20 Octobre 2015
October 20, 2015
Oct. 20, 2015 - Updated 14:35 UTC+2
The operator of the damaged Fukushima Daiichi nuclear plant has conducted the first endoscopic probe of the container that houses the core of its Number 3 reactor.
Workers with Tokyo Electric Power Company on Tuesday inserted cameras and other measuring instruments into a pipe leading to the inside of the reactor containment vessel. The unit suffered a meltdown in the March 2011 disaster, along with 2 other reactors.
The workers found radiation levels in the vessel as high as one sievert per hour. The levels were lower than those measured in the containers of the Number 1 and 2 reactors. They also confirmed that the vessel was filled with water to a height of about 6.4 meters.
The operator says Tuesday's survey found no major damage to the facility as far as it could see.
TEPCO officials suspect that most of the nuclear fuel in the reactor melted through the core and dropped into the containment vessel.
But the workers were not able to see the bottom of the vessel, as what appears to be accumulated dust in the water was in the way of the endoscope.
TEPCO plans to conduct a similar operation on Thursday. The officials will also discuss the timing of robotic probes based on the results of the endoscopy.
The utility had earlier conducted endoscopic and robot inspections of the interiors of the Number 1 and 2 reactors.
Tokyo Electric Power Co. for the first time has inserted remote-controlled cameras into the containment vessel of reactor 3 at the Fukushima No. 1 nuclear plant to gauge the extent of the damage from the core meltdown.
After the probe, Tepco said water inside the containment vessel was about 6.5 meter deep, about the same as it had estimated. The level of radiation was quite high at 1 sievert, while the water temperature was 33 to 35 degrees.
There was no visible damage inside the vessel, the utility said.
Tuesday’s operation was conducted ahead of a planned inspection using a robot to pinpoint the location of and situation surrounding the melted fuel. How to remove the melted fuel has been a huge question in the process to decommission the power plant.
On Tuesday, the utility inserted a camera into the vessel with equipment to measure radiation levels and to photograph the area above the surface of the water. Tepco will then lower a camera with a thermometer toward the bottom of the container to check the situation under the water surface.
A few days later, the company will collect water samples from inside the container to check for radioactive substances and chloride concentrations.
In April, Tepco conducted an inspection using a robot inside reactor 1. It also plans to carry out a similar inspection inside reactor 2. The water level is believed higher inside reactor 3 than in the other two units.