Passive Nuclear Cooling via Two-Phase Heat Transfer
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Solution Overview
Problem
Conventional nuclear reactors face challenges in efficient heat dissipation during emergencies, requiring manual operator intervention and external power, which can lead to accidents due to inadequate cooling and operator errors, and the pool-boiling method has a slow heat transfer rate necessitating larger systems.
Innovation Solution
A passive infinite cooling system for nuclear reactors that utilizes a self-sustaining two-phase heat transfer mechanism, where heat from the reactor core is transferred to a saturated vapor pressure cooling chamber, pressurizing cooling water to vaporize and condense, enhancing heat transfer efficiency without external power or operator intervention, and includes features like a coolant spray pipe, pressure balance pipe, and outer wall cooling module to manage heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pool-boiling method is used for heat exchange, then the system structure is simple, but the heat transfer rate is not satisfactory and the heat discharge rate is slower
Solution Approach 1:
The patent employs a two-phase heat transfer mechanism where cooling water alternates between liquid and vapor phases. The cooling water is vaporized in the first heat exchanger (absorbing heat from reactor core) and then condensed in the second heat exchanger (releasing heat to the environment), creating a continuous phase transition cycle that dramatically enhances heat transfer efficiency compared to conventional pool-boiling methods.
Solution Approach 2:
The system utilizes pressure differential driven fluid flow where the phase transition of cooling water creates pressure differences that automatically drive the circulation of cooling water through the heat exchangers without requiring external pumps. The vaporization and condensation processes generate the necessary hydraulic pressure to maintain continuous cooling water circulation.
2Ease of operation
If manual operation and external power supply are used for cooling systems, then the cooling can be controlled, but operator errors and accidents may occur and external power may be unavailable during emergencies
Solution Approach 1:
The passive cooling system is designed to operate autonomously without requiring operator intervention or external power supply. The system automatically detects temperature increases in the reactor core and initiates cooling through the two-phase heat transfer mechanism, using the thermal energy itself to drive the circulation of cooling water. This self-service capability ensures reliable operation during emergencies when operators may be unavailable or external power may fail.
Solution Approach 2:
The patent replaces active mechanical cooling systems (requiring pumps, motors, and control systems) with a passive thermal-driven system. The phase transition of cooling water naturally creates the driving force for circulation, eliminating the need for mechanical components that require external power and complex control systems, thereby improving reliability during emergencies.
3Ease of manufacture
If the heat exchanger is immersed in water for heat discharge, then the system is simple to implement, but the heat transfer rate is insufficient and the system size must be enlarged
Solution Approach 1:
The patent uses phase transition of cooling water (vaporization and condensation) to dramatically enhance heat transfer efficiency. The cooling water vaporizes in the first heat exchanger absorbing heat from the reactor core, then the vapor travels to and condenses in the second heat exchanger releasing heat to the environment. This phase change process transfers much more heat per unit volume compared to conventional immersed heat exchange, allowing for a more compact system design.
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 achieves improved heat transfer rates, reduces system size, and enhances safety by allowing autonomous operation during emergencies, preventing reactor damage and radioactive contamination through efficient heat dissipation and automatic cooling mechanisms.
Implementation Method 1
a pressure balance pipe through which the pressure in the energy release space is transferred to the energy absorbing space
Implementation Method 2
an infinite cooling circulation is performed by itself while cooling water is passively circulated by heat and pressure generated when an abnormality occurs in the nuclear reactor
Implementation Method 3
heat from the reactor core is transferred to a saturated vapor pressure cooling chamber, pressurizing cooling water to vaporize and condense
Implementation Method 4
the heat exchanger 30 generates steam in the drive system 50 using the heat absorbed from the coolant
Implementation Method 5
the heat in the steam is turned into electric energy by a generator 54 and then the steam is condensed into water again to be circulated to the heat exchanger 30
Implementation Method 6
a first cooling flow path through which the heat in the reactor vessel is transferred to the energy transfer space
Data Source
AI summary
A passive cooling system for a nuclear reactor includes an energy release space in which a reactor vessel is accommodated, an energy absorbing space separated from the energy release space, and an energy transfer space above the energy absorbing space and configured to absorb and cool heat transferred from the reactor vessel and discharge the absorbed heat to an outside of the system through an outer wall thereof. The passive cooling system further includes a first cooling flow path configured to transfer the heat in the reactor vessel to the energy transfer space, a pressure balance pipe configured to transfer the pressure in the energy release space to the energy absorbing space therethrough, and a coolant spray pipe configured to transfer the cooling water in the energy absorbing space pressurized by the pressure balance pipe to the energy transfer space may be provided.