Air samples collected on Thursday night on the roof of UC Berkeley's Department of Nuclear Engineering failed to show any significant levels of radioactivity, and then came the rain.
"The rain is a very efficient way to wash out activity in the atmosphere and get the potential activity down to us. So this is actually a much more sensitive and efficient way for sampling," Professor Professor Kai Vetter from the UC Berkeley Department of Nuclear Engineering said.
The levels may be slightly higher. According Vetter, there again he sees nothing to worry about. UC Berkeley nuclear engineers also demonstrated why it's impossible for the fuel rods in Japan to catch on fire. They exposed a piece of cladding, just like the ones found in the Japanese reactor cores to 2,000 degrees Celsius. If the cladding burnt, the nuclear fuel inside would send huge amounts of radioactive particles into the atmosphere.
"It's worse, much worse to have it on fire. The fire and the smoke become a way to spread the material that's inside," Professor Charles Yeamans from the UC Berkeley Department of Nuclear Engineering said.
The test proved the rods, while they would suffer some damage, would not catch on fire. The Japanese reactors have another layer of protection, pools of water that act as moderators unlike Chernobyl which had graphite.
"Graphite and coal can burn and burns pretty violently and so if you have a fire it distributes radioactive particles much better than just water and steam would do," Prof. Peter Hosemann from the UC Berkeley Department of Nuclear Engineering said.
"Whereas in the Japanese reactors it's a water cooled water moderated core so there is nothing that burns there," Vetter said.
The results of the water samples will take days for them to analyze and they should be in next week.
