In November 2013, Mari Yamaguchi reported for Associated Press that there are computer simulations which 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 30 cms of leaking into the ground" – a Kyoto University nuclear engineer said with regards to these estimates: "We just can't be sure until we actually see the inside of the reactors."