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Mar. 10, 2015 - Updated 04:16 UTC



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Decommissioning Fukushima Daiichi

Mar. 10, 2017

Workers are still struggling to contain high levels of radiation and contaminated water at the Fukushima Daiichi nuclear power plant, as they work to decommission the facility 6 years after the disaster.

The plant is located on the Pacific coast, more than 200 kilometers northeast of Tokyo. It suffered one of the worst nuclear accidents in history after the quake and tsunami hit on March 11, 2011.

NHK World's Ayako Sasa joins anchors Aki Shibuya and Sho Beppu in the studio.

Shibuya: Ayako, can you bring us up to speed on what's gone on at the plant since the disaster?

Sasa: This is a model of the nuclear power plant. It's facing the ocean and when the tsunami hit it caused massive damage to 4 reactor buildings and facilities. Three of them were damaged by hydrogen explosions, and reactors 1, 2 and 3 suffered meltdowns. To cool the reactors, water needed to be pumped in. They're still pumping water in today, and when it goes inside, it gets contaminated.


That water is then processed and is kept in storage tanks. There are around 1,000 of them. But what to do with all that contaminated water has not been decided. What's more, there's also underground water coming down from mountains in this direction and getting inside.

Shibuya: Tokyo Electric Power Company is trying to prevent that water from getting in.

Sasa: That's right. This is where the Ice Wall comes in. Here's a look at the underground part of the plant. Water runs down from the mountains to the ocean. It seeps through cracks in the buildings and it becomes contaminated. Tons of water flood into the buildings each day.

The Japanese government and TEPCO decided to build an underground ice wall to block the water. They put long pipes into the ground and filled them with liquid coolant, which in turn freezes the soil between the pipes. The operation began last year and still isn't completed. The final part of the process needs approval and the nuclear watchdog is still studying what they think will happen when the wall is complete.

Shibuya: Of course, the goal is to decommission the crippled plant. Can you talk about that process?

Sasa: Yes. When the meltdowns happened, nuclear fuel rods inside the reactors melted. TEPCO needs to find out what happened to that molten fuel and how much there is in order to figure out how to remove it. But here's the problem. Radiation levels are still too high for workers to get inside to see the damage for themselves. Because of this, they've sent in cameras and robots instead. Last month, the latest robot was sent in to measure the temperature, radiation and take pictures. It broke down and TEPCO gave up on it.

Seeking Solutions
Yoshihito Kametani

While the picture of what's going on inside Daiichi remains murky, engineers are pushing ahead with trying to solve one of the biggest challenges. They need to invent machines that can remove the melted fuel rods.

Earlier this year, TEPCO sent cameras into the containment vessel of the No.2 reactor. An image shows a steel grating that's covered in a yellowish substance and some parts of the floor that have caved in.

The findings surprised some experts.

"I did expect to see a hole on the floor, but there are details which I didn't imagine," says Toru Ogawa, director at the Collaborative Laboratories for Advanced Decommissioning Science. "We see so much of something, sticking all over the floor. This is what I didn't expect."

But he says it's difficult to tell what it is.

TEPCO had hoped to locate melted nuclear fuel. Removing it will be the biggest hurdle in the decommissioning process, but they've admitted that they still aren't sure where it is.

"We have yet to come to any conclusion about the exact location of the melted fuel. We intend to examine the information we have collected up until now, and then we'll come up with a more detailed judgment," says Yuichi Okamura, a TEPCO official.

High radiation levels have prevented anyone from going inside the containment vessels in the reactor buildings. Researchers, including at this company in western Japan, are rushing to develop robots to help workers involved in the decommissioning.

One machine may one day enter the crippled plant is a robotic arm about 7 meters long that can be remotely controlled. Engineers have just started testing it. But there are still many challenges ahead.

"We need to carry out maintenance remotely in the event of trouble. That's one of the toughest challenges," says Kenichi Kawanishi, an official at Mitsubishi Heavy Industries. "The most important thing is to find out how much and to what extent the fuel melted and spread."

TEPCO will inspect another reactor this month to try to find clues about the whereabouts of the molten fuel. They'll send a new robot with a small camera to the bottom of the containment vessel.

Beppu: As we've just heard, although research and development continue to get the answer they still haven't found the exact location of the melted fuel rods and this is after 6 years. What's the timeline looking like for TEPCO?

Sasa: Decommissioning the Daiichi plant will take decades, and the process is not only long but also complicated. The government and TEPCO are expected to decide this year on a broad outline for how to remove the melted fuel rods. Their aim is to start removing them from one of the reactors in 2021 and to complete the whole process in 30 to 40 years.

As for cost, the government says we can expect the price tag to quadruple from earlier estimates. That will bring things to about 70 billion dollars. The reason? The difficulty of the task and the lengthy period of time needed to do it. A project of this scale has never been done before.