Enhanced Ex-Vessel Analysis for Fukushima Daiichi Unit 1: Melt Spreading and Core-Concrete Interaction Analyses with MELTSPREAD &amp; CORQUENCH

Robb, Kevin; Farmer, M. T.; Francis, Matthew W.

doi:10.2172/1063828

Cited by 18 publications

(45 citation statements)

References 30 publications

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“…During the Fukushima accident, the integrity of the RPVs in units 1, 2 and 3 could not be retained and vessel failure is believed to have occurred in all three units. Several reports state that MCCI very likely occurred at least in units 1 and 3 [14,15]. A benchmark study of the accident progression at 1FNPS (BSAF project) was performed with the participation of sixteen organizations and eight countries (France, Germany, Korea, Russia, Spain, Switzerland, the U.S., and Japan) [16].…”

Section: The Molten-core-concrete-interaction In Fukushima Daiichimentioning

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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Section: The Molten-core-concrete-interaction In Fukushima Daiichimentioning

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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“…Thus, there is a need to employ an exvessel spreading model (MELTSPREAD) as well as account for melt-concrete interactions with below vessel structure and water on the drywell floor. Regarding local changes in debris surface elevation due to natural mechanisms during core concrete interaction (CCI), this topic can be informed not only by extending the CORQUENCH debris coolability model [11,12], but also by physical insights and observations gained from core-debris coolability experiments that are ongoing at ANL supported by international partners.…”

Section: Rationale and Objectivesmentioning

confidence: 99%

“…The answer to the second question relates not only to the extent that the core debris has spread (which determines the melt depth and available surface area for cooling), but also to the longer-term core debris coolability issue [11]; (i.e., the fraction of the overall decay heat in the core debris that is dissipated by boiling to overlying coolant versus ablation of underlying concrete). If the core debris is quenched and rendered permanently coolable, then the minimum water injection rate would be determined by the functional need to remove all the decay heat in the core debris that has relocated.…”

Section: Rationale and Objectivesmentioning

confidence: 99%

“…With this background, the principle objective of this work is to make modest upgrades to existing analytical tools (i.e., MELTSPREAD and CORQUENCH -which have been used in the Fukushima accident analyses [11]) in order to provide a technical basis for supporting development of water throttling strategies for BWRs that are aimed at keeping ex-vessel core debris covered with water while preserving the wetwell vent path. Specifically, there is currently a gap in analysis capability for evaluating core melt relocation and cooling behavior that accounts for several important factor that include: (1) the influence of below vessel structure and pre-existing water on the containment floor on melt stream breakup and subsequent spreading behvior, and (2) the effect of water throttling on spreading and long term debris coolability.…”

Section: Rationale and Objectivesmentioning

confidence: 99%

“…Upgrade and document the core debris coolability model: Incorporate appropriate modeling upgrades into an existing core debris coolability code [12] to evaluate: (1) the effect of water throttling rate (including water-starved situations) on local debris cooling behavior, but more importantly, (2) spatially dependent cavity erosion behavior across the extent of the containment by implementing a multi-nodal scheme that can account for non-uniform cavity geometries such as the Mark I. This latter proposed upgrade, which is considered to be state-of-the art, was carried manually as part of an earlier study [11]; this proposal is to implement software to automate this process for more general applications. As part of this effort, appropriate documentation would be developed for these modeling upgrades in the form of a users manual so that the upgraded code can be released to interested users to support industry R&D activities.…”

Section: Rationale and Objectivesmentioning

confidence: 99%

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Light Water Reactor Sustainability Program Reactor Safety Technologies Pathway Technical Program Plan

Corradini

Peko²,

Farmer

et al. 2016

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In the aftermath of the March 2011 multi-unit accident at the Fukushima Daiichi nuclear power plant (Fukushima), the nuclear community has been reassessing certain safety assumptions about nuclear reactor plant design, operations and emergency actions, particularly with respect to extreme events that might occur and that are beyond each plant's current design basis. Because of our significant domestic investment in nuclear reactor technology (100 operating reactors in the fleet of commercial light water reactors (LWRs) with four under construction), the United States has been a major leader internationally in these activities. The U.S. nuclear industry is voluntarily pursuing a number of additional safety initiatives. The U.S. Nuclear Regulatory Commission (NRC) continues to evaluate and, where deemed appropriate, establish new requirements for ensuring adequate protection of public health and safety in the occurrence of low probability events at nuclear power plants; (e.g., mitigation strategies for beyond design basis events initiated by external events like seismic or flooding initiators). The Department of Energy (DOE) has also played a major role in the U.S. response to the Fukushima accident. Initially, DOE worked with the Japanese and the international community to help develop a more complete understanding of the Fukushima accident progression and its consequences, and to respond to various safety concerns emerging from uncertainties about the nature of and the effects from the accident. DOE research and development (R&D) activities are focused on providing scientific and technical insights, data, and analyses methods that ultimately support industry efforts to enhance safety. These activities are expected to further enhance the safety performance of currently operating U.S. nuclear power plants as well as better characterize the safety performance of future U.S. plants. In pursuing this area of R&D, DOE recognizes that the commercial nuclear industry is ultimately responsible for the safe operation of licensed nuclear facilities. As such, industry is considered the primary "end user" of the results from this DOE-sponsored work. vi ACKNOWLEDGEMENTS Successful preparation of this report required input and support from several individuals and organizations. To get a clear industry perspective, various nuclear industry organizations provided substantial in-kind contributions by providing technical experts to participate in this process at meetings

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Potential bacterial alteration of nuclear fuel debris: a preliminary study using simulants in powder and pellet forms

Liu

Dotsuta

Sumita

et al. 2022

J Radioanal Nucl Chem

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Enhanced Ex-Vessel Analysis for Fukushima Daiichi Unit 1: Melt Spreading and Core-Concrete Interaction Analyses with MELTSPREAD & CORQUENCH

Cited by 18 publications

References 30 publications

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

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

Light Water Reactor Sustainability Program Reactor Safety Technologies Pathway Technical Program Plan

Potential bacterial alteration of nuclear fuel debris: a preliminary study using simulants in powder and pellet forms

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