Mechanical Unlatching Tool for Pressurized Water Reactor Control Rods
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Solution Overview
Problem
Existing control rod drive shaft (CRDS) unlatching tools in pressurized water reactors (PWRs) require nitrogen/air power, necessitate two personnel for operation, and are prone to flooded air cylinders, leading to increased setup time, consumables, and refurbishment needs, especially when used in flooded reactor cavities.
Innovation Solution
A mechanically actuated unlatching tool that uses a gripper assembly and a mechanical actuator to grip and raise the control rod drive shaft button, allowing single-operator operation and eliminating the need for nitrogen/air power, thus enabling safe operation in flooded conditions with reduced setup time and refurbishment requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If nitrogen-powered air cylinders are used to actuate the unlatching tool, then the tool can automatically grip and raise the control rod drive shaft, but the tool becomes susceptible to flooding, requires setup time for nitrogen supply, and needs regular refurbishment
Solution Approach 1:
The patent replaces the pneumatic system (air cylinders powered by nitrogen) with a purely mechanical actuation system. The mechanical actuator uses a screw mechanism with a motor-driven lead screw to convert rotational motion into linear motion for gripping and raising the control rod drive shaft, eliminating all pneumatic components that are vulnerable to flooding.
Solution Approach 2:
The patent removes the nitrogen supply system and air cylinder components from the unlatching tool, extracting the harmful pneumatic elements that require setup time and are susceptible to flooding while retaining the essential gripping and raising functions through mechanical means.
2Extent of automation
If nitrogen-powered air cylinders are used for unlatching operations, then the tool can perform automatic actuation, but two personnel are required for operation and setup time increases
Solution Approach 1:
The patent combines the functions of nitrogen supply management, tool actuation control, and operational control into a single integrated mechanical system. The motor-driven lead screw mechanism automatically converts electrical signals into mechanical motion, merging multiple operational steps into one automated sequence that can be controlled by a single operator through simple electrical switches.
3Extent of automation
If nitrogen supply infrastructure is provided for unlatching tools, then automatic actuation is enabled, but consumables are required and refurbishment needs increase
Solution Approach 1:
The patent substitutes the pneumatic actuation system with an electrical-mechanical system using a motor-driven lead screw. This replacement eliminates the need for nitrogen consumables entirely, as the electrical motor converts electrical energy directly into mechanical motion through the lead screw mechanism, removing all associated consumable requirements.
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 tool allows for efficient and safe single-operator operation of CRDS unlatching and re-coupling, reducing manpower and setup time, and eliminating the risk of flooded air cylinders, thereby simplifying refueling processes and minimizing tool refurbishment needs.
Implementation Method 1
a mechanical actuator fixed to the base and configured for raising and lowering the gripper assembly
Implementation Method 2
a rod movably connecting the gripper assembly to the base
Data Source
AI summary
An unlatching tool configured for actuating a movable section of a control rod drive shaft in a pressurized water reactor includes a base; a gripper assembly configured for gripping the movable section of the control rod drive shaft; a rod movably connecting the gripper assembly to the base; and a mechanical actuator fixed to the base and configured for rotating the rod to raise and lower the gripper assembly. A method for actuating a movable section of a control rod drive shaft includes installing an unlatching tool on the control rod drive shaft; latching the unlatching tool to a stationary section of the control rod drive shaft; and raising a rod connected to a gripper assembly to cause the gripper assembly to grip the movable section and move the movable section upward.