The SHARP neutronics module, PROTEUS, includes neutron and gamma transport solvers, cross-section processing tools, and tools for depletion and fuel cycle analysis. Efforts in the second quarter focused on three major priorities: multi-physics integration, intermediate-fidelity tool development, and demonstrations of applicability. Integration of the second-order, discrete ordinates (Sn method) solver of PROTEUS with the latest version of the MOAB framework (which represents and evaluates mesh data) was initiated to enable its use for multi-physics analysis. With these updates, PROTEUS can obtain the mesh specification from the MOAB framework and store its data on the MOAB mesh representation so that MOAB can manage the various meshes used by the physics modules. The intermediate-fidelity PROTEUS-2D1D module will represent power distributions and local reaction rates reduced computational cost in comparison to fully 3D methods. The equations to be solved have been formulated and are being implemented using components of the existing PROTEUS-UNIC module (to accelerate development).
Application of the code set to advanced reactor types continued, currently in support of upgrades to INL’s Advanced Test Reactor (ATR). The ATR’s complex serpentine plate-fuel geometry (Fig. 2) presents a particularly challenging problem to analysts.
Nek5000, SHARP’s thermal fluids module, provides solvers for multi-dimensional heat transfer and fluid dynamics. In the second quarter, an updated pressure solver was released, multi-physics integration capabilities were restored to the code, and initial benchmark analyses of the Russian SIBIRIA experiment were completed. The new pressure solver contains a spectral element multigrid pre-conditioner that supports the Pn-Pn formulation, which has become the discretization method of choice for large eddy simulation. This pre-conditioner significantly reduces iterations and run time compared to the previous pre-conditioner: the pressure solver is 2.5 times faster, and the overall module is 1.5 times faster. For some simulations of complex geometry, such as the detailed wire-wrapped sodium fast reactor (SFR) fuel assembly, the new solver makes the difference between solvability and intractability. Nek5000 has been re-integrated with the MOAB framework.
The updated Nek5000 module was used to perform initial simulations of experiments carried out in the Russian SIBIRIA facility have been completed (Fig. 3). In the experiments, local shear stresses were measured in a fluid flowing within a narrow annulus with and without partial blockage. The detailed stress measurements provide an important dataset for future validation efforts.