Auswirkungen eines spontanen Druckbehälterversagens beim HTR Modul

The HTR-Module (High Temperature Reactor) is supposed to be a reactor, which comprises ofthe complete know-how ofHTR-technology. The consequent goal of a passive and inherent safety philosophy in reactor design has been followed. The question remains, however, whether this is also sufficient in the Gase of a spontaneous failure of the reactor pressure vessel, which is not designed as burst-proof Due to this, the assumption of the hypothetical reactor pressure vessel failure is an unalterable boundary condition for all considerations in this thesis. The first part evaluates the non-nuclear effects. Through the means of known investigations of explosions and burst processes, a comparison measure for the HTR-Module is developed. More detailed investigations of the dynamic fragment behaviour are made with the new computer programs FRAG2 and Xerxes. In the following, it is investigated in which way the burst process also implies nuclear effects. A limitation is made to be time period immediately following the burst of the vessel, meaning that corrosion of the fuel elements is not regarded and the void fraction of the pebble bed remains constant. Thus the calculated reactivities are Input data for the analysis of the stress of the Coated Particles in the fuel elements. The fast reactivity transients are calculated with means of the pointkinetic program HTRKIN and then transformed to transient stresses with use of the new program FAST2. The stresses of the CP-laysers of interest are rated with the use of comparison values. Additionally, an investigation ofthe longterm behaviour is made in such a way, that the resulting temperature increase by the reactivity input is used as an input data for the thermohydraulic analysis with regard to the changed core structure. The result of the investigations is that the shortterm transients, which will occur without any outer influence, have a relatively small hazardous potential in comparison to experimental results. The longterm transients can be handled through a fitting accident management. The way in which the possible shortterm transients result in a remaining prefailure of the Coated Particles and negatively influence the longterm behaviour still needs to be considered