Nuclear Fuel Cycle

For a quick estimate of the total fission product activity:

$\boxed{\text{Total FP activity} \approx 10^{11} \text{ Bq per watt of thermal power}}$

So a 100 MW thermal reactor would contain approximately $10^{11} \times 10^{8} = 10^{19}$ Bq of total fission product activity at equilibrium.

On shutdown, this activity decays by approximately a factor of 10 in the first 24 hours.