Passive Air Injection for Hydrogen Control in Nuclear Reactor Offgas

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Solution Overview

Problem

Nuclear reactors face corrosion issues due to oxygen generated from water radiolysis, leading to hydrogen-rich offgas conditions that can be hazardous, requiring additional oxygen injection, but conventional methods using compressed air or oxygen may not accurately control hydrogen concentrations.

Innovation Solution

Passively injecting ambient air into the offgas system upstream of the recombiner using a coupled air injection line, with automatic valve control based on hydrogen and oxygen concentration measurements to provide a backup oxygen source, leveraging the existing condenser vacuum for air introduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If compressed air or pure compressed oxygen is injected into the offgas system to control hydrogen concentrations, then the oxygen supply reliability is improved, but the device complexity and energy consumption increase

Engineering Contradiction:

Improveoxygen supply reliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system utilizes the existing condenser vacuum to passively draw ambient air into the offgas system, eliminating the need for external compressors or active pumping mechanisms. The vacuum naturally serves the dual purpose of condensing steam and providing the driving force for air injection, making the system self-sufficient and reducing device complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The condenser vacuum system performs multiple functions: it condenses steam from the offgas, removes non-condensable gases, and simultaneously provides the driving force for passive air injection. This multi-functionality eliminates the need for separate oxygen supply equipment, reducing both device complexity and energy consumption

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If compressed air or pure compressed oxygen is injected into the offgas system, then the oxygen supply reliability is improved, but the energy consumption increases

Engineering Contradiction:

Improveoxygen supply reliabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system uses the condenser vacuum to passively draw ambient air into the offgas system, eliminating the need for external compressors or active pumping mechanisms. The vacuum naturally serves the dual purpose of condensing steam and providing the driving force for air injection, making the system self-sufficient and reducing device complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If hydrogen injection rate is increased to control corrosion, then the corrosion protection is improved, but the hydrogen concentration in offgas increases creating hazardous conditions

Engineering Contradiction:

Improvecorrosion protectionVSAvoidhydrogen-rich hazardous conditions

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system continuously monitors hydrogen and oxygen concentrations in the offgas and uses this feedback to control the air injection rate. When hydrogen concentration exceeds safe levels or oxygen becomes insufficient, the system automatically adjusts the air injection to maintain safe composition ratios, preventing hazardous conditions while ensuring adequate corrosion protection

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the oxygen content parameter by controlling the ambient air injection rate based on real-time hydrogen concentration measurements. This parameter change ensures that the offgas composition remains within safe limits (hydrogen concentration below explosive thresholds) while maintaining sufficient oxygen for corrosion protection

Inventive Principle:

Principle #35Parameter changes

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

This method effectively controls hydrogen concentrations by providing a reliable oxygen source, reducing maintenance needs and energy usage, and ensuring safe operation by reacting hydrogen and oxygen to form water vapor, thus preventing hazardous conditions.

Implementation Method 1

The oxygen and hydrogen in the combined flow react in the recombiner to form water vapor

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 2

The ambient air is drawn into the offgas line by a vacuum exerted by the offgas system

Methodology Applied

Scientific EffectVacuum: Vacuum

Data Source

PatentEP2339590B1Methods of controlling hydrogen concentrations in an offgas system of a nuclear reactor by passive air injection

Publication Date: 2015.10.28 GE HITACHI NUCLEAR ENERGY AMERICAS LLC

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AI summary

Example embodiments relate to methods of controlling hydrogen concentrations in an offgas system of a nuclear reactor by passive air injection. A method according to a non-limiting embodiment may include passively injecting ambient air through the hydrogen water chemistry system into an existing offgas line of the offgas system. The offgas line is configured to transport non-condensable gases, including hydrogen, from a condenser (102) to a recombiner (104). As a result of the passive air injection, the combined flow of hydrogen and oxygen react in the recombiner (104) to form water vapor, thereby reducing the hydrogen concentration of the offgas exiting the recombiner (104).