Post-doctoral fellowship (M/F) : Experimental studies of space-energy effects in subcritical reactors

Job Description

Missions

In the field of radioactive waste management, the separation and transmutation of long-lived radioactive elements is a research area that complements deep geological disposal. Thus, the recycling and transmutation of minor actinides (MA) would reduce their radiotoxicity and the size of the high-level waste storage facility.
The transmutation of MAs can be carried out in subcritical accelerator-driven fast neutron reactors (ADS) dedicated solely to transmutation. In this case, the external neutron source that maintains the reactor core thermal power is generated by the interaction of a high-intensity proton beam with a spallation target. However, the design, development, and operation of ADS present a series of technological challenges to be overcome. In particular, the reactor's reactivity must be measurable online; otherwise, the ADS cannot be operated. Indeed, since the advantages of the ADS are linked to its subcriticality, this must be ensured under all conditions (normal, incident, or accident).
The SPATIAL project aims to develop a reliable method for measuring reactivity by quantifying, as precisely as possible, the biases and uncertainties that will affect the reactivity measurement of a power-generating ADS throughout its operating cycle, depending on the type of detector selected. This will minimize the need for an additional margin above criticality that would result from a reactivity measurement subject to high uncertainty.
To achieve these objectives, the SPATIAL project involves:
1) Conducting a detailed study of the space-energy effects that disrupt reactivity measurements during beam interruptions by performing novel measurements during source transients at various points in a subcritical model reactor operating at near-zero power and driven by an external high-intensity, high-reliability neutron source;
2) Extending the previous results to a power ADS loaded with MA, in order to quantify the biases and uncertainties in reactivity measurements throughout the ADS's operation.
Regarding the first component, which encompasses this postdoctoral proposal, new experiments will be conducted at the GUINEVERE facility located at SCK CEN, the Belgian nuclear energy research center. This facility is a near-zero-power ADS model comprising the GENEPI-3C deuteron accelerator, built by CNRS-IN2P3 laboratories, and the VENUS-F fast-neutron subcritical reactor, coupled together via a tritiated titanium target placed at the center of the reactor, which converts deuterons into neutrons via the deuteron-tritium fusion reaction. The GENEPI-3C accelerator has recently been upgraded to generate the intense and stable neutron source essential for the SPATIAL project's measurements. Indeed, the new experiments aim to measure, for the first time, the temporal variations in reaction rates of various nuclides using miniature fission chambers placed in the core and in the reflector of VENUS-F, during transients of the external neutron source. These measurements will allow for a precise, position-dependent study of the impact of the location of fission chambers on reactivity measurements, as well as the reconstruction of spectrum index variations, in order to precisely study the variation of the energy spectrum over time and as a function of position (space-energy effects).
The postdoctoral researcher will assist in preparing the experiments, which are scheduled to begin in the fall of 2026, and in developing a detailed experimental plan. He or she will participate in data collection at SCK CEN and will be responsible for analyzing and interpreting the collected data, as well as for fully simulating the experiments conducted. Finally, he or she will contribute to the drafting of the final deliverable for the SPATIAL project.

Activity

The postdoctoral researcher's duties will include:
• Assisting with the preparation of experiments;
• Assisting with data collection and monitoring the smooth conduct of experiments at the GUINEVERE facility at SCK CEN;
• Analyzing the collected data;
• Simulating the experiments conducted;
• Comparing measurements with simulations;
• Helping to draft the final deliverable for the SPATIAL project;
• Participating in collaborative meetings.

Your Profil

Skills

Candidates must have advanced training in nuclear physics and/or nuclear reactor physics. Strong programming skills (Python and/or C++) and data analysis skills are required. Proficiency in stochastic neutron transport simulation software such as MCNP, Serpent 2, OpenMC, Tripoli, or PHITS is highly desirable.

Your Work Environment

The successful candidate will be assigned to the Nuclear Waste Management group, within the Corpuscular Physics Laboratory of Caen.
The Corpuscular Physics Laboratory of Caen (LPC CAEN), with about 130 staff, is a joint research unit (UMR 6534) under the supervision of three institutions: the CNRS, the University of Caen Normandy (UCN) and the Ecole Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN). It is located on Campus 2 of the University of Caen (Campus Côte de Nacre) and is part of the research park of ENSICAEN (www.lpc-caen.in2p3.fr/).
The Nuclear Waste Management (NWM) group comprises two faculty members from the University of Caen, one faculty member from ENSICAEN, one CNRS researcher, two PhD students, and one associate researcher. Its work covers two research areas: the measurement of nuclear data relevant to nuclear energy and the physics of nuclear reactors. Regarding the latter, the NWM group has been working for over fifteen years on ADS, in close collaboration with the Laboratory of Subatomic Physics and Cosmology (CNRS/IN2P3/LPSC, Grenoble) and with SCK CEN, whether within the framework of European projects (GUINEVERE, FREYA, MYRTE) or bilateral CNRS-SCK collaborations (MYRACL, SALMON).

Compensation and benefits

Compensation

From 3 072 € gross monthly according experience

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions