Sealed Coil Position Sensor for Nuclear Reactor Control Rods
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Solution Overview
Problem
Producing and measuring motion within high-pressure and high-temperature environments, such as in nuclear reactors, is challenging due to access limitations and mechanical stress on components, and existing sensors are costly and not robust enough for reliable operation.
Innovation Solution
A passive sensor system using a sealed electrically conductive coil magnetically coupled with a cam follower, which induces an electrical signal as the cam follower reciprocates, allowing for motion measurement without requiring power and minimizing exposure to harsh conditions, with a minimal number of electrical leads for reduced complexity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a bellows is used to produce motion inside a pressure vessel, then motion can be transmitted through the pressure vessel wall, but the long-term mechanical stress on the bellows leads to component failure
Solution Approach 1:
The patent replaces the mechanical bellows system with an electromagnetic coupling system. A motor disposed inside the pressure vessel uses magnetic fields to transmit rotational motion through the pressure vessel wall to external components, eliminating the mechanical bellows and its associated reliability issues from long-term mechanical stress.
2Ease of operation
If a glandless or glanded mechanical vessel penetration is used, then motion can be transmitted through the pressure vessel wall, but access limitations and mechanical stress problems persist
Solution Approach 1:
The patent replaces mechanical penetration systems with electromagnetic coupling. The motor inside the pressure vessel generates a magnetic field that couples with external magnetic components, allowing motion transmission through the pressure vessel wall without requiring physical mechanical penetrations or glands.
3Reliability
If expensive test sensors are used for motion measurement in high pressure environments, then reliable measurement can be achieved, but cost becomes prohibitive for testing applications
Solution Approach 1:
The patent creates a simplified sensor system that replicates the essential measurement function without requiring expensive components. The sensor uses a permanent magnet and coil arrangement that can be manufactured at lower cost while maintaining reliability for test applications, providing a cost-effective copy of industrial-grade measurement capability.
4Device complexity
If passive sensors with minimal electrical leads are used, then cost and complexity are reduced, but the sensor must still be robust and reliable in harsh environments
Solution Approach 1:
The patent employs a sealed housing that acts as a protective barrier, isolating the internal sensor components (permanent magnet and coil) from the harsh high-pressure and high-temperature environment. This sealed enclosure allows the sensor to maintain simplicity with minimal electrical leads while ensuring robustness through environmental isolation.
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
Enables accurate and reliable measurement of motion in high-pressure and high-temperature environments with reduced mechanical stress and lower costs, suitable for applications like nuclear reactors and other high-pressure systems.
Implementation Method 1
a permanent magnet that is disposed in the unsealed inner volume and is magnetically coupled with the electrically conductive coil... moves the permanent magnet respective to the electrically conductive coil to generate an electrical signal in the electrically conductive coil
Data Source
AI summary
A cam is immersed in water at an elevated temperature and/or pressure. A reciprocating cam follower also immersed in the water contacts a surface of the cam. The cam follower includes a permanent magnet. An electrically conductive coil is magnetically coupled with the permanent magnet such that movement of the cam follower induces an electrical signal in the electrically conductive coil. A sealed housing also immersed in the water contains the electrically conductive coil and seals it from contact with the water. Leads of the coil are electrically accessible from outside the sealed housing and from outside the water. Alternatively, the cam includes magnetic inserts, the cam follower is replaced by a sensor arm of magnetic material, and the sensor arm and/or the inserts are magnetized whereby rotation of the rotary element causes time modulation of the magnetic coupling and induces coil voltage.