Safely decommissioning any nuclear reactor is a challenge. However, how do you decommission a Cold War-era production nuclear reactor that’s more than 60 years old? This is the problem that engineers are facing at the Savannah River Site (SRS), a 310 square mile Department of Energy site in rural South Carolina constructed in 1952 to help the U.S. produce nuclear weapons. The five reactors at SRS – known as R, P, K, L, and C – were once used to produce plutonium and tritium. When the Cold War ended, their products were no longer needed, and the last of them was operational in 1992. But the story doesn’t end there. Closing nuclear reactors is a huge job that must be done properly, and this is the mission of the DOE Environmental Management Office. The work continues with planning for decommissioning of C Reactor.
What lies inside?
The P and R reactors were decommissioned simultaneously. The process included the removal of millions of gallons of water and the pouring of over 200,000 cubic yards of grout. To assist in the planning of this process, engineers and designers at Savannah River National Laboratory (SRNL) reviewed thousands of construction drawings for the buildings and key pieces of equipment. The team quickly realized it was difficult to fully understand what was inside the reactors because the drawings were a guide for construction, organized by phase of construction and craft. This meant that there was no real ‘map’ for what was inside the building, as there was no single drawing that could provide all of the relevant information for any given room.
To help provide the decommissioning team with a sense of space inside the reactors, the SRNL team created 3D CAD models and 3D printed models of the building structures and key equipment. Once completed, the printed models helped the team understand the building better because it presented the layers of data in a way that humans normally process data—in three dimensions. Even engineers with years of experience need to interpret two dimensional drawings into a 3D image. When the information is spread across as many drawings, interpreting the data becomes a serious challenge.
The 3D printed models also improved the safety of the decommission teams on the ground. Every entry of workers into the facilities exposed them to various dangers; tripping hazards, heat stress, and radiation exposure. Having models available for review offsite reduced the number of walkdowns required in the actual buildings and allowed the teams to plan movements more effectively before entering the facilities.
Improving the 3D planning process
The use of 3D printed models for decommissioning P and R reactors at SRS improved the overall process by saving the project team several months of planning time. However the process was still very time intensive, taking six months to interpret the drawings and create the 3D models. The SRNL team knew that if they could speed up the modeling process, it would greatly improve the decommissioning process.
Using the knowledge they gained from P and R reactors, the team explored a new variation in 3D viewing— virtual reality (VR). The SRNL team knew that experiencing the data in true 3D— not just viewing a 3D model on a computer screen—would provide far better understanding of the inside of reactors. Through VR, the team knew that it could allow planners to ‘enter’ a facility and view it in true 3D without exposing them to the hazards found in the actual facility.
As planning began for the decommissioning of C reactor, which was significantly different in design to P and R reactors, the SRNL R&D engineering team decided to use laser scanning to create a VR model of the building. Laser scanning not only speeds the modeling process, but it also collects far more data than was built for the P and R models. Whereas the P and R models only included the building structure and major equipment, the scans in the C reactor include the structure, all equipment, piping, and even signage, as color images are overlaid with the laser scan. Signage can be important, as it often lists equipment numbers, electrical circuits, and piping. This data is important, as it can lead to more understanding about the equipment in the building. The CAD and 3D printed models lacked that level of detail.
To date, the SRNL team has made more than 200 scans of the below ground areas of C reactor, which have been combined into a single VR environment that can be viewed by planners.
VR provides applications beyond planning
The 3D CAD models of P and R were created specifically for the pouring of grout to stabilize the contamination inside the reactors. But once the word spread that there were good CAD models of the buildings, many other groups requested access to the data. In some cases the CAD models could provide the detail requested, but sometimes they could not. With the increased level of information that the scans are collecting, the resulting VR model will find more uses.
For example, once work planning is complete and the actual work begins, the VR models could be used to prepare workers for job tasks before they enter the building. Using VR, supervisors can show their teams the task at hand and the hazards that are present in the building. Currently, this preparation is handled outside the facility, often using 2D pictures that need to be interpreted. Conducting the briefing in VR will allow workers to see the work and hazards in a safe environment and minimize the time needed to be in the hazardous environment.