Effects of mechanical loads of an uncontrolled power excursion (HCDA) on the reactor tank and internals of the SNR-300. Final report of calculations for the SNR-300 with the code SEURBNUK/EURDYN (V6)

The loadings on the reactor tank of the SNR-300 are investigated with the code SEURBNUK for HCDA with a mechanical energy release of 370 MJ. In an earlier report some open questions were already mentioned: the problem time covered by the calculation was too short and the influence of the breeder and reflector zone was not investigated. Both questions are answered in this report together with the consideration of hardware modifications known in meantime like wall thickness variations and changed axial distribution of wall temperature. But also the progress in code development is documented by using the new SEURBNUK versions 5 and 6. Both have an improved treatment for the complicated geometries of multifluid cells and in version 6 the kind of coupling the fluid with the structure is changed from a weak to a strong (iterative) procedure. Furthermore the treatment of the thin shells in the last version is changed from finite differences to finite elements. The results of parameter variations show a very small reduction of the peak hoop strains by the changed temperature profile and a greater, but still small decrease of the same values by the use of the new version with the strong coupling. A strong reduction to one third or the half of the starting values is reached by the introduction of an additional breeder and reflector zone. The largest strains of this calculation have the same order of magnitude which are found in the interim report. (orig./HP)