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All right. So, like I told you guys,

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Friday marked the end of the hardest

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part of the course and Monday marked the

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end of the hardest P set. So, because

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the rest of your classes are going full

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throttle, this one's going to wind down

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a little bit.

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So, today I'd say sit back, relax, and

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enjoy a nuclear catastrophe.

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Because we are going to explain what

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happened at Chernobyl. Now that you've

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got the physics and uh intuitive

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background to understand the actual

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sequence of events.

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To kick it off, I want to show you guys

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some actual footage

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of the Chernobyl reactor as it was

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burning. So, this is the part that most

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folks know about.

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This is footage taken from a helicopter

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from folks that were either surveying or

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dropping materials onto the reactor.

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That was probably a bad idea.

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Over where the smoke is. We'll get into

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what the smoke was.

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So, that

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red stuff right there, that's actually

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glowing graphite amongst other materials

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from the graphite fire that resulted

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from the R the RBMK reactor burning

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after the Chernobyl accident caused by

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both flaws in the physical design of the

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RBMK reactor and absolute operator

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stupidity and neglect of any sort of

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safety systems or safety culture. We're

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lucky to live here in the US where our

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worst accident at Three Mile Island was

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not actually really that much of an

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accident. There was a partial meltdown.

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There was not that much of a release of

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radionuclides into the atmosphere

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because we do things like build

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containments on our reactors. If you

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think of what a typical reactor looks

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like, like if you consider the MIT

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reactor as a scaled-down version of a

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normal reactor, or I

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let's say a commercial power reactor,

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you've got the core here. You've got a

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bunch of shielding around it.

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And you've got a dome

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that's rather thick

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that comprises the containment.

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That would be the core.

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This would be some shielding.

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So, this is what you find in US and most

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other reactors. For the RBMK reactors,

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there was no containment.

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Because it was thought that nothing

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could happen. And boy, were they wrong.

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So, I want to walk you guys through a

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chronology of what actually happened at

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the Chernobyl reactor, which you guys

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can read on the NEA or Nuclear Energy

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Agency website, the same place that you

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find Janice. And we're going to refer to

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a lot of the Janice cross sections to

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explain why these sorts of events

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happened.

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So, the whole point of what happened at

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Chernobyl was it was desired to see if

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you could use the spinning-down turbine

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after you shut down the reactor to power

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the emergency systems at the reactor.

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Uh this would be following something

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what's called a a loss of offsite power.

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If the offsite power or the grid was

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disconnected from the reactor, the

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reactor automatically shuts down. But

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the turbine, like I showed you a couple

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weeks ago, is this enormous spinning

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hulk of metal and machinery that coasts

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down over a long period of let's say

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hours. And as it's spinning, the

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generator coils are still spinning and

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still producing electricity, or they

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could be.

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So, it was desired to find out can we

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use the spinning-down turbine to power

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the emergency equipment if we lose

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offsite power?

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So, they had to simulate this event.

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So, what they actually decided to do is

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coast down the reactor to a moderate

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power level, a very low power, and see

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what comes out of the turbine itself, or

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out of the generator, rather.

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Um now, there were a lot of flaws in the

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RBMK design. And I'd like to bring it up

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here so we can talk about what it looks

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like and what was wrong with it.

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So, the RBMKs, unlike any of the

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United States light water reactors that

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you may have seen before, many of the

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components are the same. There's still

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uh light water reactor coolant loop

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where a water flows around fuel rods,

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goes into a steam separator, better

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known as a big heat exchanger, and the

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steam drives a turbine

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which produces energy, and then this

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coolant pump keeps it going, and then

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the water circulates. Uh what makes it

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different, though, is that each of these

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fuel rods was inside its own pressure

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tube. So, the coolant was pressurized,

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and out here,

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this stuff right here was the moderator,

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composed of graphite.

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Unlike light water reactors in the US,

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the coolant was not the only moderator

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in the reactor.

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Graphite also existed, which meant that

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if the water went away, which would

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normally shut down a light water reactor

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from lack of moderation, graphite was

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still there to slow the neutrons down

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into the high fission cross section

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area.

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And I'd like to pull up Janice

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and show you what I mean with the

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uranium cross section.

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So, let's go again to uranium 235

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and pull up its fission cross section.

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Z fission.

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Can make it a little thicker, too.

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So,

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again, the goal of the moderator is to

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take neutrons from high energies, like 1

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to 10 MeV, where the fission cross

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section is relatively low, and slow them

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down into this region where fission is,

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let's say, a thousand times more likely.

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And in a light water reactor in the US,

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if the coolant goes away, so does the

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moderation, and there's nothing left to

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slow those neutrons down to make fission

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more likely. In the RBMK,

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that's not the case. The graphite's

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still there.

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The graphite is cooled by a

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helium-nitrogen mixture

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because the neutron interactions in the

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graphite, that's slowing down,

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we've always talked about what happens

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from the point of view of the neutron.

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But what about the point of view of the

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other material?

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Any energy lost by the neutrons is

00:06:57.240 --> 00:07:02.439
gained by the moderating material. So,

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the graphite gets really hot. And you

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have to flow some non-oxygen-containing

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gas mixture, like helium and nitrogen,

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which is pretty inert, to keep that

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graphite cool.

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And then in between the graphite

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moderator were control rods, about 200

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of them or so, 30 of which were required

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to be down in the reactor at any given

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time in order to control power. And that

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was a design rule that was broken during

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the actual experiment. And then on top

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of here, on top of this biological

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shield, you could walk on top of it. So,

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those the tops of those pressure tubes,

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despite being about 350 kilo chunks of

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concrete,

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you could walk on top of them. It's

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pretty cool.

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Kind of scary, too.

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So, what happened in chronological order

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was around midnight the decision was

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made to undergo this test and start

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spinning down the turbine.

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Uh but the grid operator came back and

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said, "No, you can't just cut the

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reactor power to nothing. You have to

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maintain it at a rather high power for a

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while." About 500 megawatts electric, or

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half the rated power of the reactor. And

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what that had the effect of doing is

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continuing to create fission products,

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including xenon 135.

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We haven't mentioned this one yet.

