(Not entirely sure if that's because people with serious illness are scared of the work "nuclear", or if it's because the President couldn't pronounce it...)
I don't think there is much "supposedly" about it - Carter was a highly trained nuclear engineer as part of the US Navy nuclear power program under Admiral Rickover. Indeed Carter led a team to help with the NRX reactor accident in Canada.
"The painstaking process required each team member, including Carter, to don protective gear, and be lowered individually into the reactor to disassemble it for minutes at a time. During and after his presidency, Carter indicated that his experience at Chalk River shaped his views on nuclear power and nuclear weapons, including his decision not to pursue completion of the neutron bomb."
(Not entirely sure if that's because people with serious illness are scared of the work "nuclear", or if it's because the President couldn't pronounce it...)