Passive Nuclear Residual Heat Evacuation via Thermal Expansion
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Solution Overview
Problem
Existing nuclear reactor residual heat evacuation systems require electrical power and operator intervention, compromising safety and reliability.
Innovation Solution
A completely passive system using a thermally expandable control mechanism to operate heat exchangers without power supplies or control logics, utilizing a secondary fluid circulation and natural air or water cooling to regulate temperature by opening shutters and enhancing natural convection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active systems with electrical power supplies are used for residual heat evacuation, then the system can operate with operator intervention and control logics, but the system becomes dependent on electrical power and operator action which compromises safety and reliability
Solution Approach 1:
The system enables self-service operation through natural convection currents that automatically circulate the secondary fluid between the first heat exchanger in the reactor vessel and the second heat exchanger outside the vessel, eliminating the need for electrical power supplies, pumps, or operator intervention for residual heat evacuation
Solution Approach 2:
The patent replaces mechanical pumping systems and electrical control systems with a passive thermal convection system, where heat transfer is driven by natural density differences in the secondary fluid, substituting active mechanical components with a thermally-driven flow mechanism
2Use of energy by moving object
If passive systems without electrical power are used for residual heat evacuation, then electrical power dependency is eliminated, but the system requires sophisticated thermal expansion mechanisms and precise positioning
Solution Approach 1:
The patent employs thermal expansion of the secondary fluid and heat exchanger components as the driving mechanism for system operation, where temperature-induced density changes and dimensional expansions automatically regulate fluid circulation and heat transfer without requiring external control systems
Solution Approach 2:
The system utilizes changes in physical parameters such as fluid density, temperature, and pressure that occur naturally during heat transfer processes to control the operation of the residual heat evacuation system, eliminating the need for complex electronic control mechanisms
3Productivity
If heat exchangers are positioned at different levels in the reactor vessel, then natural convection is enhanced for passive operation, but the system requires precise vertical positioning and spatial arrangement
Solution Approach 1:
The patent utilizes the vertical dimension within the reactor vessel to position the first heat exchanger at a lower level and the second heat exchanger at a higher level outside the vessel, creating a vertical thermal loop that maximizes natural convection efficiency for passive residual heat evacuation
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
Ensures reliable and safe residual heat evacuation independent of operator intervention or electrical power, with improved natural circulation and reduced risk of fluid leakage, enhancing reactor safety and operational dependability.
Implementation Method 1
The pipe portion (23) is designed so as to be thermally expandable, in particular by effect of a temperature increase in the secondary fluid (15) circulating in it, along the axis (A)
Implementation Method 2
The heat exchanger (11) interacts with the primary fluid (5), being in particular immersed in the primary fluid (5), for transferring heat from the primary fluid (5) to a secondary fluid (15) circulating in the evacuation circuit (13) and in the heat exchangers (11, 12)
Implementation Method 3
In the heat exchanger (12) the secondary fluid (15) is cooled by an auxiliary fluid (16) (schematically represented by the arrow in FIG. 1), which circulates in a cooling duct (17) and crosses or strikes the heat exchanger (12)
Data Source
AI summary
A system for evacuating the residual heat from a nuclear reactor comprises: a first heat exchanger, which transfers heat from a primary fluid of the reactor to a secondary fluid; a second heat exchanger, where the secondary fluid is cooled by an auxiliary fluid which crosses a cooling duct; and a control portion, subject to thermal expansion by effect of the heating, induced by an increase in the temperature of the primary fluid beyond a preset threshold, of the secondary fluid in the control portion; the control portion being connected to a mechanical actuator device moved by the thermal expansion of the control portion to open the cooling duct and allow the passage of auxiliary fluid into the cooling duct and through the second heat exchanger.