Objective of the activity
The goal of the activity is to contribute to the development of a quantitative methodology to assess the behaviour of complex liquid helium cryogenic systems when a LOVA occurs with the use of the two-phase unsteady 6-equations CATHARE 3 code [R8]. The activity will focus firstly on the effect of relevant parameters (i.e. geometrical configurations, boundary and initial conditions, safety devices characteristics etc.) on the temporal and spatial dynamics of the thermal-hydraulic phenomena occurring at cryogenic temperatures. Secondly, a methodology will be developed to take into account the statistical variability of the parameters and to assess margins with respect to the safety criteria. The activity will be divided in several phases:
• Phase 1: Bibliographic review and numerical modelling update. The phase will focus initially on the collection, analysis and synthesis of the existing literature on the topic by the Candidate as long as a hands-on training on the use of CATHARE 3 for cryogenic systems.
• Phase 2: Modelling of complex cryogenic systems. During this phase, a CATHARE thermal-hydraulic model of a liquid helium cryogenic systems will be built and run within a step-by step approach of increased complexity. The thermal-hydraulic behaviour driving parameters will be explored following a sensitivity exploration matrix
• Phase 3: Development of the methodology. Once the models anchored on satisfactory results, the Candidate will contribute to the development of a quantitative methodology to assess the effects of the statistical scattering of the driving parameters on the results and the evaluation of the safety margins.
• Phase 4: Synthesis. The entire activity will be completed by the detailed synthesis of the work performed, the results and the outcomes as long as the perspectives.

Candidate requirements
The Candidate will explore the less known domain of cryogenic engineering where physics, material properties, thermodynamic and transport properties will change significantly at low temperatures with respect to standard (ambient temperature) conditions. The candidate required competences are:
• Numerical modelling and thermal-hydraulic simulations with CATHARE 3 (or 2) and its post-processing tools (Guithare),
• Scientific programming skills with Matlab™ and/or Octave and Excel™,
• Fluids mechanics and thermodynamics,
• Curiosity and autonomy. Knowledge of cryogenic processes will be an added value.

A BAC+5 (Master or Engineering school) internship if foreseen with a duration of 6 months with a starting date between January and March 2024.