Neutronic modeling of debris beds for a criticality evaluation

López, María Freiría; Buck, M.; Starflinger, Jörg

doi:10.1016/j.anucene.2019.02.034

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…and the greater resonance escape probability p P [-] (due to the self-shielding effect from the Structure-Fuel-Structure spatial arrangement [49]), the value of eff k in the Mixed model was still higher than the Homogeneous model after particle redistribution, in which the results are listed in Table 7.…”

Section: Criticality Analysismentioning

confidence: 99%

“…In addition, the Mixed model also exhibited a greater decreased range in the debris bed height than the Homogeneous model during the particle redistribution (Figure 10b); therefore, the PC effect in the Mixed model caused a higher decreased range of k e f f than the Homogeneous model after particle redistribution, as in Figure 10c. Nevertheless, since the PC effect in the Mixed model also contributes to the higher thermal utilization factor [-] (due to the higher concentrated fissile material in Fuel particles) and the greater resonance escape probability P p [-] (due to the self-shielding effect from the Structure-Fuel-Structure spatial arrangement [49]), the value of k e f f in the Mixed model was still higher than the Homogeneous model after particle redistribution, in which the results are listed in Table 7.…”

Section: Criticality Analysismentioning

confidence: 99%

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The Development of a Multiphysics Coupled Solver for Studying the Effect of Dynamic Heterogeneous Configuration on Particulate Debris Bed Criticality and Cooling Characteristics

Wang

Uchibori

et al. 2023

Applied Sciences

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For a sodium-cooled fast reactor, the capability for stable cooling and avoiding re-criticality on the debris bed is essential for achieving in-vessel retention when severe accidents occur. However, an unexploited uncertainty still existed regarding the compound effect of the heterogeneous configuration and dynamic particle redistribution for the debris bed’s criticality and cooling safety assessment. Therefore, this research aims to develop a numerical tool for investigating the effects of the different transformations of the heterogeneous configurations on the debris bed’s criticality/cooling assessment. Based on the newly proposed methodology in this research, via integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) and Monte-Carlo-based Neutronics (MCN), the coupled CFD–DEM–MCN solver was constructed with the originally created interface to integrate two existing codes. The effects of the different bed configurations’ transformations on the bed safety assessments were also quantitively confirmed, indicating that the effect of the particle-centralized fissile material had the dominant negative effect on the safety margin of avoiding re-criticality and particle re-melting accidents and had a more evident impact than the net bed-centralized effect. This coupled solver can serve to further assess the debris bed’s safety via a multi-physics simulation approach, leading to safer SFR design concepts.

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Section: Criticality Analysismentioning

confidence: 99%

Section: Criticality Analysismentioning

confidence: 99%

The Development of a Multiphysics Coupled Solver for Studying the Effect of Dynamic Heterogeneous Configuration on Particulate Debris Bed Criticality and Cooling Characteristics

Wang

Uchibori

et al. 2023

Applied Sciences

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“…Researchers at the University of Stuttgart are currently studying the effect of the corium model used in neutronic analysis of corium-water systems on the calculation results (Freiría López et al 2018López et al , 2019. In their works, they compare the homogeneous, heterogeneous-network and heterogeneous model with a random distribution of corium particles with the abstract most reliable computational model.…”

Section: Approaches To Neutronic Modeling Of Systems With Coriummentioning

confidence: 99%

Neutronic modeling of a subcritical system with corium particles and water (from international benchmark)

Smirnov¹,

Bogdanova²,

Pugachev³

et al. 2020

NUCET

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After the accident at the Fukushima Daiichi NPP, the attention of the scientific community is riveted on how the consequences are being eliminated. Removing corium – a lava-like resolidified mixture of nuclear fuel with other structural elements of the reactor – remains the most difficult task, the solution of which can take several decades. It is extremely important to exclude the occurrence of any emergency processes during the removal of corium. The purpose of this work was to solve a coordinated hydrodynamic and neutronic problem characterized by a large number of randomly oriented and irregularly located corium particles in water as part of the development of a benchmark for this class of problems. Monte Carlo-based precision codes were used to perform a neutronic analysis. The positions of corium particles were determined from the numerical simulation results. The analysis results obtained using the codes involved showed good agreement for all the states considered. It was shown that the modern neutronic codes based on the Monte Carlo method successfully cope with the geometric formation and solution of the problem with a nontrivial distribution of corium particles in water. The results of the study can be used to justify the safety of corium handling procedures, including its extraction from a damaged power unit.

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“…The use of these simplifications to model the porous structure of debris beds was extensively investigated in a previous study [19], where the influence of the particle shape, size, and spatial distribution on the criticality was analyzed. Finally, it was concluded that either a body centered cubic (BCC) or a FCC lattice of monosized spherical particles can be a very suitable model for the criticality evaluation of debris beds if an adequate particle size (equivalent diameter, d eq ) is chosen, providing accurate results with a reasonable modeling and computational effort.…”

Section: Geometrical Model Of the Debris Bedmentioning

confidence: 99%

Criticality Characteristics and Sensitivity Analysis of Fukushima Debris Beds Containing MCCI Products

López

Buck

Starflinger

2020

Journal of Nuclear Engineering and Radiation Science

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This study investigates the criticality characteristics of debris beds that may have been formed through the molten core - concrete - interaction (MCCI) at the pedestal floor of the damaged reactors in Fukushima Daiichi Nuclear Power Station. These were modeled as UO2-concrete systems submerged in water. Firstly, a conservative model was used to evaluate the impact that the presence of concrete has on the neutron multiplication factor (keff ) of debris beds. The good moderation capacities of concrete were proved and it was found that recriticality would be possible under the considered conservative assumptions. Secondly, a more realistic model was used to perform an uncertainty and sensitivity analysis of a wide range of debris parameters (debris porosity,core meltdown grade, debris size, debris composition,concrete erosion factor, etc.). In this case, the results indicate that the probability of a recriticality event is very remote. It was also found that the presence of boron (B4C) from the control rods within debris has by far the highest influence by far on keff.

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Neutronic modeling of debris beds for a criticality evaluation

Cited by 10 publications

References 7 publications

The Development of a Multiphysics Coupled Solver for Studying the Effect of Dynamic Heterogeneous Configuration on Particulate Debris Bed Criticality and Cooling Characteristics

The Development of a Multiphysics Coupled Solver for Studying the Effect of Dynamic Heterogeneous Configuration on Particulate Debris Bed Criticality and Cooling Characteristics

Neutronic modeling of a subcritical system with corium particles and water (from international benchmark)

Criticality Characteristics and Sensitivity Analysis of Fukushima Debris Beds Containing MCCI Products

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