allowed to form volatile compounds (by the addition of a reactive gas, if necessary). The element of interest could be separated by selective adsorption. Thermochromatography has also been used to separate the volatile products formed. A second approach is to form volatile compounds of elements of interest by allowing the recoiling products to chemically react with a reactive gas used in the gas jet; selective adsorption of the products by different traps could lead to the separation of the element of interest. The following sections give a summary of techniques used and specific examples of procedures used for some elements.
Fission-product selenium and tellurium have been studied by Zendel and coworkers [Zen78] using volatile products generated outside the target chamber. An ethylene-nitrogen gas mixture thermalized and carried fission products from the target chamber of a gas-phase chemistry system that was in the beam port of a reactor. Tellurium was carried by clusters, while selenium, bromine, and iodine formed volatile products and were carried by the gas stream along with krypton and xenon. A schematic of the setup used for the continuous separation of tellurium from fission products is shown in Fig. 39. The gas stream from the target chamber was passed through a charcoal trap that retained selenium, bromine, and iodine. The gas mixture was then passed through a quartz spiral heated to 860°C. The clusters were decomposed at this temperature; tellurium formed volatile compounds that were carried away by the gas stream, and all other fission products were deposited in the spiral. The gas stream passed through a charcoal trap in front of a Ge(Li) detector that retained tellurium while krypton and xenon passed through.