CANDU: The Truly Modular Reactor w/ Navid Badie

Quirky, not so much.

But every reactor has its special features.

So let's look at this diagram you have put up.

this is a pressurized water reactor.

So it relies on water that is pressurized so that it can not boil up to high temperatures, up to relatively high temperatures.

So in that sense, it is similar to the pressurized light water reactors that are used in many countries around the world.

The distinction is the use of heavy water as both the reactor coolant and the moderator.

And I'm not going to describe the function of the moderator or the coolant, but the key driver of the of the configuration that you see was the decision to use natural uranium.

And this was, as you have covered in your discussions with other guests, it was a decision, a political decision made by the Government of Canada that they were going to use natural uranium.

And of course, natural uranium has a very low isotopic content of uranium-235, which is fissile.

And each uranium, when it breaks, it produces two or three neutrons.

And you're counting on one of those neutrons to cause another fissile.

to hit another uranium-235 and cause fission.

And in order to do that, you must have enough U-35 and you must not waste any neutrons.

And the other thing that you have to do is you have to slow down the neutrons because they are emitted with high kinetic energies from the fission reaction.

And that is not the best energy to cause fission in other uranium-235 nuclei.

So you want to slow the neutrons down.

and you do not want them to be absorbed in this process of flying around and hitting other atoms to be able to slow down.

And we use heavy water.

Heavy water has two features.

It is a very poor absorber of neutrons.

So the chances of losing neutrons by getting absorbed by the water is relatively low compared to light water.

And it's also a good moderator.

It's not as good a moderator as Lightwater.

In other words, every time a neutron hits a molecule of heavy water, or in fact, it hits the deuterium nuclei in heavy water, it loses less energy than it would lose in a collision with a hydrogen nucleus, which is just a proton.