Multi-layer Core Catcher Vessel for Melt Confinement
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Solution Overview
Problem
Current nuclear reactor corium confinement and cooling systems face issues such as jamming of pellets due to uneven block designs, inadequate heat transfer, and insufficient chemical protection, leading to increased risks of heat exchanger destruction and radiation release during severe accidents.
Innovation Solution
A water-cooled, multi-layer vessel core melt cooling and confinement system with a cone-shaped guide plate, cantilever girder, and core catcher equipped with a highly heat-conductive filler and sacrificial materials to effectively guide and cool corium, while maintaining structural integrity and reducing thermal and chemical impacts on the external wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a water-cooled vessel with concrete cavity is used for corium confinement and cooling, then cooling capability is improved, but the risk of heat exchanger destruction and radiation release increases due to inadequate heat transfer and structural integrity
Solution Approach 1:
The vessel bottom is segmented into multiple layers: an inner layer made of heat-resistant material (such as ceramic or refractory concrete) that can withstand direct contact with molten corium, and an outer layer made of structural material (such as steel-reinforced concrete) that provides mechanical strength. This segmentation allows the system to simultaneously achieve high temperature resistance and structural integrity, preventing heat exchanger destruction while maintaining reliable corium cooling.
2Quantity of substance
If pellets with diluent are placed in horizontal layers of steel blocks, then corium dilution is improved, but pellet jamming occurs due to uneven block designs, reducing cooling efficiency
Solution Approach 1:
The steel blocks are designed with varying local geometries: the lower block has a centrally located hole to prevent pellet jamming during initial corium flow, while upper blocks have annular grooves or holes arranged in specific patterns to facilitate both pellet placement and corium distribution. This local quality variation ensures smooth pellet flow and effective corium dilution without jamming, maintaining high cooling efficiency throughout the corium solidification process.
3Strength
If the vessel bottom is made thick for structural strength, then mechanical integrity is improved, but heat transfer efficiency decreases, leading to overheating risks
Solution Approach 1:
The vessel bottom employs a composite structure combining materials with complementary properties: the inner layer uses heat-resistant ceramic or refractory concrete with high thermal conductivity to efficiently transfer heat from corium to the cooling water, while the outer layer uses steel-reinforced concrete with high mechanical strength to withstand structural loads. The composite design optimizes both heat transfer efficiency and mechanical integrity, preventing overheating while ensuring structural strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves efficient heat removal and structural reliability by ensuring effective heat transfer and chemical protection, reducing the risk of heat exchanger destruction and radiation release, and maintaining the integrity of the external wall during severe accidents.
Implementation Method 1
a layer of a filler 12 of a material that is highly heat-conductive in relation to the wall material is arranged between the internal and external layers 13, 11
Implementation Method 2
a water-cooled vessel
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The invention relates to nuclear power industry, namely to systems providing safety of nuclear power plants (NPP), and can be used during severe accidents leading to reactor vessel and NPP containment failure. The melt cooling and confinement system includes a cone-shaped guide plate installed under the reactor vessel bottom, cantilever girder installed under the guide plate and supporting the same, core catcher installed under the cantilever girder and equipped with cooled cladding in form of a multi-layer vessel for protection of the external heat-exchange wall from dynamic, thermal and chemical impacts, and filler material for melt dilution inside the multi-layer vessel. The said multi-layer vessel has external and internal metal walls with a filler that is highly heat-conductive in relation to wall material in between, where filler material thickness hfil meets the following criterion: 1.2hext< hfil <2.4hext, where hext is vessel external wall thickness. The technical result of the invention is the increased efficiency of heat removal from the melt and improved structural reliability