Now a compact fast-neutron lead cooled reactor would come in handy... development has been done..like the Convair NB 36H, but with 1950 tech..I wonder with modern specs and upgraded safety protocols..
However, there were certainly successful tests of actual nuclear-powered jet engines, like General Electric's X39 (a modified J47, and slated to be slapped onto that NB 36H to make a Convair X-6) and J87 (a different design for a different nuclear-powered bomber project, the WS-125).
A key issue is the shielding necessary to keep such an aircraft from irradiating everything around it (you think neighborhoods bitching about nearby airports are ornery now...); that shielding is heavy. Accidents also make such craft much riskier, which is indeed a cited reason (other than costs) why the USA and USSR both cancelled their nuclear-powered bomber programs.