As I reach back into my sci-fi memory, hmmmmm...
Nuclear pumped X-ray laser comes up.
Could be a narrow-beam neutron ray that kills but leaves equipment intact.
Or, my favorite, a 40 watt plasma rifle directly powered by polonium.
Might be a new kind of non-bomb-pumped X-Ray laser (these already exist in various forms). At the end of the Cold War, it was discovered that the Soviets had actually been further along in laser research and military applications thereof than the West had been.
X-Ray lasers are kind of scary. Ravening death beam at more than one light-minute distance.
Actually, it appears they were working on nuclear propulsion for spacecraft. It could actually be a soft X-ray projector as those can be used for spacecraft propulsion.