(GRS-A-1524) Sizewell "B" Reactivity Fault Study Phase B and C - Analysis of RCCA Bank withdrawl with the 3D Reactor Core Model QUABOX/CUBBOX-HYCA

S. Langenbuch, M. Clemente, E. Kramer

For the reactor core of Sizewell-'B1, PWR, nuclear design calculations andRCCA withdrawal transients have been analyzed by applying the 3D reactor core model QUABOX/CUBBOX-HYCA. The analysis is based on the core configuration as described in the Pre-Construction Safety Report. The basis of these nuclear calculations was a library of nuclear crosssections that was established within this project. The objective is an independent assessment of reactivity initiated transients by unintended RCCA withdrawal. The results of static and also transient calculations with the fully 3D core model of RCCA withdrawal under various conditions are used to evaluate the assumptions for the spatial power density distribution and its possible changes which are input values in safety analysis for these type of accidents. This work will be supplemented by additional calculations for very fast reactivity insertions as postulated within the rod ejection accident.