Feb 7, 2015
HITACHI, IBARAKI PREF. – A snakelike robot designed to examine the interior of one of the three meltdown-hit reactors at the Fukushima No. 1 nuclear power plant is ready to begin its expedition.
Assessing the damage in the reactors is a crucial step in decommissioning the poorly protected plant, which was crippled by core meltdowns triggered by the Great East Japan Earthquake and tsunami in March 2011.
Remote-controlled robots are essential for the job because the radiation in the reactors chambers is so high it would kill any person who got close.
Using information gathered by the robot, Tokyo Electric Power Co., the plant operator, plans to repair the damaged chambers enough so they can be filled with water in preparation to remove the melted radioactive debris, an operation planned to begin in about a decade.
The 60-cm-long robot, developed by electronics giant Hitachi and its nuclear affiliate Hitachi-GE Nuclear Energy, was demonstrated this week at a Hitachi-GE facility northeast of Tokyo. It is expected to enter the No. 1 reactor as early as April, officials said.
It has a lamp at the front and is designed to crawl like a snake through a 10-cm-wide pipe into the containment vessel. From there it must dangle and descend onto a platform just below the reactor core’s bottom, an area known as the pedestal.
There, the robot is to transform into a U-shaped crawler and capture live images and temperature and radiation levels and transmit them to a control station outside the building.
Expectations for the robot probe are high after earlier efforts at assessment met with limited success.
“Depending on how much data we can collect from this area, I believe (the probe) will give us a clearer vision for future decommissioning,” Hitachi-GE engineer Yoshitomo Takahashi said.
After its exploratory trip, which will make the robot extremely radioactive, technicians plan to store it in a shielded box. They have no plans to reuse it.
Different robots must be designed for each reactor, since each is slightly different.
According to computer simulations, all of the fuel rods in unit 1 probably melted and pooled at the bottom of the containment chamber, but there had been no way of confirming that until now.
A brief fiberscope observation conducted in 2012 produced images that were scratchy and of limited use.
To assess the debris at the bottom of the damaged reactor chambers, which are usually filled with water, an amphibious robot is being developed for deployment next year.
The damage from the melted fuel burned holes in the reactors, thwarting efforts to fill them with cooling water. As a result, water must be pumped into them continuously, producing an endless stream of radiation-contaminated water that is hampering the plant’s cleanup process.