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You'll talk about it quite a lot

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in 2205

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in neutron physics.

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Black shirt really shows chalk well.

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Okay.

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What xenon 135 does is it just sits

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there. It's a noble gas. It has a

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half-life of a few days, so it decays on

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the slow side for,

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you know, fission as fission products

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go, but it also absorbs lots and lots

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and lots of neutrons.

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Let's see if I can find which one is the

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xenon one. There we go.

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So, here I've plotted the total cross

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section for xenon 135 and the absorption

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cross section.

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And notice how for low energies, pretty

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much the entire cross section of xenon

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is made up of absorption. Did you guys

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in your homework see anything that

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reached about 10 million barns?

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No.

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Xenon 135 is one of the best neutron

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absorbers there is, and reactors produce

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it constantly. So, as they're operating,

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you'll build up xenon 135 that you have

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to account for in your sigma absorption

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cross section.

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Cuz like you guys saw on the homework,

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if you want to write what's the sigma

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absorption cross section of the reactor,

00:09:24.279 --> 00:09:28.919
it's the sum

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of every single isotope in the reactor

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of its number density

00:09:31.039 --> 00:09:34.639
times

00:09:32.559 --> 00:09:36.559
its absorption cross section.

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And so, that would include everything

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for

00:09:37.679 --> 00:09:42.479
water

00:09:39.240 --> 00:09:44.039
and let's say the uranium and the xenon

00:09:42.480 --> 00:09:46.080
that you're building up.

00:09:44.039 --> 00:09:48.199
When the reactor starts up, the number

00:09:46.080 --> 00:09:50.680
density of xenon is zero cuz you don't

00:09:48.200 --> 00:09:52.440
have any anything to have produced it.

00:09:50.679 --> 00:09:55.519
When you start operating, you'll reach

00:09:52.440 --> 00:09:57.280
the xenon equilibrium level where it

00:09:55.519 --> 00:09:59.519
will build to a certain level that will

00:09:57.279 --> 00:10:00.839
counteract the reactivity of the

00:09:59.519 --> 00:10:03.159
reactor.

00:10:00.840 --> 00:10:06.360
And in your K effective expression

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where it's sources

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over

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absorption plus leakage

00:10:11.080 --> 00:10:15.400
this has the effect of rise at raising

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sigma absorption and lowering K

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effective.

00:10:17.360 --> 00:10:20.960
The trick is it doesn't last for very

00:10:18.720 --> 00:10:23.680
long. It both decays with a half-life of

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about 5 days and when you try and raise

00:10:23.679 --> 00:10:27.639
the reactor power you will also start to

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burn it out. So if you're operating at a

00:10:27.639 --> 00:10:32.679
fairly low power level, you'll both be

00:10:29.759 --> 00:10:33.840
decaying and burning xenon without

00:10:32.679 --> 00:10:35.879
really knowing what's going on and

00:10:33.840 --> 00:10:38.120
that's exactly what happened here.

00:10:35.879 --> 00:10:40.439
So an hour or so later

00:10:38.120 --> 00:10:42.039
let me pull up the chronology again.

00:10:40.440 --> 00:10:43.760
A little more than an hour later, so the

00:10:42.039 --> 00:10:45.879
reactor power stabilized at something

00:10:43.759 --> 00:10:47.639
like 30 MW.

00:10:45.879 --> 00:10:49.639
And they were like, "What is going on?

00:10:47.639 --> 00:10:51.439
Why is the reactor power so low? We need

00:10:49.639 --> 00:10:54.000
to increase the reactor power." So what

00:10:51.440 --> 00:10:55.800
did they do? Couple things. One was

00:10:54.000 --> 00:10:57.399
remove all but six or seven of the

00:10:55.799 --> 00:11:01.279
control rods.

00:10:57.399 --> 00:11:02.959
Going way outside the spec of the design

00:11:01.279 --> 00:11:05.279
uh because 30 were needed to actually

00:11:02.960 --> 00:11:07.400
maintain the reactor at a stable power.

00:11:05.279 --> 00:11:10.439
All the while the xenon that had been

00:11:07.399 --> 00:11:11.959
building up is still there keeping the

00:11:10.440 --> 00:11:13.680
reactor from going critical. It's what

00:11:11.960 --> 00:11:16.120
was the main reason that the reactor

00:11:13.679 --> 00:11:17.519
didn't even have very much power.

00:11:16.120 --> 00:11:18.679
But it was also burning out at the same

00:11:17.519 --> 00:11:20.960
time.

00:11:18.679 --> 00:11:23.399
So all the while

00:11:20.960 --> 00:11:25.800
let's say if we were to show a graph of

00:11:23.399 --> 00:11:29.000
two things, time

00:11:25.799 --> 00:11:31.838
xenon inventory and

00:11:29.000 --> 00:11:34.759
as a solid line and let's say control

00:11:31.839 --> 00:11:34.760
rod worth

00:11:35.679 --> 00:11:39.799
as a dotted line.

00:11:37.320 --> 00:11:42.000
The xenon inventory at full power would

00:11:39.799 --> 00:11:45.120
have been at some level and then it

00:11:42.000 --> 00:11:47.039
would start to decay and burn out. Well,

00:11:45.120 --> 00:11:49.600
at the same time the control rod worth

00:11:47.039 --> 00:11:51.319
as you remove control rods from the

00:11:49.600 --> 00:11:52.839
reactor

00:11:51.320 --> 00:11:55.680
every time you remove one you lose some

00:11:52.839 --> 00:11:56.839
control rod worth would continue to

00:11:55.679 --> 00:11:58.879
diminish.

00:11:56.839 --> 00:12:01.560
Leading to the point where that stuff

00:11:58.879 --> 00:12:01.559
was going to happen.

00:12:02.159 --> 00:12:06.959
Let me make sure I didn't lose my place.

00:12:04.639 --> 00:12:08.360
So at any rate as they started pulling

00:12:06.960 --> 00:12:10.080
the control rods out a couple of

00:12:08.360 --> 00:12:11.639
interesting quirks happened in terms of

00:12:10.080 --> 00:12:12.920
feedback. So let's look back at this

00:12:11.639 --> 00:12:14.759
design.

