TRENDS AND PERSPECTIVES IN NUCLEAR THERMAL-HYDRAULICS

The Special Issue has been thought and written to honor B. R. Sehgal, G. Yadigaroglu and G. Hewitt (the honorable scientists) who recently passed away during the short time frame of less than one year: they have been giants in the area of nuclear thermal-hydraulics for more than half a century and actively contributed to the research, till the final moments of their lives. As N. Todreas wrote (see paper PII-1 in this Special Issue), “… collectively these three colleagues were since the late 1950s until their passing among the most productive researchers in our field”. The introductory group of papers PI-2, PI-3 and PI-4, the present paper constitutes PI-3, aims at synthesizing a reference view point in relation to,and. Thermal-hydraulics is embedded into the history of nuclear technology, namely water cooled reactors and not only. Attached to the word thermal-hydraulics one may find the following words or attributes (not an exhaustive list): fundamental or basic, system, applied, experimental, modeling, numerical solution methods, approximations, computational tools or codes (together with deeper details as: conservative, best estimate, 6-equations, Partial Derivative Equations [PDE], Homogeneous Equilibrium Models, lumped parameters), Navier-Stokes equations (and derived Computational Fluid Dynamics [CFD]), transient phenomena, design and safety analyses. A possible answer to the question ‘where NTH researches are now going’ constitutes the objective for the present paper; this is achieved by considering a few dozen papers submitted to the SI by scientists from different regions of the world currently engaged in improving the boundaries of knowledge in the area or, more simply, in clarifying complex issues. The SI is subdivided into three parts, the first one (which includes the present paper) providing introductory remarks and (SI) planning information, the second one celebrating the life and the scientific achievements of the three eminent researchers, the third one consisting of a collection of technical papers. Having in mind the above fixed objective, a short synthesis of the first and second parts of the SI are given in the present paper and relevant details from each of the thirty-four papers which constitute the third part are summarized. All papers in the SI are listed in the references (same order as in the ‘List of Contents’).