Virtual Reality: a way to prepare and optimize operations in decommissioning projects
A52954CC 2 operations while respecting three vital issues: worker protection by dose rate limitation, environment protection by research into lowering nuclear waste volume and activity, and financial management, which combines cost efficiency and respect of the regulations and ever stricter safety requirements. In order to address these three issues, the CEA has created a dismantling division, which runs an R&D program to provide innovative tools. This program focuses on the development and industrialization of measurement tools and techniques to better characterize in situ radiological conditions, of remote handling and cutting tools, designed for highly radioactive environments, and of intervention scenario simulations. The latter involves running pre defined scenarios and verifying their suitability for the environment. This highly realistic simulation is possible thanks to Virtual Reality (VR) technologies, which enable a user to interact with a computer simulated environment. VR environments, mostly based on visual immersion, also include additional sensory information such as sound or touch. This paper describes how VR technologies, adapted to the nuclear decommissioning context, can provide useful support to engineers in charge of scenario design. Before beginning the actual operations, such a set of tools is also well adapted to communicating and sharing information during project reviews, or to training workers and ensuring they are aware of the risks they or their equipment could be exposed to. First, the VR technologies used will be described. Secondly, the paper will present the different simulation preparation steps, like 3D reconstruction, radiological characterization, remote handling simulation. Then, application examples will be presented and show how VR simulation can be applied in decommissioning. In the last section, we will describe the limits of such simulations, and the perspectives. II. Virtual Reality and Dismantling: current practices Virtual reality (VR) is a technology widely used in various fields. For instance, in medicine, the primary use of VR in a therapeutic role is its application to various forms of exposure therapy, from phobia treatments to newer approaches to treating Posttraumatic Stress Disorder [2] Other research fields in which the use of virtual reality is being explored are physical medicine, pediatrics or surgery training [3] In industry, VR can be applied to new product design (electronics, CAD, Computer Aided Manufacturing, naval, automotive or aerospace design, etc. for urban regeneration and planning or in archeology to rebuild destroyed monuments. Applied to the nuclear industry, VR provides an intuitive and immersive human computer interface, to verify intervention scenarios and train future operators. Some research has led to the development of applications for maintenance training, or to new methodologies for disassembly evaluation of CAD model designs for maintenance [4] Some works have also focused on using VR in a training program for simulating refueling operations while reducing the doses received by workers [5] Lastly, some studies target VR decommissioning assistance, in the Chernobyl NPP dismantling, for example [6] Our work is slightly different because it is the first time that VR technologies have been used to prepare and optimize future operations, which gives more confidence and reliability to scenarios. III. PRESAGE, the Marcoule Immersive Room The CEA created the Marcoule immersive room (Fig. 1) called PRESAGE, at the end of 2008 in order to validate maintenance or dismantling operations. It is a resource shared by all the CEA decommissioning projects. PREDEC 2016: Title of the communication, February 16 18, Lyon, France 3 Abstract #A52954CC Figure 1: PRESAGE room. The PRESAGE room groups all the technologies enabling user immersion and interaction in a virtual environment. Three kinds of immersion are possible: visual, sound, and tactile. First, a stereoscopic visualization system is based on a 3.7m x 2.3m image wall, giving the user a 3D vision of the virtual environment. The size of the screen means it is very comfortable to work on lifesize simulations. The perception of 3D depth comes from the INFITEC technology [7] It has been chosen because of its high rendering quality and its good user comfort. Sound simulation has been added, to reproduce the sound received by the in situ microphone: the operator will be able to hear the sound of collisions in the monitoring room. Generally, the sense of sound is very useful to operators working with remote handling systems. It helps them to better pilot the system, because they have feedback of what they are really doing. Therefore a specific type of sound has been associated with each collision, to enhance the information sent to the user. To produce tactile immersion, haptic systems are used, enabling the sensations of touch and of