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SAS: Reactor Safety Analysis System

SAS4A/SASSYS-1 is a software simulation tool used to perform deterministic analysis of anticipated events as well as design basis and beyond design basis accidents for advanced nuclear reactors. This software can be used to assess the safety of a prescribed reactor design, but it cannot be used to configure a design to meet targeted performance objectives.

Detailed, mechanistic models of steady-state and transient thermal, hydraulic, kinetic, and mechanical phenomena are employed to describe the response of the reactor core, the reactor primary and secondary coolant loops, the reactor control and protection systems, and the balance-of-plant to accidents caused by changes in coolant flow, loss of heat rejection, or reactivity insertion. The consequences of single and double-fault accidents can be modeled, including fuel and coolant heating, fuel and cladding mechanical behavior, core reactivity feedbacks, coolant loop performance including natural circulation, and decay heat removal. Analyses are typically terminated upon demonstration of reactor and plant shutdown to permanently coolable conditions, or upon violation of design basis margins. The objective of the analysis is to quantify accident consequences as measured by the transient behavior of system performance parameters, such as fuel and cladding temperatures, reactivity, and cladding strain. Originally developed for analysis of sodium cooled reactors with oxide fuel clad by stainless steel, the models in SAS4A/SASSYS-1 were subsequently extended and specialized to metallic fuel clad with advanced alloys and to several other coolant options, including lead, LBE, and water.


The latest version of SAS4A/SASSYS-1 is 5.7.1 (September 11, 2023).

Licensing of the SAS4A/SASSYS-1 safety analysis system is available through Argonne's Technology Commercialization and Partnerships Division. To view the code package description and to submit a request for more information, please visit the licensing page. The distribution includes code manuals, executables for Mac, Windows, and Linux systems, and sample problems. Export control restrictions may apply.

A version of SAS4A/SASSYS-1 with a reduced feature-set, Mini SAS, is freely available to faculty at academic institutions for non-commercial use (i.e. research, teaching, etc.). Mini SAS is built from the same source as SAS4A/SASSYS-1, but excludes severe accident models (fuel melting and relocation, sodium boiling) and steam plant models. It is also limited to five core channels, which is adequate for most analyses.

A previous version of the code manual is available as a separate download below.


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