Jaczko isn't credible. He is a head case that drove his colleagues, including his fellow Obama appointees, to publically and unanimously condemn his tenure as NRC chairman while seated right next to him during congressional testimony. They forced him out because they'd had enough of his shit.
So now he is going to be a professional anti-nuke gadfly. Last week good 'ol Senator Harry Reid resurrected the head case and put him on the NNSA board so he can make that group dysfunctional and say scary things about the stockpile. Now that he's out of the shadows he's taking more shots as nuclear energy as well.
If you read the linked story you'll eventually learn what, specifically, his problem is with contemporary operating reactors; they are large and have enough residual heat to damage fuel after shutdown. The notion that our power reactors are too large is not new. It has been well understood since the beginning of nuclear energy production. Jaczko is talking about it because that's his job now; use the credibility of his "Former Chairman of the NRC" moniker to make headlines by saying scary things about nukes.
Incidentally this discussion raises the question; how large can a reactor be without risking fuel damage? The answer is about 60 MW thermal for traditional PWR light water designs. Common power reactors are 2000 MW thermal.
BTW, we aren't going to do anything about any of this. We're not replacing the reactors, or coal or gas or building out green energy or anything else. We're a balkanized welfare state nation occupied with feathering our environmental nest while evacuating our industrial base to Asia. The power system you have now will be approximately the power system running when you die. Maybe a reactor will melt and we'll replace our nukes with more gas consumption. That's about as much as you can expect.