Nuclear Reactor Control Rod Drop Impact Absorption
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Solution Overview
Problem
Control rods in nuclear reactors are prone to structural damage and reduced lifespan due to drop impact during free fall, which can lead to operational issues and maintenance challenges.
Innovation Solution
An apparatus comprising a fixed frame and an impact absorbing device with a main cylinder, piston, and piston rod, which uses water flow to maintain a constant drop speed and reduce impact by controlling the discharge of water through strategically designed holes and gaps, thereby minimizing the force of the control rod's impact upon insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the control rod is allowed to drop freely to quickly stop the reactor, then the shutdown speed is improved, but the control rod suffers structural damage due to drop impact
Solution Approach 1:
The patent applies beforehand cushioning by providing a buffer chamber filled with water at the bottom of the guide tube before the control rod drops. This water cushion absorbs the impact energy when the control rod reaches the end of its drop, preventing structural damage while maintaining quick shutdown capability. The buffer chamber is pre-prepared with appropriate water level and pressure to cushion the impact.
Solution Approach 2:
The patent uses water as an intermediary substance between the control rod and the guide tube bottom. The water acts as a mediator that transfers and dissipates the impact energy through compression and flow, rather than allowing direct rigid contact. This intermediary fluid cushioning mechanism protects the control rod structure while enabling rapid insertion.
2Loss of time
If the control rod drops quickly to insert into the core, then the reactor shutdown time is reduced, but the drop impact force increases causing damage
Solution Approach 1:
The buffer chamber is pre-filled with water at an optimized level and pressure before the control rod drop. This beforehand preparation ensures that when the control rod reaches the end of its rapid drop, the water cushion is already in position to absorb the impact force, minimizing both shutdown time and impact damage.
Solution Approach 2:
The patent changes the physical parameters of the cushioning medium by using water with specific density, compressibility, and flow characteristics. The water column height, pressure, and temperature are optimized to provide the right balance between allowing rapid rod insertion and absorbing impact force. The parameter optimization enables quick shutdown while limiting impact force.
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 apparatus effectively reduces the drop impact of control rods, maintaining a consistent drop speed and preventing structural damage, thus enhancing the control rod's lifespan and operational reliability.
Implementation Method 1
uses water flow to maintain a constant drop speed and reduce impact by controlling the discharge of water through strategically designed holes and gaps
Implementation Method 2
An apparatus comprising a fixed frame and an impact absorbing device with a main cylinder, piston, and piston rod, which uses water flow to maintain a constant drop speed and reduce impact by controlling the discharge of water through strategically designed holes and gaps
Data Source
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AI summary
There is provided an apparatus for drop impact absorption of a control rod of a nuclear reactor that can maintain the appropriate drop speed during the free drop of the control rod to quickly stop the operation of the nuclear reactor, and can reduce the drop impact of the control rod that occurs at the last stage when the control rod drops. An apparatus for drop impact absorption of a control rod of a nuclear reactor according to an aspect of the invention includes a fixed frame disposed at an upper side of the core of the nuclear reactor, and a impact absorbing device installed at the fixed frame to reduce the drop impact with respect to a control rod mounted at the lower part during the free drop of the control rod to be inserted into the core of a nuclear reactor.