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[en] The U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office operates the Nevada Test Site (NTS) and North Las Vegas Facility (NLVF). From 1951 through 1992, the NTS was the continental testing location for U.S. nuclear weapons. The release of radionuclides from NTS activities has been monitored since the initiation of atmospheric testing. Limitation to underground detonations after 1962 greatly reduced radiation exposure to the public surrounding the NTS. After nuclear testing ended in 1992, NTS radiation monitoring focused on detecting airborne radionuclides from historically contaminated soils. These radionuclides are derived from re-suspension of soil (primarily by wind) and emission of tritium-contaminated soil moisture through evapotranspiration. Low amounts of tritium were also emitted to air at the NLVF, an NTS support complex in North Las Vegas. To protect the public from harmful levels of man-made radiation, the Clean Air Act, National Emission Standards for Hazardous Air Pollutants (NESHAP) (Title 40 Code of Federal Regulations (CFR) Part 61 Subpart H) limits the release of radioactivity from a U.S. Department of Energy facility to 10 millirem per year (mrem/yr) effective dose equivalent to any member of the public. This limit does not include radiation not related to NTS activities. Unrelated doses could come from naturally occurring radioactive elements or from sources such as medically or commercially used radionuclides. The NTS demonstrates compliance with the NESHAP limit by using environmental measurements of radionuclide air concentrations at critical receptor locations. This method was approved by the U.S. Environmental Protection Agency for use on the NTS in 2001 and has been the sole method used since 2005. Six locations on the NTS have been established to act as critical receptor locations to demonstrate compliance with the NESHAP limit. These locations are actually pseudo-critical receptor stations, because no member of the public actually resides at these onsite locations. Compliance is demonstrated if the measured annual average concentration of each detected radionuclide at each of these locations is less than the NESHAP Concentration Levels (CLs) for Environmental Compliance listed in 40 CFR 61, Appendix E, Table 2. At any one location, if multiple radionuclides are detected, then compliance with NESHAP is demonstrated when the sum of the fractions (determined by dividing each radionuclide's concentration by its CL and then adding the fractions together) is less than 1.0. In 2009, the potential dose from radiological emissions to air, resulting from both current and past NTS activities, at onsite compliance monitoring stations was a maximum of 1.69 mrem/yr, well below the 10 mrem/yr dose limit. Air sampling data collected at all six critical receptor stations had average concentrations of radioactivity that were a fraction of the CL values listed in Table 2 in Appendix E of 40 CFR 61. Concentrations ranged from less than 1 percent to a maximum of 17 percent of the allowed NESHAP limit. Because the nearest member of the public resides approximately 20 kilometers from potential release points on the NTS, concentrations at this location would be only a small fraction of that measured on the NTS. The potential dose to the public from NLVF emissions was also very low at 0.000044 mrem/yr, 230,000 times lower than the 10 mrem/yr limit.