Terminal Weighting Element for Nuclear Reactor Control Rod SCRAM
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Solution Overview
Problem
Existing control rod/CRDM coupling assemblies in nuclear reactors face challenges in achieving rapid and reliable SCRAM due to hydraulic resistance and limited surface area for attachment, which can slow down the control rod's descent into the reactor core during an emergency shutdown.
Innovation Solution
The introduction of a terminal weighting element with a denser material filler, such as tungsten, and elongation in the SCRAM direction to increase weight and surface area, reducing hydraulic resistance while enhancing the speed and reliability of the gravitationally-induced SCRAM process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a traditional spider structure is used to couple control rods with the connecting rod, then the device complexity is reduced and ease of manufacture is improved, but the surface area for attachment is limited and hydraulic resistance increases during SCRAM
Solution Approach 1:
The patent transitions from a two-dimensional spider structure to a three-dimensional terminal weighting element with cavities filled with heavy material. This dimensional change increases the effective surface area and volume without proportionally increasing hydraulic resistance, as the heavy material is contained within cavities rather than forming solid external surfaces.
Solution Approach 2:
The terminal weighting element incorporates cavities nested within its structure that are filled with heavy material. This nesting approach allows the heavy material to be contained within the terminal element without increasing the external dimensions that would contribute to hydraulic resistance during SCRAM.
2Productivity
If the spider structure is enlarged to provide more attachment surface area, then the attachment capacity is improved, but the hydraulic resistance during SCRAM increases and slows down control rod descent
Solution Approach 1:
The patent changes the density parameter by introducing heavy material (such as tungsten or depleted uranium) with density significantly higher than stainless steel. This allows the terminal weighting element to achieve the necessary weight for rapid SCRAM without increasing the external dimensions that would create hydraulic resistance.
Solution Approach 2:
The terminal weighting element is constructed as a composite structure combining stainless steel casing with heavy material filler. This composite approach provides both the structural integrity of stainless steel and the high density of the heavy material, achieving optimal SCRAM performance without excessive hydraulic resistance.
3Weight of moving object
If heavy material filler is added to the terminal weighting element, then the weight is increased to improve SCRAM speed, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The terminal weighting element is segmented into a stainless steel casing and separate heavy material filler. This segmentation allows the heavy material to be inserted into pre-formed cavities after the stainless steel structure is manufactured, simplifying the overall manufacturing process compared to creating monolithic heavy material components.
Solution Approach 2:
The stainless steel casing acts as an intermediary structure that contains and protects the heavy material filler. This intermediary approach allows the heavy material to be handled and positioned separately during assembly, reducing manufacturing complexity while achieving the desired weight.
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 enhanced weight and surface area provided by the terminal weighting element improve the speed and reliability of the SCRAM process, offsetting increased hydraulic resistance and ensuring rapid control rod insertion during emergency shutdowns.
Implementation Method 1
the control rod, the connecting rod, and the integral or connected spider fall together toward the reactor core (with the control rod actually entering into the reactor core)
Implementation Method 2
The filler comprises heavy material having a higher density than a material comprising the casing
Implementation Method 3
the introduction of a terminal weighting element with a denser material filler, such as tungsten, and elongation in the SCRAM direction to increase weight and surface area, reducing hydraulic resistance
Data Source
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AI summary
A nuclear reactor includes a pressure vessel, and a control rod assembly (CRA) including at least one movable control rod, a control rod drive mechanism (CRDM) for controlling movement of the at least one control rod, and a coupling operatively connecting the at least one control rod and the CRDM. The coupling includes a connecting rod engaged with the CRDM and a terminal element connected with a lower end of the connecting rod and further connected with the at least one control rod. In some embodiments the terminal element includes a first portion comprising a first material having a first density and a second portion comprising a second material having a second density that is greater than the first density. In some embodiments the terminal element has a largest dimension parallel with the connecting rod that is greater than or equal to a largest dimension transverse to the connecting rod.