Orleans and Service Fabric are different. Orleans has been running in production for some time now and is actively developed on GitHub: https://github.com/dotnet/orleans. Teams inside Microsoft run it on top of Service Fabric (and Kubernetes, etc.) More details in this talk: https://youtu.be/KhgYlvGLv9c

Service Fabric has something called Reliable Actors which are heavily inspired by Orleans.

Source: I'm the project lead for Orleans