Investigation on influence of crust formation on VULCANO VE-U7 corium spreading with MPS method

Yasumura, Yusan; Yamaji, Akifumi; Furuya, Masahiro; Ohishi, Yuji; Duan, Guangtao

doi:10.1016/j.anucene.2017.04.002

Cited by 21 publications

(6 citation statements)

References 21 publications

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“…In this study, the heat transfer model and phase change model were introduced based on previous works [34][35][36][37][38][39][40]. Heat transfer calculations are essential to simulate melting-solidification behaviour.…”

Section: Heat Transfer Modelmentioning

confidence: 99%

“…In this model, the viscosity was increased up to the immobilization solid fraction called the "critical solid fraction", and the viscosity was set as a constant value above the critical solid fraction to stop flowing. This empirical equation has been widely used to reproduce meltingsolidification behaviour [34][35][36][37][38][39][40]. However, it was suggested that the critical solid fraction for flowing is significantly affected by 1 the shear rate of the fluid, 2 the cooling ratio, and 3 the material characteristics [42,43].…”

Section: Phase Change Modelmentioning

confidence: 99%

“…In general, the C value is set from 4 to 8. In this study, C = 6.4 was adopted, which was determined by previous work [38]. The calculation geometry is depicted in Figure 9, where the red particle corresponds to the high-density fluid, and the black particle corresponds to the low-density fluid.…”

Section: Phase Change Modelmentioning

confidence: 99%

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Investigation of the Outflow and Spreading-Solidification Behaviour of Stratified Molten Metal

Yokoyama

Kondo

Suzuki

et al. 2021

JNE

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The spreading-solidification behaviour of the stratified molten metals was investigated. This is important in understanding the practical fuel debris distribution spread and solidified in the primary containment vessel (PCV) of Fukushima Daiichi Nuclear Power Plants (1F NPPs). In this study, the effect of outflow diameter on the material distribution before discharging was studied both experimentally and numerically. The two simulant metals were chosen so that the density ratio could be similar to the practical fuel and structure elements of the plant. They were arranged in a vessel and discharged on a receiving plate. The spreading experiments were performed using various outlet diameters with a density and reverse density stratification arrangement. After the experiment, X-ray analysis was performed to evaluate the material distribution in the solidified material. Moreover, a numerical analysis was performed to reveal the mechanisms that affect the material distribution after solidification. As a result, the low-density metal accumulated at the centre region regardless of the outlet diameters in the density stratification. In contrast, the outlet diameters affected the material distribution in the reverse density stratification because they affected the material outflow order. These findings may help increase our understanding of the fuel debris distribution in 1F NPPs.

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Section: Heat Transfer Modelmentioning

confidence: 99%

Section: Phase Change Modelmentioning

confidence: 99%

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Investigation of the Outflow and Spreading-Solidification Behaviour of Stratified Molten Metal

Yokoyama

Kondo

Suzuki

et al. 2021

JNE

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“…A fundamental principle of nuclear safety is that the integrity of the reactor containment must be preserved in the aftermath of a severe accident, such that any consequences are limited to the site itself [1,2]. A hypothetical severe accident scenario considers a core meltdown, relocation of high-temperature lava-like mixtures of molten nuclear fuel and reactor components (corium) and breach of the reactor pressure vessel (RPV) [3]. On failure of the RPV, the high-temperature corium will impinge on the containment floor, or core catcher, resulting in a combination of surface ablation [4] and spreading over a designated area of sacrificial concrete [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…The melt temperature evolves with time due to the radioactive decay heat, conductive heat transfer from the melt to the substrate and the thermal radiation and free convection heat losses from the free surface of the melt. If the thermal losses exceed the heat generation due to radioactive decay the melt will eventually undergo solidification at the surface and the melt-substrate interface, leading to crust formation [3,7]. The viscous resistance to flow increases exponentially with the melt solid fraction [1,8] and spreading may be arrested altogether if the immobilization solid fraction [1] is attained.…”

Section: Introductionmentioning

confidence: 99%

High-temperature ex-vessel corium spreading. Part 1: experimental investigations on ceramic and sacrificial concrete substrates

Johnson

Denoix

Bouyer

et al. 2021

Journal of Nuclear Science and Technology

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Optimizing melt spreading in the aftermath of a core disruptive accident is crucial for achieving sufficient melt cooling to maintain reactor containment integrity. Two ≈ 30 kg-scale experiments performed at the VULCANO facility explore the spreading of high-temperature molten corium-concrete mixtures over ceramic and sacrificial concrete substrates. Imaging of the melt front propagation revealed a 7 % increase in spreading length and a 30 % increase in maximum front velocity during spreading over sacrificial concrete, despite a reduced mass partaking in spreading due to increased holdup within the crucible. Infrared imaging of the melt indicated surface temperatures around 45 °C lower during spreading on sacrificial concrete, which is anticipated to result in a roughly three-fold increase in melt viscosity. The 7 % observed increase in spreading length therefore likely underestimates the extent of the increase in melt spreadability on sacrificial concrete, given the reduced mass and increased melt viscosity apparent during the VE-U9-concrete test. The enhanced spreadability on sacrificial concrete could be explained by the apparent gliding motion of the melt, combined with the shallower melt profile towards the spreading front, which are consistent with reduced friction at the melt-substrate interface. Reduced friction at the melt-substrate interface is best explained by a diphasic film of molten concrete and gases generated by the molten core-concrete interaction acting as a lubricant between the melt and solid substrate.

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Moving Particle Semi-implicit method

Wang

Duan

Koshizuka

et al. 2021

Nuclear Power Plant Design and Analysis Codes

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Investigation on influence of crust formation on VULCANO VE-U7 corium spreading with MPS method

Cited by 21 publications

References 21 publications

Investigation of the Outflow and Spreading-Solidification Behaviour of Stratified Molten Metal

Investigation of the Outflow and Spreading-Solidification Behaviour of Stratified Molten Metal

High-temperature ex-vessel corium spreading. Part 1: experimental investigations on ceramic and sacrificial concrete substrates

Moving Particle Semi-implicit method

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