Passive Cooling System for PWR Reactor Core
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Solution Overview
Problem
Current passive cooling systems for nuclear power plants, such as AP1000, are not entirely passive and require external power or equipment for long-term residual heat removal after 72 hours, leaving them vulnerable to accidents beyond design basis.
Innovation Solution
A completely passive cooling system for a large-scale pressurized water reactor nuclear power plant featuring a double-layer steel-concrete composite structure with a water tank and air deflector, allowing for natural circulation and extended residual heat removal without external power, incorporating a smokestack, cooling water distribution plate, and air deflector to enhance cooling capacity and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AP1000 passive cooling system is used, then core safety can be maintained within 72 hours without operator intervention, but external power or equipment is still required after 72 hours for residual heat removal
Solution Approach 1:
The cooling system is divided into multiple independent water tanks (first water tank and second water tank) with separate spray pipe systems. This segmentation allows each tank to independently provide cooling for extended periods, and the modular design enables longer duration cooling without requiring external power by simply adding more segments rather than relying on a single large system that needs external assistance after 72 hours.
Solution Approach 2:
The system uses natural circulation and passive heat transfer mechanisms throughout. The spray pipes are positioned to utilize gravity-driven water flow from the tanks, and the condensation system operates passively without pumps or external power. This self-service approach eliminates the need for external power intervention after 72 hours, allowing the system to maintain core cooling indefinitely through its own inherent physical processes.
2Duration of action of stationary object
If water tank volume is increased to extend passive cooling duration to 15-40 days, then long-term residual heat removal is achieved, but system complexity and structural requirements increase
Solution Approach 1:
The first and second water tanks are positioned nested within or adjacent to each other within the containment structure, with the spray pipes of one system positioned to cover different zones. This nesting arrangement maximizes the cooling water storage capacity within the available space without requiring a completely separate external cooling system, thereby extending cooling duration to 15-40 days while minimizing the increase in overall system complexity.
Solution Approach 2:
The containment structure serves multiple functions: it houses the reactor core, contains the water tanks, provides radiation shielding, and acts as the structural framework for the passive cooling system. The spray pipes serve both as cooling devices and as structural elements that distribute water throughout the containment. This multi-functionality allows the system to achieve extended cooling duration through existing structural components rather than adding dedicated complex infrastructure.
3Productivity
If spray pipes are positioned above the cooling water distribution plate for optimal cooling coverage, then heat removal efficiency is improved, but water distribution uniformity becomes difficult to maintain
Solution Approach 1:
The spray pipes are positioned at different heights and angles to create localized cooling zones that match the thermal characteristics of different areas of the core. The first spray pipe system targets specific regions while the second system covers other areas, allowing each spray pipe to be optimized for its local cooling requirement rather than requiring uniform distribution across the entire core. This local optimization maintains both high heat removal efficiency and adequate water distribution uniformity.
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 long-term passive residual heat removal for the reactor core, expanding the water tank volume to hold 1500 to 12000 tons of cooling water for 15-40 days, improving structural protection and cooling efficiency, and ensuring the system operates without external assistance.
Implementation Method 1
a water inlet end of the spray pipe is connected to the bottom of the water tank and a water outlet end of the spray pipe is extended to be above the cooling water distribution plate
Implementation Method 2
the air deflector is arranged between the shield building and the containment, the upper end of the air deflector is connected to the inside of the top of the shield building
Implementation Method 3
A smokestack is arranged at the top of the shield building with a steel-concrete composite structure
Data Source
AI summary
A passive cooling system for a reactor core of a large-scale pressurized water reactor nuclear power plant includes a shield building having an outer wall and a through air inlet arranged on an upper part of the outer wall, a water tank arranged at an upper part of the shield building, a cooling water distribution plate arranged above a top of a containment within the shield building, a spray pipe arranged at an inside of the top of the shield building and having a water inlet end and a water outlet end, wherein the water inlet end is connected to a bottom of the water tank and the water outlet end is extended to be above the cooling water distribution plate, and an air deflector arranged between the shield building and the containment and having an upper end connected to an inside of the top of the shield building.