ABSTRACT
The characteristic of nuclear power plants that largely distinguishes them from other kinds of industrial plants is that they release radioactive material into the environment while operating.* A nuclear power plant also has a large permanent source term of radioactive material which is well contained but potentially available for release during a serious accident. Therefore, it is important that emergency responders and planners have at least a basic understanding of how radioactive material behaves in the environment. This chapter discusses basic meteorology, the characteristics of plumes of airborne radioactive material in the environment, the technical and environmental mechanisms for plume depletion, dose pathways to humans, and applicable standards.†
Commercial nuclear power plants are permitted to release (vent) radioactive gases into the environment during normal, routine operations. Pressurized water reactors typically release from 500 to 1000 µCi/s, primarily the noncondensable radioactive noble gases krypton and xenon. Boiling water reactors release larger amounts of radioactive efuent than pressurized water units do, typically in a range from 1000 to 3000 µCi/s. Permissible efuent (release) concentration limits are given in 10 CFR 20, Appendix B, Table 2. Individual isotope concentrations that would result in 50 mrem total effective dose equivalent (TEDE)‡ are calculated for a member of the public assumed to stand continuously at the site boundary exposed to radioactive releases for 8760 hours (1 year). Mixtures of radioactive isotopes are calculated using the ratio rule.§ For most plants, a radiological release at the technical specication limit will not be detectable offsite using standard survey instruments, although a lengthy release would be detectable by the more sensitive environmental thermoluminescent dosimeters; this is a longer term detection, as the dosimeters are typically collected and analyzed quarterly.
