A HEAT-SENSITIVE CONTROL ROD SYSTEM CONTAINING THERMOELECTRIC PAINT FOR NUCLEAR REACTORS.

Abstract

The invention relates to a control rod system containing a thermoelectric paint coating, suitable for use in nuclear reactors, which enables monitoring of the operating status of the control rods by sensing temperature changes.

Description

1 TARIFF HEAT-SENSITIVE THERMOELECTRIC PAINT FOR NUCLEAR REACTORS. A CONTROL ROD SYSTEM TECHNICAL FIELD The invention is suitable for use in nuclear reactors, sensing temperature changes to control rods. a control rod containing a thermoelectric paint layer that allows monitoring of the operating status It is related to the system. 10 PREVIOUS TECHNIQUE Nuclear reactors produce heat through controlled chain fission reactions and convert that heat into electricity. These are systems that convert energy into uranium or other fissil fuel rods in the reactor core. These fuel rods are located and the neutron flux around them increases the reactor's power level. It determines the flow of neutrons. Control rods are used to regulate the flow. rods made of neutron-absorbing materials such as boron carbide, hafnium, or cadmium They are produced and placed in specific channels within the reactor core, where they move up and down. This process allows the reactor power to be increased, decreased, or completely shut down. It can be stopped. Therefore, control rods are the most critical for reactor safety. It is one of the components. In current nuclear reactor systems, control rods are used in high-temperature, dense environments. 25 Over time, various structural changes can occur, such as swelling, surface deformation, cracking, wear, and material fatigue. They can be subject to deformations. However, current techniques prevent such structural damage to control rods. a monitoring mechanism that can track changes in the reactor in real time while it is operating None are present. Thermal anomalies in the rods, local heating, increased contact due to friction. or jamming tendencies due to deformation, but physical examination after the reactor is shut down 30 This can be detected during inspections. Therefore, the control stick is used in current systems. loss of function or difficulty in movement, inability to fully perform emergency functions, etc. Risks may not be noticed during the work process. 2 Also, what is generated during the up-and-down movement of the control rods within the reactor channels Temperature variations, friction-induced local heating, or geometric distortions are also present. This cannot be instantly detected in the technology. The operating performance of the control levers. with sensors that can evaluate, monitor structural integrity or detect early faults. One design feature is not found in known control rod structures. These shortcomings affect reactor safety. 5 This indicates a significant technical need. A BRIEF DESCRIPTION OF THE INVENTION The control rods used in current nuclear reactors expose the reactor core to high temperatures, 10 They work under intense radiation, thermal stresses, and neutron bombardment; these harsh conditions Various problems such as swelling, surface deformation, cracking, material fatigue, and shape distortion can occur in the rods. This can lead to structural problems. However, in current control lever designs, these structural issues are addressed. any way to monitor changes in real time while the reactor is operating There is no sensor layer or monitoring mechanism. Thermal anomalies in the rods are localized to 15°C. temperature increases, friction / compression tendencies, or decreases in neutron absorption performance However, this can only be detected during maintenance or when the rod is removed from the reactor. This situation, especially sudden deformations that make control rod movement difficult or neutron absorption safety-critical issues such as reduced capacity may not be detected during operation This is the reason. Therefore, the structural integrity and performance of the control rods are examined in study 20. a sensor that can directly monitor during the process and withstand high temperatures and radiation for extended periods A new, feature-rich control stick system is needed. One aim of the invention is to reduce the thermal expansion and local temperature to which the control rods are subjected during operation. To address technical problems such as increase in temperature, deformation, and surface degradation, thermal changes are 25. a controller that incorporates a thermoelectric paint layer capable of converting an electrical signal The aim is to establish the control rod system. Thus, the structural condition and temperature behavior of the control rod are determined. The reactor can be monitored directly via its electrical output while operating, allowing for early detection of potential malfunctions. Security is increased by this method. Another objective of the invention is to detect heat transfer from the external environment to the layer that acts as a sensor. thermoelectric layer to prevent degradation by convection and conduction effects a control rod system containing a vacuum intermediate zone that provides thermal insulation around it This aims to improve the stability of temperature measurements and reduce the effects of unwanted heat fluxes. The sensitivity and accuracy of the resulting electrical signal are minimized and increased. 35 3 Another aim of the invention is to address the high temperature, radiation, and mechanical stresses in the reactor core. To reduce deformations that may occur in the inner control rod due to stresses, the inner a control rod system that includes an external rod structure protecting and stabilizing the rod. The goal is to minimize risks such as friction, jamming, intra-channel contact, and geometric distortion. This reduces the need for manual operation; the stability, reliability, and service life of the control lever are increased. 5 BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a schematic representation of a multiple control rod array in a nuclear reactor core. is given. 10 Figure 2 shows the different outer rod diameters of the inner rod coated with thermoelectric paint (1.6 cm, 1.8 cm and Experimental studies showing the output voltage values ​​produced in the temperature range of 50–100°C below 2.0 cm. The results graph is shown. DETAILED DESCRIPTION OF THE INVENTION This detailed description explains that the invention is a control rod suitable for use in nuclear reactors. It is related to the system and has no limiting effects, only contributing to a better understanding of the subject. This is explained with examples that will not create a problem. 