Tritium consists of about 4.5 kilograms of plutonium-239. Since tritium undergoes radioactive decay, and is also difficult to confine physically, the much larger secondary charge of heavy hydrogen isotopes needed in a true hydrogen bomb uses solid lithium deuteride as its source of deuterium and tritium, producing the tritium "in situ" during secondary ignition. During the detonation of the primary fission bomb stage in a thermonuclear weapon (Teller-Ullam staging), the sparkplug, a cylinder of U-235/Pu-239 at the center of the fusion stage(s), begins to fission in a chain reaction, from excess neutrons channeled from the primary. The neutrons released from the
Tritium Therefore, the basin tritium concentration becomes a function of the residence times within the basin, sinks (radioactive decay) or sources of tritium, and the input function. For the Ohio River, the tritium data indicated that about 40% of the flow was composed of precipitation with residence times of less than 1 year (in the Ohio basin) and older waters consisted of residence times of about 10 years. Thus, the short residence times (less than 1 year) corresponded to the "prompt-flow" component of the two-member mixing model. As for the Missouri River, results indicated that residence times were approximately 4 years