Iodine-140, from uranium fission products

Iodine is also given off to a small extent in dissolving the uranium metal in nitric acid, but larger amounts may be obtained on steam distillation after dissolution (5). Ruthenium is often removed from the fission products by distillation of the volatile tetroxide formed by oxidation with potassium permangate, sodium bismuthate, periodic acid (38) etc. The distillation goes readily and gives a product of good purity. 

Synthesis of plutonium in significant quantities requires a sufficiently long reactor fuel irradiation period. Uranium, plutonium, and the fission products obtained after neutron irradiation are removed from the reactor and stored under water for several weeks. During such cooling periods most neptunium-239 initially formed from uranium and present in the mixture transforms to plutonium-239. Also, the highly radioactive fission products, such as xenon-133 and iodine-131 continue to decay during this period. 

Although the fission products could be recovered as byproducts from the waste from spent nuclear reactor fuel, special-purpose neutron irradiation of highly enriched uranium (isotopically separated uranium-235) followed by chemical separation is the normal production method. The major products, molybdenum-99 and iodine-131 with fission yields of 6.1 and 6.7 percent, respectively, have important medical applications. Mo-99,... 

Volatilization. Many fission-product elements, including krypton, xenon, iodine, cesium (normal boiling point 705 C), strontium (1380°C), barium (1500°C), the rare earths (3200 C), and plutonium (3235°C), are more volatile than uranium (3813°C). Cubicciotti [C17], McKenzie [M5], and Motta [M8], in laboratory experiments, showed that around 99 percent of these more volatile elements could be separated from uranium by vacuum distillation at 1700 C. Because of the high temperature and severe materials problems, volatilization has not been used as a primary separation process, but does contribute to removal of the most volatile fission products in conventional reprocessing. In fractional crystalUzation or extraction with liquid metals, distillation is used to separate uranium and plutonium from more volatile solvent metals. 

The fire in the air-cooled graphite-moderated uranium-metal-fueled reactor at Windscale in 1957 led to the release of what was estimated as 20,000 Ci of iodine-131 and much smaller quantities of some other fission products from the top of the 400-ft-high stack. The quantities of activity in the release were estimated by Stewart, Chamberlain, Dunster, and others at the time (J). This estimate was amplified later by Beattie from miscellaneous sources (4). Table I shows the activities of the released isotopes from Beattie s report (4). 

Castleman, A. W.jr., Tang, I. N. Vaporization of fission products from irradiated uranium II. Some observations on the chemical behaviour of fission products iodine and cesium. 

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