New bursts of fission at Fukushima?

Disturbingly, it sounds as though the partially melt-down reactors at the Fukushima Dai-ichi plant in Japan have spontaneously begun fission chain reactions.  This could happen if the partially melted fuel continues to physically shift, or depending on other materials (water etc.) that may be present around the fuel.  So far, it sounds like it hasn't led to any large increases in heat or other issues, but it is a sign of the fact that more than 6 months later, these reactors are not entirely under control. 

Read more:  http://www.nytimes.com/2011/11/03/world/asia/bursts-of-fission-detected-at-fukushima-reactor-in-japan.html