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Fusion Science and Technology
Fukiushima Daiichi: 10 years on
The Fukushima Daiichi site before the accident. All images are provided courtesy of TEPCO unless noted otherwise.
It was a rather normal day back on March 11, 2011, at the Fukushima Daiichi nuclear plant before 2:45 p.m. That was the time when the Great Tohoku Earthquake struck, followed by a massive tsunami that caused three reactor meltdowns and forever changed the nuclear power industry in Japan and worldwide. Now, 10 years later, much has been learned and done to improve nuclear safety, and despite many challenges, significant progress is being made to decontaminate and defuel the extensively damaged Fukushima Daiichi reactor site. This is a summary of what happened, progress to date, current situation, and the outlook for the future there.
C. J. Murphy, P. M. Anderson, C. J. Lasnier
Fusion Science and Technology | Volume 52 | Number 3 | October 2007 | Pages 539-543
Technical Paper | The Technology of Fusion Energy - High Heat Flux Components | dx.doi.org/10.13182/FST07-A1544
Articles are hosted by Taylor and Francis Online.
The lower divertor of the DIII-D tokamak has been modified to provide improved density control of the tokamak plasma during operation in a high triangularity double-null configuration. Union Carbide ATJ grade graphite tiles covering the new lower divertor and vessel floor were designed to have better tile-to-tile alignment and to withstand higher heat flux than existing tiles.Gaps between tiles were successfully reduced from 2.5 to 0.4 mm and tile top surface alignment was greatly improved from 1.0 to 0.1 mm. Small tile gaps along with good vertical edge alignment greatly reduce the number and size of thin edges visible to the plasma, thus minimizing possible carbon introduction into the plasma. Close tile-to-tile alignment was the result of the very flat divertor plate surface, carefully controlled tile positioning, well-machined graphite tiles, and hand filing.Tiles were specified to survive 27 MJ of energy deposited per toroidal row of tiles during a 10 s shot period. When this energy is applied over the narrow triangular heat flux profiles originally specified, modeling shows that the tiles exceed maximum allowable tensile stress. Modeling does show that the tiles are able to absorb the 27 MJ per row without exceeding stress limits in cases where the heat flux profile is less focused than the original design specification.This paper will compare tile design analysis with operational experience obtained during the first 12-week operations campaign with the new divertor.