During normal operation, nuclear power plants discharge small amounts of radioactive contaminants through the stack into the environment. The contaminants then disperse with the wind and may in part also deposit on the ground. The discharges have to be limited such that the resulting effective dose for the population will remain below 0.3 millisievert (mSv) per year (§ 47, German Radiation Protection Ordinance).

The nuclear power plant operators have to show at regular intervals that these limits are not exceeded and that the discharges are kept as low as possible, even below the permissible limits. The operators' information is regularly checked by the competent authorities as part of the supervisory procedure.

GO-ARTM: the GRS-developed code system for dispersion modelling
The authorities use simulation codes as tools for their reviews. One of these code systems is GO-ARTM, which was developed by GRS. With the help of  GO-ARTM it is possible to calculate both the dispersion of the contaminants in the atmosphere and  deposition on the ground on the basis of meteorological data.

Version 1.09 of the code has now been issued and is available for free download. The updated version has a range of new functions, among them:

1. the optimisation of turbulence parameterisation
So-called turbulence parameterisation was improved. In the calculation, this parameterisation ensures that an exhaust gas plume is not just shifted by the wind but that it also changes its shape and becomes broader. With the newly introduced improvements, this behaviour is modelled realistically.

2. the DARTM dose module
The DARTM dose module developed by the Federal Office for Radiation Protection was included in the code package. This way it is possible to calculate a measure of the effect of the radiation emanating from these nuclides on humans (i.e. the effective dose) directly from the radionuclide distribution  calculated with ARTM.

3. the extension of the graphic user interface
Apart from the dispersion model proper, the code package contains as a standard feature the graphic interface of GO-ARTM. This was extended for the enlarged functionalities of ARTM.

Due to the growing international interest in GO-ARTM, it is planned to release an English version in the future.