00:12:12.919 --> 00:12:16.279
Like any reactor

00:12:14.759 --> 00:12:18.919
this reactor had what's called a

00:12:16.279 --> 00:12:20.679
negative fuel temperature coefficient.

00:12:18.919 --> 00:12:22.479
What that means is that

00:12:20.679 --> 00:12:24.279
when you heat up the fuel

00:12:22.480 --> 00:12:26.680
two things happen. One, the

00:12:24.279 --> 00:12:28.879
cross-section for anything absorption or

00:12:26.679 --> 00:12:31.519
fission would go up but the number

00:12:28.879 --> 00:12:34.320
density would also go down. As the atoms

00:12:31.519 --> 00:12:36.559
physically spaced out in the fuel, their

00:12:34.320 --> 00:12:38.120
number density would go down lowering

00:12:36.559 --> 00:12:40.159
the macroscopic cross-section for

00:12:38.120 --> 00:12:41.159
fission. And that's arguably a good

00:12:40.159 --> 00:12:45.000
thing.

00:12:41.159 --> 00:12:46.559
The problem is at below about 20% power

00:12:45.000 --> 00:12:48.120
the reactor had what's called a positive

00:12:46.559 --> 00:12:50.719
void coefficient

00:12:48.120 --> 00:12:53.320
which meant that if you boil the coolant

00:12:50.720 --> 00:12:54.879
you increase the reactor power.

00:12:53.320 --> 00:12:56.560
Because the other thing that I think I

00:12:54.879 --> 00:13:00.000
mentioned this once

00:12:56.559 --> 00:13:03.119
and you calculated in the homework

00:13:00.000 --> 00:13:06.679
the absorption cross-section of hydrogen

00:13:03.120 --> 00:13:08.919
is not zero. It's small but fairly

00:13:06.679 --> 00:13:11.079
significant. Let's actually take a look

00:13:08.919 --> 00:13:12.719
at it cuz we can always see this in

00:13:11.080 --> 00:13:15.480
Janus.

00:13:12.720 --> 00:13:18.320
Go back down to hydrogen.

00:13:15.480 --> 00:13:18.320
Hydrogen one.

00:13:18.639 --> 00:13:23.240
And we look at the absorption

00:13:20.440 --> 00:13:23.240
cross-section.

00:13:24.399 --> 00:13:29.959
And of course it started us with a

00:13:25.879 --> 00:13:32.039
linear scale. Let's go logarithmic. Ah.

00:13:29.960 --> 00:13:33.560
So at low energies at you know, 10 to

00:13:32.039 --> 00:13:35.879
the minus eight to 10 to the minus seven

00:13:33.559 --> 00:13:37.799
it's around a barn.

00:13:35.879 --> 00:13:39.159
Not super high but absolutely not

00:13:37.799 --> 00:13:40.759
negligible.

00:13:39.159 --> 00:13:43.039
Which meant that part of the normal

00:13:40.759 --> 00:13:46.120
functionality of the RBMK depending on

00:13:43.039 --> 00:13:48.879
depended on the absorption of the water

00:13:46.120 --> 00:13:50.879
to help absorb some of those neutrons.

00:13:48.879 --> 00:13:53.120
With those neutrons gone, I'm sorry,

00:13:50.879 --> 00:13:54.519
with those with that water gone

00:13:53.120 --> 00:13:56.919
there was less absorption but there was

00:13:54.519 --> 00:13:58.919
still a ton of moderation

00:13:56.919 --> 00:14:00.319
in this graphite moderator. So they

00:13:58.919 --> 00:14:01.838
still could get slow but then there'd be

00:14:00.320 --> 00:14:03.960
more of them and that would cause the

00:14:01.839 --> 00:14:06.640
power to increase. And then that caused

00:14:03.960 --> 00:14:08.920
more of the water the coolant to boil

00:14:06.639 --> 00:14:10.480
which would cause less absorption which

00:14:08.919 --> 00:14:12.279
would cause the power to increase. Yeah,

00:14:10.480 --> 00:14:14.560
Charlie? So if they removed the water

00:14:12.279 --> 00:14:14.559
from

00:14:14.839 --> 00:14:18.360
They did not remove the water from the

00:14:16.399 --> 00:14:20.679
reactor. However, as the power started

00:14:18.360 --> 00:14:22.240
to rise some of the water started to

00:14:20.679 --> 00:14:23.838
boil.

00:14:22.240 --> 00:14:25.680
And so you can still have let's say

00:14:23.839 --> 00:14:27.120
steam flowing through

00:14:25.679 --> 00:14:29.039
and still remove some of the heat.

00:14:27.120 --> 00:14:31.720
However, you don't have that denser

00:14:29.039 --> 00:14:32.879
water to act as an absorber.

00:14:31.720 --> 00:14:35.200
And that's what really undid this

00:14:32.879 --> 00:14:38.240
reactor. In addition, they decided to

00:14:35.200 --> 00:14:39.879
disable the ECCS or the emergency core

00:14:38.240 --> 00:14:41.200
cooling system which you're just not

00:14:39.879 --> 00:14:42.360
supposed to do.

00:14:41.200 --> 00:14:43.600
So they shut down a bunch of these

00:14:42.360 --> 00:14:44.839
systems to see if you could power the

00:14:43.600 --> 00:14:46.000
other ones from the spinning down

00:14:44.839 --> 00:14:48.200
turbine.

00:14:46.000 --> 00:14:49.919
And then as they noticed that the

00:14:48.200 --> 00:14:53.079
reactor was getting less and less stable

00:14:49.919 --> 00:14:56.159
they had almost all the rods out. Some

00:14:53.078 --> 00:15:00.359
of these pressure tubes started to bump

00:14:56.159 --> 00:15:02.838
and jump. These 350 kg pressure tube

00:15:00.360 --> 00:15:05.039
caps were just rattling. I mean imagine

00:15:02.839 --> 00:15:08.200
something that weighs you know, 900 lb

00:15:05.039 --> 00:15:09.759
or so rattling around and there's a few

00:15:08.200 --> 00:15:11.839
hundred of them. So there was someone in

00:15:09.759 --> 00:15:14.159
the control room that said, "The caps

00:15:11.839 --> 00:15:16.120
are rattling. What the heck?"

