Passive Gravity-Driven Reactor Cooling System
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Solution Overview
Problem
Current nuclear reactor containment systems rely on pumped heat rejection systems that require a power source, making them vulnerable during station blackouts or loss-of-coolant accidents, and are insufficient to manage rapid pressure rises and heat dissipation effectively.
Innovation Solution
A passive cooling system using gravity-driven fluid flow and varying fluid densities to extract and reject decay heat from the reactor, incorporating a heat exchanger and an annular reservoir for heat dissipation, which operates independently of power sources and includes a double-walled containment structure with radial fins for enhanced heat transfer and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pumped heat rejection systems are used to remove decay heat from the reactor, then heat rejection capability is improved, but the system becomes vulnerable during station blackouts when power sources are unavailable
Solution Approach 1:
The patent replaces the mechanical pump-based heat rejection system with a passive natural circulation system that uses density differences (thermal convection) to drive coolant flow. The hot coolant rises naturally from the reactor core and the cold coolant sinks, creating continuous circulation without requiring external power sources or mechanical pumps, thus maintaining heat rejection capability during station blackouts
Solution Approach 2:
The system uses the temperature difference and density variation of the coolant itself to drive the heat rejection process. The heated coolant automatically rises and the cooled coolant automatically sinks, creating a self-sustaining circulation loop that requires no external energy input or control systems, ensuring reliable operation during power outages
2Strength
If thick concrete containment walls are used to withstand aircraft impact, then structural strength is improved, but heat dissipation capability deteriorates due to thermal insulation properties
Solution Approach 1:
The patent introduces an external heat dissipation structure (cooling fins or heat exchange surfaces) attached to the outer surface of the containment wall. This adds a new dimensional element for heat transfer to the external environment, allowing the thick concrete wall to maintain its structural integrity while the external surfaces provide efficient heat dissipation pathways
Solution Approach 2:
The patent introduces an intermediate heat transfer medium (such as water or air flowing over external surfaces) that facilitates heat removal from the containment structure. This intermediary layer allows heat to be efficiently transferred from the thick concrete wall to the environment without compromising the wall's thermal insulation properties or structural strength
3Reliability
If passive gravity-driven cooling system is implemented, then reliability during blackout is improved, but system complexity increases due to additional components
Solution Approach 1:
The containment structure serves multiple functions: it provides structural protection against impact, contains the reactor core, and acts as part of the heat rejection system through integrated external cooling surfaces. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in overall system complexity while maintaining improved reliability
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 effectively manages decay heat rejection and pressure control without power sources, ensuring continuous operation during accidents and providing enhanced structural integrity against impact and heat dissipation, maintaining containment integrity and safety indefinitely.
Implementation Method 1
The cooling water flows via gravity in a closed flow piping loop between the reactor well and the heat exchanger to reject heat through the containment vessel walls to an external heat sink
Implementation Method 2
the tank is configured and operable to flood the reactor well with cooling water which is converted into steam by heat from the fuel core
Implementation Method 3
the steam condenses in the heat exchanger forming condensate, and the condensate flows via gravity back to the reactor well
Implementation Method 4
The cooling system relies entirely on gravity and varying fluid densities to extract and induce flow of cooling water through the system which includes a heat exchanger
Implementation Method 5
The cooling system is engineered to passively extract decay heat from the reactor in the event of a LOCA station black out or another postulated accident scenario
Data Source
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AI summary
A nuclear reactor cooling system with passive cooling capabilities operable during a loss-of-coolant accident (LOCA) without available electric power. The system includes a reactor vessel with nuclear fuel core located in. a reactor well. An in-containment water storage tank is fluidly coupled to the reactor well and holds an inventory of cooling water..During a LOCA event, the tank floods the reactor well with water. Eventually, the water heated by decay heat from the reactor vaporizes producing steam. The steam flows to an in- containment heat exchanger and condenses. The condensate is returned to the reactor well in a closed flow loop system in which flow may circulate solely via gravity from changes in phase and density of the water. In one embodiment, the heat exchanger may he an array of heat dissipater ducts mounted on the wall of the inner containment vessel surrounded by a heat sink.