CNRS Model

*Contact: Mustafa Jaradat, (mustafa.jaradatinl.gov), Namjae Choi (namjae.choiinl.gov), Abdalla Abou-Jaoude ([email protected])

*Model summarized and documented by Dr. Khaldoon Al-Dawood

Model link: CNRS Model

CNRS molten salt reactor (MSR) benchmark is a coupled-phyisics numerical benchmark created to establish a verification problem for couple-physics (i.e. neutronics and thermal-hydraulics) simulation. It was originally developed by French National Center for Scientific Research (CNRS) (Aufiero, 2015). The problem is a 2x2 lid-driven cavity filled with molten salt fuel with homogeneous composition at 900 K with lid driven flow along the upper surface of the cavity as shown in the picture. A visual demonstration of the benchmark geometry is shown in the following figure.

CNRS benchmark geometry.

Details for the fuel composition and delayed neutron parameters can also be found in (Jaradat et al., 2024). No slip boundary conditions with a fluid velocity of zero are applied across the boundaries of the geometry, except for the upper surface where the fluid moves with a determined velocity . The model implements adiabatic boundary conditions across the geometry walls. A heat sink is introduced to the bulk of the fluid to represent cooling process. The heat sink is modeled using a newton heat law like model as in

The neutronics model uses the neutron diffusion approximation to solve the eigenvalue problem. Cross sections are generated only at 900 K. The feedback from the thermal hydraulic solution is applied on the fuel salt density and Doppler effect is neglected. The change in fuel density is expressed by a linear model as

The change in density is applied to the macroscopic cross section as

To demonstrate the different physics solutions in this problem, the modeling of the benchmark is performed in phases. Following is a brief presentation of the phases:

  • Phase 0: Composed of three steps of steady state single physics problems

    • Step 0.1: Solves the steady state velocity field of the salt with m/s.

    • Step 0.2: Solves the neutron criticality eigenvalue problem.

    • Step 0.3: Using velocity field obtained from Step 0.1 and the power profile obtained from Step 0.2, the temperature profile is calculated.

  • Phase 1: Composed of four steady state multiphysics coupling tests (steps):

    • Step 1.1: Using the velocity field obtained in step 0.1, the drifting of delayed neutron precursors distribution is obtained.

    • Step 1.2: Using the velocity field obtained in step 0.1, the temperature feedback is introduced to assess its impact on the reactivity and fission rate.

    • Step 1.3: Perform fully coupled modeling of the system with a zero velocity boundary condition at the cavity lid.

    • Step 1.4: Using a combination of reactor powers and lid velocities, fully coupled simulations are performed.

  • Phase 2: A single step phase for the modeling of a transient coupled multiphysics model of the CNRS.

References

Aufiero, M. (2015). Serpent-OpenFOAM coupling for criticality accidents modelling–Definition of a benchamrk for MSRs multiphysics modelling. SERPENT and Multiphysics Workshop.

Jaradat, M. K., Choi, N., & Abou-Jaoude, A. (2024). Verification of Griffin-Pronghorn-Coupled Multiphysics Code System Against CNRS Molten Salt Reactor Benchmark. Nuclear Science and Engineering, 1-34.

References

  1. M Aufiero. Serpent-openfoam coupling for criticality accidents modelling–definition of a benchamrk for msrs multiphysics modelling. In SERPENT and Multiphysics Workshop. 2015.[BibTeX]
  2. Mustafa K Jaradat, Namjae Choi, and Abdalla Abou-Jaoude. Verification of griffin-pronghorn-coupled multiphysics code system against cnrs molten salt reactor benchmark. Nuclear Science and Engineering, pages 1–34, 2024.[BibTeX]