Shimizu : Develops Deco-BIM, a Support System Makes Efficient Decommissioning Engineering Nuclear Power Plant ― Minimizing Total Cost through Logical Demolition Plan ―

September 29, 2022

Shimizu Corporation (President: Kazuyuki Inoue) developed Deco-BIM, a support system as a replacement for a series of engineering utilizing BIM to increasing the efficiency of decommissioning engineering nuclear power plants (reactors) and reducing the total cost.

Following the Great East Japan Earthquake, operations at a total of 54 nuclear power plants in Japan had been suspended by 2012. Later, operations were resumed at 10 of these plants after implementation of safety measures, but 24 of them are currently being decommissioned or have been marked for decommissioning. Going forward, decommissioning will be taking place in earnest. At the same time, a lengthy period of time is required for decommissioning as it takes 30-40 years from removal of spent fuel to demolition of reactor building in the final stage. As such, decommissioning must be carried out accurately in the upstream stage to put together a detailed plan.

Shimizu carries out a wide range of decommissioning engineering from valuation of the radioactive contamination level of the concrete in reactor buildings and reactor containment vessels to calculation of the volume of waste by contamination level, establishment of demolition plans, calculation of the man-hours and demolition schedule considering worker radiation doses, and evaluation of total costs, including the cost of waste disposal. At the same time, because of the complex structure of nuclear power plant, a tremendous amount of time and effort would be required to proceed with engineering based on 2D drawings and material. For that reason, Shimizu developed an engineering support system utilizing BIM to increase the efficiency of and enhance engineering.

When applying Deco-BIM, importing as BIM attribute information, the data from the BIM model created based on existing drawings and the results of the separately calculated radiation from the concrete are first linked, and the calculation results. Next, building a database for the system, parameters such as the standard man-hours (work rate) for the demolition method, the air dose rate, and the calculation formula for disposal costs are entered. Finally, selecting the demolition method, such as cutting or crushing the parts, based on the distribution and level of contamination of the concrete visualized in 3D. For example, if using a wire saw, the cutting dimensions, spacing of holes for the wire, and other detailed demolition conditions will be entered into the system.

Based on the entered information, Deco-BIM supports and replaces decommissioning engineering, various calculations, including the volume of waste by contamination level and the man-hours and demolition schedule considering worker radiation doses. Compared to reviewing period based on 2D drawings and materials, the same level of review can be performed in one-fifth. It allows far more demolition plans to be drafted and evaluated during the same review period, thereby reliably contributing to a reduction of total costs. In addition, linking the ID assigned to the waste in the demolition stage to the BIM data makes possible to ensure traceability of decommissioning work over the long term.

Shimizu aims to participate in decommissioning projects from the planning and review stage by proposing logical demolition plans to electric power companies utilizing Deco-BIM.

≪For Reference≫

Flow of decommissioning engineering using Deco-BIM Overview of Deco-BIM Evaluation of contamination level

The radioactive contamination levels of concrete are classified as Level Ⅱ, Level Ⅲ and CL （not requiring handling as radioactive waste）. Level Ⅱ concrete must be stored for 300 years and Level Ⅲ for 50. Both require special storage methods and facilities, so it is important to accurately segregate the waste according to contamination level in order to reduce decommissioning costs. Decommissioning a 1.1 GW class boiling water reactor （BWR） generates 2,090 m³ of radioactive concrete. This breaks down to 570 m³ of Level Ⅱ radioactive concrete and around 1,520 m³ of Level Ⅲ radioactive concrete. The treatment and disposal costs alone （excluding demolition） are estimated at 5.0 billion yen.

Results of separately calculated radiation from concrete

The decommissioning solution system developed by Shimizu is applied to evaluate the radiation level of concrete with high accuracy. The factors determining the radioactive level of the concrete in the reactor building include the shape of the reactor and the building, the elements contained in the concrete such as cobalt and europium, which have relatively long half-lives, the operating history of the reactor, the burnup of fuel in the reactor core, the state of nuclear fission （amount of neutrons generated）, and the half-life of generated radioactive substances. Taking these factors into consideration, this system performs a 3D analysis of the changes in the radiation level of concrete over time.

The information contained in this news release is the current information on the date of publication. Please be aware that this information may have changed by the time you view it. Please contact the company to inquire for further details.

News Release List