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This report details progress and activities of Idaho National Laboratory (INL) on the Nuclear Regulatory Commission (NRC) project "Development and Modeling Support for Advanced Non-Light Water Reactors."The tasks completed for this report are:• Task 2c: Explicit modeling of pebble transient temperature response. In this simulation, the 400 MWth Pebble-Bed Modular Reactor (PBMR) design, PBMR-400, experiences a 20-second power ramp from 100% to 150% power. This is followed by a similar reduction in the power back to 100%. Several multiscale pebble coupling approaches are tested with one pebble per mesh element in the active core region. The results show good conservation behavior and the stability of the coupling.• Extended scope part 1: An assessment of the computational efficiency of the Discontinuous Finite Element Method (DFEM) heat transfer solver shows good scalability. The DFEM solver is a factor of 4 more expensive in solution time than the Finite Element Method (FEM) solver for heat transfer problems due to the increased number of degrees of freedom. Nonetheless, the DFEM approach provides the user with the flexibility to model gap heat transfer problems.• Extended scope part 2: The GapHeatTransferInterfaceMaterial was improved to give the user increased flexibility with the modeling of heat transfer through gaps with the DFEM solver. A number of gap parameters can now be coupled both through functions and variables.• Extended scope part 3: Demonstration of how the gap width between hexagonal fuel cells can be calculated during a heat-up transient and used in the GapHeat-TransferInterface model. A full-domain DFEM model with gap expansion is coupled to a SubApp that models the thermal expansion of the base plate. The results show the expected physical behavior, although have not been fully benchmarked at this point in time. List of FiguresAnnular pebble bed model geometry with linear power distribution (left); Pebble model with example temperature distribution (right). . . . . . . . . 3 Pebble bed total power as function of time, 20s linear power ramp to 150% of the power and back to the 100% after 500s . . . . . . . . . . . . . . . . 4Coupling schemes between the porous medium and the pebble models. The black arrows represent the transferred quantities (the ones used as boundary conditions are followed by as

Laser pulses can effectively induce local structural changes and modify the physical properties of carbon allotropes. So far, only graphitization has been demonstrated using low laser energies (1J/cm 2). The novelty of this paper is a result of laser-induced amorphization of a highly anisotropic carbon allotrope by using high energy (1.5e15.4 J/cm 2) 5 ns, 532 nm Nd-YAG laser pulses. Moreover, cycling phase change, between an amorphous and a crystalline phase, is also obtained by adjusting the pulse energy. However, cycling ability is restricted to a few cycles as a consequence of laser-induced surface damages caused by both high temperatures during and high thermal gradients during and after laser exposure. The occurrence of graphitization or amorphization depends on the amount of solid crystalline seeds during so-lidification from the melt, which is controlled by the post-pulse temperature of the carbon surface. This study uncovers new applications of carbon allotropes, such as optically-controlled reversible phase-change memories.

The U.S. Department of Energy Office of Nuclear Energy Advanced Modeling and Simulation (NEAMS) program develops an integrated suite of advanced reactor physics tools built upon the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework. Each code generally requires an input finite element mesh on which the physics solution is calculated, reported, and transferred to other physics codes. The meshing process is often burdensome for the complex geometries present in reactors due to lack of easy-to-use, open-source meshing tools.