You also have to check with the procedures implemented at a particular plant. For example: at VY, Entergy's fleet procedures define a Sr RPT as meeting the ANSI 3.1 standard. As a result, even though VY has an old license, it does not accept 18.1s as Seniors. 18.1's can work at VY but only as Juniors. The Nuclear Utilities Fundamentals exam is required even for Juniors who only need to score 70%. There is no difference in requirements between a first year Junior and an 18.1 RPT.
I believe other Entergy sites have read the fleet procedures differently from VY.