Suyuan Yu

Future HTGR developments in China after the criticality of the HTR-10

Nuclear power has a great potential to develop in China because of Chinas fast economic increase. HTGR will be the most promising nuclear reactor to apply in the future Chinese market. After the initial criticality of the HTR-10, subsequent research and validation of the HTGR performance is by hot commissioning tests and power operation, safety demonstration experiments, R&D of gas turbine and process heat application technologies, and promotion of industrial application of HTGR technologies. The commercial prototype HTR-PM is under study and conceptual design has started. These activities will result in the safe and economic development of HTGR technologies in China.

Sealing behavior of the HTR-10 pressure vessel flanges

Abstract The flanges of 10 MW high temperature gas-cooled reactor (HTR-10) pressure vessel play an important role in sealing the primary coolant of Helium. They are bolt-connected with a metallic O-ring and a welded Ω-ring. An elastic–plastic nonlinear analysis was performed to evaluate the stress and deformation of the contact flanges with the finite element software of MSC MARC 2000. The multi-step loading process was employed to simulate the processes of pre-tightening and pressurizing of the HTR-10 pressure vessel. The structural effects of the flanges on the opening and the shifting of the HTR-10 pressure vessel flanges at the O-ring position were studied to determine the flange height and the head closure thickness. The good sealing performance of the O-ring and the Ω-ring was verified both numerically and experimentally. The finite element model analysis results compared well with the hydraulic test of the HTR-10 pressure vessel. The results show that the flanges can meet the strength requirement and that the O-ring and the Ω-ring can effectively seal the HTR-10 pressure vessel during both pre-tightening and pressurizing.

Structural design of ceramic internals of HTR-10

This article describes the structural design requirements, structural arrangement and structural features of the ceramic and metallic internals of the 10 MW high-temperature gas-cooled reactor-test module (HTR-10). The graphite properties used in the ceramic internals are provided, along with the results of an operating stress analysis of the graphite components and the metallic components. Satisfactory results were obtained for the machining and installation of the ceramic components and the stress analysis of the graphite and metallic components of HTR-10.

Adaptive Unbalance Vibration Control of Active Magnetic Bearing Systems for the HTR-10GT

An Adaptive Unbalance Vibration Control (AUVC) method is studied based on the flexible active magnetic bearing-rotor experimental system AMB-PII, which is built up to simulate the helium turbo compressor rotor of the 10MW high temperature gas-cooled reactor with direct cycle (HTR-10GT) in compliance with the dynamic similarity principle. By constructing the required frequency compensation signal automatically through different feedforward approaches, two types of control methods are realized: the “displacement nulling” control which can effectively cancel the rotor vibration amplitude within the system bandwidth, and the “current nulling” method which can let the rotor rotate around its inertia axis and eliminate the disturbances of the currents in the electromagnet windings to significantly attenuate the mechanical vibration. The simulation and experimental results have proved that this kind of AUVC integrating feedforward algorithm can achieve good performance improvements, which will provide good experience and design references for the future application of magnetic bearings in the HTR-10GT project.Copyright

Preliminary Study of Graphite Dust Resuspension in Steam Generator of HTR-10

The resuspension rate of graphite dust in steam generator of high temperature gas-cooled reactors (HTRs) is calculated both in theoretical Rock’n’Roll model and imperial model derived from precious experiments. Dust diameter, friction velocity, as well as roughness of wall is investigated in detail.Copyright

Modelling for Resuspension of Multilayer Particles

The resuspension of graphite dust in High Temperature Gas-cooled Reactors is not only an essential way to estimate the concentration of particles in the normal operating core, but also a key phenomenon related to the release of radioactive products in depressurization accidents and the safety evaluation of environment. Precise resuspension modelling is an important work in safety analysis of HTRs. Current models were based on a single particle sitting on the substrate, however, multilayers of graphite dust deposit in the core during decades of operation. This paper uses recursion to deduce Rock’n’Roll model on each layer, and finally get the resuspension fraction changing with time and flow velocity. The results showed a “lag effect” of resuspension compared with those of Biasi’s modified model. Compared with the results of multilayer resuspension, the original monolayer model overestimated the resuspension rate and fraction.Copyright

