Fuel Composition and Long Term Radioactivity
Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives. Depending on what a nuclear reactor is fueled with, the actinide composition in the SNF will be different.
An example of this effect is the use of nuclear fuels with thorium. Th-232 is a fertile material that can undergo a neutron capture reaction and two beta minus decays, resulting in the production of fissile U-233. The SNF of a cycle with thorium will contain U-233, an isotope with a half-life of 160,000 years. Its radioactive decay will strongly influence the long-term activity curve of the SNF around 1,000,000 years. A comparison of the activity associated to U-233 for three different SNF types can be seen in the figure on the top right.
The burnt fuels are Thorium with Reactor-Grade Plutonium (RGPu), Thorium with Weapons-Grade Plutonium (WGPu) and Mixed Oxide fuel (MOX). For RGPu and WGPu, the initial amount of U-233 and its decay around 10E5 years can be seen. This has an effect in the total activity curve of the three fuel types. The absence of U-233 and its daughter products in the MOX fuel results in a lower activity in region 3 of the figure on the bottom right, whereas for RGPu and WGPu the curve is maintained higher due to the presence of U-233 that has not fully decayed.
The use of different fuels in nuclear reactors results in different SNF composition, with varying activity curves.
Read more about this topic: Spent Nuclear Fuel
Famous quotes containing the words fuel, composition, long and/or term:
“The particular source of frustration of women observing their own self-study and measuring their worth as women by the distance they kept from men necessitated that a distance be kept, and so what vindicated them also poured fuel on the furnace of their rage. One delight presumed another dissatisfaction, but their hatefulness confessed to their own lack of power to please. They hated men because they needed husbands, and they loathed the men they chased away for going.”
—Alexander Theroux (b. 1940)
“The composition of a tragedy requires testicles.”
—Voltaire [François Marie Arouet] (1694–1778)
“I have not yet learned to live, that I can see, and I fear that I shall not very soon. I find, however, that in the long run things correspond to my original idea,—that they correspond to nothing else so much; and thus a man may really be a true prophet without any great exertion. The day is never so dark, nor the night even, but that the laws at least of light still prevail, and so may make it light in our minds if they are open to the truth.”
—Henry David Thoreau (1817–1862)
“Frankly, I do not like the idea of conversations to define the term “unconditional surrender.” ... The German people can have dinned into their ears what I said in my Christmas Eve speech—in effect, that we have no thought of destroying the German people and that we want them to live through the generations like other European peoples on condition, of course, that they get rid of their present philosophy of conquest.”
—Franklin D. Roosevelt (1882–1945)