New robot to inspect molten fuel

January 28, 2019

TEPCO unveils device for handling nuclear debris

https://www3.nhk.or.jp/nhkworld/en/news/20190128_32/

The operator of the Fukushima Daiichi nuclear power plant has unveiled a device that could become the first to directly handle fuel debris inside one of the facility's crippled reactors.

Tokyo Electric Power Company showed the device to the media on Monday ahead of a survey scheduled for next month at the plant's Number 2 reactor. It's one of the reactors that experienced meltdowns in 2011.

TEPCO has found what appears to be a mixture of molten nuclear fuel and structural parts at the bottom of the reactor's containment vessel.

The device, which is equipped with a camera and a dosimeter, is attached to a pole that extends up to 15 meters long. Its tip works like tongs, allowing it to pick up the possible debris.

TEPCO plans to send the device into the containment vessel to see how hard the possible debris is, and whether it can be moved.

Removing debris is a key step toward decommissioning the plant.

Toshihiro Yasuda of Toshiba Energy Systems & Solutions, which developed the device, says the survey is an important step toward coming up with ways to remove the debris.

In the second half of fiscal 2019, which starts in April, TEPCO plans to conduct a more detailed survey that would involve extracting a small sample of the debris.

The company aims to decide by March 2020 at which reactor to start removing debris. It hopes to start the work in 2021.

See also : http://www.asahi.com/ajw/articles/AJ201901290020.html

January 29, 2019

Toshiba unveils robot to probe melted Fukushima nuclear fuel

THE ASSOCIATED PRESS

Toshiba Corp. unveiled a remote-controlled robot with tongs on Monday that it hopes will be able to probe the inside of one of the three damaged reactors at Japan's tsunami-hit Fukushima nuclear plant and grip chunks of highly radioactive melted fuel.

The device is designed to slide down an extendable 11-meter (36-foot) long pipe and touch melted fuel inside the Unit 2 reactor's primary containment vessel. The reactor was built by Toshiba and GE.

An earlier probe carrying a camera captured images of pieces of melted fuel in the reactor last year, and robotic probes in the two other reactors have detected traces of damaged fuel, but the exact location, contents and other details remain largely unknown.

Toshiba's energy systems unit said experiments with the new probe planned in February are key to determining the proper equipment and technologies needed to remove the fuel debris, the most challenging part of the decommissioning process expected to take decades.

The three reactors at the Fukushima plant suffered core meltdowns after a massive 2011 earthquake and tsunami damaged key cooling systems.

In last year's probe, a camera developed by Toshiba Energy Systems & Solutions Corp. and the International Research Institute for Nuclear Decommissioning found large amounts of deposits in that area, including parts that resembled pebbles or gravel.

The 30-centimeter (12-inch) long robot unveiled Monday will carry a radiation dosimeter, thermometer, LED lights, a camera and a pair of tongs as it slowly slides down from a pipe.

The probe, attached by a cable on its back, is to dangle from the pipe and descend to the bottom of the reactor vessel's pedestal, a structure directly below the core from which the melted fuel fell.

Toshiba plans to use the new device to touch and grip the deposits with the tongs, which can hold a lump as wide as 8 centimeters (3 inches) weighing up to two kilograms (4.4 pounds), to investigate its hardness and other details, said Jun Suzuki, a Toshiba ESS group manager for the project.

"Until now we have only seen those deposits, and we need to know whether they will break off and can be picked up and taken out," Suzuki said. "Touching the deposits is important so we can make plans to sample the deposits, which is a next key step."

The probe will mainly examine the fuel debris' physical condition rather than its radioactive components or other details which require actual sampling and safe storage.

"We are taking one step at a time," said Tsutomu Takeuchi, a Toshiba ESS senior manager for the Fukushima decommissioning project. "First we'll find out if those deposits can be picked up." If the device is unable to lift anything, that's also a key finding, he said. In that case, they will need a cutting device to tear off a sample piece.

TEPCO and government officials plan to determine methods for removing the melted fuel from each of the three damaged reactors later this year so they can begin the process in 2021.