In July 2002, the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE) established the Radiological Dispersal Device (RDD, or "dirty bomb") working group to investigate how to improve the control of nuclear material in the United States. In May 2003, the working group issued a DOE/NRC report, entitled "Radiological Dispersal Devices: An Initial Study To Identify Radioactive Materials of Greatest Concern and Approaches to Their Tracking, Tagging, and Disposition." In particular, to track these radioactive source transactions in a timely manner, that report recommended developing a Web-based National Source Tracking System (NSTS), which would allow licensees to record applicable radioactive source transfers using the Internet.
The quantities of concern identified in the DOE/NRC report are similar to the Category 2 threshold values established in the Code of Conduct on the Safety and Security of Radioactive Sources, which the International Atomic Energy Agency (IAEA) issued in January 2004. Specifically, the NRC determined that the sources to be tracked nationally are Category 1 and Category 2 sources, as described by the IAEA Code of Conduct. Consequently, to align the domestic and international efforts to enhance the safety and security of radioactive sources, the NRC adopted the IAEA's list of isotopes and Category 2 values. However, the NRC also expanded the list of nationally tracked sources by adding four extra materials (i.e., Actinium-227, Polonium-210, Thorium-228, and Thorium-229).
The President signed the Energy Policy Act of 2005 on August 8, 2005. The statute contains a national source tracking provision, which required the NRC to issue regulations establishing a mandatory tracking system for radiation sources in the United States. In response to that mandate, the NSTS was developed through close cooperation with other Federal and State agencies. About 1,300 licensees began reporting their Category 1 and Category 2 source information in the NSTS in January 2009. Implementation of the NSTS, along with the Web-Based Licensing (WBL) System and License Verification System (LVS), will improve the control and management of radioactive sources.