This is John Batchel, a conversation with my colleague Henry Sikolsky of the Non-Proliferation Policy Education Center

about the unfinished heavy water reactor at Arak in Iran said to right now be part of a target package or something like it by the Israelis.

What is a heavy water reactor? And what is it for? Bombs. Here's Henry to explain.

More of this later. A heavy water reactor was, there was an attempt under the nuclear deal that

Obama negotiated to modify it, but it always is something that can be changed back to what it's

ideally suited to do, and that is to operate while you fuel it. Other reactors, you have to

shut them down to fuel them. Well, why does that matter? If you can control when the fuel

comes in and goes out in real time, you can make plutonium that is tailored to be rich in what

they call the odd isotope, particularly P.U.239,

which doesn't emit neutrons

and allows you to make bombs

with a lot less plutonium

and or more powerful bombs

for any given amount.

Well, that's a weapons

type production machine.

It's the kind we used,

the French used, the Russians used,

the Israelis are using, I can keep going.

It's a favorite for would-be bomb makers.

It makes plutonium?

Doesn't just make plutonium. It can make very high-grade, most desirable weapons usable.

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