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)
“Viewed freely, the English language is the accretion and growth of every dialect, race, and range of time, and is both the free and compacted composition of all.”
—Walt Whitman (1819–1892)
“But, when nothing subsists from a distant past, after the death of others, after the destruction of objects, only the senses of smell and taste, weaker but more enduring, more intangible, more persistent, more faithful, continue for a long time, like souls, to remember, to wait, to hope, on the ruins of all the rest, to bring without flinching, on their nearly impalpable droplet, the immense edifice of memory.”
—Marcel Proust (1871–1922)
“Art, if one employs this term in the broad sense that includes poetry within its realm, is an art of creation laden with ideals, located at the very core of the life of a people, defining the spiritual and moral shape of that life.”
—Ivan Sergeevich Turgenev (1818–1883)