37 1966 Reactor Excursion and Leak Analysis Program Soon after the birth of commercial nuclear energy, the Nuclear Regulatory Commission identified a need for reactor safety analysis software. In 1966, Idaho scientists began developing the Reactor Excursion and Leak Analysis Program (RELAP) to model reactor coolant and core behavior in a pressurized water reactor. In 1996, INL copyrighted the non- NRC-funded parts of the RELAP code, introducing the RELAP5-3D version in 1998.Today, RELAP is the international gold standard for reactor safety analysis, reactor design, operator training and university education.The next iteration, RELAP-7, is under development.