Today, complex computer codes allow the simulation of many different processes in nuclear power plants, from normal operation up to severe accidents. The input data generation for these codes and the evaluation of the results is, however, difficult and requires a high level of expert know-how. The possibilities of present-day computer technology make it possible to simplify the use of simulation codes by way of modern user interfaces and graphic processing of results.

One important tool in this area is the ATLAS simulation environment developed by GRS. The underlying objective of the development of is a consistent work bench for different process models. ATLAS allows the representation and assessment of the computational results with the help of user defined process charts (example shown below). It also enables the interactive control of the simulation, with intervention possibilities similar to those of a real power plant. Currently ATLAS is being extended by new modules for graphical modelling, interactive code input data generation and interfaces to the data analysis and visualisation tool “ParaView”.



There are a number of dynamic simulation codes available in ATLAS, covering a wide spectrum of reactor safety analyses. They presently include ATHLET/ ATHLET-CD, COCOSYS, ASTEC, MELCOR and S-RELAP. These codes comprise models for the reactor coolant system with thermal hydraulics and heat transfer, for reactor systems and instrumentation & control, for neutron dynamics, for core destruction processes and for the pressure build-up and fission product behavior in the containment.

ATLAS is used by research and regulatory organisations worldwide for a wide range of tasks. Particularly noteworthy are the detailed analysis simulators developed on behalf of the Federal Environment Ministry for German nuclear power plants, the training of personnel in the understanding of the dynamic plant behaviour during incidents and severe accidents, and the application in reactor safety analysis as pre and post processing tool for the mentioned simulation codes.

The latest code version available is ATLAS 5.1P1.

Some of the main new features:

  • Additional simulation data sets may be loaded at any time by the menu choice "File->Add NC File". This feature enables interactive data comparison. For details see the ATLAS User's manual.
  • Automatic diagrams for flammability of hydrogen (Shapiro)
  • Automatic diagrams for melt in lower plenum (AIDA)