The release of radioactive material due to accidents or terroristic actions can result in radioactive contamination of the environment and may lead to intake and incorporation of radionuclides with the consequence of prolonged radiation exposure. In this case, a decision about countermeasures must be carried out as soon as possible to reduce the resulting radiation dose. In order to be prepared for such a scenario, an Assessment and Documentation System has been developed to support the rapid assessment of internal exposures and to assist in decision making. Radionuclide distributions, excretion rates, and resulting exposures have been calculated on the basis of a reference scenario. The documentation of the results in the form of tables and graphs allows the easy and quick interpretation of measurements in terms of exposure and intake. The system in its present status gives information about possibilities of countermeasures; it is the intention of the next steps of development to give advice on the basis of estimated avertable doses.