You would be teaching at Power School, I presume, not at one of the prototypes (I'm not aware of any Direct Input Instructor positions at the Prototypes, just Power School). So you'd be teaching basic classes to students with little to no background in Nuclear Theory, at a pace that forces them to memorize rather than truely understand the material. As scotoma said, it is a highly prescribed lesson plan without terribly much leeway for your own additions.
If I were you, I'd stick with Exelon and depending on why you were medically disqualified for the Navy, and your interests try and go into Operations. As you know, there are a ton of plants in IL so you'd be close to home and be making more money than you would be in the Navy.
My background: I worked at the Navy Prototype in NY for 6 years in Operations/Training and now am in SRO License Classes at Exelon.