I am one of the "OLD DOG" Navy Nucs. I went through Nuclear Power School as a EM1 in 1963. Instead of Electrical Operator (EO) training I chose Reactor Operator (RO) training.
When I got to the S3G (yea, I'm that old) prototype I wanted to qualify as a EO/RO operator. A sage old Chief ET advised me to drop the RO and stick with EO as he had heard that the Navy was going to make the RO qualification ET only. This I did and sure enough all the non-ET ratings that qualified as RO had to switch to ET or qualify for a EO or MO watchstation.
By the way; In 1963 we had Sonarmen, Aviation Mechanist's, Enginemen and several other ratings going through Nuc School.
I qualified at S3G first in my class, stayed for 3 years at S3G as an in-hull instructor (by the way; one of my EO trainees (an EM2) qualified as a RO/EO operators) then went to sub school and USS Tinosa (SSN 606) where I qualified for my Dolphins and made EMC(SS). I then went to a "Boomer" (SSBN 619) then to S1C protype where I qualified as Engineering Officer of the Watch. After S1c I rode the USS Halibut (SSN87) for a couple of years. The Halibut and I retired together.