There's a ton of money pouring into nuclear power right now, both fusion and fission. There are dozens of small VC-funded startups now in addition to the more "traditional" billionaire-funded nuclear startups. Each of them need SWEs to help with automating the physics/design simulations, document creation/management, plant design configuration/change management, QA compliance, construction management, experiment IT (instruments, controls, data collection, data reduction). Most companies have nuclear engineers like me who picked up some software skills along the way, but I've found it's always a huge benefit to bring in some nuclear-interested SWEs to help get things running with best practices. Some SWEs I've hired in the past felt a little isolated, but others have engaged well with the nuclear and mechanical engineers and had a great time. Be prepared for some weird fights with nuclear IT teams who are extra afraid of criminal penalties associated with export control laws.