Photo/IllutrationA robot on March 18 took this image of a valve and a pipe in cooling water at the bottom of the containment vessel of the No. 1 reactor at the Fukushima No. 1 nuclear power plant. (Provided by the International Research Institute for Nuclear Decommissioning)

Cooling water in the No. 1 reactor of the Fukushima No. 1 nuclear plant has improved in transparency, which should make it easier to pinpoint the location of melted nuclear fuel, the plant’s operator said.

The improved transparency, compared with the level two years ago, was confirmed on March 18, when a research robot took an image that clearly showed a valve and a pipe in the water at the bottom of the reactor’s containment vessel, Tokyo Electric Power Co. said March 19.

Devices on the robot measured radiation levels of 7.8 sieverts per hour on a metal stage for workers and 1.5 sieverts per hour in the water.

The research robot on March 20 and 21 will study areas where the melted nuclear fuel could exist.