Nuclear Reactor Cavity Floor Passive Heat Removal
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Solution Overview
Problem
Existing ex vessel corium retention systems face challenges such as concrete ablation and heat build-up due to high corium temperatures, and inefficient heat removal from the bottom surface of the corium, leading to potential containment integrity issues during nuclear reactor meltdowns.
Innovation Solution
The implementation of an ex vessel corium retention system with flow channels embedded in the concrete floor, featuring an inlet and outlet configuration that facilitates natural recirculation of water to enhance cooling, combined with zirconia insulation and metal plates to prevent cracking, and a refueling water storage tank to maintain a water supply for flooding the reactor cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high temperature insulating tiles are used to minimize corium interaction with concrete, then concrete ablation is reduced, but heat build-up occurs at the bottom surface of the corium
Solution Approach 1:
The cooling system is segmented into multiple flow channels embedded in the concrete floor, allowing distributed heat removal from different locations. The inlet and outlet are positioned at different elevations to create multiple flow paths for natural circulation, enabling simultaneous cooling of various concrete regions while preventing localized heat accumulation under the corium.
Solution Approach 2:
Water flowing through the embedded flow channels acts as an intermediary cooling medium between the corium and the concrete floor. The water absorbs heat from the concrete through the flow channels and removes it via natural circulation, preventing direct heat transfer from corium to concrete while avoiding heat build-up at the corium bottom surface.
2Productivity
If active ECC system designs with pumps are used to inject cooling water, then heat removal effectiveness is improved, but system complexity and power requirements increase
Solution Approach 1:
The cooling system utilizes natural circulation driven by density differences between hot and cold water to achieve self-powered operation. Hot water rises from the outlet at higher elevation while cooler water sinks and flows back through the inlet, creating continuous circulation without external power input. This eliminates the need for pumps, batteries, or diesel generators while maintaining effective heat removal.
Solution Approach 2:
The mechanical pump system is replaced with a passive thermal-hydraulic system based on natural circulation principles. The density-driven flow mechanism substitutes for mechanical pumping, eliminating moving parts and power requirements while achieving the same heat removal function through thermodynamic principles.
3Device complexity
If passive ECC system designs are used to reduce complexity, then system simplicity is improved, but heat removal capability is reduced
Solution Approach 1:
The system transitions from two-dimensional horizontal cooling to three-dimensional vertical cooling by embedding flow channels at different elevations in the concrete floor. The inlet and outlet positioned at different heights create vertical flow paths that increase the effective heat transfer area and improve heat removal capability while maintaining passive operation.
Solution Approach 2:
The system exploits hydraulic principles of natural circulation, where density differences in the coolant fluid drive continuous flow through the embedded channels. This passive hydraulic system achieves effective heat removal by optimizing flow path geometry and elevation differences, eliminating the need for active mechanical components.
4Productivity
If the reactor cavity floor is filled with water for cooling, then heat removal is improved, but concrete ablation from high corium temperatures worsens
Solution Approach 1:
The embedded flow channels with circulating water act as an intermediary cooling system between the corium and the concrete floor. This intermediate water layer absorbs heat from the concrete through the channel walls and removes it via natural circulation, preventing direct high-temperature contact between corium and concrete while maintaining effective heat removal.
Solution Approach 2:
The direct water flooding approach is replaced with a controlled natural circulation system through embedded channels. This substitution prevents uncontrolled water-corium interaction that could cause rapid steam generation and concrete spalling, while maintaining steady-state heat removal that protects the concrete structure.
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 design effectively reduces concrete ablation and heat build-up, minimizing the risk of containment compromise by promoting natural circulation of water through the flow channels and providing a robust cooling mechanism for the concrete floor, thereby enhancing the integrity of the containment structure during ex vessel retention scenarios.
Implementation Method 1
an inlet and outlet configuration that facilitates natural recirculation of water to enhance cooling
Implementation Method 2
The ex vessel corium retention system may further include zirconia insulation disposed on the concrete floor located underneath the nuclear reactor
Implementation Method 3
The reactor cavity is flooded with water to provide external reactor vessel cooling
Data Source
AI summary
A nuclear reactor includes a reactor core disposed in a reactor pressure vessel. A radiological containment contains the nuclear reactor and includes a concrete floor located underneath the nuclear reactor. An ex vessel corium retention system includes flow channels embedded in the concrete floor located underneath the nuclear reactor, an inlet in fluid communication with first ends of the flow channels, and an outlet in fluid communication with second ends of the flow channels. In some embodiments the inlet is in fluid communication with the interior of the radiological containment at a first elevation and the outlet is in fluid communication with the interior of the radiological containment at a second elevation higher than the first elevation. The radiological containment may include a reactor cavity containing a lower portion of the pressure vessel, wherein the concrete floor located underneath the nuclear reactor is the reactor cavity floor.