Nuclear power plants are designed to prevent the escape of radioactive materials. As nuclear power plants age, the danger of release of radioactive materials increases. All nuclear power plants contain a vast network of pipe to carry coolant through the different components of the system. As these pipes age, the danger of corrosion and cracks allowing radioactive materials to leak increases. Monitoring and maintaining the network of pipes in a nuclear power plant is a critical task.
Most of the commercial power reactors in the world today are pressurized water reactors (PWR). In a PWR, the primary coolant is water. Radioactive water and steam are pumped through a closed system of pipes that carries them to the core to be heated by the heat released from the nuclear fission reaction. From there they are carried to a heat exchanger that transfers the heat to water circulating in secondary network of pipes. The water in the secondary system is converted to steam that is fed into a turbine to create electricity.
A failure anywhere in the network of pipes could be a major problem. The Nuclear Regulatory Commission is concerned that pipes in nuclear power plants may be undergoing corrosion that could result in leaks and ruptures. This could lead to disasters in which the function of the plant is impaired and/or radioactive materials are released into the environment.
It is difficult to monitor corrosion inside pipes. One source of corrosion is from gases that might be trapped inside the pipe network. Gases mixed with water naturally rises to the highest spot in the container. In a network of pipes, the highest points can become places where gases accumulate, and corrosion occurs. One of the ways to detect potential problems spots is to map the network of pipes.
If highest points can be correctly identified, then vents can be installed in those parts of the pipe network to allow gas to escape and prevent corrosion. The old system to mapping pipe networks utilized hand tools which required staff to spend a lot of time in and around the pipe network. This could result in exposure to dangerous levels of radiation. And, using hand tools is a crude system and could easily miss important information about the pipe network.
Exact Metrology (EM) is a company that specializes in 3D and CT scanning. A few EM technicians can scan the entire pipe network of a nuclear power plant using Leica HDS scanners. These scanners are able to capture full-volume, 360° 3D point clouds for a location in just three minutes. A point cloud is a very accurate digital record of an object or space. Some rooms only require one such scan, while other rooms require multiple scans. Once the scanner is set up and started, the rest of the process is automatic, and the technician can retreat to a safer area if necessary. Once all the scans have been carried out, the separate scans are combined into a single point cloud.
Once the complete point cloud is created, sophisticated computer algorithms are used to identify the pipe sizes, centerlines and positions, even if some section of pipe are concealed from view. The point cloud for nuclear reactor pipe networks is able to identify sections of pipe which are crystalized and leaking.
Once the scanning and point cloud assembly are completed, 3D CAD models are created. Computer snapshot are recorded with elevations descriptors marked on the pipe runs. These snapshots are sent to engineers at the facility to determine if it is necessary to install vents at particular high points.
One big benefit of 3D scanning is that the scans can be carried out at ground level. This means that technicians do not need to climb ladders and scaffolding which reduces the danger to the technicians. Another benefit of 3D scans is that additional measurements can be conducted without the need to return to the actual pipe network. The point cloud assembled in the computer can be accessed to provide the additional measurements.
The development of 3D scanning systems has been of great benefit to the nuclear power industry.