13 Février 2017
February 13, 2017
By HISASHI HATTORI/ Senior Staff Writer
A recent tour of the Fukushima No. 1 nuclear power plant shows not only the damage to the reactors, but also the progress that has been made in improving the working environment for those preparing the site for decommissioning. (Video footage by Hisashi Hattori)
On visiting the crippled Fukushima No. 1 nuclear power plant in 2013, journalists had to don full facial masks and bulky protective clothing because of the high radiation levels.
But on a tour on Feb. 6, except for a face mask and vest containing a dosimeter, normal clothing was all that was necessary to enter the site.
While conditions on the grounds of the plant may have improved in the six years since the catastrophic triple meltdown, there are many signs that the decommissioning of the reactors will be drawn out.
A group of reporters from Japan National Press Club member organizations were given a tour on Feb. 6 of the plant site by officials of Tokyo Electric Power Co., the plant operator.
The latest visit was the fifth for the writer since the March 2011 nuclear accident triggered by the Great East Japan Earthquake and tsunami.
A bus carrying the journalists stopped on a hill overlooking the four crippled reactor buildings. The No. 1 reactor building stood about 80 meters away. The dosimeter held by the TEPCO official accompanying the group recorded a reading of 0.149 millisieverts per hour.
The No. 1 reactor building was once covered to prevent the spewing of radioactive materials because the roof had been blown off in a hydrogen explosion in the early days of the accident. However, that cover was removed in November 2016.
"The ceiling remains collapsed," the TEPCO official said.
The rubble remains untouched on the upper part of the building, and the metal skeleton was clearly visible.
At the No. 3 reactor, work continues to remove spent nuclear fuel from the storage pool located at the upper part of the reactor building. The bent metal parts that looked like a bird's nest have been removed, but cracks remain along the thick concrete side walls of the building, exposing the metal reinforcement.
The exterior of the No. 2 reactor building is largely unchanged from before the accident, mainly because the building was not hit by an explosion.
However, images from the interior painted a different picture. In January, what appeared to be a lump of melted nuclear fuel that flowed out of the pressure vessel was captured on camera. An analysis of the images led to the estimation that a maximum radiation level of 530 sieverts per hour existed in the containment vessel.
On Feb. 9, another robot was forced to abort its operations and the estimate was made that the radiation level was 650 sieverts per hour.
Experts now believe that an unexpectedly large amount of melted nuclear fuel has likely spread throughout the reactor.
The exponentially large level of radiation is apparent when a comparison is made with the 1999 accident at the JCO uranium reprocessing facility at Tokai, Ibaraki Prefecture, when a criticality accident led to the deaths of two workers. At that time, the radiation level for the individual exposed to the lower level was between six to 10 sieverts.
The bus took the group close to the No. 2 and No. 3 reactors.
Approaching within a few meters of the No. 3 reactor building, the TEPCO official said that the radiation level on the dosimeter was 0.245 millisieverts per hour.
While that may seem infinitesimal next to the No. 2 reactor containment vessel, exposure to it for five hours would be equivalent to the annual limit of 1 millisievert considered safe for humans.
Rubble in the area is being removed by remotely controlled cranes and other heavy equipment. Robots are used for indoor work, but progress is hampered by the high radiation levels.
The plant site at one time included an abundance of forested area, but that has been cut down.
In its place are rows upon rows of tanks up to three floors high holding radiation-contaminated water. There are a total of about 1,000 such tanks on the plant grounds.
From immediately after the nuclear accident, water continued to be pumped into the three reactors to cool the melted nuclear fuel. In addition, groundwater flows into the reactor building basements at a rate of about 150 tons a day. While the volume of water flowing in has decreased, it still becomes contaminated by radiation.
No decision has yet been made on what to do about the approximately 960,000 tons of contaminated water on the plant site.
On the other hand, noticeable steps have been taken to improve the working environment of those preparing the reactors for decommissioning.
At one time, radioactive materials that had spewed out of the reactor buildings fell on large areas of the plant site. Those areas have been largely covered with mortar, reducing the areas of the plant grounds where workers must wear full face masks and protective clothing to prevent inhaling or swallowing radioactive materials.
"Workers can move around in light clothing at about 90 percent of the plant site," said Shunji Uchida, the head of the Fukushima No. 1 plant.
A nine-floor facility that can accommodate 1,200 workers has been constructed where workers can take a break and rest. A new headquarters building has also been constructed with an atrium.