to "most fuel in the RPV (some fuel in PCV)". For Unit 2 and Unit 3 it was estimated that the "fuel is cooled sufficiently". According to the report, the greater damage in Unit 1 (when compared to the other two units) was due to the longer time that no cooling water was injected in Unit 1. This resulted in much more decay heat accumulating, as for about 1 day there was no water injection for Unit 1, while Unit 2 and Unit 3 had only a quarter of a day without water injection. In November 2013, Mari Yamaguchi reported for Associated Press that there are computer simulations that suggest that "the melted fuel in Unit 1, whose core damage was the most extensive, has breached the bottom of the primary containment vessel and even partially eaten into its concrete foundation, coming within about of leaking into the ground" – a Kyoto University nuclear engineer said with regard to these estimates: "We just can't be sure until we actually see the inside of the reactors." According to a December 2013 report, TEPCO estimated for Unit 1 that "the decay heat must have decreased enough, the molten fuel can be assumed to remain in PCV (primary containment vessel)". In August 2014, TEPCO released a new revised estimate that Reactor 3 had a complete melt through in the initial phase of the accident. According to this new estimate within the first three days of the accident the entire core content of Reactor 3 had melted through the RPV and fallen to the bottom of the PCV. These estimates were based on a simulation, which indicated that Reactor 3's melted core penetrated through of the PCV's concrete base, and came close to of the PCV's steel wall. In February 2015, TEPCO started the muon scanning process for Units 1, 2, and 3. With this scanning setup it will be possible to determine the approximate amount and location of the remaining nuclear fuel within the RPV, but not the amount and resting place of the corium in the PCV. In March 2015 TEPCO released the result of the muon scan for Unit 1 which showed that no fuel was visible in the RPV, which would suggest that most if not all of the molten fuel had dropped onto the bottom of the PCV – this will change the plan for the removal of the