I'm a professional nuclear engineer (Ph.D. & PE) with 20 years of experience in advanced reactors and fuel cycle. I promise you it's not 300-500 yrs unless you do full recycle with minor actinide partitioning and transmutation.

The publication above shows the graph vs. time in terms of radiotoxicity, which is widely considered to be the key metric.

What'd you use for the calculations? Generally you need to use something like ORIGEN to get it right.

Perhaps I was a bit unclear. The waste will _definitely_ be dangerously radioactive for tens of thousands of years. No questions here.

But in aggregate, it will be less radioactive than the uranium (and its natural daughter products in secular equilibrium) that was expended to produce the waste.

We're aligned on that metric. I'm using the 'less radioactive than the ore from which it was mined' as the metric here as well. It's between 10,000 and 100,000 years.

Though couldn't you get under 'less radioactive than the ore from which it was mined' by just mixing your waste with a big enough quantity of eg ocean water?

No, because this metric is normalized as radiotoxicity per tonne of heavy metal. You could dilute it with lots of tonnes of natural or depleted uranium, I suppose, to game it.

Interesting, thanks!

I guess that specific metric would make heavy water infinitely radioactive?