About MACCS

From a given release of radioactive material into the atmosphere, MACCS estimates the extent and magnitude of radiological contamination, offsite doses, protective actions, socioeconomic impacts and costs, and health effects. MACCS simulates atmospheric transport with a straight-line Gaussian plume segment model. Since the weather at the time of an accident is not predictable, MACCS samples from historical weather data as a surrogate for future weather and can run Monte Carlo simulations to evaluate the impact of weather variability. From the estimated air and ground concentrations, MACCS models dose projections through several dose exposure pathways both during and after plume passage. MACCS also models protective actions during the emergency response (e.g., evacuation, sheltering) and long-term recovery (e.g., relocation, farmland restrictions, decontamination) of the accident. While protective actions help reduce dose accumulation to individuals, they also cause social and economic impacts. MACCS models the extent of displaced individuals and land contamination, and the cost of offsite property damage, economic disruptions, and various accident expenditures caused by protective actions. Finally, from the dose accumulation, MACCS estimates early and stochastic health effects according to dose-response models.

MACCS-HYSPLIT Tools is an optional set of utility codes that can help generate input data for a MACCS simulation using resources from the U.S. National Oceanic and Atmospheric Administration (NOAA). These resources include publicly available NOAA weather data and the HYSPLIT code. The HYSPLIT code is an advanced three-dimensional atmospheric transport and dispersion (ATD) model provided by NOAA and one of the most extensively used models in the atmospheric sciences community. In MACCS, users may use the results of a HYSPLIT ATD calculation as an alternative to the original MACCS ATD model. MACCS-HYSPLIT tools include the following three codes:

• MacMetGen: This is a utility code that generates MACCS weather files from NOAA weather datasets or other meteorological sources. Users running the MACCS ATD model may use MacMetGen as an alternative to generating weather data from a site weather tower or other source. Users running the HYSPLIT ATD model should use MacMetGen so that the weather data used in HYSPLIT and the weather data used in MACCS (for other purposes) are consistent.
• GenHysplit: This is a utility code that runs the HYSPLIT code to generate output files of air and ground concentrations.
• HyGridConvert: This utility code converts GenHysplit output files into MACCS input files.

MACCS Data Flow

• User activates modules only as needed to determine results of interest.
• Activated modules determine input files that are required.
• Some required input files may be used as transmitted with MACCS (without user modification).

User Community

The MACCS user community includes both domestic and international users, to include the NRC, DOE, several research organizations, nuclear industry licensees/applicants, and academic institutions. Primary uses of MACCS include performing regulatory cost-benefit analysis, environmental analyses of Severe Accident Mitigation Alternatives (SAMAs) and Severe Accident Mitigation Design Alternatives (SAMDAs), evaluations for emergency planning, Level 3 PRA studies, consequence studies, and other risk-informed activities.