Innovative methods for hydrogen analysis and control in reactor core-melt accidents. Final report of part 1 of HGF-Strategiefonds-Project 98/07

The objective of part 1 of the HGF-Strategiefonds-project 98/07 is the deterministic description of hydrogen distribution and combustion processes during core-melt accidents in pressurized water reactors (PWRs). The results are used for optimization and improvement of hydrogen control methods in operating and future nuclear reactors. The activities aim at further reduction of the residual risk from the operation of nuclear installations. The main result of part 1 of the HGF-Strategiefonds-project 98/07 is the development of a complete and consistent analysis methodology for the hydrogen behaviour in core-melt accidents. The now existing tools permit a sufficiently precise 3d computation of the hydrogen and steam distribution in a complex reactor containment, the estimation of the maximum possible combustion velocities and the numerical 3d simulation of the respective combustion regime (slow deflagration, fast turbulent deflagration or detonation). This analysis procedure was applied fully or in parts to severe accident sequences in pressurized and boiling water reactors (8 PWRs, 3 BWRs). The computations for German plants have supported the licensing process of catalytic recombiners in German PWRs by confirming the effectiveness of the utility concept with high resolution 3d simulations. The programs developed in this project for hydrogen distribution (GASFLOW) and turbulent combustion (COM3D) are now used by Framatome for design and proof of a hydrogen control concept in the European pressurized reactor (EPR). The theoretical and experimental know-how gained in the nuclear field will also be applied to non-nuclear hydrogen safety investigations. (orig.)