3 results for month: 06/2010

What's in Spent Nuclear Fuel? (after 20 yrs)

Lately I've been looking a lot at spent nuclear fuel, particularly what's in it and what's radioactive after a while. I've seen graphs of fission product distributions before, but they're always of fission products by atomic mass, and they're usually showing the distribution right after the fission event. I wanted to know what was in there from an elemental perspective, because if you're going to do chemical processes on the spent nuclear fuel, you'll be removing elements, not isotopes. So how do they all rack-and-stack overall? Well, here's the results for a typical light-water-reactor fuel element, irradiated for a modest 400 days and then ...

Eight Presidents, One Goal

This is hilarious and heart-breaking at the same time: The Daily Show With Jon StewartMon - Thurs 11p / 10c

Picture of Neutron Poisons

In nuclear reactor design, we describe the cross-section of different nuclides in a unit called a "barn". It has units of area. So what does that mean? Well, take a look at this picture. This shows five important nuclides plotted against each other, with their size determined by their "barns". You can see that one of them is absolutely HUGE. That is xenon-135, as far as I know, the nuclide with the largest cross-section to absorb thermal neutrons. Next on the list of trouble is samarium-149, which is really big, but not nearly as big as xenon-135. Again, to the best of my knowledge, samarium-149 is number #2 on the list of trouble. For ...