FUKUSHIMA PREFECTURE, Japan — One of the reactor buildings at Japan’s damaged Fukushima Daiichi nuclear plant looks far different from the others. Once just a squat rectangle, the No. 4 unit is now wrapped inside a fortress of iron beams, rising as high as a 10-story apartment.
Working from platforms and catwalks atop this new steel tower, Japanese engineers will soon begin extracting the No. 4 unit’s fuel rods, in what the plant operator calls a delicate but groundbreaking step in a cleanup that is expected to take decades.
The operation could begin within a week or two, officials here say, marking the first time since the March 2011 meltdowns that Japan has removed fuel from any of its wrecked reactors.
If it goes smoothly, the extraction of the rods will reduce one of several risks that workers at the plant are contending with, including sustained ocean leaks of contaminated water. Japan’s nuclear regulator last month gave approval to the plant operator, the Tokyo Electric Power Co. (Tepco), to begin the rod-removal process.
The operation amounts to a nuclear high-wire act, carried out with cranes and other machinery operating on scaffolding above the No. 4 unit — an area accessible via several hundred stairs or a skeletally built elevator.
As workers wearing protective white suits prepared some of the equipment Thursday, Tepco led a foreign media tour that included an up-close look at the fuel rods inside the unit.
For 21 / 2 years, the rods have been a source of sharp fear and, later, apprehension.
At the time of the massive earthquake and tsunami in March 2011, the No. 4 unit wasn’t in operation; it was shut down for maintenance, and its fuel rods tucked away. The problem was the storage location; the rods were stowed in a pool of water on a high shelf, about 100 feet above the ground.
As nuclear fuel in units 1, 2 and 3 melted down, U.S. and Japanese government officials feared that cracks may have formed in the concrete basin that held the water of the No. 4 pool. The fear was unfounded, but there was no immediate way to know that, because radiation levels were high enough to prevent access to the pool.
Had the water drained out of the pool, the thousands of unprotected uranium fuel rods would have begun melting within eight hours.
Workers at the plant have since reinforced the pool against aftershocks. But experts say the rods could be stored far more safely at ground level. Once the extraction operation is complete, they will be.
From the scaffolding above the No. 4 reactor, one can see a pool of murky blue water, as wide and long as a backyard swimming pool but with several times the depth. The 13-foot-long fuel rods are submerged in the water, bunched into 1,533 clusters of 80 rods each.
The clusters will be removed one at a time by a green crane that one Tepco spokesman described as a “robot arm” and carefully placed into a cask that has been lowered into the water. Once a cask has 22 clusters, a process that will take a week, it will be capped, raised out of the water, lowered to a waiting truck and transported to a storage building about 100 feet away.
During the tour Thursday, plant superintendent Akira Ono and several Tepco spokesmen took pains to reiterate that the removal process would not be risky or, in Ono’s words, “particularly dangerous.” They said that the crane and other machinery use redundant wires and brakes, and that even in the event of an earthquake or tsunami, the crane won’t drop any fuel.
But there are a few potential complications. Small bits of debris, the result of a March 2011 hydrogen explosion, remain in the pool and could make it hard for engineers to cleanly pull out the rods. Some of the rods could be damaged and, therefore, could leak radiation.
This removal of fuel is a “totally different operation” from the usual, Shunichi Tanaka, the chairman of Japan’s nuclear regulatory agency, told reporters last month.
After the fuel from the No. 4 unit is removed, Tepco will extract the spent fuel from far-less-crowded pools in units 1, 2 and 3.
The trickier step — removing fuel that is thought to be in melted lumps at the bottom of the 1, 2 and 3 reactor vessels — will not begin until 2020.
Tepco hopes to remove all the fuel within 20 to 25 years.