Bloomberg is reporting that in the IAEA's opinion, "melted fuel in the No. 1 reactor building may be causing isolated, uncontrolled nuclear chain reactions." This conclusion comes as a result of research conducted after it was admitted that TEPCO workers observed neutron beams at the site at least 13 times.
The Bloomberg article also goes on to say that Japan may now be seriously considering entombing the plant in concrete, as opposed to dismantling it which could take up to thirty years. The possibility of exposure to further neutron beams adds another danger to workers at the site.
This is just a quick update. I am not a scientist, engineer or any kind of nuclear expert, whatsoever. But I try to only source my information from "credible" sources.
The article has this to say about
neutron beams the "uncontrolled nuclear chain reactions":
Nuclear experts call these reactions "localized criticality," which will increase radiation and hamper the ability to shut down the plant. The reactions consist of a burst of heat, radiation and sometimes an "ethereal blue flash," according to the U.S. Energy Department’s Los Alamos National Laboratory web site. Twenty-one workers have been killed by "criticality accidents" in the past, the site said.