ABSTRACT
A portable apparatus for the separation of krypton from environmental air samples was tested. The apparatus is based on the cryogenic trapping of gases at liquid nitrogen temperature followed by controlled releases at higher temperatures. The setup consists of a liquid nitrogen trap for the removal of H(2)O and CO(2), followed by charcoal-filled coils that sequentially collect and release krypton and other gases providing four stages of gas chromatography to achieve separation and purification of krypton from mainly N(2), O(2), and Ar. Residual reactive gases remaining after the final stage of chromatography are removed with a hot Ti sponge getter. A thermal conductivity detector is used to monitor the characteristic elution times of the various components of condensed gases in the traps during step-wise warming of the traps from liquid nitrogen temperatures to 0 °C, and then to 100 °C. This allows optimizing the switching times of the valves between the stages of gas chromatography so that mainly krypton is selected and loaded to the next stage while exhausting the other gases using a He carrier. A krypton separation efficiency of ~80 % was determined using a quadrupole mass spectrometer.
Subject(s)
Air/analysis , Krypton/isolation & purification , Mass Spectrometry/methods , Carbon Dioxide/chemistry , Krypton/chemistry , Lasers , Temperature , Water/chemistryABSTRACT
Membrane introduction mass spectrometry has been applied to inert gas measurements in blood and tissue, but gases with low blood solubility are associated with reduced sensitivity. Countercurrent extraction of inert gases from a blood sample into a water carrier phase has the potential to extract most of the gas sample while avoiding dependence of signal on blood solubility. We present the design of a membrane countercurrent exchange (CCE) device coupled with a conventional direct insertion membrane probe to measure partial pressure of low solubility inert gases in aqueous samples. A mathematical model of steady-state membrane CCB predicts that countercurrent extraction with appropriate selection of carrier and sample flow rates can provide a mass spectrometer signal nearly independent of variations in solubility over a specified range, while retaining a linear response to changes in gas partial pressure over several orders of magnitude. Experimental data are presented for sulfur hexafluoride and krypton in water samples. Optimal performance is dependent on adequate equilibration between the sample and carrier streams, and the large resistance to diffusion in the aqueous phase for insoluble gases presents a substantial challenge to the application of this principle.
Subject(s)
Mass Spectrometry/methods , Noble Gases/analysis , Animals , Biomedical Engineering , Countercurrent Distribution , Diffusion , Humans , Krypton/analysis , Krypton/blood , Krypton/isolation & purification , Models, Theoretical , Noble Gases/blood , Noble Gases/isolation & purification , Solubility , Sulfur Hexafluoride/analysis , Sulfur Hexafluoride/blood , Sulfur Hexafluoride/isolation & purificationABSTRACT
In the irradiation apparatus where unsealed 85Kr gas is used as an internal radiation source for liquid-phase chemical reaction, the 85Kr gas dissolved in a liquid reactant must be removed after irradiation. Experiments on removal of dissolved 85Kr by the vacuum degassing method were carried out to examine the influence of degassing temperature, initial 85Kr concentration and stirring of a solution on the removal. The liquid reactant used was a water of 500 ml in which 85Kr gas was dissolved. The removal effect became greater with increasing temperature. The dissolved 85Kr concentration after removal decreased exponentially with the reciprocal of degassing temperature. Further, the removal effect was intensely affected by stirring of the solution and was independent of the initial 85Kr concentration. The removal factor of dissolved 85Kr at 33 degrees C reached 5 X 10(3) after a 30 minute lapse.
Subject(s)
Krypton/isolation & purification , Radioisotopes/isolation & purification , Gases , Methods , Solutions , Temperature , Vacuum , WaterABSTRACT
Excitation functions were measured for the formation of both 77Kr and 79Kr by interaction of protons with bromine of natural isotopic composition. The theoretical yields are 62.8 mCi/muAh for 77Kr in the energy range from 45 to 32 MeV, with 1.5% 76Kr and 11.7% 79Kr impurities, and 14.9 mCi/muAh for 79Kr in the energy range of 45 to 0 MeV, respectively. The experimental yield after dry distillation separation of the krypton isotopes from irradiated NaBr targets, lies between 40 and 60% of the theoretical ones. Below the melting point of NaBr, krypton is released by diffusion, caused by lattice defects in the target material.
Subject(s)
Krypton , Radioisotopes , Bromine , Krypton/isolation & purification , Particle Accelerators , Protons , Radioisotopes/isolation & purificationABSTRACT
A recovery-purification system for radioactive Kr was constructed by enclosing an 85Kr testing apparatus with an airtight vessel. Experiments were carried out to examine the recovery rate of leakage Kr and the purity of Kr recovered with the system. The concentration of the leakage Kr in the airtight vessel was decreased to a detection limit of 0.3 ppm by the system. The recovery rate corresponded to 99.976%. The concentration of the Kr recovered was over 99.9908%. It shows that almost 100% of the radioactive Kr leaked out into the airtight vessel could be recovered and the He content in the Kr recovered could be reduced to less than 100 ppm.