The radiation level in the containment vessel of reactor 2 at the crippledFukushima No. 1 power plant has reached a maximum of 530 sieverts per hour, the highest since the triple core meltdown in March 2011, oTokyo Electric Power Co. Holdings Inc. said Thursday. The reading means a person could die from even brief exposure, highlighting the difficulties ahead as the government and Tepco grope their way toward dismantling all three reactors that suffered core meltdowns in the March 2011 disaster. Tepco also announced that, based on image analysis, it has discovered a 2-meter hole in the metal grating beneath the pressure vessel inside reactor 2's containment vessel, and discovered a portion of it is warped. The hole could have been caused by melted fuel penetrating the vessel after the March 11, 2011 mega-quake and massive tsunami triggered a station blackout that crippled the plant's ability to keep the reactors cool. The new radiation level, described by some experts as "unimaginable," far exceeds 73 sieverts per hour, the previously highest radiation reading monitored in the interior of the reactor.
The high radiation estimates in the No. 2 reactor of the stricken Fukushima No. 1 nuclear plant will probably force a rethink of the nationalized utility's robot-based strategy for locating its molten fuel. According to an analysis of Thursday's abbreviated probe, the radiation in the primary containment vessel is about 650 sieverts per hour, more than the 530 sieverts estimated late last month, Tokyo Electric Power Company Holding Inc. said. That level could kill a person quickly and indicates the fuel likely burned through the pressure vessel during the meltdown and is somewhere nearby. Tepco, as the utility is known, halted Thursday's robot after its camera went dark. The company suspects the problem was caused by the radiation.
The operator of the disaster-hit Fukushima No. 1 nuclear power plant said Wednesday it has completed its first attempt to use a remote-controlled probe to manipulate melted fuel accumulating at the bottom of one of the crippled reactors. During the nearly eight-hour operation, Tokyo Electric Power Company Holdings Inc. inserted the probe that is equipped with a camera, radiation meter and tong-like grips into the primary containment vessel of the No. 2 reactor. Of the six locations that were surveyed, the probe, which is 30 centimeters tall and 10 cm wide, successfully lifted several centimeters of deposits at five locations, a TEPCO official said at a news conference. But in the remaining area that resembled clay, the probe could not pick up any of the deposited material, indicating it was relatively solid. The findings from the operation will provide important information to help in the decommissioning of the Nos. 1 to 3 reactors at the plant that suffered core meltdowns in the nuclear crisis that began in March 2011, according to Tepco.
The International Research Institute for Nuclear Decommissioning (IRID) carried out the experiments using a 20-meter wide, 12-meter high model of the No. 2 reactor's suppression chamber and torus room -- areas located below the reactor's containment vessel. IRID was established in 2013 by nuclear plant makers, power firms and government organizations to develop technology needed for the decommissioning of the Fukushima plant, which was damaged by the March 3, 2011 earthquake and tsunami. After the disaster, three of the plant's reactors suffered meltdowns in the world's most severe nuclear crisis since the 1986 Chernobyl disaster. The model is located at the Naraha Remote Technology Development Center, near the crippled Fukushima No. 1 plant. "We would like to continue testing until next summer, approximately, and use (the outcomes) in deciding methods to retrieve fuel debris," Atsufumi Yoshizawa, IRID executive director, said.
During recent investigations conducted using cameras and robots at the site of Fukushima No. 1 nuclear power plant, after six years of the triple meltdown, it has likely identified melted fuel rods for the first time underneath the damaged reactor 2, Japan Times reported. Before this investigation, robots were also sent inside the reactor 2, in mid-February, which was the first time since the plant's meltdown in 2011, but due to extreme high radiation levels, even those could not survive, the Guardian had reported. Read: Fukushima News: Even Robots Failed To Survive In'Unimaginable' Nuclear Reactor Radiation The Fukushima Daiichi tragedy is the world's worst nuclear disaster since Chernobyl that occurred April 26, 1986. Although experts have pointed out that getting a peek into the vessel of reactor 2 was an accomplishment but the investigation also highlighted the difficulty level of reaching the exact location of the melted fuel. Removing it is still a distant thought.