Concentric Strainer Filter Medium for Nuclear ECCS Debris Control
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Solution Overview
Problem
Current strainers in nuclear power plant emergency core cooling systems allow significant amounts of debris to bypass, leading to equipment damage, clogging, and hydraulic head loss, as they lack an effective filter medium that could become clogged, causing loss of head pressure and cavitation.
Innovation Solution
A custom-designed knitted or woven stainless steel wire mesh filter medium is inserted between the strainer modules, providing secondary filtration and altering water flow velocity to promote non-uniform debris accumulation, increasing bypass resistance and entrapment of debris without significant pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter medium is added to the strainer, then debris bypass is reduced and filtration is improved, but head pressure is lost and cavitation occurs
Solution Approach 1:
The strainer system is segmented into multiple functional zones: an outer strainer for coarse debris removal, an inner strainer for fine debris removal, and a filter medium for fibrous debris filtration. This segmentation allows each component to handle specific debris types, improving overall filtration reliability while distributing the pressure drop across multiple stages rather than one single restrictive element.
Solution Approach 2:
Different regions of the strainer system have different filtration characteristics. The outer strainer has larger openings for coarse debris, the inner strainer has smaller openings for fine debris, and the filter medium has specific pore structures for fibrous materials. This local differentiation optimizes debris capture at each location while maintaining adequate flow paths to minimize excessive pressure loss.
2Reliability
If the strainer openings are made smaller to reduce debris bypass, then filtration is improved, but flow capacity is reduced and head pressure increases
Solution Approach 1:
The strainer is divided into outer and inner strainer sections with different opening sizes. The outer strainer uses larger openings to maintain high flow capacity while capturing coarse debris, while the inner strainer uses smaller openings to capture fine debris. This segmentation allows the system to maintain both high productivity and effective filtration across different debris sizes.
Solution Approach 2:
Different zones of the strainer system have optimized for different functions. The outer region prioritizes flow capacity with larger openings, while the inner region prioritizes fine filtration with smaller openings. The filter medium provides additional localized filtration for fibrous debris. This spatial differentiation allows simultaneous optimization of both flow capacity and filtration effectiveness.
3Object-affected harmful factors
If filter medium is used to reduce debris bypass, then equipment damage is prevented, but the filter medium becomes clogged and requires maintenance
Solution Approach 1:
The filtration system is segmented into three hierarchical levels: outer strainer for coarse debris, inner strainer for fine debris, and filter medium for fibrous debris. This segmentation distributes the debris load across multiple components, preventing any single element from becoming completely clogged. The outer and inner strainers act as protective barriers that capture larger debris before it reaches the more sensitive filter medium.
Solution Approach 2:
Different components handle different debris types based on their local function. The outer strainer handles coarse debris, the inner strainer handles fine debris, and the filter medium handles fibrous debris. This differentiation ensures that each component operates within its optimal capacity range, reducing the likelihood of complete clogging and simplifying maintenance requirements compared to a single-stage filtration system.
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 significantly reduces debris bypass and accumulation, minimizing equipment damage and hydraulic head loss, ensuring reliable operation of the emergency core cooling system with reduced risk of clogging and pressure loss.
Implementation Method 1
a woven or knitted stainless steel filter medium that is inserted between an external and an internal double wall concentric tube type strainer and through which water must pass and be filtered
Implementation Method 2
This filter medium alters the approach velocity of the water at the strainer surface resulting in non-uniform fibrous debris accumulation on the strainer surface
Data Source
AI summary
A filter medium for strainers used in the emergency sump of a nuclear power plant ECCS. The filter medium is employed with double wall, concentric tube type strainer modules. The filter medium is preferably constructed of a woven or knitted stainless steel wire material and is shaped in a cylinder so that it can be inserted between two concentric strainer walls, concentric tube type strainer in such a manner that water that passes through the strainer must pass through and be filtered by the filter medium before the water can be pumped to the reactor core. The filter medium is inserted through the bottom of the strainer module and is held in place by an x-shaped retainer. The filter creates varied approach velocity of the fluid and results in non-uniform fibrous debris accumulation on the strainer, insuring acceptable strainer debris hydraulic head loss.