ASYST
Adaptive SYStem Thermal-hydraulics for Advanced Reactor Safety
Next-Generation Reactor Safety Analysis
ASYST (Adaptive SYStem Thermal-hydraulics) is a detailed integral Best Estimate Plus Uncertainty (BEPU) accident analysis code developed for reactor and advanced fluid systems safety analysis and training. Developed through the international ADTP consortium, ASYST represents the evolution of nuclear safety analysis with advanced modeling capabilities for both existing and next-generation reactors.
Integrated Uncertainty Analysis
Built-in uncertainty quantification using both source code and input parameters for robust BEPU analysis.
Interactive 3D Visualization
Advanced graphical displays with 3Dgui, Adv3Dgui, and RHYS platform for comprehensive analysis.
International Development
Developed by 100+ organizations across 32+ countries through the ADTP international consortium.
Two Development Branches for Different Needs
ASYST offers specialized versions optimized for different reactor types and applications
ASYST VER 3.x Series
Light Water Reactor Focus
- Specialized for LWR and HPWR systems
- Extended SCDAPSIM modeling for severe accidents
- Fukushima Daiichi lessons learned incorporated
- Addresses MELCOR and MAAP limitations
- Advanced late-phase severe accident modeling
ASYST VER 4.x Series
Advanced Reactor Framework
- Modern FORTRAN for portability and maintenance
- Multi-fluid property options (SCWRs, molten metals/salts)
- Three-fluid, non-equilibrium, 9-equation capabilities
- Subchannel thermal-hydraulic analysis support
- Molten material behavior modeling
Ready to See ASYST in Action?
Discover how ASYST 3.x or 4.x can meet your specific reactor analysis needs
Request DemoUnique Capabilities Beyond Standard Codes
Advanced features that distinguish ASYST from US NRC and INL system codes
Integrated Uncertainty Analysis (IUA)
Unique capability to perform uncertainty analysis using both source code and input parameters, significantly reducing uncertainties from user effects and training requirements compared to traditional approaches.
Interactive 3D Visualization
Advanced graphical displays including 3Dgui and Adv3Dgui for input verification, plus the RHYS Platform desktop simulator environment with pre-processing, simulation, and post-processing stages.
Advanced Multi-D Modeling
Multi-dimensional, multi-fluid hydrodynamic models with detailed SCDAPSIM module for fuel, core, and vessel behavior, plus 2D finite element COUPLE module for porous media and debris behavior.
Comprehensive Material Properties
Extensive MATPRO-based materials library covering nuclear fuels, cladding materials, control materials, structural materials, and molten materials with option for proprietary correlations.
Interested in these advanced capabilities?
Schedule a DemoWide Reactor Type Support
From traditional light water reactors to next-generation advanced designs
Light Water Reactors
PWR, BWR, and VVER systems with comprehensive modeling
Supercritical Water
SCWRs with advanced fluid property modeling
Heavy Liquid Metal
HLM-cooled reactors with specialized correlations
CANDU Reactors
Detailed fuel channel and calandria vessel modeling
Research Reactors
Flexible modeling for experimental facilities
Advanced Designs
SMRs and alternative coolant systems
Work With Any Reactor Type
From traditional LWRs to next-generation advanced designs, ASYST has you covered
Request Demo for Your Reactor TypeKey Advantages Over Other Codes
Why leading organizations choose ASYST for safety analysis
Mechanistic Modeling
Unlike MELCOR and MAAP which rely on user-defined core slumping temperatures, ASYST uses mechanistic models that significantly improve accident progression predictions and eliminate user parameter uncertainties.
Result: More realistic predictions of molten corium composition, energy content, and vessel failure progression
Real Accident Experience
Incorporates lessons learned from Fukushima Daiichi decommissioning R&D activities, providing more realistic late-phase severe accident modeling based on actual accident analysis and recovery operations.
Result: Enhanced confidence in severe accident analysis and emergency response planning
Reduced User Effects
Desktop simulator environments and advanced visualization tools significantly reduce uncertainties from user modeling choices and training requirements compared to traditional codes.
Result: More consistent analysis results and faster analyst training
Single Integrated Code
Analyze everything from normal operations through severe accidents in a single code framework, eliminating the need for multiple specialized codes and interface uncertainties.
Result: Streamlined workflow and reduced analysis time
See how ASYST outperforms traditional codes for your specific application
Request Comparative DemoTechnical Foundation
Built on proven technology with advanced computational methods
RELAP/SCDAPSIM Compatible
Fully compatible with RELAP/SCDAPSIM input models and data formats. RELAP5 models run with minimal modification, sharing common two-fluid, non-equilibrium, 6-equation field equations.
Validated SCDAPSIM Module
Detailed fuel rod behavior models compatible with FUELSIM steady-state code. Validated against experiments since the 1970s including QUENCH and PARAMETER test series.
Flexible Integration
Standardized interfaces allow coupling with 2D/3D CFD codes and third-party software libraries for extended capabilities.
Development Team Leadership
Dr. Chris Allison
Technical Leader - Former director of SCDAP/RELAP5 development at Idaho National Laboratory (1981-1996). Consultant for US NRC, DOE, IAEA, and Fukushima Daiichi emergency response.
Core Development Team
-
Fu Zheng & Jiang Shuying
Advanced thermal-hydraulic numerics, fluids, porous media -
Raimon Pericas
Fukushima R&D code development, reactor kinetics -
Marina Perez-Ferragut
Integrated uncertainty analysis, ATF models -
Victor Martinez
Thermal-hydraulics and reactor kinetics modules
International Collaboration
100+ organizations across 32+ countries through SDTP/ADTP consortium
Join the ADTP International Consortium
Gain access to cutting-edge development and collaborate with leading organizations worldwide
Applications Across Nuclear Industry
From regulatory analysis to advanced reactor development
LOCA Analysis
Loss of coolant accident analysis for PWR and BWR systems
Station Blackout
Extended loss of power scenarios with severe accident progression
Severe Accidents
Core melt, vessel failure, and MCCI analysis
Advanced SMRs
Small modular reactor safety analysis and design optimization
Training & Education
Desktop simulator environment for analyst and operator training
Research & Development
New fuel designs and accident-tolerant fuel evaluation
Explore how ASYST can support your specific application
Request Application DemoComprehensive Output & Analysis Tools
Powerful post-processing capabilities for detailed results analysis
Quick Plotting
Immediate visualization after calculation completion
Excel Export
Direct export to spreadsheet formats for reporting
3D Visualization
Interactive 3D results display and analysis
Sensitivity Analysis
Automated parameter sensitivity studies
Experience ASYST's powerful analysis capabilities firsthand
See ASYST in ActionExperience Next-Generation Safety Analysis
Join the international ADTP consortium and gain access to the most advanced thermal hydraulic safety analysis code for both existing and next-generation reactors.
Interested in joining the ADTP consortium? Contact us to learn more