Charcoal radon-trapping

The instruments include an ionization chamber, the charcoal-trap technique, a flow-type ionization chamber (pulse-counting technique), a two-filter method, an electrostatic collection method and a passive integrating radon monitor. All instruments except for the passive radon monitor have been calibrated independently. Measurements were performed... 

Charcoal-Trap Method (ACC). The Charcoal-Trap Method has been used for sampling radon gas in the atmospheric air and for measuring radon emanation rate from the soil surface by some researchers (e. g. 

After the third extraction, we measure the radon and its yield by adding several cc STP of carrier Ar to the melt water with He to 1.3-atm pressure and allow the radon to build up for 4 days. We also replace the spiral glass C02 trap with a charcoal trap to insure the collection of the carrier Ar with the radon. We then He-purge the water and collect the Rn with the carrier Ar on the charcoal at liquid air temperature. The Ar plus Rn is recovered from the charcoal at 300 °C purified over hot Ti and counted in a proportional counter. 

The cold sample gas flows at 1001/min into a 0.2-1 charcoal trap that is cooled to -90°C to adsorb radon. Xenon flows through the trap and is then collected on the 2-1 main charcoal trap at -120°C. Nitrogen, oxygen, and the lighter rare gases helium, neon, argon, and krypton pass through this trap. 

Both forms of sampling rely on the extraction of radioactive material from the passing air on a collection medium. This medium will be specific, to some extent, to the material to be collected. For example, particulate material can be removed on coarse fibre filters, while charcoal beds are employed to sample radon gas and iodine vapour, and tritiated water can be collected in a water trap. 

---