Hemispherical RPV Test Device for Severe Accident Simulation
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Solution Overview
Problem
Current test systems for simulating RPV heat exchange characteristics in nuclear power plants fail to accurately replicate the three-dimensional flow conditions of a severe accident, leading to inadequate cooling and potential radioactive leakage.
Innovation Solution
A heating and temperature measuring device with a hemispherical lower head and a tube portion, equipped with a heating assembly and temperature measuring assembly, including thermocouples inserted perpendicular to the inner wall surface, simulates the heat exchange characteristics by allowing cooling water to flow in any direction, replicating the three-dimensional flow state of the RPV's outer wall surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a one-dimensional or two-dimensional test section is used with parallel heating rods and flow channels, then the device structure is simple and easy to manufacture, but the three-dimensional flow state of the RPV outer wall surface cannot be simulated accurately
Solution Approach 1:
The patent transitions from one-dimensional and two-dimensional test sections to a three-dimensional hemispherical test section that accurately simulates the RPV outer wall surface geometry. The hemispherical lower head with radially arranged heating holes and flow channels creates genuine three-dimensional flow patterns, transforming the test from simplified planar configurations to a spatially accurate representation of the actual reactor pressure vessel geometry.
Solution Approach 2:
The patent employs a hemispherical lower head geometry instead of flat or cylindrical test sections. This curved spherical geometry accurately represents the actual RPV lower head shape, enabling realistic simulation of heat and fluid flow patterns on the curved outer wall surface. The spherical coordinate system with radially distributed heating holes and flow channels matches the geometric characteristics of the real reactor pressure vessel.
2Manufacturing precision
If cooling water flows only in one direction from bottom to top in a narrow flow channel, then the flow channel design is simple, but the actual three-dimensional flow condition outside the RPV lower head cannot be replicated
Solution Approach 1:
The patent creates three-dimensional flow patterns by arranging multiple flow channels in different radial directions around the hemispherical lower head. Cooling water can flow through multiple interconnected channels in various directions (radially outward, tangentially, vertically), replicating the complex three-dimensional flow field that occurs outside the actual RPV lower head during severe accidents, rather than confined one-directional flow.
Solution Approach 2:
The patent divides the flow channel system into multiple separate channels distributed around the hemispherical geometry. Each flow channel can be independently configured with specific orientation and connectivity, allowing the system to simulate different flow paths and patterns. This segmented approach enables realistic representation of multi-directional cooling water injection and flow distribution over the RPV lower head surface.
3Measurement precision
If temperature measuring holes and heating holes are arranged along the spherical center direction, then the temperature distribution and heat flux measurement are comprehensive, but the device structure becomes more complex
Solution Approach 1:
The patent positions temperature measuring holes and heating holes at specific locations along the spherical center direction to capture critical thermal information. Temperature holes are strategically placed at different radial depths to monitor temperature gradients, while heating holes are positioned to create controlled heat flux patterns. This localized, purposeful arrangement of measurement and heating points provides comprehensive thermal data with minimal intrusion into the overall hemispherical structure.
Solution Approach 2:
The patent arranges temperature measuring holes at multiple depths along radial lines from the spherical center, creating a three-dimensional temperature measurement network. This radial-depth configuration enables measurement of temperature gradients in the wall thickness direction and heat flux distribution across the curved surface, providing comprehensive thermal characterization that planar arrangements cannot achieve.
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
This configuration enables real-time monitoring of temperature changes and heat flux distribution on the RPV's surface, providing data to assess the effectiveness of severe accident mitigation systems, such as pit water injection systems, and simulates the actual flow conditions more accurately than previous one-dimensional and two-dimensional tests.
Implementation Method 1
a heating assembly for heating the lower head
Implementation Method 2
the temperature measuring assembly includes a number of sets of thermocouples
Implementation Method 3
allowing cooling water to flow in any direction, replicating the three-dimensional flow state of the RPV's outer wall surface
Data Source
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AI summary
A test system, and a heating and temperature measuring device for simulating RPV heat exchange characteristics of a nuclear power plant. The heating and temperature measuring device includes a tube portion, a hemispherical lower head connected to a lower end of the tube portion, a heating assembly for heating the lower head, and a temperature measuring assembly disposed in the lower head. The temperature measuring assembly is configured to monitor a temperature change in a wall thickness direction of the lower head to monitor a surface temperature change of the lower head. The test system for simulating the RPV heat exchange characteristics of the nuclear power plant is used for simulating a process that a high-temperature core melt is transferred to an RPV wall surface and flows outside of the RPV wall surface under the condition that a severe accident occurs to the nuclear power plant, thereby studying the distribution of CHF and three-dimensional cooling water flow characteristics at different positions on an RPV outer wall surface under a three-dimensional flow condition, thereby providing data support for studying the effectiveness of a severe accident mitigation system -a pit water injection system.