Methodology for the qualification of thermal-hydraulic codes nodalization

A rigorous (as far as possible) procedure to develop nodalization or input decks for system thermal-hydraulic codes is proposed. The nodalization is the interface between the code, including assumption and approximations and the reality which is known with some approximation, too. The nodalization proved to be the origin of more or less large differences between the code prediction and the experimental data. The proposed procedure aims at reducing those differences. The procedure consists of four main parts: a) Development according to the features of the codes, i.e. following user manual and additional recommendations. b) Comparing values of geometry and material data coming from a given source and part of the input deck. c) Comparing values of initial steady state and reference (preferably measured) data of the system. d) Comparing transient data predicted by the code and data measured (if possible) in the concerned system. The steps b) and c) are called ‘nodalization qualification at the steady state level’. The step d) is called ‘nodalization qualification at the on-transient level’. In the case of steps b) c) and d) acceptability thresholds are proposed for the comparison processes.