In this TEPCO video you will see the steps taken to test, transport, and assembly the cover over Unit 1 reactor building.
The purpose of cover for the reactor building
A cover for a reactor building is installed for the purpose of preventing diffusion of radioactive materials (radioactive materials discharged from the reactor, water vapor from spent fuel pool, rubbles and dust with radioactive materials, etc.) and stopping rain water from entering into the reactor building.
The installation of the cover is a temporary emergency measure until a midterm measure is developed.
Summary of the structure
The cover has a steel frame structure, where four pillars are built around the reactor building, with beams connecting the four pillars. Roof panels and wall panels are fitted with film materials made of vinyl chloride resin coating and polyester fiber fabric which prevents diffusion, and these panels cover the whole reactor building.
Dimension of the cover structure is approx. 47m (North-South direction) x approx. 42m (East-West direction), and approx. 54m of height.
The design of the cover for the reactor building meets safety requirements in the event of an earthquake or high wind.
Installation technology
In order to reduce the exposure dose as well as shorten the construction period, TEPCO used the following installation technology that minimized workers’ access to the reactor building.
Large scale modules
Steel frame beam (40m), filmed panels for walls (approx. 20m), and filmed panels for the roof (approx. 40m) were assembled into large modules. Large modules were put together on the site using crawler cranes.
The large modules were then transported by ship to Onahama port outside the Fukushima site. A mock-up installation was performed at this location.
Measuring / control technology
In order to enable remote installation, TEPCO used the latest technology such as systems to control lifted materials from rotating and detach rigging equipment by wireless signals, 3D laser scanning of the turbine building areas, real-time measurement and control of locations of materials in assembly process.