The installation of piece weighing about 55 tons completes work on a half-cylinder roof on the No. 3 reactor building at the Fukushima No. 1 nuclear power plant on Feb. 21. (Kenji Notsu)

Work was completed Feb. 21 on a half-cylinder roof designed to trap radioactive substances emitted when spent fuel rods are removed from the No. 3 reactor building at the Fukushima No. 1 nuclear plant.

Tokyo Electric Power Co., the plant’s operator, plans to remove the spent fuel from the building’s storage pool as early as this autumn.

Construction work on the roof--23 meters wide and 57 meters long--started in July 2017.

The final piece, weighing about 55 tons, was lifted by a crane and put into place on Feb. 21. The roof is located directly above the storage pool.

A hydrogen explosion severely damaged the original roof of the No. 3 reactor building days after the March 2011 Great East Japan Earthquake and tsunami triggered the meltdowns at the plant.

The 566 fuel assemblies in the storage pool pose a serious risk in the event of another disaster striking the plant.

Completion of the roof should advance TEPCO’s plans to remove the fuel rods as soon as possible.