Downward Flow Basket for Zinc Pellet Bed Stabilization
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Solution Overview
Problem
Conventional zinc feedwater systems in boiling water reactors face issues with zinc pellet fluidization and chipping due to high feedwater flow rates, leading to undesirable spikes in zinc concentrations in the reactor.
Innovation Solution
A downward flow basket design that directs fluid flow downward through a bed of zinc pellets, preventing fluidization by using a vertical wall with holes near the top, a solid bottom, and a central pipe, which compresses the pellets and reduces chipping, along with a method for loading pellets into the basket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If upward flow through zinc pellets is used, then zinc concentration control is achieved, but pellet fluidization and chipping occur
Solution Approach 1:
The patent inverts the conventional upward flow direction to downward flow through the zinc pellets. This reversal prevents fluidization and pellet chipping while maintaining zinc concentration control, directly resolving the contradiction between achieving zinc dosing and maintaining pellet stability
2Productivity
If high feedwater flow rate is used, then dosing efficiency is improved, but pellet fluidization increases
Solution Approach 1:
By reversing the flow direction to downward flow, the system can maintain high feedwater flow rates for efficient dosing without causing pellet fluidization. The downward flow compresses rather than fluidizes the pellet bed, resolving the contradiction between dosing efficiency and pellet bed stability
3Device complexity
If conventional basket design is used, then simplicity is maintained, but pellet chipping occurs
Solution Approach 1:
The patent modifies the conventional basket by inverting the flow direction through design changes such as positioning the inlet at the top and outlet at the bottom, with a perforated plate at the base. This simple structural inversion prevents pellet chipping and zinc particle intrusion while maintaining design simplicity
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 downward flow basket effectively minimizes zinc pellet chipping and fluidization, maintaining stable zinc concentrations in the reactor feedwater by redirecting fluid flow and compressing the pellets, thus preventing pellet movement and damage.
Implementation Method 1
when the rate of flow of feedwater passing through the bed of zinc pellets 30 is relatively high, the pellets tend to move in a fluidized manner. This fluidization increases the possibility of pellet chipping
Data Source
Figure 1
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Figure 3A~3D
AI summary
Provided is a replacement basket (100) configured to house a pellet bed (30) through which fluid may pass. The flow direction of the fluid prevents the bed of pellets (30) from fluidizing within the replacement basket (100). Provided also is a system using the replacement basket (100) and a method of providing pellets (30) in the replacement basket (100). The replacement basket (100) includes a top surface portion (105), a bottom (110), and at least one vertical wall (115) with a hole (120). The hole (120) is configured to allow a flow of fluid to enter the replacement basket (100). A plenum (140), below the pellet bed (30), may allow a flow of fluid to proceed through the pellet bed (125) in a downward direction. A central pipe (145) is provided in the replacement basket (100) to allow the flow of fluid in the basket (100) to exit the replacement basket (100).