20 The control rod system described in the invention is subjected to high temperatures inside the reactor core. changes that occur under temperature, radiation, thermal stresses, and mechanical stresses In order to be perceived, it must have at least one internal rod and at least one external rod surrounding this internal rod. a thermoelectric paint layer positioned between this inner and outer bar and this layer 25 It includes a surrounding vacuum space. This structure arises in the control rod system. By converting temperature differences and thermal anomalies into electrical signals, the rod's operation is controlled. It makes it possible to monitor their performance in real time. As shown in Figure 1, the inner rod, one of the basic components of the control rod system, is 30 By performing neutron absorption in the reactor core, it helps regulate reactor power. It is the main active element that plays a direct role. If preferred, the inner rod is boron carbide. Made from cadmium, hafnium, or similar materials with neutron-absorbing properties. The scope of protection of the invention depends on the material from which the inner rod is made. It is independent. The reactor environment involves high temperature, intense neutron flux, gamma radiation, and thermal 35. Because it is directly exposed to stresses and mechanical strains, the inner rod has a high melting point. 4 to the point, low deformation tendency, dimensional stability under radiation and long-term It is configured to provide structural integrity. Another important component of the control rod system within the scope of this invention is the external rod. The external rod, The high temperature, intense neutron flux, gamma radiation, and mechanical stress in the reactor's core region. It is a housing structure that physically protects the inner rod against friction conditions. It is preferred. In this case, the outer bar shall be made of at least one of the following groups: stainless steel or zirconium-based alloys. It can be manufactured. Because there is a vacuum space between the inner and outer rods, the outer rod an external boundary surface that ensures the continuity of thermal insulation and protects the integrity of the system It serves as a mechanical support. 10 A vacuum intermediate zone is to be positioned between the aforementioned inner rods and outer tines. The vacuum space in question has a pressure range of 10⁻² to 10⁻⁶ torr. This vacuum intermediate zone greatly reduces heat transfer, connecting the thermoelectric paint layer to the external environment. 15 that can occur between (reactor channel wall, coolant or outer rod casing). It minimizes heat transfer through convection and conduction. Thus, The thermoelectric paint layer responds only to actual temperature fluctuations transmitted through the inner rod. This ensures accurate readings and prevents measurement errors caused by external factors. Vacuum intermediate The presence of this region allows for a sharper, more stable, and more accurate depiction of the thermal changes occurring in the inner rod. By enabling the transfer of the sensor function to a thermoelectric paint layer, the sensitivity of the sensor function is increased by 20. It increases. The control rod system within the scope of this invention incorporates a thermoelectric paint layer. This layer is applied to the outer surface of the inner rod. This layer is the inner rod in the reactor core. by converting the thermal changes occurring on it into electrical voltage via the Seebeck effect 25 The actual temperature behavior and structural condition of the control rod system during operation. It enables timely monitoring of conditions such as high temperature, radiation, and chemical corrosion. It is formulated to operate stably for extended periods under heavy reactor conditions. The layer is a application in the form of a thin film ranging from a few hundred microns to a few millimeters, coming from the inner rod By enabling rapid and linear heat transfer across the layer, high temperature differences are achieved. 30 It ensures that the signal is accurately converted into an electrical signal. The thermoelectric paint layer also... Since it is surrounded by a vacuum interstitial zone, it is protected from heat fluxes and convective effects from the external environment. This blocks the electrical signal produced by the layer, thus only affecting the actual thermal conductivity in the inner rod. It corresponds to changes. Thanks to this structure, the thermoelectric paint layer, control rod the system's deformation tendencies, abnormal temperature increases, friction-induced local 35 Heating and structural degradation that could affect neutron absorption performance during operation It acts as a highly sensitive sensor layer capable of direct detection. To achieve all of the aforementioned, the thermoelectric paint layer incorporates its essential functions. It contains at least one thermoelectric component that provides this function. This thermoelectric component is Bi- Sb-Te based compounds, Cu-Ag-Se based compounds, Pb-Se-Te based compounds, oxide based compounds thermoelectric compounds, Si-Ge based alloys, zinc phase based compounds, clathrate, Half-Heusler type The compounds may contain at least one compound from the skutteride type group. Thermoelectric component 5 Its primary function is to maintain the temperature difference between the inner and outer rods under reactor operating conditions. An electrical potential difference is created when charge carriers migrate within the material. The aim is to bring about this. Thanks to this mechanism based on the Seebeck effect, the thermoelectric element is cheerful, control rod an active system that converts thermal changes occurring on the surface of the system directly into electrical signals. It acts as a sensor and thus monitors the thermal condition of the control rod system during operation. This makes it possible to monitor their behavior. The thermoelectric paint layer incorporates electrical conductivity to increase the electrical conductivity of the thermoelectric compound. at least one conductor to ensure that the potential