Nuclear, O&M, Reactors, Waste Management & Decommissioning

TEPCO: Fukushima nuclear Unit 1 did melt down in 2011 accident

The Tokyo Electric Power Corp. says Unit 1 at the Fukushima Daiichi nuclear power plant did, in fact, meltdown during the 2011 accident.
TEPCO released results from a nearly month-long study that started Feb. 12 of the Unit 1 reactor building jointly with the International Research Institute for Nuclear Decommissioning. The two companies collected data until March 10. The project used cosmic rays to inspect the interior of the building. By analyzing the flow of muons, which are subatomic particles generated when cosmic rays collide with the atmosphere, TEPCO was able to generate X-ray like images of the interior of the reactor. Muons can pass through concrete and iron, but they are blocked and change direction when they hit high-density substances such as plutonium and uranium, creating a “shadow.”
TEPCO said the fuel had melted because there were no shadows around the reactor’s core, indicating that the fuel was not where it is supposed to be and that the fuel had likely melted and “moved downward.” The operator also said there was no accumulation of water in the core of the reactor pressure vessel and that there was possibly fuel debris in the spent fuel pool, but the size would be calculated later.
TEPCO said the results confirmed previous assumptions of a meltdown. The utility plans to continue measurement until it gains enough data to conduct a statistical analysis, and said the data gained will help workers figure out where in the PCV the debris are so a plan can be made to remove the debris. The removal will most likely be performed by robots due to the high amounts of radiation in the reactor.
For pictures of the inside of the reactor, click here.
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