Remotely controlled robot designed for research and cleaning up the damaged reactor at the Japanese nuclear station “Fukushima-1” had to urgently evacuate after its navigation camera dramatically darkened because of the impact of incredibly powerful radiation levels.
The failure of the mission suggests that the background radiation inside the reactor of the station is much higher than reported last week. In addition, it means that even robots need a lot of time in order to deal with this mess.
Last week, it was reported that the existing behind the protective shell of the reactor No. 2 level of radiation has reached catastrophic 530 SV/h – enough to kill a human in just a few seconds. However, some officials from the Japanese government challenged this testimony, as Tokyo Electric Power Holding Company (TEPCO), a company engaged in the rubble at the “Fukushima-1” was used for these purposes, the front-end camera of the robot, through which she explores the territory, but has not conducted the necessary measurements directly by using Geiger counters and other radiation monitors.
But as it turned out, the original calculations were even lower than the real picture now. This is due, most likely, so that the robot TEPCO is getting closer to the molten nuclear fuel. Near the accumulations of spent fuel, as a rule, more elevated background radiation.
Recently, remotely controlled robot had to pull out after after a couple of hours of work inside the damaged reactor began to refuse his camera. If you believe the reports TEPCO, the radiation level at that time was about 650 SV/h, which is already at 120 sieverts greater than said records of the last month (although in new reports and indicated a 30 percent error). The robot is designed to operate with accumulated radiation level of 1,000 sieverts, which probably didn’t help his cell, given that just a few hours after starting the job she has failed. This may mean that the molten radioactive fuel has leaked from your tank even during the crash of 2011 and could be somewhere nearby from the last point of stay of the robot.
It is important to consider that the radiation is only retained inside the station and, fortunately, does not affect the nearby station regions. In addition, nothing indicates that there is some leakage of radioactive fuel outside the station. The effects of radiation on the air and the nearby ocean is also not marked. In addition, no marked increase in the level of radiation inside the station. Its level in the testimony of TEPCO becomes higher because the robot is approaching to the main source of radiation, i.e. to the radioactive fuel. The previous highest level in 73 SV/h was recorded back in 2012 and at a more remote distance from the epicenter.
A few days ago, TEPCO sent a robot into reactor No. 2 for carrying out the research work and preparing the space for further solution. It was the first time since the earthquake and tsunami that occurred 6 years ago and triggered the catastrophe at the “Fukushima-1” when the robot entered directly in the reactor itself. His task was to clean the thick layer of radioactive debris from melted and hardened pieces of paint and the insulation of cables under the Plenum, which contains the reactor core. TEPCO is trying to clear the way for another robot, which will have to do further work. The second robot, called “Scorpion”, would have to carry out measurements of radiation levels and temperature inside the reactor and to assess the condition of the reactor and the remaining residues of radiation fuel.
However, before this happens, you must clear a passage. The robot, TEPCO, is equipped with a powerful hydrant and brush, to date, been able to clear only part of the journey to the place that company in the future wants to explore. The car was cleared only a few metres of sediment from the burnt debris near the outer part of the skin’s primary protective shell of the reactor, however, to go further could not, as these deposits proved to be too strong for cleaning. Every inch of frosting black-and-gray mass of radioactive fuel, the outer skin and other parts became thicker and thicker. After a couple of hours since the start of the picture received from the camera of the robot, has deteriorated significantly, pointing to the impending catastrophic failure. Its operators had made an emergency decision to halt the mission until they completely lost control of the car.
Now TEPCO is most troubling is that “Scorpion” will not be able to reach the desired point of destination under the skin of the reactor and, like its predecessor, will not be able to work for long time in such conditions (the second robot designed can operate at 1000 sieverts). Extreme radiation levels may force TEPCO to review its strategy of rubble with the use of robots, and shift attention to the radioactive fuel. In General, work on the clearance of radiation is only at the initial stage. The overall level of work may require decades. As long as TEPCO does not establish the exact location of radioactive fuel and does not know the exact status and possible levels of structural damage in each of the three reactors to remove the fuel and eventually to dismantle the station will not work.