Publications

Certain regulatory actions under 10 CFR Parts 50, 52, or the proposed part 53 require the assessment of the potential off-site consequence risks to public safety and the environment from a hypothetical severe accident. As an important part of these analyses, atmospheric transport and dispersion (ATD) modeling relies heavily on the prevailing weather patterns of a site. When considering future deployment of new reactor designs in areas where historical onsite meteorological data is not available, there exists a need to assess the potential range of severe accident consequences using synthetic weather data. MACCS is designed to estimate consequence measures such as air concentrations, ground depositions, areas under deposition isopleths, radiological doses, and health and economic impacts on an annual-averaged basis by using inputs such as population and site-specific meteorological data. The objective of this work is to investigate the feasibility of supplementing observed site specific weather files with synthetic weather data to calculate these consequence measures. Understanding the probabilistic consequences estimated using synthetic data compared to site-specific observational meteorological data may lead to more agility and flexibility in performing calculation for future situations. This report details the results of research tasks associated with this goal. First, a review was performed to compile a list of potential site-specific meteorological data sources and evaluate their compatibility with MACCS. After selecting a subset of meteorological data, observed and synthetic MACCS weather files were developed for four regions with distinct weather and terrain conditions (Alaskan coastal, large river valley, flat terrain, and gulf coast). Consequence parameters, such as peak time-integrated air and ground concentrations and area under deposition isopleths as a function of distance, were determined for each site and meteorological data set using two distinct source terms. The results demonstrate that use of synthetic meteorological datasets result in consequence values with differences of less than a factor of two from site-specific observational data. The comparisons provided herein can provide decision-makers with additional insight to help evaluate the potential benefit of using national modeled weather data, especially in instances where site specific data over multiple previous years may not be available. The results of these analyses are provided and discussed in this report.

A variety of dose conversion factor files (DCF files) have been supplied for use with the MACCS code since it was initially released. For MACCS 4.2, the MACCS DCF files have been updated to include coefficients used in the computation of acute skin doses from within the MACCS software to increase functionality and to add a pseudo-organ to represent the total effective dose equivalent (TEDE) (as defined in 10 CFR 20.1003) based on International Commission on Radiological Protection (ICRP) Publication 30. This report provides a description of how these changes have been implemented and a summary of the various DCF files supplied with MACCS 4.2. The report also provides supplemental discussions to assist the reader in understanding the technical basis for the MACCS DCFs. These supplemental discussions include a summary of basic dosimetry modeling concepts and a brief review of the Federal Guidance Reports (FGRs) upon which MACCS dose coefficients have historically been based.