Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-07-14
Abstract： [Background]: In pursuit of promoting the diversified development of energy cooperation demands among countries participating in the Belt and Road Initiative and address the demand for secure and efficient energy supply along the Belt and Road Economic Belt, Xi'an Jiaotong University has actively innovated and proposed a small modular fluoride-salt-cooled high-temperature advanced reactor FuSTAR. [Purpose]: Although the conceptual design of FuSTAR has been completed, the reactor's ability to operate with load tracking and its safety are still need to be verified. [Methods]: The FuSTAR system was modeled and calculated by using VITARS software for detailed thermal-hydraulic and control system modeling, and its anti-interference characteristics and load operation tracking capability were analyzed in depth. [Results]: FuSTAR has demonstrated load tracking capability without relying on an external control system, mainly due to its inherent safety features, which allow the reactor to self-stabilize and regulate under load variations. With the adoption of a constant coolant outlet temperature control scheme, the load tracking capability of FuSTAR has been further enhanced. In the tests of 10% FP load step change and 5% FP/min rate linear load rise and fall, the overshoot of nuclear reactor power is strictly controlled within 5%. [Conclusions]: Because of the negative temperature reactivity feedback and the existence of control system, the small fluoride-salt-cooled high-temperature reactor has a good load tracking ability, which fully meets the requirements of safe operation of the reactor.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-07-02
Abstract： [Background] CF series fuel assemblies are the core components of nuclear power independently developed by China National Nuclear Corporation(CNNC), which together with the drive mechanism, constitute an important part of a large pressurized water reactor. And they are related to the stability and safety of nuclear reactor operation. [Purpose] The development of any fuel assembly and related equipment must undergo friction and rod drop test to verify its structural integrity and the property. The experimental study has been carried out for analyzing the friction and rod drop performance of the drive line’s moving parts of the self-developed CF2 fuel assembly under water and air working conditions with different eccentricity. [Methods] The traditional friction and rod drop performance test can only be carried out with small eccentricity to obtain the test data such as friction force and rod drop curve. It can't be achieved to analyze and study the performance with multiple eccentricities, especially the larger eccentricity. And there are no more studies on comparative mechanical analysis of the friction force of the driving mechanism through full displacement and in the two media of water and air. a 1:1 simulated CF2 fuel assembly was used in the test with an independently-developed rotatable top cap. The integration of multiple eccentricity was initially implemented for scientific and accurate regulation. The method to study the performance of the driving mechanism was optimized. The friction force and rod drop performance data were obtained through the experiments of the driving mechanism in water and air through full displacement and under different eccentric conditions. [Results] The control rod has been uniformly raised from the lowest to the highest position in the air at an ambient temperature of 22°C and with an eccentricity of 4.67 mm, 6.0 mm and 9.4 mm, respectively. When the eccentricity is 4.67 mm, the friction force at the lowest and highest positions is 26.5 N and 32.1 N, respectively. And when the eccentricity is 9.4 mm, the friction force at the lowest and highest position is 37.1 N and 39.2 N, respectively. Then the control rod has been uniformly raised from the lowest to the highest position in the static water at a temperature of 18°C and with an eccentricity of 4.67 mm, 6.0 mm and 9.4 mm, respectively. The friction force at the lowest position and the highest position is 54.8 N and 39.5 N respectively when the eccentricity is 4.67 mm. When the eccentricity is 9.4 mm, the two force values in the water are 62.8 N and 44.1 N, respectively. As the control rod is gradually raised, the friction force in the air increases much more than that in static water. The maximum value in the air occurs at the highest position, while the maximum value in static water occurs at the lowest position. By comparing and analyzing the rod drop performance and parameters like velocity, displacement and vibration, it can be seen that with the continuous increase of the eccentricity, the friction during rod operation also increases correspondingly, and the maximum speed during rod drop gradually decreases. The data shows that the impact of the various eccentricities on the buffer time is small and the value can be basically consistent. The minimum rod drop time occurs when the eccentricity is 0 mm. The time for control rod reaching to the buffer port is 1.049 s, and the time reaching to the bottom is 1.477 s. [Conclusions] The centering work has been successfully completed by using the self-developed top cap, which changes the traditional drive mechanism centering way. It’s an innovation for fast centering with multiple eccentricities, and it greatly improves the test efficiency and reduces the test cost. The numerical comparison of friction force between in the air and static water through full displacement and under multiple eccentricities has been carried out, which expands the research scope in this field. Through multiple friction and rod drop performance tests, the fuel assembly and control rod run well, the friction does not exceed the limit value, and no jamming of the rod occurs under the maximum eccentric condition. It can verify the rationality of the design of CF2 fuel assembly, and provide an important test basis for the design, safety evaluation and software development of this series fuel assemblies.
Key words CF2 fuel assembly, Rod Drop Performance, Friction
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-29
Abstract： [Background]: CF series fuel assemblies are the key reactor-core components of the advanced third-generation nuclear power, which are independently developed by China National Nuclear Corporation(CNNC). [Purpose]: The purpose is to analyze the friction force and rod drop performance of CF2 fuel assembly combined control rod drive line moving parts in water and air under different eccentricity. [Methods]: a 1:1 simulated fuel assembly was used in the test with an independently-developed rotatable top cap. The integration of multiple eccentric was initially implemented for scientific and accurate regulation. [Results]: The method to study the performance of the driving mechanism was optimized. The friction force and rod drop performance data of the driving mechanism in water and air at different heights and under different eccentric conditions were obtained. The total rod drop time and the time for rod reaching the buffer increased with the increase of eccentricity while the buffer time was basically constant. The fuel assembly and control rod functioned properly under the maximum eccentricity. The friction did not exceed the allowable limit. And no jamming of control rod occurred under large eccentric condition. [Conclusions]: The experimental results provide an important experimental basis for the design optimization , safe evaluation and software development of CF fuel assembly. The method can be extended to the subsequent CF3 and other fuel assembly scientific research projects.
Key words CF2 fuel assembly, Rod Drop Performance, Friction
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-26
Abstract： [Background]: CF series fuel assemblies are the key reactor-core components of the advanced third-generation nuclear power, which are independently developed by China National Nuclear Corporation(CNNC). [Purpose]: The purpose is to analyze the friction force and rod drop performance of CF2 fuel assembly combined control rod drive line moving parts in water and air under different eccentricity. [Methods]: a 1:1 simulated fuel assembly was used in the test with an independently-developed rotatable top cap. The integration of multiple eccentric was initially implemented for scientific and accurate regulation. [Results]: The friction force and rod drop performance data in water and air at different heights and under different eccentric conditions were obtained. The total rod drop time and the time for rod reaching the buffer increased with the increase of eccentricity while the buffer time was basically constant. The fuel assembly and control rod functioned properly under the maximum eccentricity. The friction did not exceed the allowable limit. And no jamming of control rod occurred under large eccentric condition. [Conclusions]: The experimental results provide an important experimental basis for the design optimization , safe evaluation and software development of CF fuel assembly. The method can be extended to the subsequent CF3 and other fuel assembly scientific research projects.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-12
Abstract： Accurate measurement of the control rod worth in physical tests is of great significance for the safe operation of the reactor. The research on the calculated method of multi-group space-time neutron kinetics based on hexagonal geometry was carried out, and the advanced dynamic rod worth measurement suitable for hexagonal geometry was studied. This method owns high accurate and fast, which has a wide range of applications. The results show that the deviation between the control rod worth measured by the method and the theoretical value is within 10%, which demonstrated that the calculation accuracy of this method is high. The results also show that the calculation time of the method is short, and the calculation efficiency is high.
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