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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.
Min Woo Seo, Jae Woo Park
Nuclear Technology | Volume 168 | Number 3 | December 2009 | Pages 938-942
Miscellaneous | Special Issue on the 11th International Conference on Radiation Shielding and the 15th Topical Meeting of the Radiation Protection and Shielding Division (PART 3) / Radiation Protection | doi.org/10.13182/NT09-A9330
Articles are hosted by Taylor and Francis Online.
A fiber-optic dosimeter model is constructed with a small piece of Gd2SiO5 (GSO) scintillator optically attached to a low attenuating plastic optical fiber. The lights generated in the scintillator are transmitted through the fiber and read by a current-type photomultiplier tube (PMT). The dosimeter model was tested with two 60Co standard sources of 1.85 and 37 MBq by measuring the PMT current as a function of the source-to-detector distance. It was then tested in a 60Co irradiation chamber with an activity of [approximately]244.2 TBq. MCNPX simulations were performed for the source and dosimeter arrangements to calculate the deposited energy in the GSO scintillator. When tested with standard 60Co sources of 1.85 and 37 MBq, the dosimeter model did not produce satisfactory results. However, better results were obtained with the higher-activity source. In the test in a 60Co irradiation chamber of 244.2 TBq, the measured data well coincide with the MCNPX simulation results. In a direct comparison with a Farmer-type ion chamber, it is found the dosimeter readings can be simply converted to the air kerma doses by proper calibration.
