Methods for simulating crane-deployment plans used in construction of nuclear power plants

Abstract

To construct nuclear power plants no later than delivery dates for certain, Hitachi adopts the "opentop construction method." This method requires civil and mechanical installation works to be carried out concurrently. Therefore, civil and mechanical contractors must share cranes for carrying in materials such as rebar, piping components, and equipment. First, civil contractors make cranedeployment plans, which consist of crane locations, load capacities, and its operation schedule. Since it is difficult to estimate quantities of installation material exactly in an early construction-planning phase (in which the detailed design is not completed), plans are made on the basis of the planner's experiences, not quantitative evaluations. Due to such undefined conditions, it is often the case that actual utilization rates of cranes are larger than expected. To resolve this issue, scheduling extra dayand night-work shifts and increasing the number of cranes are typical solutions. A simulation system for quantitatively evaluating the validity of crane-deployment plans was developed. It applies 4D simulation technology, integrating 3D models and a time dimension, to calculate utilization rates of cranes. To calculate utilization rates automatically and accurately, two functions were developed. The first function maps data between 3D objects and carry-in tasks by using a method called "fast geometric interference checking." The second one estimates installation material quantities in early construction-planning phases by using a statistical method called "random forests," which infers data from the results of previous projects. The result of verification tests based on previous construction data indicates that the proposed simulation system will significantly reduce the time required to create crane-deployment plans and improve their accuracies.