January 29, 2023
On March 11, 2023, it will soon be 12 years since the world’s worst accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant (Okuma and Futaba, Fukushima Prefecture), which caused the meltdown of Units 1 through 3. There is still no word on when the nuclear fuel (debris) that has melted down inside the containment vessels will be removed. On March 27, a team of reporters from this newspaper went inside Unit 5, which is almost the same type as Units 1-3 where the accident occurred, but was spared from the accident. The team was confronted with the difficulty of working inside the reactor to bring the accident under control. (Kenta Onozawa, photo by Takeshi Yamakawa)
Unit 5 was not in operation at the time of the accident at the nuclear power plant in 2011, as it was undergoing routine inspection.
 Wearing protective clothing that covered his entire body, he tried to enter the work space for equipment maintenance, located directly under the “pressure vessel” that contained the nuclear fuel, and hit his head. Above his head hung a device for moving the control rods that are inserted into the nuclear fuel, and he had to crouch down to enter the space. The circular work space is about four meters in diameter. It was so narrow that it was difficult to move.

The workspace is located directly below the pressure vessel of Unit 5, which is almost the same type as Units 1-3. The control rod drive unit and other equipment looms overhead in this narrow space of about 4 meters in diameter at TEPCO’s Fukushima Daiichi Nuclear Power Plant.

Once down at the bottom of the containment vessel, one cannot walk straight due to the complex arrangement of various piping and equipment above one’s head and under one’s feet.
 In Unit 1, this thick wall of concrete had been removed, leaving the reinforcing steel inside exposed.

TEPCO plans to put a robot inside the opening after March to examine the overall damage to the wall. However, we wondered whether the robot could really enter the narrow space, which is believed to contain much debris and collapsed equipment. A TEPCO spokesperson minced no words, saying, “Without actually checking the damage to the wall with the robot, we cannot determine whether the earthquake resistance has been maintained.
 Meanwhile, on the seaward side of the Unit 5 reactor, work was steadily progressing on a water tank to temporarily store water diluted with a large amount of seawater in preparation for the discharge of contaminated water into the ocean after purification. The government expects to begin discharging the water “in spring or summer,” but it is unclear how to gain the “understanding” of fishermen, which is a prerequisite for such a release.

Workers constructing a water tank to temporarily store treated water before it is discharged into the ocean. A lifeline is attached to the workers at the TEPCO’s Fukushima Daiichi Nuclear Power Plant on March 27.

The reporter was exposed to about 50 microsieverts (μSv) in about three hours of reporting. This is one twentieth of the annual exposure limit for the general public, and this is calculated to have occurred in only a short period of time. The debris removal, which is the main task of restoring order after the accident, is still in the preparation stage, and the situation inside the reactor is still not fully understood. We were reminded once again of the magnitude of the remaining problems.