since people are talking about requirements to become SRO, and advancement.
First off, as someone who's seen the informal list of requirements for moving into SLT/management roles and up, almost all of the SLT positions require a cert at a minimum. So the license is a huge bump.
Secondly, for engineers becoming an SRO at an exelon plant, here's what you'll need (I just got in to ILT).
6 months on site minimum. 3 years of "responsible power plant experience" at a comparable reactor type. This generally refers to time that you are actually fully qualified to perform your job function, not just time working at a plant. Up to 2 of this MAY be substituted for your degree, but they don't like doing that and I think it goes against your ranking for selection. You also need an engineering/sciences degree from an ABET accredited university. If you have mech/EE/Nuke degree your fine. If you have chemical engineering, or a number of other things, they will need to look at it more.
I would recommend getting on site as a system engineer, getting very active in troubleshooting and making yourself known, and taking a shot at it once you've learned about the plant you want to be at....if you are trying to get in through engineering. It is uncommon for them to take an external hire to ILT, who is also an engineer (not an operator), but it does happen.
Good luck