difference it produces is efficiently transmitted across the surface. It contains a conductive phase. This conductive phase must be at least one of the following groups: graphite, graphene, black carbon, or activated carbon. This is possible. This conductive phase is homogeneously distributed in the paint matrix. High surface area, Thanks to its high electrical conductivity and thermal stability properties, this conductive phase is thermoelectric. It facilitates the transmission of the voltage difference created within the paint layer, ensuring the integrity of the layer. It enhances electrical performance and contributes to increased sensor sensitivity. The thermoelectric paint layer also structurally combines the thermoelectric component and the conductive phase. at least one binder to hold and provide a strong adhesion to the surface of the control rod system. It contains a binding component, namely sodium silicate, potassium silicate, or a combination thereof. It contains a mixture. The binder component functions as a high-temperature resistant, glass-like substance. Thanks to its hardening properties and chemical stability, it offers thermal and mechanical resistance under reactor conditions. It ensures the preservation of integrity. The silicate binder adheres to the surface of the thermoelectric paint layer. it spreads evenly, forms a strong adhesion with the rod surface, and is thermoelectric. It contributes to the mechanical protection of conductive paths. The thermoelectric paint layer created by combining these components enables the reactor to operate at 30°C. High temperature resistance, chemical stability, and electrical conductivity that allow it to adapt to various conditions. and creates an integrated sensor structure that offers thermoelectric sensitivity. Thermoelectric This multi-component structure of the paint layer allows for the generation of voltage due to the thermoelectric effect, and This enables the efficient transmission of this voltage to the external connection elements. Similarly Over time, the thermoelectric paint layer is applied to the surface of the control rod system for a long period of 35 days. It ensures that it holds together and maintains its integrity under mechanical stress. 6 The components used in thermoelectric paint coatings have been previously defined in different technical fields. This has been discussed in detail in two main patent documents, with application number 2023 / 011975. The first document presented describes n- and p-type Bi–Sb–Te based thermoelectric compounds, graphite doping, and Regulations concerning the assembly of sodium silicate binders in paint form. It explains. The other patent document with application number 2025 / 002919, the second thermoelectric 5 The paint application text expands these components to include chalcogenide types such as Cu–Ag–Se and Pb–Se–Te. The use of skutterudite and half-Heusler type advanced thermoelectric materials, as well as sodium and potassium silicate mixtures as a binding phase providing high temperature resistance. The subject of this discussion is the evaluation of the thermoelectric paint components mentioned in these two techniques. Carbon-based conductive phases and silicate binders, material composition of thermoelectric paint 10 These are known elements in this respect. However, thermoelectric paint is described in existing patents. Their compositions are designed solely for surface coating or energy recovery applications, regarding their use for integration into nuclear reactor components or for in-reactor thermal monitoring purposes It does not involve any regulation. The main novelty of this invention lies in the fact that it has not been used in different contexts before. These thermoelectric paint formulations, described above, were first applied to a nuclear control rod system in 15 integrated as a sensor layer and formed between the inner and outer rods in the reactor core It is used to monitor the thermal behavior of thermoelectric components in real time. The Seebeck effect transfers the voltage-generating capacity to the control rod surface, thus controlling it. The rod system directly addresses problems such as deformation, increased friction, or thermal abnormalities. The ability to generate electrical signals, a capability not found in existing techniques and exclusive to this invention, is possible. It is an original arrangement that has been introduced. In the control rod system within the scope of the invention, the sensor function of the thermoelectric paint layer is fundamental. It operates using a Seebeck mechanism. The Seebeck mechanism is a mechanism that utilizes a thermoelectric material. When a temperature difference occurs between the two ends, electron or hole carriers within the material become hotter. an electrical voltage is generated as a result of movement from a cold region to a cold region. It is based on the principle of neutron absorption in the reactor core by the control rod system. Due to heating, the inner surface of the thermoelectric paint layer applied to the inner rod surface becomes more... It reaches a high temperature. The thermoelectric paint layer faces the vacuum interface on the outside. The surface, being isolated from external influences, remains at a lower temperature. Thus, the paint 30 A temperature gradient (ΔT) is formed across the layer. This temperature difference creates a thermoelectric paint. It initiates heat-induced carrier flow in thermoelectric compounds located within the layer. In n-type materials, electrons move from the hot side to the cold side, while in p-type materials, positive charge carriers move from the hot side to the cold side. It is moving towards one side. The movement of these carriers is measurable between the two ends of the layer. It creates a DC potential difference. The magnitude of the voltage produced depends on the thermoelectric 35 used. This depends on the Seebeck coefficient of the material and the magnitude of the temperature difference across the layer. Thanks to this inherent physical behavior of the Seebeck mechanism, the thermoelectric paint layer is controlled. 7 The temperature changes occurring in the rod system are converted into an instantaneous and linear electrical signal. by transforming it, information about the structural condition, motion behavior and thermal stability of the control rod. It provides real-time monitoring capabilities. The working principle of this system is as follows: The control stick consists of two interlocking sticks. 