Controlled-Debris Elements for ECCS Strainer Pressure Head Loss

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Nuclear power plant suction strainers face significant pressure head loss during a loss of cooling accident (LOCA) due to the accumulation of fibrous and particulate debris, which can lead to flow blockage and damage to ECCS pumps, and existing solutions either require costly modifications to strainer structures or are impractical for implementation.

Innovation Solution

Introducing controlled-debris elements with a specific gravity matching that of the cooling water, which are designed to intermix with debris and form open structures on the strainer surface, preventing the formation of dense debris beds and maintaining flow through perforations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If strainers are used to remove debris from cooling water, then pump protection is improved, but pressure head loss increases due to debris accumulation

Engineering Contradiction:

Improvepump protectionVSAvoidpressure head loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention converts the harmful effect of debris accumulation into a beneficial effect by introducing controlled debris elements that intentionally accumulate on the strainer surface. These elements form an open-structured debris bed that actually improves flow characteristics and reduces pressure head loss compared to uncontrolled debris accumulation, thereby protecting the pump while maintaining energy efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The controlled debris elements act as an intermediary layer between the cooling water and the strainer surface. This intermediate debris bed serves as a filter that protects the pump from damaging debris while its open structure prevents excessive pressure drop, mediating between the need for protection and the need for flow efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If multiple perforated strainer elements are used to increase surface area, then debris removal capacity is improved, but device complexity increases

Engineering Contradiction:

Improvedebris removal capacityVSAvoidstrainer structure complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The invention employs self-service by allowing the strainer to accumulate its own protective debris layer from the cooling water flow. The controlled debris elements are naturally transported by the flow and self-organize into an open-structured bed on the strainer surface, eliminating the need for complex mechanical structures or active control systems to achieve debris removal capacity.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If debris bed forms on strainer surface, then filtration is improved, but flow blockage occurs increasing pressure head loss

Engineering Contradiction:

Improvefiltration effectivenessVSAvoidcooling water flow rate

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The invention applies local quality by creating a debris bed with specific local characteristics - an open-structured configuration with controlled void spaces. This localized structural quality allows the debris bed to provide effective filtration while maintaining sufficient flow pathways, preventing the uniform densification that would lead to complete flow blockage.

Inventive Principle:

Principle #3Local quality

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 controlled-debris elements effectively mitigate pressure head loss across strainers by preventing the formation of dense debris beds, ensuring continuous flow and reducing the risk of pump damage during LOCA events without the need for costly strainer modifications.

Implementation Method 1

Each element has a specific gravity substantially the same as the circulating water during at least a portion of time following the LOCA onset for entraining the element in the flow of water in the reservoir toward the strainer

Methodology Applied

Scientific EffectSpecific gravity matching: Archimedes' Principle (Buoyancy)

Implementation Method 2

The elements are configured to form open spaces between adjacent elements in the debris/element layer, which tests show mitigates pressure head loss across the strainer

Methodology Applied

Scientific EffectOpen structure formation:

Data Source

PatentUS10755824B2Nuclear reactor using controlled debris to mitigate ECCS strainer pressure head loss

Publication Date: 2020.08.25 CONTINUUM DYNAMICS INC

AI summary

Controlled-debris elements inhibit the formation of a fibrous/particulate debris bed that unduly increases the pressure head loss through the perforated plates of strainers in a nuclear power plant emergency core cooling system. In a loss of cooling accident, pumps draw cooling water through the plates, which retain on their surfaces fibrous material in the circulating water to prevent it from reaching the pumps while permitting entrained particulate matter to pass through the perforations. The controlled-debris elements have a specific gravity substantially the same as the circulating water so they are entrained in the cooling water that is drawn toward the strainers and intimately intermix with the fibrous and particulate matter in the cooling water. The elements are configured to provide open structures in the bed formed on the plate surfaces to distribute fibers in the flow away from the surface and maintain cavities between the elements for the particulates.