effort. We chose to equip the room with two haptic interfaces, 6D Virtuose by Haption (Fig. 2) which give force feedback on all six degrees of freedom, together with a large workspace and high torques [8] They are especially recommended for scale 1 manipulation of virtual objects such as assembly/disassembly simulations, ergonomic studies, or maintenance training. The Presage room is equipped with two haptic systems in order to simulate work with either two hands or two operators in collaboration. Figure 2: 6D Virtuose. PREDEC 2016: Title of the communication, February 16 18, Lyon, France Abstract #A52954CC 4 A physics engine generates the forces to be applied to avoid objects' inter penetration and sends the right information to haptic interfaces to create force feedback.A52954CC 4 A physics engine generates the forces to be applied to avoid objects' inter penetration and sends the right information to haptic interfaces to create force feedback. To interact with the simulation, motion capture is used to track a flystick enabling navigation in the virtual environment. Based on eight IR cameras, the device position is tracked in real time and its virtual position is therefore updated [9] It is also possible to track head position: as a result, when the user moves his head, the point of view of the simulation changes as if a genuine movement had taken place within the VR surroundings (Fig. 3) Last, the room is equipped for the use of a whole motion capture suit, which enables a virtual human to be inserted into the simulation, thanks to targets located on each part of the operator's body. Figure 3: flystick (left) tracked glasses (middle) and suit (right) IV. From real to virtual: the steps to build the simulation In order to do VR studies on decommissioning projects, certain steps are necessary to build the VR simulation. To run such simulations, a new software, called iDROP, has been developed by the CEA. This software is made up with several real time modules: collision detection, robotics, virtual human, and dose rate calculation. It allows a scenario global approach, taking into account all the aspects of a decommissioning project. IDROP takes 3D models, remote handling model and radiological data in input. This part describes all the steps necessary to build a iDROP simulation. A. Step one: build the 3D models 3D models of the environment have to be built. First, 2D facility plans are collected and used to build the corresponding 3D model. To verify if the 2D plans are up to date, an in situ photo campaign can be necessary. In some cases, this step is enough and the 3D model is made up from 2D plans. If the 2D facility plans available are not sufficiently up to date to design a precise digital mock up, 3D reconstruction is necessary to be sure the 3D model will be faithful to reality. Two main rebuilding techniques exist and can now be used in a nuclear environment. The photogrammetic reconstruction enables a 3D model to be built up, using the parallax obtained between the images acquired depending on the different points of view. It implements the correlation calculation between the digital images to give a 3D reconstruction of the model. After an in situ photo campaign, processing consists in identifying and digitalizing the points with common physical details on the photos, as well as the apparent contours of lines and cylinders. This reconstruction is semiPREDEC 2016: Title of the communication, February 16 18, Lyon, France 5 Abstract #A52954CC automatic, and is carried out from basic trade elements (tube valve, nut, screw, elbow. This technique was used on the APM Cell 414 decommissioning project, and the study was carried out by the subcontractor ESIC SN [10] It consisted in taking 700 photos along the existing rails (Fig. 4) for one week. The 3D reconstruction took four weeks. The model obtained is accurate to about 5 cm. Nevertheless, the photos taken do not allow all the pipes to be seen, especially those located behind other elements. Figure 4:4 of 700 photos taken during the measurement campaign. The images below enable the comparison between a real photo and a VR view of the same scene (Fig.5) Figure 5: a real photo (left) and 3D view (right) The other technique available is 3D laser scanning. It is based on a scanner, and the measurement is done via a laser beam. The scanned environment is transferred into points. The result is a 'cloud' of tens of millions of points, each defined by a 3D (X, Y and Z) value. This 3D 'point cloud' serves as a basis for 3D reconstruction, e.g. in a CAD tool. Laser scanning meets the need for highly accurate, complete and quickly obtained images. In both techniques, CAD models can be directly imported in the immersive room. However to enhance performances, simplifications can be made to reduce the size of the 3D model, by for example removing fastenings (screws, nuts, washers. filling holes (deleting drilling or simplifying extrusion profiles) and suppressing non visible or hidden objects. B