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R&D researcher for PWR neutronics/thermal-hydraulics coupled modelling H/F

Vacancy details

General information


The French Alternative Energies and Atomic Energy Commission (CEA) is a key player in research, development and innovation in four main areas :
• defence and security,
• nuclear energy (fission and fusion),
• technological research for industry,
• fundamental research in the physical sciences and life sciences.

Drawing on its widely acknowledged expertise, and thanks to its 16000 technicians, engineers, researchers and staff, the CEA actively participates in collaborative projects with a large number of academic and industrial partners.

The CEA is established in ten centers spread throughout France



Position description


Thermohydraulics and fluid mechanics



Job title

R&D researcher for PWR neutronics/thermal-hydraulics coupled modelling H/F


Contribution to the validation of a neutronics/thermal-hydraulics coupled model for the study of the Main Steam Line Break accidental transient in a Pressurized Water Reactor

Contract duration (months)

12 months (renewable once)

Job description

The Main Steam Line Break (MSLB) transient in a Pressurized Water Reactor (PWR) is a reactivity insertion design-basis accident. A postulated sudden break in the secondary circuit is the accident initiator. The MSLB accident generates asymmetrical cooling in the core, leading to a radial core power distortion. There is a power increase on the side of the secondary loop where the break has occurred. Thus, a proper simulation of these power tilting phenomena have to represent three-dimensional effects.

Such a transient is classically modelled today at CEA with a multiphysics SCT (Scientific Calculation Tool) coupling three single-physics SCTs, i.e. CRONOS2 for neutronics, FLICA4 for core thermal-hydraulics and CATHARE2 for system thermal-hydraulics, within the CORPUS platform using SALOME. It is a best-estimate calculation route, which means that it provides a good trade-off between calculation time and accuracy. This transient will have to be modelled using the new generation of codes APOLLO3 and CATHARE3 developed at CEA.

Validation of coupled SCTs and the corresponding uncertainty quantification are crucial issues to be addressed in a reactor safety demonstration. This validation process remains to be firmly established in the very general multiphysics framework; this is a topic of active research.

The objective of the post-doctoral work is to provide numerical validation elements for the CEA best-estimate MSLB coupled calculation route, for the purpose of quantifying the impact of modelling choices on the calculated safety parameters (i.e. departure from nucleate boiling ratio and fuel melting temperature).

 The post-doctoral work will begin with a PIRT (Phenomena Identification and Ranking Table) analysis to identify the prevailing physics phenomena impacting the MSLB transient. This work will rely on prior PIRTs available in the international bibliography, which will have to be adapted.

 As part of the validation work, it will be necessary to estimate the impact of different modelling scales 0D/1D/3D used to represent the core and system behavior, as well as the impact of mesh refinements in neutronics (in space and energy) and in thermal-hydraulics (in space) calculations of the core power peak with feedbacks. The relevance of using simpler, faster-running approximations will be assessed by propagating the uncertainties of the physical models built into the closure laws (thermal transfer, turbulence, pressure drop, etc).

 The expected outcome of this post-doctoral work are formal recommendations for the development of a neutronics/thermal-hydraulics coupled model for simulating a MSLB transient in a PWR.

 This work will be part of the CEA contribution to the ongoing OECD Expert Group on Multiphysics Experimental data, Benchmark and Validation (EGMPEBV).

The results will be published in a peer-reviewed journal and will be presented at an international conference.

Methods / Means

reactor physics codes (APOLLO3, CATHARE3, FLICA4)

Applicant Profile

PhD required in reactor physics simulation
Good knowledge in PWR operation in accidental conditions

Position localisation



Job location

France, Ile-de-France


Route du Cyclotron, 91400 Saclay, France

Candidate criteria


  • English (Fluent)
  • French (Beginner)

Recommended training

PhD required