抄録
Nuclear power generation has become an increasingly attractive alternative in the United States (U.S.) power market due to several factors: growing demand for electric power, increasing global competition for fossil fuels, concern over greenhouse gas emissions and their potential impact on global warming, and the desire for energy independence. Currently there are more than 19 utilities and nuclear energy groups in the U.S. have announced plans for new plants to submit permit applications of Early Site Permits (ESP) and/or Combined Licenses (COL). In support of the permit applications, the following assessments are required: ・ potential dispersion of radioactive material from, and the radioactive consequences of, design-basis accidents to aid in evaluating the acceptability of a site and the adequacy of engineered safety features for a nuclear power plant; ・ maximum potential annual radiation dose to the public resulting from the routine release of radioactive materials in gaseous effluent; ・ habitability of the control room during postulated design-basis radiological accidents and hazardous chemical releases; ・ near-real-time atmospheric transport and diffusion estimates immediately following an accidental releases of airborne radioactive material to provide input to the evaluation of the consequences of radiological releases to the atmosphere and to aid in the implementation of emergency response decisions; ・ the potential dispersion of radioactive materials from, and the radiological consequences of, a spectrum of accidents to aid in evaluating the environmental risk posed by a nuclear power plant; and ・ the non-radiological related environmental effects, such as fogging, icing, and salt drift from cooling towers or ponds, to aid in evaluating the environmental impact of a nuclear power plant. The paper presents an overview of dispersion modeling approaches/techniques. Common regulatory conformance issues, particularly regarding (i) available computer modeling tools (including the USNRC-endorsed dispersion models), model application limitations and model input requirements, and (ii) use of meteorological data collected onsite and/or data collected on regional meteorological network, will be fully discussed. Lessons learned in performing these atmospheric dispersion analyses and practical model user tips are also included.
