The development and application of digital refueling mock-up for China initiative accelerator driven system

Highlights

• The digital refueling mock-up for CiADS has been developed based on the immersive virtual reality platform.

• The optimized logical structure for the automatic refueling simulation in real-time visualization has been designed.

• The feedforward and feedback control to the digital refueling mock-up have been detailed in the refueling procedure.

• Optimization and reliability assessment method can evaluate the refueling scenario both quantitatively and qualitatively.

Abstract

The refueling procedure in China initiative Accelerator Driven System (CiADS) is extremely complex, since there are some complicated structures in the coupling system, and the liquid lead-bismuth coolant turns the dynamic refueling process into the opaque experience. Building a real-scale physical mock-up system for the simulation of refueling procedure had always been considered as an effective way. However, the refueling design of CiADS will demand frequent changes in the preliminary design stage, which makes the approach time-consuming, not economic, and lack of flexibility. Another reason making this method not appropriate is that the refueling procedure will always accompany by the radioactive process and the release of airborne radionuclide, which will cause the possibly potential risks to the workers in nuclear reactor building. Considering these situations, Institute of Modern Physics, Chinese Academy of Sciences (IMPCAS) has developed an immersive virtual reality based digital refueling mock-up for the project of CiADS. The proposed refueling simulation system has some attractive features, including the real-time visualization for the automatic refueling simulation, feedforward and feedback control to the digital refueling mock-up, the interference and collision detection in the simulation process, and the sequential optimization and reliability assessment method in the refueling procedure, which can meet the requirement of frequent changes, and evaluate the refueling scenario both quantitatively and qualitatively.

Introduction

China initiative Accelerator Driven System (CiADS) is a lead-bismuth cooled, pool-type experimental transmutation reactor that is capable of supplying 10 MW of thermal power (Zhan and Xu, 2012). This coupling system is consists of three main parts, including accelerator, spallation target, and subcritical reactor, whose aim is to test the coupling characteristics of the three main parts and the transmutation effect in subcritical reactor instead of generating electricity as in the commercial nuclear power plants (Li et al., 2018a). This project was supported by the National Development and Reform Community (NDRC) in China since 2015. And nowadays, the CiADS has moved into the land leveling stage, where the location of factory site is in the city of HuiZhou in south China's GuangDong province.

In order to make the CiADS can be operated safely and reliably, the refueling procedure of the coupling system should be carefully considered. The functional requirements of the refueling procedure in CiADS are typically different from the conventional liquid metal fast reactor, since there are some complicated structures and particular designs in the coupling system. Firstly, there is a spallation target in the center of the subcritical reactor, which can not be moved or rotated. Secondly, the operations of refueling procedure should be finished in a high temperature and opaque environment, which is very hard for the process control and management. Lastly, the facility of CiADS inevitable discharges airborne radionuclide under the normal operation conditions, which means the main container of CiADS should be completely closed during the refueling procedure. All these features make the loading and refueling operations in CiADS into a very difficult and complex task.

For the purpose of designing the refueling procedure in CiADS, one better way is to establish a real-size physical refueling equipment. However, this method will greatly extend the development cycle of CiADS and increase the project cost. Additionally, the downside of this approach lacks flexibility in order to meet the requirement of frequent updated refueling scenarios in the preliminary design stage. In this context, an immersive Virtual Reality (VR) based digital refueling mock-up has been developed in IMPCAS for the project of CiADS.

The VR technology based system can provide a safe and economic way to simulate the CiADS refueling process in a realistic environment with real-time visualization. The use of virtual reality techniques has already been demonstrated with general acceptance in the field of nuclear engineering and design (da Silva et al., 2016). For example, Jeong et al. have developed a virtual environment for their nuclear power plant to train workers, in order to avoid the high radiation levels and work difficult during decommissioning of nuclear facilities, which can save a lot of costs and bring some benefit to the modifications of scenarios (Jeong et al., 2014). Besides, Silva et al. have developed a more detailed computational model based on the Brazilian IEN nuclear facility by means of the virtual reality techniques, which is aiming to perform simulations of physical security strategies (da Silva et al., 2015). Moreover, Freitas et al. have proposed an optimized operational procedure in radioactive waste repository based on the virtual reality techniques for the purpose of enabling virtual relocation in the radioactive wastes, which can fulfill the off-line mode of control without connecting to the remote handling devices (Freitas et al., 2014).

In this study, the feedforward and feedback control to the digital refueling mock-up has been established based on the VR techniques to describe the logic process, which is the cyclic decision process. Additionally, a fast ray-casting method has been used in the interference and collision detection process in order to get the real-time response and the speedier screen refresh in the immersive VR platform (Maier et al., 2012). Finally, one kind of criteria has been established to assess and optimize the refueling procedure, which can evaluate the refueling scenarios both quantitatively and qualitatively, and provide some useful experiences and references to the refueling design.

The article is organized as the following: In Section 2, the structure of CiADS and refueling equipment are detailed. Section 3 shows the logic process of digital refueling mock-up and the corresponding collision detection process. In Section 4, the evaluation of CiADS refueling procedure is described. Finally, conclusions are drawn in Section 5.