00:15:14.159 --> 00:15:19.519
Uh didn't quite make it down the spiral

00:15:16.120 --> 00:15:21.480
staircase because about 10 seconds later

00:15:19.519 --> 00:15:22.799
everything went wrong.

00:15:21.480 --> 00:15:24.879
And so I want to pull up this actual

00:15:22.799 --> 00:15:27.199
timeline so you can see

00:15:24.879 --> 00:15:29.200
it splits from minutes to seconds

00:15:27.200 --> 00:15:33.120
because the speed at which this stuff

00:15:29.200 --> 00:15:35.759
started to go wrong was pretty striking.

00:15:33.120 --> 00:15:38.560
So for example, the control rods raised

00:15:35.759 --> 00:15:40.439
at 1:19 in the morning.

00:15:38.559 --> 00:15:42.319
2 minutes later

00:15:40.440 --> 00:15:43.920
when the power starts to become unstable

00:15:42.320 --> 00:15:47.000
the caps on the fuel channels which

00:15:43.919 --> 00:15:48.799
again are like 350 kg blocks start

00:15:47.000 --> 00:15:51.240
jumping in their sockets.

00:15:48.799 --> 00:15:53.240
And a lot of that was we go back to the

00:15:51.240 --> 00:15:55.799
RBMK reactor.

00:15:53.240 --> 00:15:57.720
As the coolant started to boil here,

00:15:55.799 --> 00:15:59.838
well that boiling force actually creates

00:15:57.720 --> 00:16:02.000
huge pressure instabilities which would

00:15:59.839 --> 00:16:04.120
cause the pressure tubes to jump up and

00:16:02.000 --> 00:16:06.480
down eventually rupturing almost every

00:16:04.120 --> 00:16:09.879
single one of them with enough force to

00:16:06.480 --> 00:16:10.920
shoot these 350 kilo caps

00:16:09.879 --> 00:16:14.639
and still what did they what did they

00:16:10.919 --> 00:16:16.559
say? I like the language that they used.

00:16:14.639 --> 00:16:17.480
Jumping in their sockets.

00:16:16.559 --> 00:16:19.759
So

00:16:17.480 --> 00:16:21.639
50 seconds later

00:16:19.759 --> 00:16:22.799
pressure fails in the steam drums which

00:16:21.639 --> 00:16:25.799
means there's been some sort of

00:16:22.799 --> 00:16:27.719
containment leak. So all the while

00:16:25.799 --> 00:16:30.519
the coolant was boiling, the absorption

00:16:27.720 --> 00:16:32.720
was going down, the power was going up

00:16:30.519 --> 00:16:34.600
repeat, repeat, repeat and the power

00:16:32.720 --> 00:16:37.759
jumped to about 100 times the rated

00:16:34.600 --> 00:16:39.800
power in something like 4 seconds.

00:16:37.759 --> 00:16:42.838
So it was normally a 1000 MW electric

00:16:39.799 --> 00:16:45.838
reactor which is about 3200 MW thermal.

00:16:42.839 --> 00:16:48.120
It was producing nearly

00:16:45.839 --> 00:16:50.600
yeah, half a terawatt of thermal power

00:16:48.120 --> 00:16:52.039
for a very short amount of time until it

00:16:50.600 --> 00:16:53.560
exploded.

00:16:52.039 --> 00:16:55.360
Now this is interesting. A lot of folks

00:16:53.559 --> 00:16:57.679
called Chernobyl a nuclear explosion.

00:16:55.360 --> 00:17:00.519
That's actually a misnomer. A nuclear

00:16:57.679 --> 00:17:02.279
explosion would be a nuclear weapon.

00:17:00.519 --> 00:17:05.319
Something set off by an enormous chain

00:17:02.279 --> 00:17:07.559
reaction principally heated by fission

00:17:05.319 --> 00:17:10.159
or fusion. That's not actually what

00:17:07.559 --> 00:17:11.838
happened at Chernobyl nor at Fukushima

00:17:10.160 --> 00:17:14.320
nor was that the worry at Three Mile

00:17:11.838 --> 00:17:16.519
Island. Not to say it wasn't a horrible

00:17:14.319 --> 00:17:17.799
thing but it wasn't an actual nuclear

00:17:16.519 --> 00:17:20.119
explosion.

00:17:17.799 --> 00:17:21.639
At first what happened was a pressure

00:17:20.119 --> 00:17:24.438
explosion.

00:17:21.640 --> 00:17:27.800
So there was an enormous release of

00:17:24.439 --> 00:17:30.200
steam as the power built up to 100 times

00:17:27.799 --> 00:17:32.279
normal operating power the steam force

00:17:30.200 --> 00:17:34.120
was so large that it actually blew the

00:17:32.279 --> 00:17:35.720
reactor lid

00:17:34.119 --> 00:17:37.519
up off of the thing.

00:17:35.720 --> 00:17:40.720
And I think I have a picture of that

00:17:37.519 --> 00:17:40.720
somewhere here too.

00:17:42.119 --> 00:17:46.239
Should be further down. Yeah. To give

00:17:44.200 --> 00:17:47.600
you a little sense of scale

00:17:46.240 --> 00:17:50.359
the reactor cover which weighed about

00:17:47.599 --> 00:17:52.359
1000 tons launched into the air

00:17:50.359 --> 00:17:54.279
and landed above the reactor

00:17:52.359 --> 00:17:56.599
sending most of the reactor components

00:17:54.279 --> 00:17:59.039
up to a kilometer up in the air.

00:17:56.599 --> 00:18:01.079
4 seconds later

00:17:59.039 --> 00:18:02.519
that was followed by a hydrogen

00:18:01.079 --> 00:18:05.039
explosion.

00:18:02.519 --> 00:18:07.359
Let me get back down to that chronology.

00:18:05.039 --> 00:18:10.399
So yeah.

00:18:07.359 --> 00:18:11.719
At 1:23 and 40 seconds in the morning.

