[yk]

These are not death as in murder, these are a statistical measure called excess death and it is usually very model dependent. I looked a bit into the models for nuclear accidents. There the problem is, that there is just no good data in the relevant range of radiation. We have data from very low doses due to background radiation and for high doses due to accidents, we don't have good data for large scale releases. Either you can do what is suggested for higher acute doses, then you end up with 40 000 dead due to Chernobyl, or you can fit a second order model, then you will end up with something in the order of 10. (Or you do what Greenpeace did and you look at correlations between irradiation and cancer rates in former Soviet oblasts, where you then have some influence of Soviet industry, etc...) And that is if you want to look at catastrophic risk at all. (After all an RMBK had several design flaws, that modern reactors don't have.)

The number basically tells you that according to a specific model, that is hopefully a good approximation of our understanding of the risks, a certain percentage of the death rate should be due to that factor. However I think these numbers carry not much more information than 32 other bits of the same sentence and to really use them you have to look at the specific model and you need to develop an opinion if the model reflects the relevant arguments well.