Krypton disposal

The krypton disposal problem is characterized by the fact that there is no easy way of converting it into a nongaseous form stable at ambient temperature. There are interesting experiments in progress to fix krypton in zeolites by adsorption under high pressure. In England a pilot plant for krypton implantation in metals is under construction. Nevertheless, the containment technique presently envisaged for technical use is pressurization in steel bottles. 

The off-gas treatment involves primarily iodine, krypton, and xenon. There are a variety of processes for capturing the iodine and disposing of it. Kr and Xe are captured by either cryogenic techniques or selective absorption, such as absorption in chlorofluoromethane. Most of the off-gas volume is due to Xe ( 800 L/Mg fuel) with the activity being mostly 10.7-y 85Kr ( 11,000 Ci/Mg fuel). 

From this clue came also the later discovery of three other inert elements of the air. From liquid argon, the same scientists separated new neon, hidden krypton, and xenon (the stranger) present to the extent of one part in eighty thousand, twenty million, and one hundred and seventy million parts of air respectively. With modern apparatus at his disposal it is not difficult to believe that Cavendish might have been the discoverer of these noble gases one hundred years before they were given to the world. 

The preferred method of disposal of radioactive krypton isotopes, after being separated from other volatile fission products, is by dumping at sea as the compressed gas, confined in steel cylinders. According to a report by Bryant and Jones the cumulative quantities of Kr and in the environment by the year 2000 are such that these nuclides will pose no significant health problem. 

With these purely thermodynamic questions disposed of, one can hope that the future will bring a number of really complete experimental studies (both isotherm and calorimetric measurements, including heats of immersion and heat capacities in some cases) of the simplest possible systems—for example, argon or krypton adsorbed on nonpolar, non-porous adsorbents. Work along these lines is already in progress in the laboratories of J. A. Morrison and G. Jura. Aside from intrinsic interest, a backlog of detailed thermodynamic data of this type should prove invaluable for future theoretical attempts to understand the nature of adsorbed films. 

Like xenon hexafluoride or xenon tetrafluoride, krypton difluoride reacts with water, giving highly explosive hydrolysis products. The best way for disposing of krypton difluoride is to allow it to react with carbon tetrachloride (see caution note under xenon tetrafluoride procedure). 

For a few decades, Kr-85 artificial production shows a continuous increase of its average volumic activity into the atmosphere. In the North hemisphere, the atmospheric concentration was of 0.1 Bq m" in 1959, 0.8 Bq m" in 1980, and 1.2 Bq m in 2001 (Berard et al., 2001). One cannot say that the removal of tritium and krypton from gaseous waste is an immediate waste management requirement, but it may become one in the future (Lennemann et al., 1975). Opinions differ as to the need to isolate Kr-85. Thus, Geary (1988) states that dispersal is almost certainly preferable to disposal, based on the relatively low inventories and hazards involved. Mellinger (1985) suggested that the population risks arising from the routine release of Kr-85 would not exceed the occupational risk associated... 

IAEA. 1980. Separation, storage and disposal of Krypton 85. Technical Reports Series 199. Vierma, Austria International Atomic Energy Agency. 

When disposal becomes necessary, vent neon, krypton, and xenon gas slowly to a well-ventilated outdoor location remote from personnel work areas and building air intakes. Do not dispose of any residual neon, krypton, and xenon in compressed gas cylinders. Return cylinders to the supplier with residual pressure, the cylinder valve tightly closed, and the valve caps in place. 

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