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Undeclared uranium hitches a ride on cobalt exports from Congo, study says
Philippe (left) and Manzuk quantified the amount of uranium that has been exported from the DRC in cobalt shipments or left behind in the environment. (Photo: Joel Hallberg/UW–Madison)
Researchers at the University of Wisconsin–Madison and Princeton University have published a study in Nature Communications that calls attention to a blind spot in nuclear nonproliferation: The Democratic Republic of the Congo (DRC) has exported thousands of metric tons of uranium, and there is no accounting for where it has gone.
In partnership with Lighthouse Reports and the Financial Times, UW–Madison nuclear engineering professor and nuclear security expert Sébastien Philippe and Ryan Manzuk, a geologist and research fellow in Philippe’s group and at Princeton, conducted the study using countrywide mineralization and geochemical data.
Zhen Wang, Jonny Rutqvist, Yuan Wang, Colin Leung, Andrew Hoch, Ying Dai
Nuclear Technology | Volume 187 | Number 2 | August 2014 | Pages 158-168
Technical Paper | Radioactive Waste Management and Disposal | doi.org/10.13182/NT13-76
Articles are hosted by Taylor and Francis Online.
We present an extended multiple interacting continua (Ex-MINC) model of fractured rock masses that uses Oda's crack tensor theory to upscale the hydraulic and mechanical properties. The Ex-MINC concept includes separate connected continua representing active fractures, inactive fractures, and matrix to represent the fracture-matrix system. The crack tensor theory was used to calculate the stress-dependent permeability tensor and compliance tensor for individual grid blocks. By doing this, we transformed a discrete fracture network model into a grid-based continuum model. The Ex-MINC model was verified against an existing analytical solution, and the entire Ex-MINC/crack tensor model approach was applied to a benchmark test (BMT) related to coupled stress, fluid flow, and transport through a 20-×20-m model domain of heavily fractured media. This BMT was part of the international DECOVALEX project for the development of coupled models and their validation, thus providing us with the opportunity to compare our results with the results of independent models. We conducted the coupled hydraulic and mechanical modeling with TOUGH-FLAC, a simulator based on the TOUGH2 multiphase flow code and the FLAC3D geomechanical code. The results of our simulations were generally consistent with the results of the other independent modeling approaches and showed how inactive fractures impeded solute transport through the fractured system by providing an additional fracture surface area as an avenue for increasing fracture matrix diffusion.