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Nuclear Incident Response Program
MACCS is a fully integrated, engineering-level computer code developed at Sandia National Laboratories (SNL) for the Nuclear Regulatory Commission (NRC). MACCS simulates the impact of severe accidents at nuclear power plants (NPPs) and other nuclear facilities on the surrounding environment. As the only code used by the NRC to support Level-3 probabilistic risk assessments (PRAs), MACCS can use a site’s weather data to determine hypothetical land contamination levels, doses to individuals, health effects and risks on populations based on protective action recommendations, and economic losses resulting from a NPP accident.



The full MACCS Code Suite includes MACCS, WinMACCS, MelMACCS, SecPop, AniMACCS, and MACCS/HYSPLIT Tools. To download software, new code users should first submit a software request for NRC approval following the instructions on the MACCS site.

Approved code users can obtain software through their account using the Downloads link below. MACCS and WinMACCS come together as a single installation file. The other software components are available as separate installations. All software components work on Windows, and a Linux version of MACCS is also available.

Software requests for "MACCS/WinMACCS," "MelMACCS," or "SecPop" provides only partial access to the MACCS Code Suite. Users can submit a new request for the "MACCS Code Suite" to obtain access to all of the software.

Note: Access to AniMACCS and MACCS/HYSPLIT Tools comes automatically with any request that includes MACCS v4. Upgrades to MACCS v4 are available to eligible users of previous MACCS versions and do not require a new formal software request.



See the MACCS site for details about software eligibility, fees, and request instructions as well as links to the NRC email contact for other requests and details.

Software & Downloads