Tepco on Tuesday began dismantling the temporary shroud covering the wrecked reactor 1 building at the Fukushima No 1 nuclear plant.

Tokyo Electric Power Co. installed the cover in October 2011 to keep radioactive materials from dispersing.

Workers used a crane Tuesday to remove one of the six panels that form the shroud's roof. Each panel is about 7 meters wide and about 42 meters long.

As the panel came off, the upper part of the reactor building could be seen for the first time since December, when part of the cover was temporarily removed. The building's exterior was shattered in a hydrogen explosion in March 2011, in the first few days of the crisis.

Tepco plans to complete removing the shroud in fiscal 2016 and to clear debris and install equipment for the sensitive process of removing the 392 spent fuel assemblies currently lying in the building's storage pool. That procedure is expected to begin in fiscal 2020.

Takao Kikori, a senior nuclear safety official in the Fukushima Prefectural Government, called for care to be taken in the dismantling work to ensure the safety of local people.

The utility plans to remove the second panel in early August or later and complete the removal of all six panels by the end of this year. Later it will remove the side panels and install windbreaker sheets ahead of clearing the debris.

The cover was installed as an emergency measure to keep radioactive dust from scattering. Tepco initially planned to dismantle it in fiscal 2013 or 2014 but was forced to delay the work to take additional dust control and other measures.