Fukishima reactor meltdown7/23/2023 ![]() ![]() In addition, the chemical reaction between the fuel cladding and steam generated a substantial amount of hydrogen. This led to the fuel rods releasing radioactive materials. Hence, the fuel cladding, which is a metal tube that covers the fuel rods, was damaged by the high temperatures. Since we were unable to sufficiently cool the fuels inside the reactors, the water level inside the reactor pressure vessel (RPV) of each unit decreased resulting in the bare exposure of the fuels to the inside atmosphere of the reactor. This disabled the reactor monitoring and cooling operations at the main control room. Furthermore, the implementation of accident response measures was seriously hampered by not only the shutdown of off-site power and EDGs, but the situation of the batteries being rendered inoperable by flooding from the tsunami or running out of energy caused a loss of DC power. Afterwards, a large tsunami struck the station that flooded and knocked out the electric equipment such as the EDGs and the cooling seawater pumps. Although all off-site power supply was lost at Fukushima Daiichi NPS, the emergency diesel generators (EDGs) started up automatically and ensured the station power, and the emergency cooling system kept cooling the reactors. The reactors of Units 1-3 shut down safely with all the control rods automatically inserted into the reactor core in response to the earthquake's seismic intensity. Site Map of the Fukushima Daiichi Nuclear Power Station Operational status of Fukushima Daiichi NPS units during the Tohoku - Pacific Ocean Earthquake Unitįigure 1. At the time the Tohoku - Pacific Ocean Earthquake struck, Unit 1, Unit 2 and Unit 3 were operating at rated power output while Unit 4, Unit 5 and Unit 6 were undergoing periodical inspections. TEPCO also plans to use the data to create a three-dimensional map of melted fuel and debris details, which would take about a year.There are 6 reactors (Units 1-6) at Fukushima Daiichi NPS. Matsuo said the data collected from the latest probe will help experts come up with methods of removing the debris and analyze the 2011 meltdowns. The pile is lower than the mounds seen in images taken in previous internal probes at two other reactors, suggesting that the meltdowns in each reactor may have progressed differently, company officials said. ![]() The video taken by the robot also showed equipment that slipped down as well as other types of debris, possibly nuclear fuel that fell from the core and hardened, piling up as high as 40-50 centimeters (1.3-1.6 feet) from the bottom of the primary containment chamber, Matsuo said. Masao Uchibori urged TEPCO to “swiftly evaluate levels of earthquake resistance and provide information in a way prefectural residents can easily understand and relieve concern of the residents and people around the country.” The amount is about 10 times the damaged fuel that was removed in the cleanup of the Three Mile Island nuclear plant in the United States after its 1979 partial core meltdown.įukushima Gov. Robotic probes have provided some information, but the status of the melted debris is still largely unknown. The images of the exposed steel reinforcement have triggered concerns about the reactor's safety.Ībout 880 tons of highly radioactive melted nuclear fuel remain inside the three reactors. TEPCO spokesperson Keisuke Matsuo told reporters Tuesday that the steel reinforcement is largely intact but the company plans to further analyze data and images over the next couple of months to find out if and how the reactor's earthquake resistance can be improved. ![]() The area inside the pedestal is where traces of the melted fuel can most likely be found.Īn approximately five-minute video - part of 39-hour-long images captured by the robot - showed that the 120-centimeter (3.9-foot) -thick concrete exterior of the pedestal was significantly damaged near its bottom, exposing the steel reinforcement inside. It came back with images seen for the first time since an earthquake and tsunami crippled the plant 12 years ago. The new findings released Tuesday were from the latest probe conducted at the end of March.Īn underwater remotely operated vehicle named ROV-A2 was sent inside the Unit 1 pedestal, a supporting structure right under the core. The plant's operator, Tokyo Electric Power Company Holdings, has been sending robotic probes inside the Unit 1 primary containment chamber since last year. TOKYO - Images captured by a robotic probe inside one of the three melted reactors at Japan's wrecked Fukushima nuclear power plant showed exposed steel bars in the main supporting structure and parts of its thick external concrete wall missing, triggering concerns about its earthquake resistance in case of another major disaster. ![]()
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