00:18:10.400 --> 00:18:13.679
Oh yeah, so I should mention why this

00:18:11.720 --> 00:18:15.600
happened. Emergency insertion of all the

00:18:13.679 --> 00:18:17.400
control rods.

00:18:15.599 --> 00:18:19.119
The last part that this diagram doesn't

00:18:17.400 --> 00:18:21.320
mention is these control rods and I'll

00:18:19.119 --> 00:18:23.959
draw this up here were tipped with about

00:18:21.319 --> 00:18:26.359
6 in of graphite.

00:18:23.960 --> 00:18:29.240
So if these were two graphite channels,

00:18:26.359 --> 00:18:31.559
let's say these are carbon

00:18:29.240 --> 00:18:34.599
and this is your control rod the goal

00:18:31.559 --> 00:18:37.119
was to get this control rod

00:18:34.599 --> 00:18:39.158
all the way into the reactor.

00:18:37.119 --> 00:18:41.399
One part they didn't mention

00:18:39.159 --> 00:18:43.440
was they were tipped with about 6 in of

00:18:41.400 --> 00:18:46.040
graphite which only functions as

00:18:43.440 --> 00:18:48.559
additional moderator. Graphite is one of

00:18:46.039 --> 00:18:50.440
the lowest absorbing materials in the

00:18:48.559 --> 00:18:51.759
periodic table, second I think only to

00:18:50.440 --> 00:18:53.799
oxygen.

00:18:51.759 --> 00:18:56.799
And if we pull up graphite's

00:18:53.799 --> 00:18:56.799
cross-sections

00:18:57.079 --> 00:18:59.799
I've plotted here the total

00:18:58.440 --> 00:19:01.440
cross-section

00:18:59.799 --> 00:19:05.480
the elastic scattering cross-section and

00:19:01.440 --> 00:19:08.000
down here in the point 001 barn level is

00:19:05.480 --> 00:19:09.640
the absorption cross-section. About 1000

00:19:08.000 --> 00:19:11.240
times lower than water. So you're

00:19:09.640 --> 00:19:13.440
shoving more material in the reactor

00:19:11.240 --> 00:19:14.799
that slows down neutrons even more

00:19:13.440 --> 00:19:17.240
bringing them into the high fission

00:19:14.799 --> 00:19:19.879
region without absorbing anything and

00:19:17.240 --> 00:19:22.319
they jammed about halfway down, about 2

00:19:19.880 --> 00:19:24.760
and 1/2 ft down leaving the extra

00:19:22.319 --> 00:19:26.480
graphite right in the center of the core

00:19:24.759 --> 00:19:28.720
where it could do the most damage. And

00:19:26.480 --> 00:19:30.759
it didn't take that much time. Yeah? Um

00:19:28.720 --> 00:19:32.480
so my understanding is that also one of

00:19:30.759 --> 00:19:34.158
the designs was that the control rods

00:19:32.480 --> 00:19:36.519
didn't like immediately drop down but

00:19:34.159 --> 00:19:38.560
they were slowly lowered. Yep. Um so

00:19:36.519 --> 00:19:39.720
They took they took 7 to 10 seconds.

00:19:38.559 --> 00:19:41.200
Okay, if they had a system where they

00:19:39.720 --> 00:19:43.400
did drop them would that have possibly

00:19:41.200 --> 00:19:45.159
actually shut the system down properly?

00:19:43.400 --> 00:19:47.040
I'm not sure. I don't know whether

00:19:45.159 --> 00:19:49.280
lowering control rods into something

00:19:47.039 --> 00:19:51.119
that was undergoing steam explosions

00:19:49.279 --> 00:19:53.119
would have actually helped. I mean to me

00:19:51.119 --> 00:19:54.159
by this point it was all over.

00:19:53.119 --> 00:19:56.079
Um

00:19:54.160 --> 00:19:58.120
whether or not, you know, so the extra

00:19:56.079 --> 00:20:00.079
the extra abs- what is it? The extra

00:19:58.119 --> 00:20:01.679
moderator that was dumped in was the

00:20:00.079 --> 00:20:04.199
last kick in the pants this thing needed

00:20:01.680 --> 00:20:06.320
to go absolutely insane.

00:20:04.200 --> 00:20:08.720
And if we go back to the timeline on the

00:20:06.319 --> 00:20:12.639
second level, control rods inserted at

00:20:08.720 --> 00:20:16.120
1:23 and 40 seconds, explosion 4 seconds

00:20:12.640 --> 00:20:18.880
later. Ah, to 120 times full power.

00:20:16.119 --> 00:20:22.159
Getting towards a terawatt, so. 1 second

00:20:18.880 --> 00:20:24.560
later, the 1,000 ton lid launches off

00:20:22.160 --> 00:20:26.720
from the first explosion.

00:20:24.559 --> 00:20:29.519
Very shortly after that, second

00:20:26.720 --> 00:20:32.120
explosion. And that happened because of

00:20:29.519 --> 00:20:35.759
this reaction.

00:20:32.119 --> 00:20:38.199
Well, any- just about anything

00:20:35.759 --> 00:20:41.359
corroding with water will make pretty

00:20:38.200 --> 00:20:43.600
much anything oxide

00:20:41.359 --> 00:20:45.240
plus hydrogen. The same chemical

00:20:43.599 --> 00:20:47.559
explosion that was the undoing of

00:20:45.240 --> 00:20:49.039
Fukushima and was the worry at Three

00:20:47.559 --> 00:20:51.319
Mile Island that there was a hydrogen

00:20:49.039 --> 00:20:53.359
bubble building because of corrosion

00:20:51.319 --> 00:20:55.159
reactions with whatever happened to be

00:20:53.359 --> 00:20:57.079
in the core. This happens with zirconium

00:20:55.160 --> 00:20:58.680
pretty vigorously, but it happens with

00:20:57.079 --> 00:21:01.439
other materials, too.

00:20:58.680 --> 00:21:02.920
If you oxidize something with water, you

00:21:01.440 --> 00:21:05.400
leave behind the hydrogen, and the

00:21:02.920 --> 00:21:08.360
hydrogen in a very wide range of

00:21:05.400 --> 00:21:09.600
concentrations in the air is explosive.

