IIRC, there are around 10^24 molecules of water per milliliter. So, 10^9 decays per second ( a “becquerel”) sounds like a lot… and it would be if it continued ad nauseam.

What we’ve not been told are repeated (time series) measurements from these places (inside the turbine buildings), to see exactly what has been changing.

They have been publishing hourly the radiation dose outside the building, at various points on the grounds of the power station.