nuclear reactors: A review of experimental works and solidification effects

Cited by 37 publications

References 92 publications

Numerical Study on the Effect of Jet Cross Section Shape on the Corium Jet Breakup Behavior With Lattice Boltzmann Method

Numerical Study on the Effect of Jet Cross Section Shape on the Corium Jet Breakup Behavior With Lattice Boltzmann Method

An improved multiphase SPH algorithm with kernel gradient correction for modelling fuel–coolant interaction

Calculation of stationary thermal detonation wave in the multiphase system “water drops, surrounded by steam films, in continuous molten lead”

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