Main Pumping System Research Articles

Optimization and testing of a Mass Spectrometer Leak Detection (MSLD) system

A rapid helium mass spectrometry leak detection method is established to respond to problems of low sensitivity and efficiency in detecting leaks in large vessels. The optimized multistage tandem leak detection system improves leak detection sensitivity by increasing the amount of gas entering the analysis chamber. By involving the main pumping system in the detection process, the effective pumping speed is increased, resulting in a significant reduction in system response time. Additionally, the optimal leak detection vacuum required for maximizing the leak velocity indicating gas movement is determined, thereby further decreasing the system’s response time. Our application demonstrates that the optimized leak detection system increases sensitivity by one to two orders of magnitude, reduces system response time by over 90%, and shortens evacuation time by 7 h. Ultimately, the optimized design of the vacuum system developed for large vessels demonstrates greatly improved leak detection efficiency and overall capability.

Lubrication performance analysis of Lead-Bismuth Internal-Feedback bearings in the nuclear main pump system

The significant equipment of the rotor system and circulating pump are lubricated bearings. Lead-bismuth pumps use high-temperature liquid lead–bismuth as the lubricant in its internal feedback dynamic and hydrostatic bearings. Through the numerical simulations, the lubrication capabilities of a lead–bismuth bearing are examined in this work. The pressure distribution, load-carrying capacity, minimum film thickness and power loss of a lead–bismuth bearing with various radial gaps are evaluated in relation to three parameters: rotational speed, eccentricity, and differential pressure. The findings demonstrate that the lead–bismuth internal-feedback hybrid bearing's bearing capacity is mostly dependent on static pressure, with some support from dynamic pressure. The dynamic pressure effect is related to the eccentricity, rotating speed and radius gap of lead–bismuth bearings. Throttling is accomplished via the feedback groove. Lead-bismuth bearings with various radius gaps exhibit a similar pattern in their static properties. These bearings need a particular construction to support radial forces because of their unique physical characteristics, which include low dynamic viscosity and high density. Their spiral and feedback grooves are crucial components for heat dissipation and hydrostatic throttling. This article can serve as a reference for the lead–bismuth bearing's lubrication theory.

An insight into the flow field characteristics of the high temperature liquid Sodium (Na) with cavitation effects in the 600 MW fast reactor system

The paper explores the flow field characteristics of liquid Sodium pump, the flow field calculation model is established. The head and efficiency curves of sodium pump obtained by simulation are compared with the test data to verify the accuracy of the model. Flow characteristics inside the impeller, guide vane and the volute are investigated and summarized. The pressure distribution and velocity distribution characteristics of the steady flow field and the pressure fluctuation and fluid force characteristics of the unsteady flow field are further analyzed, which provides the basis for the calculation of flow induced vibration and sound field. The dynamic processes of Sodium cavitation effects are stimulated and studied systematically. The causes of fluid excited vibrations in Sodium pump are preliminarily revealed. Researches have remarkable guiding significances for the analysis of flow characteristics of Sodium pump system of the new generation 600 MW nuclear main pump system.

Analysis of the flow noises of the nuclear main pump caused by the high temperature liquid Sodium in the two-circuit main loop liquid Sodium pump system

The paper investigates the flow noises caused by the high temperature liquid Sodium in the nuclear main pump system. Three-dimensional unsteady CFD coupled sound field methods are exploited. Spectrum characteristics of sound source load are obtained. Directional sound pressure level distribution based on sound source load of rotor blades and guide vanes are presented and discussed. Distribution of sound pressure level of inlet and outlet pipes along the flow direction are also further discussed. Results indicate that with the increase of blade passing frequency, the amplitude of sound pressure level decreases. Response of sound field mainly depends on the load characteristics of rotor blades. Research results have remarkable significances for the analysis of flow noises in liquid Sodium pump systems.

