These are remarkably uninformative data. One Becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. One banana, containing about half a gram of potassium, has enough radioactive potassium to expose the eater to 15 Bq. So it's a pretty tiny radiation rate. Actually, the banana's hardly at fault. The amount of potassium necessary for a healthy 70 kg. adult is enough to expose the person internally to 5400 Bq of radioactive decays, constantly through the person's adult lifetime.
One mole of oxygen gas, O2, weighs 32 g.
One mole of O2 contains 6.022 times 1023 atoms. That's Avogadro's number.
One mole of 239neptunium has a mass of 239 g. and the same number of atoms.
The half-life of 239neptunium is 2.34 days, which is much shorter than the 24 thousand years for its decay product 239plutonium, and is therefore millions of times more radioactive.
So, anyway, 239 grams of 239neptunium or 239plutonium will contain near enough 6.02 x 1023 atoms.
Neptunium-239 has a half-life of 2.34 days. There are 8640 seconds in a day so that's just over 202 thousand seconds. To find out the mass of 239Np released, we multiply the Bq rate by 202,000, and by 239, and divide by Avogadro's number, 6.022x1023, to find the mass of half the neptunium, in grams. So it's 2.39x102 times 2.02x105 times 7.6x1012 /6.022x1023.
First simplify the powers of 10.
We get (2.39 x 2.02 x 7.6)x10-4/6.022 It comes to 0.0609/10000 grams, 6.09 micrograms, where one microgram is a millionth of the mass of one cc of water. But that's the amount of 239Np that will become 239Pu in 2.4 days. There'll still be half of the neptunium left. Actually, That calculation doesn't take into account that the radioactivity is decreasing exponentially during the 2.4 days. There might be as much as 15 micrograms of 239Np on the first day. But it's still a wild exaggeration of the danger to write about billions of becquerels, when it's a few micrograms. On the other hand, enough plutonium to emit 120 billion Bq might be in the range of a gram. But that's still nothing compared with the ash, toxic acid gases, and global warming CO2 from the coal burning power plants that will be fired up to substitute for the loss of the functioning nukes.