I have a lot of respect for Chris Martenson, but like he says:

At this point in time, I cannot fully support 100% of my concerns with hard data and evidence.

Bearing that in mind, this isn't the only possible explanation:

There have been reports from Japan's nuclear agency that radioactive cesium and iodine were detected outside of the facility, which can only happen if the core has been exposed somehow.

I disagree. The upper level of the reactor buildings contain spent fuel cooling ponds which are external to the reactor core. It's possible these ponds were damaged by the earthquake or by the hydrogen explosions and spent fuel rods were thereby exposed. This would also produce cesium and iodine isotopes, but at a lower rate, which seems consistent with the amount being detected. I can't support this with any hard data either, I just offer it as a possible alternate explanation.

ebear