NPRE 14 - Prof. David Ruzic PDF

Preview

Summary

Prof. David Ruzic...

Description

NPRE 101 Homework 14 Alyssa Tong 1. Fusion is hard to achieve because you need to have the Lawson Criterion fulfilled, which is a very high temperature and the density x confinement time. All three of those are hard to achieve. Temperature is the hardest because it has to get up to about 100 million ˚F. In general, it takes an insane amount of either density x confinement time or a lot of heat to create a reaction. The sun is so successful because it has such a huge mass that there is an insane amount of density in the center, and the sun can reach such high temperatures that the conditions are just what it needs to be for fusion. 2. A breeder reactor produces more fuel than it consumes because it turns the fertile material (that can’t be used as nuclear fuel) into fissile material (that can be used as nuclear fuel) and it has very good neutron usage so it ends up producing more fuel than it uses. 3. The Oklo natural nuclear reactor is in west Africa and produced a natural nuclear reaction about 2 billion years ago. It was able to produce these reactions because it had high enough U235 in the fuel and many other conditions. Because the half-life of U235 is so much shorter than the half-life of U238, 2 billion years ago, the concentration of U235 was at about 3%, which is what it needs to be for a reaction. Now, a lot of the U235 is gone, so the concentration is much lower. The size of the deposit was also exactly what it needed to be for the reaction to be contained enough to keep the neutrons fission-ing. And the groundwater in the ground probably acted as the moderator so the neutrons could slow down enough to actually fission. Finally, the high-level wastes were incorporated into the aluminum phosphate materials around....