Research About Eddy Effect and Dynamic Force of the Magnetic Thrust Bearing

The eddy effect of the magnetic thrust bearing (MTB) is researched by the finite element analysis (FEA). The active magnetic bearing (AMB) is an advanced bearing, used in HTR-PM. The alternating current in the bearing windings will decrease the electromagnetic force and cause phase lag, especially in the MTB which has no lamination structure. According to the calculation in this paper, simple sinusoidal current has large eddy effect. The force decreases obviously and the phase lag is large. However, the current containing direct part and sinusoidal part, which is closer to actual current, has less eddy effect. That is to say, because of the direct part in the current, the eddy effect of the sinusoidal part decreases.Copyright

The Stress and Reliability Analysis of HTR’s Graphite Component

The high temperature gas cooled reactor (HTR) is developing rapidly toward a modular, compact, and integral direction. As the main structure material, graphite plays a very important role in HTR engineering, and the reliability of graphite component has a close relationship with the integrity of reactor core. The graphite components are subjected to high temperature and fast neutron irradiation simultaneously during normal operation of the reactor. With the stress accumulation induced by high temperature and irradiation, the failure risk of graphite components increases constantly. Therefore it is necessary to study and simulate the mechanical behavior of graphite component under in-core working conditions and forecast the internal stress accumulation history and the variation of reliability. The work of this paper focuses on the mechanical analysis of pebble-bed type HTRs graphite brick. The analysis process is comprised of two procedures, stress analysis and reliability analysis. Three different creep models and two different reliability models are reviewed and taken into account in simulation. The stress and failure probability calculation results are obtained and discussed. The results gained with various models are highly consistent, and the discrepancies are acceptable.

A Numerical Analysis on Graphite Dust Deposition and Resuspension in HTR-10 Steam Generator

The behavior of graphite dust is important to the safety analysis of High-Temperature Gas-cooled Reactor (HTGR). The fission products released by fuel elements would enter the primary loop and combine with dust, resulting in that the dust has a high load capacity of cesium, strontium, iodine and tritium. It would bring difficulty and inconvenience to the maintenance and repair of steam generator. Therefore, the behavior of graphite dust in the steam generator is essential to the safety of High Temperature Gas-cooled Reactors. The present study focused on the deposition and resuspension of graphite dust in steam generator of HTR by numerical method. The results show that the graphite dust in steam generator deposits on the surface of heat transfer tube through turbulent deposition, thermophoretic deposition, and other depositional mechanisms, of which thermophoretic deposition is the main mechanism for the particles with the diameter of 2.2μm in the present study. The preliminary calculation result shows that about 6760mg/m2 of graphite dust tends to load on the tube surface.Copyright

Behavior of a Magnetically Suspended Rotor Dropped Into Auxiliary Bearings

Auxiliary bearings (ABs), as the back-up support when the Active Magnetic Bearing (AMB) system doesn’t work, play an important role on the assurance of AMB system’s safety. According to the structure design of ABs-rotor system on back-up helium circulator of 10MW high temperature gas-cooled reactor (HTR-10) equipped with AMB, this paper presents a simplified finite element model (FEM) in Ansys, applied in the transient response of the dropped rotor. The ABs load characteristics were determined based on Hertz contact theory. Furthermore, a special spring element named Combin40, which is coupled to a gap, was introduced to communicate information of displacement and force between auxiliary bearings which were simplified into nonlinear spring elements and rotor which was simplified into beam elements. Based on the developed FEM, the behavior of vertical and horizontal magnetically suspended rotor dropped into the ABs was analyzed respectively and the safety of the rotor and ABs was evaluated. The results provide an important reference to the ABs design and application in HTR-10 and High Temperature Reactor-Pebblebed Modules (HTR-PM).© 2013 ASME