We seem to manage nuclear very well, and one piece of evidence is how horrifying it is that four people died in this story, and the degree of concern it generated. Nuclear stuff is like airline safety; there's a good cultural and governmental stance around taking its risks seriously.

But more importantly, not responsible enough compared to which alternatives? In this case, it was a device for radiation therapy. The solution here can't be that lots of people die of cancer because nuclear is too dangerous. That just doesn't add up. For nuclear tech more generally, I posit that we are far less responsible with fossil fuels, and that they have done, and will continue to do, vast amounts of damage. Using nuclear would save a lot of lives. You can't just weigh the risk of some course of action against the absence of that risk; you have to weigh it against the risks of the alternatives or the risk of not solving the problem at all. No one is using this tech just for fun.

I think some of this is a psychological effect: awful things that are (or seem like) the status quo get priced into our sense of risk, while exotic-seeming tech with very-differently-shaped risks seem irresponsible. We're also bad at weighing widespread, generalized damage against the low risk of disasters, even if some simple thought experiments make it clear which is better.