Research On Radiation Dose Assessment Method For Decommissioning Of Nuclear Facilities Based On Virtual Reality

Nuclear radiation is one of the major considerations in nuclear decommissioning,because it has a significant effect on the overall cost,risks,safety measures,equipment,resources,etc.for decommissioning of nuclear facilities.The working environments in nuclear facilities are inherently under high radiation,and the existence of radiation makes it much more difficult for people to perform their tasks.In the preparation and implementation phase of nuclear facility decommissioning,it is essential to perform radiation safety analysis for personnel.This plays an important role in ensuring the safety of occupational workers,the public and environments.Since the nuclear radiation is harmful to human health,it is difficult to perform experiments or training through actual scenarios.Consequently,researchers consider the application of simulation technology for safety analysis in hazardous environments,which has proven to be a more efficient,safer and less costly research method.The simulation technology for decommissioning of nuclear facilities plays an important role in the pre-work planning and optimization,ensuring personnel safety,improving work efficiency and reducing costs and time.The dissertation focused on the requirements of radiation dose assessment for personnel training and pre-work planning during decommissioning of nuclear facilities,and carried out research on radiation dose assessment methodologies based on virtual reality technology,including the methods of the geometric modeling method of radiation calculation based on CAD(Computer aided design)technology,gamma radiation calculation,external exposure dose assessment and work-path planning.Finally,a radiation dose assessment system for nuclear facility decommissioning was developed.The main research contents and contributions are as follows:(1)The CAD-based radiation modeling method was studied.In order to calculate radiation field for arbitrary geometrics,the research builds initial 3D models with CAD tools,and two modeling methods of cutting operation and arbitrary geometries are proposed based on CAD models,respectively.The proposed methods can ensure the accuracy of geometric models and improve the flexibility of radiation modeling.It makes it possible to analyze the radiation distribution caused by arbitrary geometries generated by cutting,dismantling and other operations.(2)The calculation method of gamma radiation field in virtual environment was studied.Based on the real-time simulation requirements of personnel training,an adaptive radiation calculation method of arbitrary geometry is proposed based on the point kernel method(PKM),and it can greatly improve the computational efficiency while maintaining model accuracy.In addition,for the refined assessment requirements in the pre-work planning,a local modular method of characteristic(LMMOC)method for solving the local radiation field is proposed based on the three-dimensional method of characteristic(MOC),and it is used to improve the accuracy of PKM.(3)The method of external dose assessment in the virtual environment was studied.In order to take the working posture into account,the research combines skeletal animation technology with virtual human model,and controls the posture via skeletal animation,making the geometric description of dose assessment closer to the actual situation.On this basis,for the real-time simulation requirements of personnel training,a dose assessment method based on organ-monitoring-points was proposed by using PKM;for the refined assessment requirements in the pre-work planning,a dose assessment method based on MOC was proposed,and both methods enable organ-level dose assessment.(4)Path planning for complex nuclear radiation environments was studied.The research takes the path planning as a measure of radiation protection to provide path navigation for personnel in complex radioactive environments,helping them avoid unnecessary radiation exposure.In order to improve the efficiency of path optimization in complex environments,such as obstacle clustered,narrow channel and dynamic environment of obstacles and radiation source movement,two algorithms GB-RRT*and DL-RRT*were proposed by combining the graph search method with sampling algorithm.These methods can improve the efficiency and accuracy of path planning in complex radioactive environments,ensuring that people's actions are maneuverable,responsive and efficient.(5)A radiation dose assessment system for nuclear facility decommissioning was developed.The system was developed on the Visual Studio 2010 platform using the C++programming language,and its virtual scene is rendered by the 3D graphics engine OGRE,and the human-machine interface is designed by using the graphical user interface application development framework QtThe research results present a safe,efficient and low-cost computing platform for optimal decision-making in radiation protection and personnel training,and provide a basis for the simulation system development in nuclear facility decommissioning.Furthermore,it can provide technical support for radiation analysis during maintenance,and in emergency.