Preliminary Design of GDC System for KTX Device

KeDa Torus for eXperiment (KTX) is a reversed field pinch magnetic confinement fusion research device whose main parameters are between in the RFX and MST. The base vacuum of KTX is 1 × 10−6 Pa. Six sets of turbomolecular pumps parallel installed in the six horizontal ports which served as the main pumping system for KTX and the diameters of the ports are 0.15 m. Before plasma discharge, glow discharge cleaning (GDC) system is applied to clean C, O and hydrocarbon impurity on the vacuum vessel (VV) surfaces of KTX. An inflation system and residual gas analyzer system are designed to supply the working gas and monitoring the effect of GDC respectively. According to the GDC experiment practice, the working gas pressure of the KTX GDC system is designed as 0.3 Pa, with average current density of 0.15 A/m2. Two sets of the GDC probes are installed in KTX horizontal ports symmetrically with interval angle of 180o and the input current of each anode is 1.6 A. According to the current density distribution, the centre of the VV cross section is the superior working area for GDC anode, a screw-nut pairs with the cooperation of bellows can transfer the anode from its storage position to its working position, and the stroke of the screw-nut pairs is 0.5 m. Based on the temperature rise calculation, the maximum equilibrium temperature of the anode during glow discharge is about 275 °C (under 200 °C baking). The thermal stresses caused by the temperature distribution on the anode’s components especially in the vacuum brazing areas are inspected during GDC process. All the simulation results show that the structure and base material of the KTX GDC anode can work normally without additional active cooling system.

Experiences on vacuum conditioning in the cryostat of KSTAR tokamak

Korea Superconducting Tokamak Advanced Research (KSTAR) device has been successfully operated for the plasma experiment from KSTAR 1st campaign to 4th campaign. The main pumping system for the cryostat has to maintain the target pressure below 1.0×10−4mbar at room temperature and 1.0×10−5mbar at extremely low temperature for the plasma experiment against the air leak coming from ports of vessel and/or the helium leak from cooling loops in the cryostat.No leak has been detected at room temperature. Unexpectedly, the cold-leak appeared in the cryostat at temperature around 50K during the cool-down in the KSTAR 2nd campaign. We carefully analyzed the characteristics of detected cold leak because it can cause the increase of the base pressure in the cryostat.After the cool-down, the leak detection was performed to locate the position and size of the leak by the pressurizing the loops. As a result, it is found that the cold leak was located at cooling loops for PF/CS coils and CS structure. Nevertheless, the vacuum inside the cryostat was well maintained below 6.0×10−8mbar during the entire operation period. The impact of the He-leak in present status on the plasma operation is negligible. However, we have found that the leak rate increases as a function of time. Therefore careful monitoring on cold-leak is an important technical issue for the operation of superconducting tokamak.

The design and performance of the LEP vacuum system at CERN

The design of the 27 km long ultra-high vacuum system of LEP has been based largely on past experience with high energy electron and positron storage rings. However, stimulated by the large size of the machine and by the large number of individual components, new concepts had to be found in many areas of mechanical design such as flange connections between vacuum chambers and improved reliability with respect to vacuum leaks. The intense synchrotron radiation emitted by the electron and positron beams produces strong outgassing from the vacuum chamber walls during operation. This gas load exceeds by many orders of magnitude the static pressure and must be absorbed by a large, distributed pumping system around the whole machine circumference. LEP is the first large accelerator vacuum system which uses a combination of non-evaporable getter strip (NEG) and small, lumped ion pumps as its main pumping system. The operation of LEP for high energy physics requires a beam lifetime of many hours and thus an average vacuum pressure below 3 × 10 −7 Pa in the presence of circulating electron and positron beams. The performance and the operational experience with this new system are described.

Ceramic turbomolecular pumping system in reactor structure of FER

Abstract A new pumping system consisting of ceramic turbomolecular pumps and their ceramic fore-pumps has been studied as the main pumping system of FER since these pumps have been developed at JAERI recently. The turbomolecular pump has a rotor of silicon nitride, which is driven by a gas turbine, oil free gas bearings and a non-contact spiral groove seal. The effects of neutron radiation, heat loads and magnetic fields on the ceramic pumps are evaluated based on the FER design conditions.