National Emission Standards for Hazardous Air Pollutants Calendar Year 2005

Abstract

The Nevada Test Site (NTS) is operated by the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office (NNSA/NSO). From 1951 through 1992, the NTS was operated as the nation’s site for nuclear weapons testing. The release of man-made radionuclides from the NTS as a result of testing activities has been monitored since the first decade of atmospheric testing. After 1962, when nuclear tests were conducted only underground, the radiation exposure to the public surrounding the NTS was greatly reduced. After the 1992 moratorium on nuclear testing, radiation monitoring on the NTS focused on detecting airborne radionuclides that are resuspended into the air (e.g., by winds, dust-devils) along with historically-contaminated soils on the NTS. To protect the public from harmful levels of man-made radiation, the Clean Air Act, National Emission Standards for Hazardous Air Pollutants (NESHAP) (40 Code of Federal Regulations 61 Subpart H) limits the release of radioactivity from a U. S. Department of Energy (DOE) facility (e.g., the NTS) to 10 millirem per year (mrem/yr) effective dose equivalent (EDE) to any member of the public. This is the dose limit established for someone living off of the NTS for inhaling radioactive particles that may be carried by wind off of the NTS. This limit assumes that members of the public surrounding the NTS may also inhale “background levels” or radioactive particles unrelated to NTS activities that come from naturally-occurring elements in the environment (e.g., radon gas from the earth or natural building materials) or from other man-made sources (e.g., cigarette smoke). The U. S. Environmental Protection Agency (EPA) requires DOE facilities (e.g., the NTS) to demonstrate compliance with the NESHAP dose limit by annually estimating the dose to a hypothetical member of the public, referred to as the maximally exposed individual (MEI), or the member of the public who resides within an 80-kilometer (50-mile) radius of the facility who would experience the highest annual dose. This dose to a hypothetical person living close to the NTS cannot exceed 10 mrem/yr. C.1 This report has been produced annually for the EPA Region IX, and for the state of Nevada since 1992 and documents that the estimated EDE to the MEI has been, and continues to be, well below the NESHAP dose limit. The report format and level of technical detail has been dictated by the EPA and DOE Headquarters over the years. It is read and evaluated for NESHAP compliance by federal and state regulators. Each section and appendix presents technical information (e.g., NTS emission source estimates, onsite air sampling data, air transport model input parameters, dose calculation methodology, etc.), which supports the annual dose assessment conclusions. In 2005, as in all previous years for which this report has been produced, the estimated dose to the public from inhalation of radiological emissions from current and past NTS activities is shown to be well below the 10 mrem/yr dose limit. This was demonstrated by air sampling data collected onsite at each of six EPA-approved “critical receptor” stations on the NTS. The sum of measured EDEs from the four stations at the NTS boundaries is 2.5 mrem/yr. This dose is 25 percent of the allowed NESHAP dose limit. Because the nearest member of the public resides approximately 20 kilometers (12 miles) from the NTS boundary, this individual receives only a small fraction of this dose. NESHAP compliance does not require DOE facilities to estimate annual inhalation dose from non-DOE activities. Therefore, this report does not estimate public radiation doses from any other sources or activities (e.g., naturally-occurring radon, global fallout).