According to TEPCO, they began making the map in late March with the aim of measuring radiation levels at 230 locations in the plant.

Following the map’s data, by April 23, the radiation levels measured at most of locations were under 100 millisieverts/hour.

However, the radiation level at more than other 30 spots around the reactors No.1 to No.4 still exceeded 100 millisieverts/hour.

Basing on the map, TEPCO could transfer their workers to the plant to repair and tidy up the ruins in safe conditions.