Krypton-85

Abstract: IN 1949 Kety proposed that if the rate of removal from the site of injection of an intramuscularly injected radioactive isotope was limited principally by flow, then the clearance of the tracer from the injection site could be used to measure local blood flow.' In the past, sodium-24 or iodine-131 has been used for this purpose, but with considerable variability in the results obtained in serial studies of the same persons.2 The chemically inert gases krypton-85 and xenon-133 have certain advantages over Na24 and I 131. They are chemically and physiologically inert; they are not normally present in the body; and they are rapidly excreted from the body via the lungs.3 The long physical half-life of Kr 85 ( 10.3 years) and the half-life of Xe'33 (5.27 days) make the use of these nuclides more convenient than Na 24 (15 hours). Finally, the lower gamma ray energies of Kr85 (0.513 mev) and Xe'33 (0.081 mev) are more suitable for external radiation detection than the high energy of Na24 (1.368 mev), which is difficult to localize accurately in the body. Accordingly, blood flow to forearm muscle was estimated by external monitoring of the rate of disappearance of radioactivity following intramuscular injection of an aqueous solution of Kr85 or Xe 33

Abstract: With two high‐pressure quasi‐stationary diffusion cells, one depending upon ionization current measurement and the other scintillation detection of radioactive tracer activity, Fick's law diffusivities were determined for the diffusion of tracer amounts of krypton‐85 in dense gases of krypton, argon, nitrogen, helium, carbon dioxide, and ethylene for isotherms about room temperature and densities to 15 mole/liter. In order to obtain absolute diffusivities, the cross‐sectional area to length ratio of a primary standard porous plug consisting of a bundle of glass capillaries was precisely determined by weight‐of‐mercury and resistance‐of‐mercury calibrations. Stirring in the end chambers of the ionization cell was found to increase the determined diffusivity of krypton‐85 in argon at 35°C by as much as 4.5% at a density of 12 mole/liter. The density—diffusivity product increases with density in the lower density region below about five moles per liter for all the isotherms. Extrapolations of the experimental data to low densities yield diffusivities which are in good agreement with low‐pressure results by other investigators and Chapman—Enskog dilute‐gas‐theory predictions. Krypton self‐diffusion coefficients calculated according to the real‐gas modified Enskog theory with PVT properties, agree remarkably well with the experimental data over the density range investigated. The binary diffusivities of krypton‐85 in dense base gases of argon, nitrogen, and ethylene are best predicted by the real‐gas modified Enskog theory with PVT properties evaluated at a base‐gas reduced temperature corresponding to the temperature of the system reduced by the mixed interaction potential temperature. In terms of precision of results and technological ease of operation the ionization cell proved to be superior to the scintillation cell.

Abstract: Abstract To measure the 85Kr and 133Xe content in the atmosphere approximately 60 m3 of dried and CO2-removed air are pumped through activated carbon (pressure 300 torr, temperature 77 K) during one week. When sampling time is over, the carbon is heated to 570 K. This gives a gas sample of 41 with more than 90% of the atmospherical krypton and xenon within two hours. With a further step of enrichment, the volume of sample is reduced to 100 ml. The final separation and purification of the rare gases from O2, N2, CO and CO2 is made chromatographically. First the xenon is separated in a column filled with molecular sieve (5A) at 390 K, after that the krypton is separated in a column with activated charcoal at room temperature with methane as a \"carrier gas\" and is simultaneously transported to a proportional counter (230 ml). In the first half-year of 1977 the activity levels of 85Kr and 133Xe ran to 17.7 respectively 0.19 pCi/m3 air. The variations of the rare gas-activities are indeed rather high. The xenon-activities are not correlated with the krypton-activities. In a preliminary discussion we try to find reasons for these variations.