Gravity-Driven Fluidic Device for Safety Injection Tank Flow Control
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Solution Overview
Problem
Conventional safety injection tanks face challenges in efficiently transitioning from high flow to low flow emergency core cooling water injection modes and suffer from early nitrogen gas injection, which disrupts reactor system condensation and complicates thermal hydraulic analysis.
Innovation Solution
A gravity-driven fluidic device with a spring-biased vertically movable water tub and low flow inlet ports located near the lower hemispherical surface, allowing for passive control of high flow inlet ports and preventing nitrogen gas discharge, enabling a simple estimation of turndown ratio and complete discharge of emergency core cooling water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional vortex type fluidic device is used with multiple inlet ports and complex internal structure, then flow mode transition can be achieved, but the device complexity increases and turndown ratio estimation becomes difficult
Solution Approach 1:
The patent extracts and eliminates the complex internal vortex chamber structure from the fluidic device. Instead of using a vortex chamber with multiple inlet ports and complex internal geometry, the invention uses a simple vertical pipe with inlet and outlet ports, achieving flow mode transition through a buoyant plate mechanism rather than complex fluid dynamics
Solution Approach 2:
The patent segments the flow control function into separate components: the buoyant plate handles the high-to-low flow transition by blocking the inlet port, while the outlet valve handles discharge control. This segmentation simplifies each component's function and reduces overall device complexity
2Device complexity
If the supply line inlet port is exposed to nitrogen gas in the tank during low flow mode, then the device structure is simple, but early nitrogen gas injection occurs which disrupts reactor system condensation
Solution Approach 1:
The patent introduces a buoyant plate as an intermediary element between the supply line inlet port and the nitrogen gas environment. The buoyant plate passively blocks the inlet port during low flow mode when water level drops, preventing nitrogen gas from entering the supply line while maintaining simple device structure without complex active control systems
3Object-generated harmful factors
If a buoyant plate is used to close the inlet port, then early nitrogen gas injection can be prevented, but the plate may become fixed to the inlet port during standby and fail to operate
Solution Approach 1:
The patent applies self-service through passive operation: the buoyant plate automatically responds to water level changes and flow conditions without external control. During standby, the plate remains free-floating and responsive to water level changes, preventing fixation while maintaining readiness for operation
Solution Approach 2:
The patent makes the buoyant plate dynamic rather than static by allowing it to move freely with water level changes and flow conditions. The plate's position is determined by real-time hydrodynamic conditions rather than being fixed or mechanically actuated, ensuring reliable operation during both standby and active phases
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 solution effectively prevents early nitrogen gas injection, allows for precise control of turndown ratios, and increases the effective volume of discharged cooling water, enhancing reactor safety by maintaining core cooling water levels and preventing quick temperature increases during low flow injection.
Implementation Method 1
a buoyant plate, which passively opens or closes an inlet port provided in an upper end of a vertical pipe
Implementation Method 2
a gravity-driven fluidic device, installed in the safety injection tank, as time goes by after operation of the safety injection tank
Data Source
AI summary
A safety injection tank, used for quickly injecting emergency core cooling water (ECCW) to a reactor vessel in the case of a cold leg large break accident (CLLBA) in a pressurized water reactor (PWR), is disclosed. The safety injection tank has a gravity-driven fluidic device configured to efficiently change the ECCW injection mode from a high flow injection mode to a low flow injection mode. The gravity-driven fluidic device includes a spring placed in the upper end of the vertical pipe, and a vertically movable water tub placed on the spring so as to be movable in a vertical direction. When ECCW contained in the pressure vessel is discharged and the water level is reduced lower than the height of the tub, the tub is moved downwards such that the lower surface thereof comes into contact with the vertical pipe and closes the high flow inlet port.