A second robotic probe was abandoned after completing its survey mission inside a reactor containment vessel at the crippled Fukushima No. 1 nuclear plant, Tokyo Electric Power Co. said.
A second robotic probe was abandoned after completing its survey mission inside a reactor containment vessel at the crippled Fukushima No. 1 nuclear plant, Tokyo Electric Power Co. said.
TEPCO, operator of the plant, said April 20 that it has wrapped up the study of the highly radioactive environment at the No. 1 reactor and given up efforts to retrieve the robot.
“We have gathered sufficient information on the inside of the containment vessel,” a TEPCO official said.
The utility started the survey of the containment vessel by sending in a tubular-shaped robot to shoot images and monitor radiation levels and temperatures on April 10. The robotic probe, however, became inoperable.
The second robot entered the containment vessel on April 15.
TEPCO said images taken by the devices showed that scattered cables and other debris are unlikely to hamper the next stage of the decommissioning process there.
The plant operator said the photos revealed no obstacles in an area connecting the first floor and the basement, and that the surrounding facilities are more or less intact.
TEPCO on April 20 released additional images taken by the robots, including piping, conduits, ladders and pumps to circulate water inside the reactor.
The images snapped by the second robot confirmed TEPCO’s assumption that the first robot became stuck in the iron-mesh first floor of the container vessel.
A monitoring camera installed in the containment vessel to control the second robot later malfunctioned because of high radiation levels, forcing TEPCO to give up its plan to retrieve the robot.
“Attempts to forcibly retrieve the robots could pose the larger risk (of further damaging it),” a TEPCO official said.
After analyzing radiation levels, temperatures and other data obtained by the robotic probes, TEPCO plans to start a robotic survey of the basement of the containment vessel, where coolant water is circulating.
This phase is scheduled to start by the end of March next year and is intended to gather more detailed information for preparations to remove the melted nuclear fuel, the toughest part of the decommissioning process.