AFFTAC stands for the "Analysis of Fire Effects on Tank Cars." Southern Rockies Consulting serves as the custodian for this software, under the auspices of the RSI-AAR Tank Car Safety and Research Project.
Currently, the official released version of AFFTAC is AFFTAC 4.0. It is available for download here: AFFTAC 4.0 Download Page
For the latest information on bugs in AFFTAC, be sure to look at "All" issues at: AFFTAC Issue Tracker at BitBucket.org
AFFTAC 5.10 is under Alpha testing and will be made available for general Beta testing after the Alpha testing phase is complete.