[en] Nuclear spectroscopy has been successfully employed to monitor the operation and performance of a number of different pilot plant and production scale mass transfer systems. Unparalleled insights were gained in a few cases that would have been nearly impossible using conventional procedures. An external gamma scanning device is described that was used to obtain direct measurement of packed column, cold trap, and fixed bed concentration/loading profiles. A number of these operating scans are presented to demonstrate the analytical capability and general utility of the method. Current interest is being directed toward the development of a gamma spectroscopy-based process control system

[en] Process performance and reliability have been demonstrated on an engineering scale with 10 years of pilot plant operation, including extended testing with ⁸⁵Kr, ¹³³Xe, and ¹³¹I. The selective absorption process is based on exploitation of solubility differences which exist among the noble gases and other gas-phase constituents in a fluorcarbon solvent. Much information now exists on the solubilities of various components in CC1₂F₂, which is the reference solvent, and on other aspects of this fluorocarbon system. The effects of carrier gas coabsorption and solvent vaporization/condensation on noble gas mass transfer inside the absorption and stripping zones have been determined. The effects of column size on mass transfer have also been measured and rigorous engineering models have been derived for the process hardware. Many improvements and simplifications have been made to the original version of the process, and depending upon the separation task, a variety of system configurations is possible. The selective absorption process is applicable to essentially all types of nuclear facilities, and several gas cleanup tasks have been considered. One of these, post-accident reactor cleanup, is described

[en] Oak Ridge has developed a noble gas removal system, as part of the Consolidated Fuel Reprocessing Program, that could be used to help decontaminate the containment vessel of a power reactor following core release of fission gas in the event that containment venting is judged to be unacceptable. The system is based on a fluorocarbon selective absorption process, which has been well demonstrated on an engineering scale with over 10 years of pilot plant operation

[en] Since the late 1960s, the Oak Ridge Gaseous Diffusion Plant, in conjunction with the Oak Ridge National Laboratory, has developed a fluorocarbon-based selective absorption system for removal of ⁸⁵Kr and ¹⁴CO₂ from nuclear fuel reprocessing facilities. Process performance and reliability have been well demonstrated with over 10 years of operation using simulated reactor and reprocessing plant dissolver off-gases and three generations of pilot plant scale equipment. A major development of this work is a combination absorption and stripping column which results in a simplified process with improved reliability and lower cost. The process has shown excellent flexibility in simultaneously removing and concentrating the radioactive gases of interest, i.e., > 99% removal is easily obtainable for Kr, Xe, and CO₂. With the incoming feed gas containing around 10 ppM Kr, the product concentration of Kr from the single column is typically in the 1 to 10% range. Additional purification of the single-column product allows nearly pure components (> 90% Kr) to be obtained, thereby minimizing final storage or disposal requirements. Several alternatives for product purification have been investigated. In one system, 13X molecular sieve is used to first remove the process solvent vapor. Selective adsorption on 5A molecular sieves and silver mordenite is then used to separately remove the already concentrated CO₂ and Xe, respectively. At this point Kr, which was withdrawn from the column at the present concentration level, has now been further purified by the removal of the other components and can be collected in a cold trap. This paper summarizes the performance capabilities of the single-column and discusses product purification system options, including selective desublimation, solid sorbent, and cryogenic charcoal adsorption techniques

[en] In the 1968 joint IAEA/USAEC Symposium on Treatment of Airborne Radioactive Wastes the initiation of a development programme on removal of radioactive noble gas using a selective absorption technique was outlined. Since that time, development of this absorption process has been essentially completed. Process performance and reliability have been demonstrated on an engineering scale with ten years of pilot plant operation, including extended testing with ⁸⁵Kr, ¹³³Xe, and ¹³¹I. The selective absorption process is based on exploitation of solubility differences which exist among the noble gases and other gas-phase constituents in a fluorocarbon solvent. Much information now exists on the solubilities of various components in CCl₂F₂, which is the reference solvent, and on other aspects of this fluorocarbon system. The effects of carrier gas co-absorption and solvent vaporization/condensation on noble gas mass transfer inside the absorption and stripping zones have been determined. The effects of column size on mass transfer have also been measured and rigorous engineering models have been derived for the process hardware. Many improvements and simplifications have been made to the original version of the process and, depending upon the separation task, a variety of system configurations is possible. The selective absorption process is applicable to essentially all types of nuclear facilities, and several gas cleanup tasks have been considered. One of these, post-accident reactor cleanup, is described because it is of current interest and also serves to illustrate the process application area. (author)