00:21:08.359 --> 00:21:12.679
We're actually not allowed to use

00:21:09.599 --> 00:21:13.759
hydrogen at above 4% in any of the labs

00:21:12.680 --> 00:21:16.080
here because that reaches the

00:21:13.759 --> 00:21:18.119
flammability or explosive limit.

00:21:16.079 --> 00:21:20.599
So, we were doing some um for my PhD, we

00:21:18.119 --> 00:21:22.439
were doing these experiments corroding

00:21:20.599 --> 00:21:24.639
materials in liquid lead, and we wanted

00:21:22.440 --> 00:21:26.640
to dump in pure hydrogen to see what

00:21:24.640 --> 00:21:28.840
happens when there's no oxygen. We were

00:21:26.640 --> 00:21:30.160
told absolutely not. We had to drill a

00:21:28.839 --> 00:21:32.959
hole in the side of the wall so that the

00:21:30.160 --> 00:21:34.560
hydrogen would vent outside. And do some

00:21:32.960 --> 00:21:36.319
calculations to show if the entire

00:21:34.559 --> 00:21:38.480
bottle of hydrogen emptied into the lab

00:21:36.319 --> 00:21:40.599
at once, which it could do if the cap of

00:21:38.480 --> 00:21:42.920
the bottle breaks off, it would not

00:21:40.599 --> 00:21:44.240
reach 4% concentration.

00:21:42.920 --> 00:21:46.240
So, hydrogen explosions are pretty

00:21:44.240 --> 00:21:48.920
powerful things. Have you guys ever seen

00:21:46.240 --> 00:21:50.480
people making water from scratch?

00:21:48.920 --> 00:21:51.240
Mix hydrogen and oxygen in the bottle

00:21:50.480 --> 00:21:52.920
and

00:21:51.240 --> 00:21:54.160
light a match?

00:21:52.920 --> 00:21:56.039
We've got a video of it circulating

00:21:54.160 --> 00:21:58.080
somewhere around here because for RTC,

00:21:56.039 --> 00:22:00.159
for the reactor technology course, I do

00:21:58.079 --> 00:22:01.799
this in front of a bunch of CEOs. Watch

00:22:00.160 --> 00:22:03.519
them jump out of their chairs

00:22:01.799 --> 00:22:06.839
to teach basic chemical reactions, but

00:22:03.519 --> 00:22:08.839
it's pretty loud. Enough uh about enough

00:22:06.839 --> 00:22:10.480
hydrogen and oxygen

00:22:08.839 --> 00:22:12.159
to just fill this cup or fill a half

00:22:10.480 --> 00:22:13.920
liter water bottle makes a bang that

00:22:12.160 --> 00:22:16.600
gets your ears ringing. Not quite

00:22:13.920 --> 00:22:17.840
bleeding, but close enough.

00:22:16.599 --> 00:22:19.399
So, that's what happened here, except on

00:22:17.839 --> 00:22:22.199
a much more massive scale. So, there was

00:22:19.400 --> 00:22:24.840
a steam explosion followed seconds later

00:22:22.200 --> 00:22:26.759
by a hydrogen explosion from hydrogen

00:22:24.839 --> 00:22:28.199
liberated from the corrosion reaction of

00:22:26.759 --> 00:22:29.720
everything with the water that was

00:22:28.200 --> 00:22:33.039
already there.

00:22:29.720 --> 00:22:33.039
And that's when

00:22:33.519 --> 00:22:36.359
this happened.

00:22:54.679 --> 00:22:59.480
So, that smoke right there

00:22:57.400 --> 00:23:02.679
is from the graphite fire.

00:22:59.480 --> 00:23:02.679
Not normal smoke.

00:23:20.799 --> 00:23:23.879
Spoke too soon.

00:23:53.119 --> 00:23:56.599
This actually provides a perfect conduit

00:23:55.119 --> 00:23:58.599
to transition from the second to the

00:23:56.599 --> 00:23:59.799
third parts of this course. A lot of you

00:23:58.599 --> 00:24:01.000
have been waiting to find out what are

00:23:59.799 --> 00:24:02.720
the units of dose and what are the

00:24:01.000 --> 00:24:04.519
biological and chemical effects of

00:24:02.720 --> 00:24:06.480
radiation. Well, this is where you get

00:24:04.519 --> 00:24:09.279
them. From neutron physics, you can

00:24:06.480 --> 00:24:10.360
understand why Chernobyl went wrong.

00:24:09.279 --> 00:24:12.119
With honestly, you've just been doing

00:24:10.359 --> 00:24:13.759
this for three or four weeks, but with

00:24:12.119 --> 00:24:15.839
your knowledge of cross sections,

00:24:13.759 --> 00:24:17.599
reactor feedback, and criticality, you

00:24:15.839 --> 00:24:19.839
can start to understand why Chernobyl

00:24:17.599 --> 00:24:20.959
was flawed in its design. And what we're

00:24:19.839 --> 00:24:23.159
going to teach you in the rest of the

00:24:20.960 --> 00:24:25.000
course is what happens next. What

00:24:23.160 --> 00:24:27.440
happens when radionuclides are absorbed

00:24:25.000 --> 00:24:30.079
by animals and the human body? And what

00:24:27.440 --> 00:24:31.640
was the main fallout, let's say, in the

00:24:30.079 --> 00:24:34.159
in the uh

00:24:31.640 --> 00:24:37.320
colloquial sense and the actual sense

00:24:34.160 --> 00:24:38.600
from the Chernobyl reactor.

00:24:37.319 --> 00:24:40.919
Let's look a bit what they did next,

00:24:38.599 --> 00:24:40.919
though.

00:25:45.960 --> 00:25:50.039
That's not quite true. We'll see why.

00:25:58.960 --> 00:26:02.279
That actually did happen.

00:26:08.480 --> 00:26:11.920
I think that pretty much summarizes the

00:26:10.039 --> 00:26:13.920
state of things now.

00:26:11.920 --> 00:26:16.440
They uh they built a sarcophagus around

00:26:13.920 --> 00:26:18.120
this reactor, a gigantic tomb, which

00:26:16.440 --> 00:26:20.880
according to some reports is not that

00:26:18.119 --> 00:26:22.559
structurally sound and is in danger of

00:26:20.880 --> 00:26:24.400
partial collapse.

