A robot captured images inside one of the three severely damaged reactors at Japan’s Fukushima nuclear power center.
The Fukushima center was damaged by a powerful earthquake and tsunami that struck eastern Japan on March 11, 2011.
The latest images showed that metal in the main support structure and parts of a wall were severely damaged or missing. The images raise concerns about the plant’s earthquake resistance in case of another disaster.
The plant's operator is Tokyo Electric Power Company Holdings (TEPCO). The company has been sending robots inside the Unit 1 main containment structure since last year. The containment structure surrounds the nuclear reactor.
The new video images released Tuesday were taken at the end of March.
An underwater vehicle was sent inside the Unit 1 pedestal, a supporting structure under the core, or center of the reactor. The vehicle returned with images of an area seen for the first time since the plant was destroyed 12 years ago. The area inside the structure is where some of the melted nuclear fuel is likely to be found.
The robot took a five-minute video and 39 images. It showed that the 120-centimeter-thick wall outside of the pedestal was severely damaged near its bottom.
Keisuke Matsuo is the TEPCO spokesperson. He told reporters Tuesday the company plans to gather more data and images over the next several months. The company hopes to find out if and how the reactor's earthquake resistance can be improved.
The images of the exposed metal support structure have caused concerns about the reactor's safety. About 880 tons of highly radioactive melted nuclear fuel remain inside the three reactors.
Robots have provided some information, but the condition of the melted debris is still largely unknown. The amount is about 10 times the damaged fuel that was removed in the cleanup of the Three Mile Island nuclear plant. The plant in the United States had a partial meltdown in 1979.
Masao Uchibori is the Fukushima governor. He urged TEPCO to measure “levels of earthquake resistance and provide information” to ease the “concern of the residents and people around the country.”
The video taken by the robot showed equipment and material that fell down. It also showed other kinds of substances, possibly nuclear fuel, that fell from the core and hardened. The material piled as high as 40 to 50 centimeters from the bottom of the containment structure, Matsuo said.
However, the pile is lower than piles seen in images taken in earlier studies at two other damaged reactors. That suggests that the meltdowns in each of the affected reactors may have progressed differently, company officials said.
Matsuo said the new data will help experts decide how to remove the material and to study the 2011 meltdowns. TEPCO also plans to use the data to create a detailed map of melted fuel and material, which would take about a year.
Based on data collected from earlier studies, experts have said most of the melted fuel inside Unit 1 fell to the bottom of the main containment structure. But some might have even fallen through into the concrete foundation. That would make the already difficult job of removing the melted fuel even harder.
An earlier attempt to remove melted material from Unit 2 is expected to begin later this year after a two-year delay. Used fuel removal from the Unit 1 reactor's cooling pool is to start in 2027 after a 10-year delay. After all the used fuel is removed, the other melted materials can be removed from the reactors starting in 2031.
I’m Dan Novak.
Dan Novak adapted this story for VOA Learning English based on reporting by The Associated Press.
Words in This Story
(nuclear) reactor — n. a complex device that produces nuclear energy through fission using radioactive fuel
tsunami — n. a powerful and damaging ocean wave caused by an undersea earthquake
radioactive — n. releasing a lot of radiation caused by atomic activity in some chemical elements
debris –n. pieces that are left after something is destroyed
resident — n. a person who normally lives in a place
pile — v. to place a group of things on top of one another
foundation — n. the base on which everything in a building or similar structure is built