The unnamed 'reputable scientist' Gundersen is probably referring to is probably Chris Busby, who with all due respect has the credibility of the tooth fairy. Gundersen himself spends most of the argument saying how much worse things are going to get and only near the end says that the things he's talking about have - in his likely inflated estimation - only a 10% or 20% chance of happening.

The big PWR civil power plant designs in the US evolved from the early designs for sub reactors in the 50s, so it could be said this isn't stealing anyone's idea, but just getting back to where we started from.