Nuclear Shutdown Cooling via Steam Generator Heat Exchanger
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Solution Overview
Problem
The existing shutdown cooling systems for nuclear reactors face challenges such as increased risk of loss-of-coolant accidents due to direct connections to the reactor vessel, high flow resistance, and the need for multiple systems and heat exchangers, which complicates the cooling process and increases the time required for shutdown cooling operations.
Innovation Solution
A shutdown cooling system utilizing a secondary flow path of a steam generator, incorporating a pressure controller, and omitting the component cooling system to simplify the design and improve safety, while maintaining a sufficient suction head and flow rate through the use of valves and a bypass channel, thereby reducing the likelihood of accidents and streamlining the cooling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shutdown cooling system is directly connected to the reactor vessel, then the cooling operation can be performed, but the risk of loss-of-coolant accidents increases
Solution Approach 1:
The patent introduces a shutdown cooling heat exchanger as an intermediary component between the shutdown cooling system and the reactor vessel. The heat exchanger enables thermal coupling for cooling operation while preventing direct fluid connection, thus eliminating the loss-of-coolant accident risk pathway while maintaining cooling functionality.
2Reliability
If the diameter of the connection nozzle is increased to eliminate large loss-of-coolant accident, then the suction head condition is improved, but the flow resistance in the connection nozzle increases
Solution Approach 1:
The shutdown cooling heat exchanger serves as a mediator that decouples the nozzle diameter requirements. The heat exchanger can have a large effective heat transfer area without requiring large connection nozzles to the reactor vessel, thus achieving loss-of-coolant accident mitigation while minimizing flow resistance through small nozzles.
3Productivity
If the shutdown cooling system is directly connected to the reactor coolant system, then the cooling function is achieved, but multiple systems and heat exchangers are required which complicates the system
Solution Approach 1:
The patent extracts the heat exchange function from the direct connection between the shutdown cooling system and reactor coolant system. By taking out the heat transfer process and placing it in a dedicated shutdown cooling heat exchanger, the system achieves the cooling function while simplifying the overall configuration by eliminating unnecessary intermediate systems.
4Device complexity
If the flow rate in the shutdown cooling system is reduced to cool the reactor coolant system, then the flow resistance is decreased, but the shutdown cooling time increases
Solution Approach 1:
The patent changes the key parameter from flow rate to heat transfer area. By increasing the effective heat transfer area of the shutdown cooling heat exchanger, the system can maintain low flow rates (and thus low flow resistance) while achieving adequate cooling performance through enhanced heat transfer surface area rather than high flow velocity.
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 enhances safety by reducing the risk of loss-of-coolant accidents, simplifies the cooling system, and shortens the shutdown cooling time, improving the economical efficiency of nuclear facilities by eliminating unnecessary components and maintaining consistent flow conditions.
Implementation Method 1
a shutdown cooling heat exchanger to receive cooling water introduced into the shutdown cooling system through the steam line connecting portion, and cool the cooling water heated up while circulating along a secondary flow path of the steam generator
Data Source
AI summary
The present disclosure provides a stopped cooling system including: a steam line connecting portion connected to a steam line so as to receive cooling water through the steam line connected to an outlet of a steam generator; a stopped cooling heat exchanger for receiving cooling water that enters the stopped cooling system through the steam line connecting portion, and discharging same through a passage of the heat exchanger; a stopped cooling pump activated to perform stopped cooling of the nuclear reactor upon normal stoppage of the nuclear reactor after primary cooling of the nuclear reactor cooling system or when an accident occurs, and for forming a circulating flow of cooling water that circulates between the steam generator and the stopped cooling heat exchanger; and a water supplying pipe connecting portion connected to the heat exchanger passage and a water supplying pipe, which is connected to the inlet of the steam generator, so as to supply the cooling water cooled in the stopped cooling heat exchanger to the steam generator through the water supplying pipe.