Nuclear thermal hydraulics

Prof. Yann Bartosiewicz – Université Catholique de Louvain


150 hours study time

30 contact hours theory

24 contact hours exercises/laboratory sessions/visits

14 contact hours personal work

Learning Outcomes

  • To learn how to estimate the volumetric heat generation rate in fission reactor cores under normal operation and shutdown conditions
  • To learn how to analyse the thermal performance of nuclear fuel elements
  • To learn the basic fluid mechanics of single phase reactor cooling systems
  • To learn to calculate pressure drop in reactor systems, including tube bundles, and spacer grids
  • To learn to analyse the heat transfer characteristics of single phase reactor cooling systems
  • To learn the basic fluid mechanics of two-phase systems, including modelling approaches, flow regime maps, void-quality relations, and pressure drop evaluation
  • To learn the fundamentals of boiling heat transfer, and its implications for reactor design
  • To calculate and analyze the coolant conditions throughout a reactor loop including the determination of natural convection regime
  • To learn the fundamentals of core thermal design, e.g. flow rate/pressure drop relation under different conditions (friction dominated/gravity dominated) for the evaluation of cooling performances
In addition of supervised exercises, a mini-project is organized about modelling and computing pressure drop in a boiling channel (different conditions and assumptions may be treated over the years).


  • Thermal design principles/reactor heat generation
  • Reminders about single phase transport equations (prerequisite)
  • Two-phase flow models, transport equations
  • Thermodynamic (vessels/pressurizer) and power conversion cycle (steam)
  • Heat transfer analysis in a fuel element
  • Reminders about single phase fluid mechanics and heat transfer (prerequisite)
  • Two-phase fluid mechanics and pressure drops
  • Two-phase heat transfer (pool boiling, flow boiling)
  • Single heated channel (thermal and flow problems)
  • Flow loops (steady state natural convection)

Course material and reference books

The PowerPoint presentations of the lectures, and extensive lecture notes, are available on the BNEN website.

Other useful references:

  • Todreas, N.E. and Kazimi, M.S. Nuclear System I: Thermal Hydraulic Fundamentals,
  • Taylor & Francis, Boca Raton, 2012.

Pre-assumed knowledge or prerequisites

A relevant course about introduction to nuclear energy
Fundamentals of fluid mechanics, heat transfer, thermodynamics

Grading and examination

The final mark is composed of (i) a written exam (80%, closed book) including an exercise and a theoretical part, and (ii) evaluation of a mini-project (20%).