"NRC's [U.S. Nuclear Regulatory Commission's] Office of Nuclear Material Safety and Safeguards (NMSS) regulates the decommissioning activities at fuel cycle facilities, uranium recovery facilities, and nuclear materials facilities. NMSS regulates the decommissioning of power reactors after certain licensing actions are completed. NRC's Office of Nuclear Reactor Regulation (NRR) regulates the decommissioning of most power reactors during the early stages of decommissioning. NRR also regulates decommissioning activities at research and test reactors. Agreement States implement and enforce the regulations for decommissioning source, byproducts, and small quantities of special nuclear material at facilities and sites in their states."
Government Printing Office: http://www.gpo.gov/