5 It is formed and the outer rod is the first component to be directly exposed to the neutron flux in the reactor core. Therefore, the outer bar is subject to higher temperatures over time, increasing the risk of deformation and material degradation. It is more susceptible to degradation compared to the inner rod. The inner rod, on the other hand, remains at a lower temperature. It acts as a relatively stable reference surface. Between these two rods, a bonding agent is provided. and a thermoelectric paint layer that senses the temperature difference. Thermoelectric paint 10 the layer in direct contact with the inner surface of the outer rod and the outer surface of the inner rod, creating a gap between them. sealing the vacuum gap and acting as a mechanical connector and thermoelectric sensor between the two rods. It performs the function of an outer rod through neutron absorption and radiation effects while the reactor is operating. The inner rod begins to heat up; the inner rod, however, remains at a lower temperature. Thus, a natural interaction occurs between the two surfaces. A temperature difference is created. The thermoelectric paint layer converts this temperature difference into 15 degrees Celsius using the Seebeck effect. It converts the generated voltage into electrical voltage. The generated voltage is then transmitted through thermal changes on the outer rod surface. They are directly proportional. Deformation, swelling, increased friction, and neutron absorption in the outer rod. When disruptions such as a decrease in capacity occur, local temperature increases happen, and The paint layer instantly detects these changes as a louder or more irregular electrical signal. It produces thermoelectric paint. The vacuum intermediate zone prevents heat transfer from the outside environment to the inside. 20 the layer only responds to the actual temperature difference between the outer and inner rods This allows measurement of the coolant, guide channel wall, or other thermal conductivity of the reactor. It becomes independent of the effects. Thanks to this structure, the monitoring system monitors the thermal activity in the outer rod. It detects anomalies in real time and alerts the operator to possible deformation and jamming tendencies. or can provide warnings about situations such as performance loss before the reactor is shut down. 25 The control rod system covered by the invention is located in the fuel core of a nuclear reactor. vertically in the channels of the special control rod system between the bundles They are positioned. Depending on the reactor design, each control rod system is located at the top. It is lowered into the core via a control rod drive mechanism (CRDM) or 30 It can be pulled upwards. Inner rod, thermoelectric paint layer, vacuum spacer and outer rod. The entire composite structure, consisting of its components, is designed to fit a standard control stick geometry in a single form. It is placed inside these channels as an integrated module. The control rod system controls the reactor. Because it operates within the region through which the coolant flows, the outer rod surface is exposed to the coolant flow. It is exposed to hydrodynamic effects and radiation fields. However, thermoelectric paint 35 Because the layer and vacuum intermediate zone are located on the inner side facing the inner rod, they are protected from the coolant flow. It is isolated from thermal and mechanical effects. The control rod system regulates the neutron flux of the reactor. 8 Because it is inserted into and removed from the core for the purpose of regulation, the control stick moves vertically during this process. all components of the system, especially the outer rod and vacuum spacer, intra-core contact, and friction. and is designed to withstand thermal imbalances. Thus, the control rod system It performs the traditional neutron absorption task and, in its operating position, the thermal and It offers the possibility to monitor its structural behavior in real time. 5 To evaluate the technical specifications of the control rod system obtained within the scope of the invention. A test setup was created for this purpose. A glass stirring rod with a diameter of 6 mm was used to represent the inner rod, and thermoelectric paint layer on the surface (Bi2Te2.7Se0.3 / wt%2Cu for n type and also for p type) It is coated with Sb1.5Bi0.5Te3. The drumstick has 1.6 cm, 1.8 cm and 2.0 cm diameters, representing the outer bar in the model. They are placed inside glass tubes of varying diameters. These tubes are designed to prevent swelling or other issues that may occur in the reactor environment. Deformation scenarios were selected to simulate the conditions. All models were used in hot water at 50–100°C. It was tested inside and the output voltage produced by the thermoelectric paint was measured. The results depend on the tube diameter. It has been shown that as the voltage increases, the voltage obtained at the same temperature decreases significantly. 1.6 cm diameter The signal, reaching approximately 300 mV in the tube, was halved at 1.8 cm, and approximately 50 mV at a diameter of 2.0 cm. It has decreased to the mV level (shown in Figure 2). With the increase in diameter, the inner and outer rods... Increasing the distance between the tubes reduced the temperature difference and the stress produced by the Seebeck effect. This has led to its weakening. The results obtained show that the control rod system is deformed and jammed. or that it can clearly detect changes in thermal behavior via the thermoelectric output. This confirms the experiment. Although the experimental setup is simple, the thermoelectric paint layer on the rod 20 It can precisely distinguish changes in its geometry, and the proposed sensor-equipped control rod its structure is technically feasible for real-time monitoring in nuclear reactors has shown. The scope of protection of the invention is specified in the claims attached hereto and is absolutely not included in this detailed description. 25 It cannot be limited to what has been described for illustrative purposes. Because a person who is an expert in the field can understand the main aspects of the invention. without deviating from the theme, it can create similar structures in light of what has been described above. It is clear.

