Seite - 92 - in Water, Energy, and Environment - A Primer

It turns out that somuch energy is released in this process (a simple, back-of-the-envelope calculation is shown below) that, if the process can be harnessed onEarth, an unlimited source of energy is available. Fusion has other advantages as well as serious technological problems, which are discussed below. First,why are the numbers so intriguing? While many fusion reactions are possible and take place in stars, most attention has been directed to the deuterium–tritium (D–T) fusion reaction that has the lowest energy threshold. Both deuterium (1H2) and tritium (1H3) are heavier isotopic forms of the common element hydrogen (1H1). Deuterium is readily available from seawater (most seawater is two parts ordinary hydrogen to one part oxygen; one out of every 6240 seawatermolecules is two parts deuterium to one part oxygen). Tritium supplies do not occur in nature – it is radioactive and disappears quickly due to its short half-life – but can be bred fromacommonelement, lithium,when exposed to neutrons: 6 3Li+10 n 42 He+31H+4.8MeV D-T is also the reaction that largely powers our sun (although other fusion reactions do occur), routinely converting massive Figure7.3 TheD–T tohelium fusion reaction (Source:AtomicArchive). Water,Energy, andEnvironment–APrimer92