Project description:
Radon is a naturally radioactive gas and the most common cause for lung cancer, except smoking. It is colorless, tasteless and odorless and therefore not noticeable for human senses. Radon is produced by the decay from natural radioactive substances in the ground. Due to the outside air radon is diluted and therefore normally not a problem but radon can infiltrate buildings and change the room air. The radiation protection law regulates therefore the protection from radon indoors and workplaces. The reference value for indoors and workspaces is about 300 becquerels per cubic meter for the average annual radon-222 activity concentration in the air (section 124 and 126 of the radiation protection act). 300 becquerels per cubic meter are equivalent to 300 radon decays per second and per cubic meter in the air.
In the last years, the significance and the public focus on the comprehensive coverage of the radon concentration increased much.
Direct measurements of the alpha particles during the decay of radon and further products are not trivial. For the cumulative measurements, which record the average load over a period of weeks to several months, passive working nuclear track measuring devices are used.
Active alpha detectors are used to record outside short-term changes from the radon concentration. This group of measuring devices belong to the ionization chamber. An ionization chamber consists of an electric shielded container which includes measuring electrodes inside and which are connected to a sensitive amplifier. In this context every alpha particle leaves a trail of ionized ions and electrons as is passes through the air. Through an electric field between the electrodes the load can be collected and evaluated.
These systems which are known as Alpha-Impuls-Ionisation-Kammern (AIIK) surround volumes of several liters and allow accurate, fast measurements from the Radon concentration.
As part from the EU project RadonNET and the cooperation with the Physikalisch-Technischen-Bundesanstalt in Braunschweig, an AIIK was developed and constructed at the institute. In this context it is possible to measure Radon concentrations of less than 10 Bq/m^3.
