There were two main contractors, GE and Pratt & Whitney, each with a different approach. GE focused on developing a direct-cycle engine in which air from the turbojet would pass directly through a reactor to produce thrust. Pratt & Whitney aimed to develop an indirect-cycle engine, in which a liquid-metal coolant would carry heat from the reactor to a heat exchanger in the turbojet. Most of the information I've found so far relates to the GE effort, which got quite a bit further, including running several atomic-powered turbojets in static tests. Pratt & Whitney, among other things, developed a reactor design that would eventually evolve into the Molten Salt Reactor, better known today as the Liquid Fluoride Thorium Reactor.
The project, after many ups and downs, was eventually shuttered in 1961 for a variety of reasons. When the program was shut down GE produced a series of 21 comprehensive technical reports, detailing every phase of the project, as a sort of cheat sheet in case the government ever decided to reactivate the project. What I've acquired is two of those reports and two-thirds of a third: APEX-901, Project Summary; APEX-910, Application Studies; and Parts B & C of APEX-908, the XNJ140E nuclear turbojet, the final incarnation of the system. I've gotten these through the "adopt-a-doc" system, so two of them are already available on the Department of Energy's Information Bridge server (APEX-901, APEX-908C), and the other two should show up tomorrow. Be warned: these are big pdfs!
So what's in these documents? Let's take a look!