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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.
V. Subramanian, R. Baskaran, J. Misra, R. Indira
Nuclear Technology | Volume 176 | Number 1 | October 2011 | Pages 83-92
Reactor Safety | doi.org/10.13182/NT11-A12544
Articles are hosted by Taylor and Francis Online.
In core disruptive accident conditions of sodium-cooled fast reactors, the reactor containment building (RCB) is filled with a large amount of sodium aerosols, along with fuel and fission product aerosols. The environmental source term depends on the quantity of aerosols released from RCB, which in turn depends on the quantity of aerosols that remains suspended in the RCB volume. The sodium aerosols are generated by the combustion process, resulting in micrometer-sized aerosols, while fuel and fission product aerosols are generated by vaporization condensation, resulting in nanometer-sized aerosols. To ascertain the behavior of mixed aerosols generated by the different processes, experiments are conducted by generating sodium aerosols and nonradioactive fission product aerosols and then studying their behavior in a closed vessel. The study includes (a) the initial size distribution of CeO2 and SrO2 aerosols, (b) the behavior of suspended mass concentration as a function of time, and (c) the behavior of suspended number concentration as a function of time. The initial size of the sodium combustion aerosols is [approximately]1.0 m, whereas the initial size of the fuel and fission product aerosols is nanometer sized ([approximately]30 nm). In the context of the behavior of the two different-sized aerosols, sodium aerosol behavior dominates the overall suspended mass concentration of the system. The rate of change of number concentration exhibits two regions. The timescale involved for the Brownian coagulation region is found to be [approximately]80 min for nonradioactive fission product aerosols, whereas it lasts only 20 to 30 min when the aerosol system is mixed with sodium aerosols.
