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Dong Z.,Tsinghua University | Dong Z.,Key Laboratory of Advanced Reactor Engineering and Safety
IEEE Transactions on Nuclear Science | Year: 2015

The modular high temperature gas-cooled reactor (MHTGR) is an important type of small modular reactors (SMRs) with inherent safety. It is clear that power-level control is crucial in providing safe and stable operation as well as in realizing load-following function so that the MHTGRs can be grid-appropriate. However, there always exists the reactor parameter uncertainty and control input nonlinearity such as saturation and dead-zone practically, which seriously intensify the difficulty in designing power-level control. Thus, it is quite necessary to study MHTGR power-level control method against reactor parameter variation as well as control input saturation and dead-zone. Motivated by this, model-free MHTGR power-level control laws against the input saturation, dead-zone and both saturation and dead-zone are proposed in this paper, which are not only insensitive to reactor parameter but also able to compensate the control input nonlinearities. It is proved theoretically that these newly-built MHTGR power-level control laws guarantee strong closed-loop stability. Numerical simulation results illustrate the relationship between the control performance and some parameters of the controllers and input nonlinearities. © 1963-2012 IEEE. Source


Tang Y.,Beijing University of Technology | Zhang L.,Key Laboratory of Advanced Reactor Engineering and Safety | Guo Q.,Beijing University of Technology
Journal of Nuclear Science and Technology | Year: 2015

Granular flow is the shearing motion of a collection of discrete solid particles which are commonly seen and widely utilized in various industrial applications. One of the essential applications of dense slow granular flow in engineering is the pebble flow in pebble-bed nuclear reactor (PBR). A number of numerical models have been established for researching the basic physical mechanisms and properties of granular flow. For the purpose of generating an appropriate model for high temperature reactor-pebblebed modules (HTR-PM) in the future, numerical models on granular flow in hoppers and some of their previous applications on PBRs are reviewed. In this paper, basic transport and contact mechanisms of granular flow are firstly introduced, then kinetic theory from gas molecules and plastic theory from metal mechanics approaches give descriptions of the macroscopic behavior of rapid flow and quasistatic flow regimes, respectively, subsequently kinematic continuum method and discrete element method (DEM) are presented to describe the bulk features of dense slow flow in hoppers. Since various kinematic models, DEM models and their modified versions for dense slow granular flow in hoppers have been experimentally verified and applied in prediction of pebble flow in PBRs, a promising model for HTR-PM is expected with further work to generate pebble flow profile in the future. © 2014 © 2014 Atomic Energy Society of Japan. All rights reserved. Source


Dong Z.,Tsinghua University | Dong Z.,Key Laboratory of Advanced Reactor Engineering and Safety
Mathematical Problems in Engineering | Year: 2015

Small modular reactors (SMRs) are those fission reactors whose electrical output power is no more than 300 MW SMRs usually have the inherent safety feature that can be applicable to power plants of any desired power rating by applying the multimodular operation scheme. Due to its strong inherent safety feature, the modular high temperature gas-cooled reactor (MHTGR), which uses helium as coolant and graphite as moderator and structural material, is a typical SMR for building the next generation of nuclear plants (NGNPs). The once-through steam generator (OTSG) is the basis of realizing the multimodular scheme, and modeling of the OTSG is meaningful to study the dynamic behavior of the multimodular plants and to design the operation and control strategy. In this paper, based upon the conservation laws of mass, energy, and momentum, a new differential-algebraic model for the OTSGs of the MHTGR-based multimodular nuclear plants is given. This newly-built model can describe the dynamic behavior of the OTSG in both the cases of providing superheated steam and generating saturated steam. Numerical simulation results show the feasibility and satisfactory performance of this model. Moreover, this model has been applied to develop the real-time simulation software for the operation and regulation features of the world first underconstructed MHTGR-based commercial nuclear plant - HTR-PM. © 2015 Zhe Dong. Source


Dong Z.,Tsinghua University | Dong Z.,Key Laboratory of Advanced Reactor Engineering and Safety
IEEE Transactions on Nuclear Science | Year: 2014

The modular high temperature gas-cooled reactor (MHTGR), which has the inherent safety feature, high thermal efficiency and satisfactory economic feasibility, can be applied for electricity and process heat production. Power-level control is an important technique for providing both the stable operation and load-following performance. Since the coolant temperature sensors of an MHTGR are usually installed near the primary side of the corresponding steam generator, there must be time-delay effect in the feedback loop of the coolant temperatures. Moreover, the measurement signal transducing may also induce time-delay effect. Therefore, it is meaningful to give the power-level control design method by considering this time-delay effect. In this paper, a simple output-feedback power-level control is proposed for the MHTGRs by using the delayed measurement signal of average reactor coolant temperature. In the aspect of theoretical analysis, a sufficient condition, under which it is well guaranteed that this newly-built power-level control is a globally asymptotic stabilizer, is firstly given. In the aspect of verification, numerical simulation results not only verify the feasibility of the theoretical results but also show the relationship between the performance and values of parameters of this novel power-level controller. The meaning of this work lies in two aspects. The first one is deeply revealing the relationship between the closed-loop stability and values of the controller parameters. The second one is giving the approach of designing a simple and effective power-level control strategy to suppress the negative influence induced by the time-delay in the feedback loop of the coolant temperatures. © 1963-2012 IEEE. Source


Dong Z.,Tsinghua University | Dong Z.,Key Laboratory of Advanced Reactor Engineering and Safety
IEEE Transactions on Nuclear Science | Year: 2014

Because of its inherent safety feature and potential economic competitiveness, modular high temperature gas-cooled reactor (MHTGR) has been seen as one of the best candidates for building the next generation nuclear plants. As a typical small modular reactor (SMR), MHTGR can be incorporated with new energy resources to build micro-grids, and can also be utilized to build large nuclear energy systems having inherent safety feature at any power rating. The nuclear steam supplying system (NSSS) of MHTGR-based plants is composed of an MHTGR and a once-through steam generator (OTSG). The NSSS coordinated control is crucial for providing the load-following function. Motivated by this, a nonlinear coordinated control for MHTGR-based NSSSs is proposed in this paper. Based upon theoretical analysis, sufficient conditions for this newly-built control law to guarantee globally asymptotic closed-loop stability are given. The feasibility of this novel coordinated control strategy is verified through numerical simulation, and simulation results show that this new control law can provide satisfactory regulating performance for the NSSS by properly choosing its feedback gains. Moreover, this coordinated control has a very simple form, which means that it can be easily implemented in practical engineering. © 2014 IEEE. Source

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