The material was produced at the Safari-1 reactor located at the Pelindaba research center. Safari-1 is a light-water "tank-in-pool" reactor that operated at power level of 20MW. The design is similar to that of the ORR reactor in Oak Ridge. Safari-1 historically used HEU fuel with enrichment of 90% and 45%. Mo-99 production traditionally involved irradiation of targets that contain HEU with enrichment of 45%.
UPDATE 09/13/10: The Safari-1 reactor was converted to LEU fuel in June 2009. The operators also completed conversion of targets and radiochemical processes to LEU and are awaiting final approval from medical regulators. The U.S. shipment is apparently part of this approval process.