Hydropneumatic Actuator for Rapid Reactivity Control

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Solution Overview

Problem

Light water nuclear fission reactors face challenges in controlling reactivity due to delayed temperature responses when there is a loss of coolant flow, which can lead to adverse temperature effects such as sodium boiling, and existing systems lack rapid, passive responses to fluid flow disruptions.

Innovation Solution

A hydropneumatic actuator system that directly reacts to a loss of fluid flow by mechanically moving neutron modifying materials within the reactor core to rapidly insert or withdraw negative reactivity without triggering a scram event, using a converging-diverging passage design and a biasing member to apply forces based on fluid pressure variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermal feedback is used to insert negative reactivity, then reactivity control is achieved, but significant time delay occurs between temperature increase and reactivity response

Engineering Contradiction:

Improvereactivity controlVSAvoidtime delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The hydropneumatic actuator pre-positions the neutron modifying material in a ready state within the reactor core, allowing immediate insertion upon loss of coolant flow without waiting for thermal feedback. The actuator uses stored hydraulic pressure to maintain the control assembly in a predetermined position that enables rapid reactivity adjustment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces thermal feedback mechanisms with a hydraulic-mechanical system. Instead of relying on temperature changes to trigger reactivity control, the system uses hydraulic pressure variations caused by coolant flow changes to directly actuate the control assembly, providing immediate mechanical response.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If pump flow loss occurs, then coolant circulation is disrupted, but rapid passive response is needed to avoid adverse temperature effects

Engineering Contradiction:

Improveadverse temperature effectsVSAvoidresponse speed

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

The system implements direct hydraulic feedback where changes in coolant flow pressure are immediately transmitted to the hydropneumatic actuator. The loss of pump flow causes a drop in hydraulic pressure that automatically triggers the actuator to reposition the control assembly, creating a closed-loop feedback mechanism without electronic intermediaries.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent employs a hydropneumatic actuator that uses hydraulic fluid pressure to actuate the control assembly. The system leverages the hydraulic principles where pressure changes in the coolant flow are directly converted into mechanical motion, enabling rapid response to flow disruptions.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Temperature

If neutron modifying material is inserted to control reactivity, then temperature increase is prevented, but electronic control systems may fail or be too slow

Engineering Contradiction:

Improvereactor core temperatureVSAvoidelectronic control dependency

Core Design Contradiction:

TemperatureVSExtent of automation

Solution Approach 1:

The hydropneumatic actuator is designed to autonomously respond to coolant flow changes without external electronic control. The system uses the inherent hydraulic pressure changes from the coolant system itself to actuate the control assembly, making the system self-regulating and independent of electronic power or control systems.

Inventive Principle:

Principle #25Self-service

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 system provides a rapid, passive response to fluid flow disruptions, avoiding adverse temperature effects by quickly adjusting reactivity without the need for electronic control, thus enhancing reactor safety and stability.

Implementation Method 1

a biasing member positioned to apply a biasing force that repositions the first piston, the rod, and the neutron modifying material in response to a loss of pump flow

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Implementation Method 2

using a converging-diverging passage design and a biasing member to apply forces based on fluid pressure variations

Methodology Applied

Scientific EffectConverging-diverging passage: Venturi Effect

Data Source

PatentUS10311983B2Automatic hydropneumatic actuation device

Publication Date: 2019.06.04 TERRAPOWER LLC

AI summary

A control assembly for a nuclear reactor having a pump includes a duct having an inner volume and defining a coolant flow path, a plug fixed to the duct, a rod disposed within the inner volume and having a rod end that is configured to engage a neutron modifying material, a first piston disposed within the inner volume, slidably coupled to the duct, and coupled to the rod, and a biasing member coupled to the rod and the first piston. The biasing member is positioned to apply a biasing force that repositions the first piston, the rod, and the neutron modifying material in response to a loss of pump flow without scram condition.