Reactor Glass (Big Reactors)

The Reactor Glass is a transparent block that can be used to make up the walls of a Big Reactor. Important to note is that the Reactor Glass is one of two blocks, alongside the Reactor Casing, that can be reasonably used to make the walls of the reactor. Reactor Glass can NOT be used to make the frame of a Big Reactor.

That said, unlike the Reactor Casing, the Reactor Glass isn't necessary for the creation of a Big Reactor.