Viewing a single comment thread. View all comments

mfb- t1_jbstgii wrote

If you have the same number of atoms and you don't consider any possible subsequent decays, yes.

If you store a sample of initially pure Sr-90 then over a week or so its decay product Y-90 will accumulate until you get one Y-90 decay per Sr-90 decay.

13

not_natty OP t1_jbxy8gs wrote

Is this Y-90 accumulation where you get one Y-90 decay per Sr-90 decay similar to saturation in pharmacokinetics where at 5 half-lives the levels are 'stable'?

Assuming Sr-90 and Y-90 are pure beta emitters, does this mean that if I start with pure Sr-90 at x Bqs, given some time I'll actually end up with more radioactivity in the system, as in the combined Bqs of Sr-90 and Y-90 will be greater than the initial radioactivity of pure Sr-90?

1

mfb- t1_jby09vc wrote

Could be similar to pharmacokinetics but I'm not familiar with the use of saturation there. You get this effect whenever you have an (almost) constant production and a decay that's proportional to the concentration. If we look at something like a month then Y-90 production is almost constant because Sr-90 decays slowly over decades. Y-90 decays are proportional to the amount of Y-90, so you start with almost nothing and approach an equilibrium within a few times the half life (~1 week).

If you start with a pure Sr-90 sample then its overall activity will double in that time frame, yes.

3