Name: 27.核材料----物質中的輻射損害和影響 (27. Nuclear Materials — Radiation Damage and Effects in Matter)
Uploaded: 2021-01-14T10:26:54.000Z
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PROFESSOR: So I got much more than one request

and I think it's just about the right time.

That you guys know enough about radiation

to actually make sense of nuclear materials and radiation

and show you why I think it's interesting.

It starts off with the single-atom atomic defects

that make up the basic building blocks of damage

and ends up with things that break in nuclear reactors

you've got to know everything from the single atoms

where things evolve over years or even decades.

So who here has had any courses in material science?

That's good because I'm assuming that there is a--

I know there's a couple material scientists in the class,

and I'll apologize ahead of time if it's a bit of a review.

But we'll be going mostly through what are materials

and what are the defects that change their material

So then tomorrow, we can see how radiation causes those defects

and actually changes material properties.

So there's a whole laundry list of different ways

everything from simple overload, which means you

stress something too much and it just breaks,

we have to worry about because they're only activated

And in this case, this isn't quite ionization by radiation,

but it's actual radiation slamming into nuclei

And we've got one figure that we had recently

in a paper that sums up the entire multi-scale picture

of radiation damage, from the femtosecond to, let's say,

Maybe gigasecond would be the right word for that.

And all the way down from the angstrom to the meter scale.

And I want to walk you through sort of a lens scale

by lens scale depiction of radiation damage.

It all starts with knocking atoms out of place.

when we talked about nuclear stopping power,

and this is where it actually comes into play.

Sometimes an incoming neutron or photon or ion

can displace an atom from its original site,

and we call that a physical-- it's a displacement.

And then that atom comes off with quite a bit

of kinetic energy and can knock into a whole bunch

Now this loss of the solid crystalline structure,

you can't really tell what the original structure looked like,

It actually comprises a very small, localized zone

at thermal energies, like the thermal neutrons

be moving about at, let's say, a few hundred eV.

So actually, it's been theorized that there's

a little pocket of atoms around three to five nanometers wide

that reaches, like, 10,000 Kelvin for a very, very

knock into the ones around them, and this

is how the process of heat transfer occurs.

called the quench, where most of those atoms

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27.核材料----物質中的輻射損害和影響 (27. Nuclear Materials — Radiation Damage and Effects in Matter)

sort

bunch

tough

extremely