Hybrid Reactor Cooling System for Blackout Decay Heat Removal
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Solution Overview
Problem
Current reactor cooling systems, such as the reactor isolation condenser and gravity-driven cooling systems, require external cooling water supply to maintain core cooling over extended periods after a station blackout or loss-of-coolant accident, limiting their ability to cool the reactor core continuously without external support.
Innovation Solution
A hybrid reactor cooling system incorporating a reactor pressure vessel with a dry well and suppression pool, a cooling water pool, a steam discharge apparatus, and a reactor cooling apparatus with evaporator and condenser units, allowing for continuous cooling using both water and air cooling methods, with valves operated by batteries for power loss scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motor-driven pump is used to supply cooling water to the heat exchanger, then the decay heat can be removed effectively, but electricity is required to drive the pump which may be lost during external power loss
Solution Approach 1:
The reactor cooling system is designed to cool itself using natural convection and gravity-driven water flow. The condenser is positioned above the reactor pressure vessel, allowing condensed water to return to the reactor automatically without pumps. The system uses the heat itself to drive the cooling cycle through natural convection currents.
Solution Approach 2:
The patent replaces motor-driven pumps with gravity-driven water flow and natural convection mechanisms. The condenser and evaporator are positioned to utilize natural convection currents for heat transfer, eliminating the need for mechanical pumping systems that require external power.
2Reliability
If a reactor isolation condenser with condenser pool is used for cooling, then core cooling is enabled during station blackout, but external cooling water supply is required for extended period cooling
Solution Approach 1:
The reactor cooling system serves multiple functions: it acts as both a condenser and an evaporator in a closed cycle. The same cooling water that condenses steam in the condenser is then heated in the evaporator, creating a self-sustaining thermal cycle that can operate indefinitely without external water supply.
Solution Approach 2:
The system utilizes phase transitions of water (liquid to vapor and back to liquid) to transfer heat continuously. Steam from the reactor condenses in the condenser, releasing latent heat, and the condensed water is reheated in the evaporator, creating a continuous cycle that maintains core cooling without consuming water.
3Ease of operation
If valves are operated manually or with electric actuators, then precise control is achieved, but operation becomes impossible or difficult during power loss scenarios
Solution Approach 1:
The valve control system is designed to operate automatically using the thermal state of the system itself. The control mechanism responds to temperature and pressure changes without requiring external power, allowing valves to open or close based on the natural state of the reactor and condenser.
Solution Approach 2:
The patent replaces electrically-actuated valves with mechanically-operated valves that respond to thermal expansion, pressure differential, or gravity. These passive control mechanisms eliminate the need for external power while maintaining reliable valve operation during power loss scenarios.
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
Enables continuous core cooling over extended periods without external cooling water supply, leveraging initial water cooling for high decay heat removal and subsequent air cooling as heat generation decreases, ensuring prolonged reactor safety.
Implementation Method 1
a first reactor containment vessel (3) internally having a dry well (4) and a pressure suppression chamber (5) mutually isolated, the pressure suppression chamber forming a suppression pool (6) being filled with cooling water
Implementation Method 2
a condenser (16) disposed above the cooling water pool (8) between the first reactor containment vessel (3) and the second reactor containment vessel (7) for condensing steam of the cooling medium
Implementation Method 3
an evaporator (15) installed in the reactor pressure vessel (2) for evaporating a cooling medium
Data Source
AI summary
When a power source is lost after an operation stop of a nuclear power plant, a first open/close valve is opened via a first battery at an early stage and steam in a reactor pressure vessel (RPV) is condensed in a suppression pool. The heat of the water in the suppression pool is transmitted to a cooling water pool located below inner space between first and second reactor containment vessels surrounding the RPV. A second open/close valve is opened via a second battery at the early stage and cooling water in a tank is injected into the RPV. After the early stage, a third open/close valve is opened via a third battery, and a cooling medium becomes steam by an evaporator in the RPV, the steam being condensed by a condenser disposed in the inner space to become a liquid of the cooling medium and is returned to the evaporator.