If it's American billions, that would be 1.2 trillion so there's a discrepancy with a concomitant headline listing 120 billion becquerels of plutonium, 7.6 trillion becquerels of neptunium.

Well, for one thing, there probably wasn't much neptunium being released

Responsible persons measure quantities of neptunium and plutonium in grams, not radiation rates.

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, O_{2}, weighs 32 g.
One mole of O_{2} contains 6.022 times 10^{23} atoms. That's Avogadro's number.

One mole of ^{239}neptunium has a mass of 239 g. and the same number of atoms.

The half-life of ^{239}neptunium is 2.34 days, which is much shorter than the 24 thousand years for its decay product ^{239}plutonium, and is therefore millions of times more radioactive.

So, anyway, 239 grams of ^{239}neptunium or ^{239}plutonium will contain near enough 6.02 x 10^{23} 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 ^{239}Np released, we multiply the Bq rate by 202,000, and by 239, and divide by Avogadro's number, 6.022x10^{23}, to find the mass of half the neptunium, in grams.
So it's 2.39x10^{2} times 2.02x10^{5} times 7.6x10^{12} /6.022x10^{23}.

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 ^{239}Np that will become ^{239}Pu 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 ^{239}Np 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.