ALARA Planning and Teaching Tool Based on Virtual-Reality Technologies

1. ALARA Planning and Teaching Tool Based on Virtual-Reality Technologies Di Zhang1, X. George Xu1, D. Hussey2, S.Bushart2 1Nuclear Engineering and Engineering Physics, Rensselaer Polytechnic Institute, Troy, New York, USA 2Electric Power Research Institute, Palo Alto, CA, USA ( contact Professor X. George Xu at xug2@rpi.edu ) Graphic interactive interface Visual Basic. NET (VB.NET) was used to develop the graphic interface. It is convenient for VB.NET to combine EON files into the software. For dose calculation, the communication between EON and VB.NET is critical. So in VB.NET an “instance” (i.e., an object in computer memory), which represents EON file, was generated. And the information of the avatar’s coordinate could be transmitted through this instance. The coordinate is refreshed in real-time and the dose is calculated and accumulated per second. INTRODUCTION In recent years, the nuclear power industry has shown an increasing interest in using the latest computer visualization and virtual-reality (VR) simulation tools for job optimization, ALARA training, and security inspection. Most of the software tools developed from previous studies, however, have focused on the technologies involving immersive VR interfaces. In order for the VR technology to be useful in the ALARA planning, such simulations should be based on data on the effective dose equivalent (EDE) required by the U.S. NRC for radiation protection purposes. This paper presents an on-going project to develop a VR based interactive radiation dose simulation tool for the nuclear power plant. Dose calculation Two radiation source terms are provided in the software. The first one is dose map mode, while the other one is fixed radiation source mode involving a gamma source.For dose map mode, the environment is surveyed to define exposure rate for the entire floor. The dose-map obtained by a radiation survey can be specified by a user for a realistic nuclear power plant environment.When a worker is moving around for a job, he/she is exposed to radiation and the total dose is accumulated. For the fixed source mode, the source and the corresponding radioactivity is specified by the user. The gamma-constant of a point-like source is used to calculate the dose to the worker according to the distance between the avatar and the source. In both modes, the exposure is converted to effective dose equivalent that have been using the ICRP exposure-to dose conversion methodologies. The effective dose equivalent per kerma is energy and geometry dependent. MATERIAL AND METHOD The VR Dose Simulator soft package was developed using Computer-Aided-Design model of a nuclear power plant, augmented Virtual-Reality computer technology, and advanced software programming. All 3-D CAD models of the buildings, floor and radiation facility were imbedded into a VR authoring environment called EON that enables a high level of interactivity. The VR technology implemented by object-oriented software design methodology. Two avatars were used to represent a male and female worker who move around inside the radiation areas to carry our various user-specified tasks. Dose calculation, a game-like scoring system and interfaces were designed to stimulate the interactivity between a user and the computer. Fig.1 shows the flow chart of the whole software development approach. RESULTS A virtual avatar, which is used to represent a worker, is controlled by the user. This avatar is required to accomplish several virtual jobs in different ‘way points”in the power plant. The shorter time the worker spent in finishing these jobs, the less dose he/she would receive. A score is given to the player based on the number of virtual jobs that have been finished and the accumulated dose the worker has received. The software provides two navigation methods: automatic navigation and interactive navigation to allow the player a flexibility in carrying out the jobs. Each player needs to select an avatar at the beginning of the game (see Fig. 3 a), and then specify both the time spent on each way point and navigation mode (Fig. 3 b). Then, the source terms and corresponding information need to be defined (Fig. 3 c). After all the parameters are provided by a player, augmented Virtual Reality environment offers a game-like interactivity to allow a player to be immersed in the environment. During the whole process, the accumulated time, the accumulated dose to an avatar, the current position of the avatar and the current dose rate are shown in real-time on the screen (see Fig.3 d). Fig. 1 Flow chart of the solution 3D model of the nuclear power plant Multigen Creator was used to modify the surface model of the nuclear power plant, which is shown in Fig.2. Considering the efficiency and compactness, the original CAD model was simplified. Collision Detection algorithm was used to make sure that the avatars will not walk into walls. Some facility components were divided into multiple pieces to carefully define the environment. Two avatars representing a male and a female workers had “jointed body parts” so the arms or legs can be positions to simulate different postures. (d) Virtual working environment (a) Selection of worker (c) Definition of the source (b) Specification of parameters of virtual work Fig. 3 Graphic interfaces of the virtual-reality software package CONCLUSIONS A Virtual-reality based training software package, VR Dose Simulator, has been demonstrated using 3-D CAD and VR authoring technologies. It provides an interactive, vivid, and easy way to educate a worker about ALARA principle in a nuclear power plant. The interface is user-friendly and game-like, providing the intuitive interface. With the incorporation of EDE dose calculations, the dose to the worker is useful for demonstrating compliance with the radiation protection regulations. Fig. 2 3D model of the nuclear power plant facility ACKNOWLEDGEMENT Simulation of the virtual reality environment A powerful VR authoring software, EON Reality, was used as the tool to implement the virtual environment. The 3D models of both modified nuclear power plant facility and avatars were imported into the EON. Interactive controlling effect was added for the user to control the movement and posture of the avatars. Collision detection module made sure that an avatar interacts realistically with the environment including things such as always walking on a surface and not going through the wall etc. This project was sponsored by the Electric Power Research Institute.