Validation of the reactor dynamics code TRAB

The one-dimensional reactor dynamics code TRAB (Transient Analysis code for BWRS) developed at VTT was originally designed for BWR analyses, but it can in its present version be used for various modelling purposes. The core model of TRAB can be used separately for LWR calculations. For PWR modelling the core model of TRAB has been coupled to circuit model SMABRE to form the SMATRA code. The versatile modelling capabilities of TRAB have been utilised also in analyses of e.g. the heating reactor SECURE and the RBMK-type reactor (Chernobyl). This report summarises the extensive validation of TRAB. TRAB has been validated with benchmark problems, comparative calculations against independent analyses, analyses of start-up experiments of nuclear power plants and real plant transients. Comparative RBMK type reactor calculations have been made against Soviet simulations and the initial power excursion of the Chernobyl reactor accident has also been calculated with TRAB. TRAB has been extensively used for analyses of the TVO ABB Atom type BWR reactors and within SMATRA for PWR analyses of the Loviisa VVER-440 reactors and VVER-91 type reactors. TRAB is also used outside VTT both for BWR analyses and, within SMATRA, for PWR analyses by the Finnish Centre for Radiation and Nuclear Safety (STUK) and the Imatran Voima Oy (IVO) power company