00:26:22.559 --> 00:26:27.240
So, yeah, more difficult efforts are

00:26:24.400 --> 00:26:29.720
ahead. But let's now talk about

00:26:27.240 --> 00:26:31.000
what happened next.

00:26:29.720 --> 00:26:33.440
I'm going to jump to the very end of

00:26:31.000 --> 00:26:35.039
this. The actual way that the accident

00:26:33.440 --> 00:26:37.519
was noticed

00:26:35.039 --> 00:26:41.799
was the spread of the radioactive cloud

00:26:37.519 --> 00:26:43.759
to not so close by Sweden.

00:26:41.799 --> 00:26:45.960
So, it was noticed that folks entering a

00:26:43.759 --> 00:26:47.119
reactor in Sweden had contaminants on

00:26:45.960 --> 00:26:48.400
them, which they thought was coming from

00:26:47.119 --> 00:26:50.199
their own reactor, good first

00:26:48.400 --> 00:26:51.880
assumption. When it was determined that

00:26:50.200 --> 00:26:54.200
nothing was amiss at the reactor in

00:26:51.880 --> 00:26:55.880
Sweden, folks started to analyze wind

00:26:54.200 --> 00:26:57.960
patterns and find out what happened, and

00:26:55.880 --> 00:26:59.440
then it was clear that the USSR had

00:26:57.960 --> 00:27:01.240
tried to cover up the Chernobyl

00:26:59.440 --> 00:27:04.400
accident. But you can't cover up

00:27:01.240 --> 00:27:05.880
fallout. And it eventually spread

00:27:04.400 --> 00:27:08.759
pretty wide

00:27:05.880 --> 00:27:11.240
covering most of Europe and Russia and

00:27:08.759 --> 00:27:13.640
surprisingly not Spain. Lucky them for

00:27:11.240 --> 00:27:14.720
the wind patterns that day or those few

00:27:13.640 --> 00:27:16.880
days.

00:27:14.720 --> 00:27:19.519
So, what happened is a few days after

00:27:16.880 --> 00:27:21.280
the actual accident, a graphite fire

00:27:19.519 --> 00:27:23.679
started to break out because graphite

00:27:21.279 --> 00:27:25.440
when exposed to air, well, you can do

00:27:23.679 --> 00:27:29.360
the chemistry.

00:27:25.440 --> 00:27:29.360
Add graphite plus oxygen,

00:27:29.720 --> 00:27:34.279
you start making carbon dioxide.

00:27:32.279 --> 00:27:37.559
So, graphite burns when it's hot. And as

00:27:34.279 --> 00:27:37.559
you could see from the video,

00:27:39.119 --> 00:27:44.119
where is that nice still of

00:27:42.240 --> 00:27:45.559
mol- burning graphite? Yeah. That

00:27:44.119 --> 00:27:48.079
graphite was pretty hot. So, a lot of

00:27:45.559 --> 00:27:50.039
that smoke included burning graphite and

00:27:48.079 --> 00:27:51.199
a lot of the materials from the reactor

00:27:50.039 --> 00:27:53.559
itself.

00:27:51.200 --> 00:27:55.160
Now, when you build up fission products

00:27:53.559 --> 00:27:57.039
in a reactor and they get volatilized

00:27:55.160 --> 00:27:58.400
like this, the ones that tend to get out

00:27:57.039 --> 00:28:00.879
first would be things like the noble

00:27:58.400 --> 00:28:03.080
gases. So, the whole xenon inventory of

00:28:00.880 --> 00:28:05.160
the reactor was released. It's estimated

00:28:03.079 --> 00:28:08.559
about 100%.

00:28:05.160 --> 00:28:10.480
And I can actually pull up those figures

00:28:08.559 --> 00:28:12.839
when we talk about how much of which

00:28:10.480 --> 00:28:14.720
radionuclide was released.

00:28:12.839 --> 00:28:17.119
Uh that's also a typo. If somebody wants

00:28:14.720 --> 00:28:20.559
to call in, there's no 33 isotope of

00:28:17.119 --> 00:28:21.919
xenon. It's supposed to be 133.

00:28:20.559 --> 00:28:23.279
Um that would be interesting if someone

00:28:21.920 --> 00:28:24.480
wants to call in and say the NAA's got a

00:28:23.279 --> 00:28:27.279
mistake.

00:28:24.480 --> 00:28:28.640
So, 100% of the inventory released. That

00:28:27.279 --> 00:28:30.200
should be pretty obvious because it's a

00:28:28.640 --> 00:28:31.200
noble gas and it just kind of floats

00:28:30.200 --> 00:28:33.440
away.

00:28:31.200 --> 00:28:35.799
The real dangers, though, came from

00:28:33.440 --> 00:28:37.600
iodine 131,

00:28:35.799 --> 00:28:41.200
about 50%

00:28:37.599 --> 00:28:43.599
of a three exabecquerel activity.

00:28:41.200 --> 00:28:45.200
So, we're talking like megacuries or

00:28:43.599 --> 00:28:47.559
might be giga. I can't do that math in

00:28:45.200 --> 00:28:49.679
my head. Lot a lot of radiation. And the

00:28:47.559 --> 00:28:52.918
problem with that is iodine behaves just

00:28:49.679 --> 00:28:54.519
like any other halogen. It forms salts.

00:28:52.919 --> 00:28:57.320
It's rather volatile. Have any of you

00:28:54.519 --> 00:28:59.279
guys played with iodine before?

00:28:57.319 --> 00:29:01.559
Uh no one does Oh, you have. Okay. What

00:28:59.279 --> 00:29:02.319
happens when you play with it? I mean,

00:29:01.559 --> 00:29:04.799
it just

00:29:02.319 --> 00:29:07.039
absorbs the stuff like

00:29:04.799 --> 00:29:10.399
for instance, everything

00:29:07.039 --> 00:29:12.440
and it just reacts with like acids and

00:29:10.400 --> 00:29:13.720
stuff. I haven't done very much with it,

00:29:12.440 --> 00:29:15.360
so. Okay.

