Wow! This thread is on fire.
Anyway:
First, yes, I am aware that Hydrogen combustion is invisible, but there would still be a flash fro other combustible particles in the air. It was a brief flash that looked like a rising bubble. To me, it is consistent with a Hydrogen ignition.
Second, Cesium in the air, does NOT necessarily mean a fuel failure or a cladding failure. Tramp Uranium impurities in the cladding will release fission products directly to the reactor coolant. Also, Xenon (an abundant fission product gas) decays to Cs-137. Xenon and Cesium from Tramp Uranium, plus Xenon from a possible gap release, can cause the presence of Cesium in the plume.
Third, I am stunned that Robert Bezell from NBC News has finally been a voice of calmness and reason from a major news outlet. He will be proven to have been correct that this is NOT a deadly situation. Compared to the earthquake, the tsunami, the loss of structural integrity in housing and public buildings, the breakdown of physical infrastructure, the unsanitary conditions due to loss of water treatment and sewage systems, the hydrocarbons and toxic chemicals being released by the burning refineries, the impact on hospitals, the delay and over-taxing of emergency response, .... the overheated nuclear plant is NOT the biggest - or even one of the top ten - threats to public health in Japan.