I think the gotcha here is they are saying : safer === less deaths.
If you purely want the safety of power sources at a minimum you have to look at deaths, unnecessary human suffering and also potential for long term deaths & suffering. I think another thing that I find missing from the article is acknowledgement of the long term challenge of safely storing nuclear waste and the potential loss of life/suffering it could cause in the future.
https://en.m.wikipedia.org/wiki/Kyshtym_disaster
Seeing how debatable the issue of deaths caused by actual nuclear disasters is (varying from 400 to 60000 for Chernobyl), I can't imagine how little agreement two parties could have on the comparative amounts of human suffering caused by different energy sources. You would have to encompass land use changes, air quality, long term statistical health outcomes, respiratory illness, wildlife impacts, the list goes on ad infinitum..
I don't think that Mayak is relevant, as it is a secretive, poorly regulated nuclear weapons production facility. Similarly, the impacts of Therac-25 [1] patients or the Goiania Incident[2] don't get counted against nuclear energy.