Claims

9 REQUESTS 1. A control rod system for a nuclear reactor, characterized by: It must contain at least one internal control rod to enable neutron absorption, and this internal control 5 applied to the outer surface of the rod to convert the temperature difference into electrical voltage. It is a thermoelectric paint that contains at least one suitable thermoelectric component, the paint layer in question surrounds and allows heat transfer by conduction and convection. a vacuum-reducing intermediate zone and at least one external element located outside the vacuum-reducing intermediate zone It contains a rod. It detects the electrical voltage generated in thermoelectric paint and transmits it to an external measuring unit. It must contain at least one suitable electrical connection component.

2. A control rod system conforming to Claim 1, the feature of which is; the thermoelectric paint in question. It contains Bi-Sb-Te based compounds and Cu-Ag-Se based compounds as thermoelectric components. compounds, Pb-Se-Te based compounds, oxide-based thermoelectric compounds, Si-Ge based 15 alloys, zinc phase-based compounds, clathrate, Half-Heusler type compounds, skutteride type It must contain at least one of the following compounds:

3. A control rod system conforming to claim 1 or 2, featuring thermoelectric paint. It contains at least one conductive phase, and this conductive phase can be graphite, graphene, or black 20. It must contain at least one of the carbon or activated carbon groups.

4. A control rod system conforming to any of claims 1-3, and having the characteristic of being thermoelectric. The paint contains at least one ingredient including sodium silicate, potassium silicate, or a mixture thereof. It contains a binding component. 25 5. A control rod system conforming to any of requirements 1-4, and having the characteristic of being thermoelectric. The paint contains Cu-doped Bi₂Te₂.₇Se₀.₃ or Sb₁.₅Bi₀.₅Te₃ as a thermoelectric component. at least one of its compounds, graphite as the conductive phase and sodium silicate as the binder. It includes. 30 6. A control stick system conforming to any of requirements 1-5, the feature of which is; the outer stick It must be either a zirconium-based alloy or a type of stainless steel.

7. A control stick system conforming to any of requirements 1-6, and having the following characteristics: 35 electrode, conductive film, conductive strip or conductive coating as an electrical connection component It must include at least one of the following groups.

8. A control stick system conforming to any of claims 1–7, featuring: internal It consists of two rods positioned inside each other, a main rod and an outer rod. and the thermoelectric paint layer will be placed between these two rods the fact that it is regulated and the outer rod with the thermoelectric paint layer in question The presence of a vacuum between them. 5

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