Japans nuclear fuel rod removal from Fukushima Nuclear Power Unit 3 has been delayed for more than four years

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 Japans nuclear fuel rod removal from Fukushima Nuclear Power Unit 3 has been delayed for more than four years

The original title: More than four years later, Japan began to take out the nuclear fuel rods of Fukushima Nuclear Power Unit 3 today.

(Observer News)

Eight years after the Fukushima nuclear power plant accident in Japan, the removal of fuel rods from its No. 3 engine finally began after several delays.

According to the Japanese Broadcasting Association (NHK) on April 15, at 8:50 local time, the first fuel rod removal of Aircraft 3 was officially started four years and four months after the initial plan was postponed. In Unit 3, 514 highly radioactive nuclear fuel rods were used and 52 new fuel rods were not used. It is also the first time in the world that fuel rods have been removed from nuclear power plants that have melted down their cores.

It is reported that the difficulty of this operation is not only the large number of fuel rods, but also the excessive radiation in the nuclear reactor. In addition, due to the hydrogen explosion, there are many more difficult debris on the top of the nuclear reactor.

According to NHK, Tokyo Electric Power Company operated the whole operation remotely. Firstly, spent fuel rods (about 4 meters long) in the cooling pool are hoisted to large containers in the cooling pool, and 3 to 4 rods are planned to be hoisted on the 15th day. A few days later, when the large container is full of 7, another large crane is used to transfer the whole container to the outside of the plant. It is expected that all remaining fuel rods in Unit 3 will be removed by 2020.

The live teleoperation can be seen in the correspondents office at Fukushima Nuclear Power Station. The grabbing machine adjusts its position while slowly descending. After grasping the handle of the fuel assembly, it is slowly hoisted. As you can see in the picture, there are still debris on the suspended nuclear fuel tank.

Tepco hopes to complete the fuel rod removal work by next year. NHK pointed out that how to safely and steadily complete the remote operation is the core issue of this task.

On March 11, 2011, the earthquake and tsunami struck northeastern Japan, directly leading to the Fukushima nuclear accident. Subsequently, TEPCO plans to begin the removal of fuel rods from Unit 3 by the end of 2014. However, due to excessive radiation and other reasons, the plan has been delayed repeatedly. In March this year, the fuel rod removal plan was delayed again because of abnormal alarm of cable engine during operation training. After many repairs, the fuel processor and the crane lifting the transport container were basically eliminated and put into operation on April 15.

Status of other units

Fukushima Daiichi Nuclear Power Station has six units, which were put into operation in the 1970s. At present, all units 1 to 4 are in low temperature stop state. Because the spent fuel pool of Unit 4 did not operate at the time of the accident, it was easier to remove it. More than 1,000 fuel rods were removed at the end of 2014. Units No. 5 and 6 were scrapped in January 2014 because their spare power supply was not destroyed and the damage was minor.

Unit 1 is still in the investigation stage with 392 remaining fuel rods. TEPCO had previously deduced that most of the nuclear fuel in the core of Unit 1 should have penetrated the reactor pressure vessel and fallen into the containment, possibly accumulating in the underground part of the containment. On March 28, Japans International Reactor Abandonment Research and Development Agency (IRID) demonstrated six types of ship-type robots that will investigate Unit 1 reactor. The robot has diving function and can take all-round photographs. It is reported that the robot is expected to be put into use in summer and the investigation will last for several months.

Unit 2 was once considered the most severe form, with 615 fuel rods remaining inside. As early as 2017, Tokyo Electric Power Company said that the radiation in Unit 2 had high intensity. In February of this year, the East Power Investigation ushered in a turning point. They touched the melted nuclear fuel (fuel debris) in the reactor containment of Unit 2 and confirmed the hardness and other characteristics. In addition, TEPCO has successfully picked up small rocky deposits that may be fuel debris. Dashan Shengyi, head of public relations at Dongdian Power Company, said at a press conference: By moving, it has proved that fuel debris can be removed. However, for objects that cannot be clamped and removed, relevant equipment needs to be developed.

According to Xinhua News Agency, Zengtian Shanghong, the head of the waste reactor at Fukushima Daiichi Nuclear Power Station, said it would take 30 to 40 years to complete the work of scrapping the reactor completely, that is, until 2041 to 2051, it would be possible to complete the work thoroughly.

Responsible Editor: Zhang Di