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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.
Ray S. Booth
Nuclear Technology | Volume 198 | Number 2 | May 2017 | Pages 217-227
Technical Paper | doi.org/10.1080/00295450.2017.1299494
Articles are hosted by Taylor and Francis Online.
Functionals derived from the finite Laplace transforms of time moments of experimental data are used to fit these data to exponential functions. The functionals provide linear relationships for individually determining parameter values successively. This new and unique fitting method is first derived and then applied to data containing up to four exponentials to demonstrate its capabilities. Advantages of this fitting procedure include the following. (1) Parameters of the fit can be determined from the data region where they are most important by a wide verity of methods, including conventional ones. (2) Fitting algorithms are available that are simple to program; use conventional “stripping techniques”; are quite robust; and have been tested for a wide range in the number of data points, statistical errors, data ranges, and parameter values. (3) Fitting algorithms are included that use the conventional correlation coefficient of two expressions to fit data with even or uneven time intervals. (4) Decay constants and their associated magnitudes are determined separately and independently from different functionals. (5) Each iteration of the fit requires relatively few computations, usually only selected integrals, which can be completed quite rapidly. (6) Parameter errors can be estimated by conventional techniques.