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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.
Jeffrey W. Lane, David L. Aumiller, Jr., Lawrence E. Hochreiter, Fan-Bill Cheung
Nuclear Technology | Volume 177 | Number 2 | February 2012 | Pages 176-187
Technical Paper | Thermal Hydraulics | doi.org/10.13182/NT12-A13364
Articles are hosted by Taylor and Francis Online.
A three-field countercurrent flow limitation (CCFL) model based on the classic flooding curve methodology has been developed and successfully demonstrated in a derivative of the COBRA-TF code. The various physical mechanisms (wave reversal, liquid bridging, and wave interfacial instability) supposed to govern the flooding and flow reversal phenomena are extremely complex and geometric dependent. As a result universally applicable numerical models for these phenomena are not currently available. The chosen approach provides flexibility and leverages the available experimental data to improve the predictive capability of the code. The model is an extension of the standard two-field (liquid-vapor) CCFL model to a three-field (liquid films, vapor, and liquid droplets) CCFL model. This extension includes providing the appropriate set of momentum equations, definitions of required superficial velocities, and new entrainment rate correlations based on CCFL conditions. Necessary criteria to enter and exit the model in a numerically stable manner are also described. The implementation of the model was verified and was shown to provide increased numerical stability in the code predictions. Improvement in the code-to-data agreement of the allowable downward liquid penetration rate for the Dukler and Smith experiments is also demonstrated.