Benchmark Study of the Accident at the Fukushima Daiichi NPS: Best-Estimate Case Comparison

Pellegrini, Marco; Dolganov, K.; Herranz, L.E.; Bonneville, H.; Luxat, David; Sonnenkalb, M.; Ishikawa, Jun; Song, J. H.; Gauntt, Randall O.; Moguel, L. Fernandez; Payot, F.; Nishi, Yoshihisa

doi:10.13182/nt16-63

Cited by 57 publications

(18 citation statements)

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“…An example of such behavior can be observed in the Fukushima Daiichi Unit 3 accident, during the operation of the Reactor Core Isolation Condenser (RCIC) [2,3]. Lumped parameter codes under-estimated the maximum pressure by about 160 kPa when assuming mixed pool conditions, whereas a much better agreement was obtained assuming pool stratification [4].…”

Section: Introductionmentioning

confidence: 99%

Pool stratification and mixing induced by steam injection through spargers: analysis of the PPOOLEX and PANDA experiments

Gallego-Marcos

Kudinov

Villanueva

et al. 2018

Nuclear Engineering and Design

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Spargers are mutli-hole injection pipes used in Boiling Water Reactors (BWR) and Advanced Pressurized (AP) reactors to condense steam in large water pools. A steam injection induces heat, momentum and mass sources that depend on the steam injection conditions and can result in thermal stratification or mixing of the pool. Thermal stratification reduces the steam condensation capacity of the pool, increases the pool surface temperature and thus the containment pressure. Development of models with predictive capabilities requires the understanding of basic phenomena that govern the behavior of the complex multi-scale system. The goals of this work are (i) to analyze and interpret the experiments on steam injection into a pool through spargers performed in the large-scale facilities of PPOOLEX and PANDA, and (ii) to discuss possible modelling approaches for the observed phenomena. A scaling approach was developed to address the most important physical phenomena and regimes relevant to prototypic plant conditions. The focus of the tests was on the low steam mass flux and oscillatory bubble condensation regimes, which are expected during a long-term steam injection transient, e.g. in the case of a Station Black Out (SBO). Exploratory tests were also done for chugging and stable jet conditions. The results showed a similar behavior in PPOOLEX and PANDA in terms of jet induced by steam condensation, pool stratification, and development of hot layer and erosion of the cold one. A correlation using the Richardson number is proposed to model the erosion rate of the cold layer as a function of the pool dimensions and steam injection conditions.

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Section: Introductionmentioning

confidence: 99%

Pool stratification and mixing induced by steam injection through spargers: analysis of the PPOOLEX and PANDA experiments

Gallego-Marcos

Kudinov

Villanueva

et al. 2018

Nuclear Engineering and Design

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“…Based on a mixed pool assumption, lumped parameter codes underestimated the maximum pressure by about 160 kPa. In contrast to this, the assumption of a thermally stratified pool showed a much better agreement, suggesting that stratification was the cause of the fast pressure increase [5].…”

Section: Introductionmentioning

confidence: 71%

Pool stratification and mixing induced by steam injection through spargers: CFD modelling of the PPOOLEX and PANDA experiments

Gallego-Marcos

Kudinov

Villanueva

et al. 2019

Nuclear Engineering and Design

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Spargers are multi-hole injection pipes used in Boiling Water Reactors (BWR) and Generation III/III+ Pressurized Water Reactors (PWR) to condense steam in large water pools. During the steam injection, high pool surface temperatures induced by thermal stratification can lead to higher containment pressures compared with completely mixed pool conditions, the former posing a threat for plant safety. The Effective Heat Source (EHS) and Effective Momentum Source (EMS) models were previously developed and validated for the modelling of a steam injection through blowdown pipes. The goal of this paper is to extend the EHS/EMS model capabilities towards steam injection through multi-hole spargers. The models are implemented in ANSYS Fluent 17.0 Computational Fluid Dynamics (CFD) code and calibrated against the spargers experiments performed in the PPOOLEX and PANDA facilities, analysed by the authors in [1] (Gallego-Marcos, I., et al., 2018). CFD modelling guidelines are established for the adequate simulation of the pool behaviour. A new correlation is proposed to model the turbulent production and dissipation caused by buoyancy. Sensitivity studies addressing the effect of different assumptions on the effective momentum magnitude, profile, angle and turbulence are presented. Calibration of the effective momentum showed an inverse proportionality to the sub-cooling. Differences between the effective momentum calibrated for PPOOLEX and PANDA are discussed. Analysis of the calculated flow above the cold stratified layer showed that the erosion of the layer is induced by the action of turbulence rather than mean shear flow.

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“…This work was presented in the frame of the OECD/ NEA/CSNI Benchmark Study of the Accident at the Fukushima Dai-ichi Nuclear Power Station (BSAF) project [8]. During 2012 and 2014 years, the purpose of this project was both to study, by mean of severe accident codes, the Fukushima accident in the three crippled units, until six days from the reactor shut-down and to give information about in particular the location and composition of core debris.…”

Section: Introductionmentioning

confidence: 99%

Possible in-vessel corium progression way in the Unit 1 of Fukushima Dai-ichi nuclear power plant using a phenomenological analysis

Payot

Seiler

2015

EPJ Nuclear Sci. Technol.

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Abstract. In the field of severe accident, the description of corium progression events is mainly carried out by using integral calculation codes. However, these tools are usually based on bounding assumptions because of high complexity of phenomena. The limitations associated with bounding situations ([J.M. Seiler, B. Tourniaire, A phenomenological analysis of melt progression in the lower head of a pressurized water reactor, Nucl. Eng. Des. 268, 87 (2014)] e.g. steady state situations and instantaneous whole core relocation in the lower head) led CEA to develop an alternative approach in order to improve the phenomenological description of melt progression. The methodology used to describe the corium progression was designed to cover the accidental situations from the core meltdown to the molten core concrete interaction. This phenomenological approach is based on available data (including learnings from TMI2), on physical models and knowledge about the corium behavior. It provides emerging trends and best estimated intermediate situations. As different phenomena are unknown, but strongly coupled, uncertainties at large scale for the reactor application must be taken into account. Furthermore, the analysis is complicated by the fact that these configurations are most probably three dimensional, all the more so because 3D effects are expected to have significant consequences for the corium progression and the resulting vessel failure. Such an analysis of the in-vessel melt progression was carried out for the Unit 1 of the Fukushima Dai-ichi nuclear power plant. The core uncovering kinetics governs the core degradation and impacts the appearance of the first molten corium inside the core. The initial conditions used to carry out this analysis are based on available results derived from codes like MELCOR calculation code

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Benchmark Study of the Accident at the Fukushima Daiichi NPS: Best-Estimate Case Comparison

Cited by 57 publications

References 0 publications

Pool stratification and mixing induced by steam injection through spargers: analysis of the PPOOLEX and PANDA experiments

Pool stratification and mixing induced by steam injection through spargers: analysis of the PPOOLEX and PANDA experiments

Pool stratification and mixing induced by steam injection through spargers: CFD modelling of the PPOOLEX and PANDA experiments

Possible in-vessel corium progression way in the Unit 1 of Fukushima Dai-ichi nuclear power plant using a phenomenological analysis

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