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Jordan, Spencer

Publications and source records attributed to Jordan, Spencer.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Voronoi Meshing to Accurately Capture Geological Structure in Subsurface Simulations

Mesh generation lies at the interface of geological modeling and reservoir simulation. Highly skewed or very small grid cells may be necessary to accurately capture the geometry of geological features, but the resulting poorly scaled or small grid cells can have a substantial negative impact on simulator accuracy and speed. One way to minimize numerical errors caused by gridding complex structures is to simulate on high-quality Voronoi meshes, which reduce grid orientation effects in fluid flow. This work presents a complete methodology to create Voronoi simulation grids, model fluid flow in complex geological systems, and visualize the results. A recently developed Voronoi meshing method that can automatically generate provably good unstructured meshes that conform to input surfaces creating closed volumes is used. Initially an analytical benchmark simulation is presented to validate the quality of the meshes and simulation results and demonstrate the superiority of simulation results using Voronoi meshes over flexed-hexahedral meshes on a domain with internal features. Next, meshes are created for test structures representing four of the most common geological features in the subsurface: layering, pinch-out, an interior lens that tapers to zero thickness on all sides and a fault with offset. Two benchmark flow simulations are run for each test structure. Finally, a realistic geological example for CO 2 injection into an anticline is simulated. Three realizations of the Voronoi mesh at the same resolution are generated for the simulations. Each mesh is highly refined near the injection wells and coarse in areas of less interest. These three meshes are used to model the CO 2 plume in the subsurface as it migrates to the top of the structure and then fills downward. Simulations on the meshes with randomly generated elements inside the input volumes each give slightly different fingering patterns for the viscous-unstable buoyant gas flow. The results presented in this work show a promising step towards utilizing fully automated Voronoi meshing for subsurface flow simulations in complex geology.

58 GEOSCIENCES↗
DOE OSTI2019

Y-12 Lessons Learned: Process Drift

Criticality Safety lessons learned in Uranium Chip Recovery, Briquettes, Reduction Sand Separator, Slag Accumulation, Holden Gas Furnace, and Accumulations in Casting Lines.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

URANIUM ACCUMULATIONS IN CASTING OPERATIONS

In December 2017, unexpected accumulations of uranium were discovered in several locations throughout the casting process area at the Y-12 National Security Complex that subsequently placed casting operations on hold. The Y-12 uranium casting process takes place in enclosures and hoods, many of which are open to a large floor surface area that has limited visibility and access. At the time of discovery, there were no Nuclear Criticality Safety (NCS) analyses or limits for material accumulations in the casting processing areas. Due to changes in the operation of the casting process and invalid assumptions in the criticality safety evaluation, significant material accumulations were occurring inside the enclosures. The material accumulations were identified as a result of an extent of condition review from another process, and an occurrence report was filed. The NCS organization worked with Production and Operations personnel to identify additional areas of uranium accumulation in the casting area, which resulted in several iterations of cleaning and material collection. Following material recovery, a causal analysis was performed that identified several contributing factors that allowed the accumulations to go unnoticed. In order to resume operations, the criticality safety evaluation was revised to analyze and control uranium accumulations in the casting area. Additionally, improvements in nuclear material control and accountability (NMC&A) controls were required. Casting operations have since resumed with frequently required material collections, which have limited the amount of uranium material accumulation.

61 RADIATION PROTECTION AND DOSIMETRY↗