The Japanese government has mandated the decommissioning of all of its nuclear reactors that are more than 40 years old. Each decommissioning typically requires up to several thousand workers and 10 years to complete, and can cost JPY 36 to JPY 77 billion per reactor. The project goal was to develop a repeatable methodology to accurately calculate the amount of waste materials that must be managed as radioactive substances for each nuclear power plant so that a safe, rational, and cost-effective approach can be determined for each plant. The waste material will be cut up into cubes, placed into lead-lined containers, and buried for a 100 years.
The Hitachi-GE Nuclear Energy team thought through the disassembly process of nuclear plants and changed its approach from the consideration of plant weight to the consideration of plant volume. Using data from the company’s CAD system, in conjunction with a customization of MicroStation and i-models, Hitachi-GE Nuclear determined the volume of each part of the plant, the amount of radioactive material in each part, and what the radiation exposure to workers would be from that particular volume, taking into account the man-hours required for demolition and to cut the equipment/piping into container-size cubes.
The 3D model of the plant, in which the dose rate has been mapped and waste container modeled, can be displayed on an iPad, enabling a quick response to changes at the site and enhancing safety. The models also allow simulations of waste materials handled in various decommissioning scenarios. This will enable long-term waste material traceability and make operational cost visible. In addition, estimating man-hours required by accurately forecasting the volume of radioactive waste materials helped the company develop a plan that will minimize the environmental impact of the decommissioning process.
Hitachi-GE Nuclear Energy used MicroStation and i-models to prepare all 3D plant models and as-built models, including calculating radiation dose rates. The team also used these models to simulate the automated cutting of equipment/piping and packing of this radiated waste in containers.