The NERVA program was disbanded about 30 years ago. The team that did it is long gone. By now, quite a few of them are retired or dead. Those left have long since moved on to other projects. While the documentation almost certainly exists on microfilm somewhere, it'd take a long time to build a new team and get them up to the level where NERVA left off. It's almost as bad as trying to revive the Saturn V.

NERVA was pretty bold for it's day but it probably isn't the way they're wanting to go with the new program. NERVA was a solid core reactor that generated thrust by heating hydrogen (also served as a coolant). From what I read a long time ago, I think NERVA was designed for an operational life of perhaps an hour. There is also the problem of storing hydrogen for years. That has never been done before on a spacecraft, so some new technology would be needed. That wouldn't be a good solution to the Jovial Tour mission profile.

I have not read any technical details of the new proposal. If I had to guess, I'd speculate it's a nuclear-electric design where a small nuclear reactor generates electricity to power some form of electric propulsion. While I'd love for that propulsion to be VASIMR, it may be as simple as a conventional ion engine.