Dome Collector Steam Separator for Nuclear Reactors

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Solution Overview

Problem

Conventional steam separators in nuclear boiling water reactors face challenges in effectively removing moisture from two-phase flow streams, leading to increased moisture carry-over, which elevates radioactivity levels and maintenance costs due to flow-accelerated corrosion in the main steam line and turbine.

Innovation Solution

The introduction of a dome collector separation stage with a curvilinear outer channel and an elbow extension with a curved section, both designed to separate water from the two-phase flow stream using density differences and centripetal forces, respectively, to reduce moisture carry-over. Additionally, a streamlined steam separator with pick-off rings and controlled expansion regions is employed to enhance separation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional steam separators are used with high FS velocity and high inlet moisture content, then steam generation efficiency is maintained, but moisture carry-over increases leading to radioactivity exposure and maintenance costs

Engineering Contradiction:

Improvesteam generation efficiencyVSAvoidmoisture carry-over

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The steam separator is divided into multiple functional stages: a preliminary separation section with a pick-off ring that removes bulk moisture, followed by a controlled expansion region that further separates remaining droplets. This multi-stage segmentation allows efficient moisture removal without sacrificing steam generation productivity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces a controlled expansion region that creates a radial outward flow component perpendicular to the axial steam flow direction. This dimensional change in flow pattern allows moisture droplets to be separated from the steam stream through centrifugal forces and impaction on the separator walls, effectively reducing moisture carry-over while maintaining high steam generation efficiency

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If FS velocity is increased to maintain steam generation rate, then productivity is improved, but moisture carry-over increases due to droplet entrainment

Engineering Contradiction:

Improvesteam generation rateVSAvoidmoisture removal effectiveness

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The pick-off ring is positioned to perform preliminary moisture removal at the inlet of the steam separator, before the steam enters the main separation chamber. This preliminary action removes the bulk of moisture droplets early in the process, allowing the subsequent controlled expansion region to handle only residual moisture, thereby maintaining reliable moisture removal effectiveness even at high steam generation rates

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If conventional separation designs are used, then device complexity is low, but moisture carry-over leads to flow-accelerated corrosion and increased maintenance costs

Engineering Contradiction:

Improveseparator structure simplicityVSAvoidflow-accelerated corrosion

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The controlled expansion region utilizes the kinetic energy and momentum of the high-velocity steam flow to create radial outward movement of moisture droplets, causing them to impact on the separator walls and be removed. This converts the potentially harmful high-velocity flow into a beneficial separation mechanism, effectively reducing moisture carry-over and preventing flow-accelerated corrosion while adding only moderate structural complexity

Inventive Principle:

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

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

These designs significantly reduce moisture carry-over, minimizing radioactivity exposure and maintenance costs by effectively separating water from steam, thereby improving the operational performance and safety of nuclear boiling water reactors.

Implementation Method 1

a portion of the outer side wall within the upper section may be curvilinear such that the outer channel is configured to cause the at least some water to separate from the two-phase FS when the two-phase FS impacts the curvilinear portion of the outer side wall, due to a density difference between water and steam portions of the two-phase FS

Methodology Applied

Scientific EffectDensity difference: Density Gradient

Implementation Method 2

an elbow extension with a curved section, both designed to separate water from the two-phase flow stream using density differences and centripetal forces, respectively

Methodology Applied

Scientific EffectCentripetal force: Centrifugal Force

Data Source

PatentUS11398317B2Apparatuses for steam separation, and nuclear boiling water reactors including the same

Publication Date: 2022.07.26 GE HITACHI NUCLEAR ENERGY AMERICAS LLC

AI summary

According to at least some example embodiments, a dome collector separation stage includes an inner side wall that defines an inner channel; and an outer side wall that, together with the inner side wall, defines an outer channel, the inner channel being configured to receive a two-phase flow stream (FS) of water and steam, and pass the two-phase FS to the outer channel via inlets included in the inner side wall, the outer channel being configured to separate at least some water from the two-phase FS, and pass moisture-reduced steam out of the steam separator stage via outlets included in the outer side wall.