More than six years after the core meltdowns triggered by March 2011 mega-quake and tsunami, Tokyo Electric said Saturday that the robot probing reactor 3 at the defunct Fukushima No. 1 power plant had likely spotted fuel debris for the first time at the bottom of its primary containment vessel. Some of the debris looks like rocks and sand, and was accompanied by scaffolding and other objects from the reactor that had formed a pile about a meter high. On Friday, Tokyo Electric Power Company Holdings Inc. announced that the same robot had found what appeared to be melted fuel at the bottom of the pressure vessel, which holds the core. On Saturday, images released by the utility showed black, lava-like objects discovered by the so-called mini sunfish robot. "It's natural to assume that the debris melted and dropped," said a Tepco official who briefed reporters.

Tokyo Electric said Thursday that it failed to get any photos of potential fuel debris during a five-day probe of the primary containment vessel at reactor 1 of the Fukushima No. 1 power plant. Tokyo Electric Power Company Holdings Inc., however, stressed that the investigation was worthwhile because its robot was able to take underwater images in the pool of water at its bottom and gauge its radiation level, which will help it estimate where the melted fuel lies. The monstrous tsunami of March 11, 2011, tipped reactors 1, 2 and 3 into core meltdowns. The molten fuel rods then penetrated their pressure vessels before apparently dropping to the bottom of the giant containment vessels. There is about a 2.5-meter deep water pool at the bottom of the primary containment vessel of reactor 1, and Tepco believes most of its melted fuel rods fell into it.

FUKUSHIMA – A radiation level of 11 sieverts per hour has been detected in tainted water inside a reactor containment vessel at the Fukushima No. 1 nuclear power plant, Tokyo Electric Power Company Holdings Inc. said Tuesday. The reading was measured in a survey using a robot on Sunday at a point some 30 cm above the bottom of the containment vessel of the plant's reactor 1. This is the highest radiation level detected in water inside the containment vessel. If exposed to this level of radiation, a person likely would die in about 40 minutes. The survey showed accumulation of sandy substances at the bottom, but Tepco said it does not believe they are melted nuclear fuel.

The operator of the crippled Fukushima No. 1 nuclear complex said Tuesday it suspended its plan to start examining the inside of reactor 1 with a self-propelled robot after having camera trouble. Tokyo Electric Power Company Holdings Inc. is checking the cause of the problem and hoping to resume the survey Wednesday in its latest attempt at ascertaining the condition of melted fuel debris in order to extract it. While preparation was underway to send the robot inside the containment vessel after launching the day's work shortly after 10 a.m., a camera monitoring inside a box containing the robot, cables and other related equipment was found to be showing no images, it said. The box is located just outside the containment vessel. The malfunctioning camera is separate from one attached to the survey robot and is used to check whether the devices are functioning properly, according to the utility. Tepco has been hoping to view the debris through a camera embedded in the shape-shifting robot in order to decide how to extract the deposits of fuel presumed to have penetrated the reactor pressure vessel and melted through the containment vessel, which is supposed to hold the fuel.

The operator of the disaster-struck Fukushima No. 1 nuclear power plant said Thursday it will attempt to examine the inside of reactor 1 next Tuesday using a remote-controlled robot. The move follows a botched attempt by another self-propelled robot to take a look inside reactor 2, which had also sustained a meltdown after the March 11, 2011, Great East Japan Earthquake and tsunami. That robot became unable to move when it encountered debris and eventually could not be retrieved. These are the first attempts by Tokyo Electric Power Co. Holdings Inc. to examine the insides of the wrecked reactors since the nuclear disaster started. For the reactor 1 inspection, Tepco said the new robot will carry out a four-day probe inside the containment vessel.

The radiation level in the containment vessel of reactor 2 at the crippled Fukushima No. 1 power plant has reached a maximum of 530 sieverts per hour, the highest since the triple core meltdown in March 2011, Tokyo Electric Power Co. Holdings Inc. said. Tepco said on Thursday that the blazing radiation reading was taken near the entrance to the space just below the pressure vessel, which contains the reactor core. The high figure indicates that some of the melted fuel that escaped the pressure vessel is nearby. At 530 sieverts, 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 crippled by the March 2011 disaster. Tepco also announced that, based on its analysis of images taken by a remote-controlled camera, that there is a 2-meter hole in the metal grating under the pressure vessel in the reactor's primary containment vessel.