Messung der Krypton-85-und Xenon-133-Aktivität der atmosphärischen Luft / A Method for Measurement of the Krypton-85 and Xenon-133-content in the Atmosphere

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.