One of the major objectives of the 6th Framework EC RTD EURANOS (European Approach to Nuclear and Radiological Emergency Management and Rehabilitation Strategies) project was to improve the RODOS (Real-time on-line decision support) system in its operational applicability. In the first phase of the project two possibilities for the main system development has been discussed: either to carry out refinements in the current version of RODOS or to consider a complete software re-engineering. The RODOS Users Group (RUG) finally concluded that the latter option was one to be realised. As a result a JAVA based version named JRODOS has been developed introducing a cross-platform solution capable to run on most operation systems, including Windows, Macintosh and the main UNIX derivates. The re-engineered system preserves computational models from RODOS, adding a powerful GIS support and applying modern database technologies with flexible configuration possibilities. Furthermore, these new GIS functionalities allowed implementing advanced simulation models for simulating countermeasures in inhabited areas (ERMIN - European Model for Inhabited Areas) and food production systems (AGRICP – Agricultural Countermeasure Program). Both simulation models have been part of the EURANOS project and represent state of the art modelling capabilities in their respective area.