Nuclear Control Drum Rotation Apparatus with Gravity Bias

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Solution Overview

Problem

Nuclear reactors with control drums reliant on stepper motors for operation face risks during emergency shutdowns and transportation due to potential electrical power loss, which can lead to unintended reactor startups or failures.

Innovation Solution

A rotation apparatus with a mechanism that biases the control drum shaft towards a shutdown position using a counterweight and permanent magnets, and a rotation management system including an eddy current brake and lock, allowing the control drum to automatically transition to a shutdown position without electrical power and maintain it during transport.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If stepper motors are used to rotate the control drum, then the control drum can be positioned to face the reflector portion toward the core for operational state, but electrical power loss causes loss of control and potential unintended startup

Engineering Contradiction:

Improvecontrol drum positioningVSAvoidcontrol maintenance during power loss

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A counterweight mechanism is attached to the control drum shaft that automatically rotates the shaft to a predetermined position (with absorber portion facing the core) when electrical power is lost. The counterweight uses gravitational force to overcome the stepper motor's holding torque, ensuring the control drum assumes a safe shutdown configuration during power failure or transport conditions.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Adaptability or versatility

If the control drum is designed to transport between locations, then mobility is improved, but the risk of unintended startup increases if the reflector portion inadvertently faces the core during transport

Engineering Contradiction:

Improvetransport capabilityVSAvoidunintended reactor startup

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The counterweight mechanism is pre-configured to automatically position the control drum shaft in a safe configuration (absorber portion facing the core) before transport begins. This preliminary action ensures that even if power is lost during loading, unloading, or transport, the control drum cannot inadvertently cause reactor startup, as the safe configuration is established in advance.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If stepper motors maintain control drum orientation, then operational control is achieved, but the motors cannot prevent rotation during power loss

Engineering Contradiction:

Improvecontrol drum orientation controlVSAvoidelectrical power dependency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The counterweight mechanism serves itself by using the gravitational force naturally acting on the control drum shaft to automatically reposition it during power loss. No additional energy source or active control system is required—the mechanism exploits the existing gravitational field and the mass distribution of the control drum assembly to achieve automatic safe positioning.

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

Ensures rapid and reliable shutdown of the nuclear reactor in case of power loss and maintains the shutdown state during transport, preventing unintended startups and ensuring safety.

Implementation Method 1

a rotation mechanism that is structured to apply to the shaft in an operational position a force that biases the shaft to rotate toward a shutdown position

Methodology Applied

Scientific EffectGravity: Gravitation

Implementation Method 2

a rotation management system that controls the rotation of the shaft

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Data Source

PatentUS11373766B2Rotational apparatus usable with control drum apparatus in nuclear environment

Publication Date: 2022.06.28 WESTINGHOUSE ELECTRIC CORP

AI summary

A rotation apparatus is usable with a control drum in a nuclear environment. The control drum is situated on a shaft that is rotatable about a horizontal axis of rotation, and the control drum includes an absorber portion and a reflector portion. The rotation apparatus includes a rotation mechanism that is structured to apply to the shaft in an operational position a force that biases the shaft to rotate toward a shutdown position, with the force being resisted by a motor to retain the shaft in the operational position when the motor is powered. The force is not resisted when the motor is unpowered. The rotation apparatus further includes a rotation management system that controls the rotation of the shaft.