Resumen
The Greek Research Reactor (GRR-1) is an open pool type, light water moderated and cooled heterogeneous reactor with thermal power at 5 MW. The reactor has been in extended shut down since July 2014 and the decommissioning planning and costing is now in progress. In the present paper, the inventory as well as the preliminary classification of the reactor components and systems is presented, since this underlies the planning and costing of decommissioning. The strategy of the future decommissioning of the reactor is the removal of all activated and contaminated components and systems without demolition of the biological shielding. Thereupon, the concrete is not included in the inventory presented in this paper.