00:29:13.720 --> 00:29:17.039
I happen to have extensive practice

00:29:15.359 --> 00:29:18.119
playing with iodine in my home cuz I did

00:29:17.039 --> 00:29:19.759
all the stuff you're not supposed to do

00:29:18.119 --> 00:29:21.479
as a kid. Going to build your own

00:29:19.759 --> 00:29:22.559
chemistry stuff, things that somehow,

00:29:21.480 --> 00:29:24.360
you know, leak out of your local high

00:29:22.559 --> 00:29:27.039
school, somehow.

00:29:24.359 --> 00:29:29.918
Iodine's pretty neat.

00:29:27.039 --> 00:29:31.480
Yeah, it happens sometimes. Um if you

00:29:29.919 --> 00:29:33.600
put iodine in your hand, it actually

00:29:31.480 --> 00:29:35.880
sublimes. The heat from your hand is

00:29:33.599 --> 00:29:39.119
enough to directly go from solid to

00:29:35.880 --> 00:29:40.880
vapor. And so, the iodine was also quite

00:29:39.119 --> 00:29:42.399
volatile. Some of it may have been in

00:29:40.880 --> 00:29:44.280
the form of other compounds, some of it

00:29:42.400 --> 00:29:45.759
may have been elemental, probably not

00:29:44.279 --> 00:29:47.799
likely, but there was certainly some

00:29:45.759 --> 00:29:50.400
iodine vapor, and about half of that was

00:29:47.799 --> 00:29:53.839
released. The problem is then it

00:29:50.400 --> 00:29:56.280
condenses out and falls on anything

00:29:53.839 --> 00:29:57.839
green, anything with surface area. So,

00:29:56.279 --> 00:30:01.599
the biggest danger to the folks living

00:29:57.839 --> 00:30:03.519
nearby was from eating leafy vegetables

00:30:01.599 --> 00:30:05.559
because the the leaves that leaves got

00:30:03.519 --> 00:30:07.639
lots of surface area, iodine deposits on

00:30:05.559 --> 00:30:10.440
them, and it's intensely radioactive for

00:30:07.640 --> 00:30:12.280
a month or so or depositing on the grass

00:30:10.440 --> 00:30:14.080
that cows eat, which led to the problem

00:30:12.279 --> 00:30:16.119
of radioactive milk.

00:30:14.079 --> 00:30:17.839
And so, that's why milk in the Soviet

00:30:16.119 --> 00:30:19.000
Union was banned for such a long time

00:30:17.839 --> 00:30:22.079
because this was one of the major

00:30:19.000 --> 00:30:23.759
sources of iodine contamination.

00:30:22.079 --> 00:30:27.679
The other one which we're worrying about

00:30:23.759 --> 00:30:29.480
now from Fukushima as well is cesium

00:30:27.680 --> 00:30:31.840
which has similar chemistry to sodium

00:30:29.480 --> 00:30:33.079
and potassium, again a rather salty

00:30:31.839 --> 00:30:34.879
compound

00:30:33.079 --> 00:30:37.079
or rather salty element, but it's got a

00:30:34.880 --> 00:30:38.560
half-life of 30 years.

00:30:37.079 --> 00:30:40.279
And if we look it up in the table of

00:30:38.559 --> 00:30:42.799
nuclides

00:30:40.279 --> 00:30:45.319
we'll see what it actually releases. Oh,

00:30:42.799 --> 00:30:47.159
good. It's back online.

00:30:45.319 --> 00:30:48.879
Anyone else notice this broken couple

00:30:47.160 --> 00:30:50.240
days ago?

00:30:48.880 --> 00:30:52.080
Yeah.

00:30:50.240 --> 00:30:54.599
Well, luckily Brookhaven National Lab

00:30:52.079 --> 00:30:57.759
has a good version up, too. But, let's

00:30:54.599 --> 00:31:00.000
grab cesium.

00:30:57.759 --> 00:31:02.240
Yeah, there's plenty out there.

00:31:00.000 --> 00:31:04.359
Cesium 137

00:31:02.240 --> 00:31:07.720
beta decays to barium, but also gives

00:31:04.359 --> 00:31:10.079
off gamma rays, and most of the decays

00:31:07.720 --> 00:31:13.440
end up giving off one of those gamma

00:31:10.079 --> 00:31:15.639
rays. Let's say a 660 keV gamma ray. So,

00:31:13.440 --> 00:31:17.360
it's both a beta and a gamma emitter.

00:31:15.640 --> 00:31:18.840
Now, which of those types of radiation

00:31:17.359 --> 00:31:20.919
do you think is more damaging to

00:31:18.839 --> 00:31:24.119
biological organisms?

00:31:20.920 --> 00:31:24.120
The beta or the gamma?

00:31:24.319 --> 00:31:28.960
You say the gamma. Why do you say so?

00:31:27.119 --> 00:31:30.719
Doesn't beta get stopped by like skin or

00:31:28.960 --> 00:31:33.440
clothing? It does.

00:31:30.720 --> 00:31:35.400
But, if cesium is better known as

00:31:33.440 --> 00:31:37.960
Yes.

00:31:35.400 --> 00:31:39.519
That's right. So Did I get to tell you

00:31:37.960 --> 00:31:41.920
guys this question, the four cookies

00:31:39.519 --> 00:31:42.759
question?

00:31:41.920 --> 00:31:44.440
Yeah.

00:31:42.759 --> 00:31:46.079
You eat the gamma cookie because most

00:31:44.440 --> 00:31:47.440
gammas that are emitted by the cookie

00:31:46.079 --> 00:31:48.879
simply leave you and irradiate your

00:31:47.440 --> 00:31:51.160
friend, which is going to be the topic

00:31:48.880 --> 00:31:52.560
of piece at number eight.

00:31:51.160 --> 00:31:54.600
You'll see. That's why you guys are

00:31:52.559 --> 00:31:56.079
getting your whole body counts. Speaking

00:31:54.599 --> 00:31:58.839
of, who's who's gotten their whole body

00:31:56.079 --> 00:32:00.759
counts at DHS?

00:31:58.839 --> 00:32:02.399
Awesome. So, that's almost everybody.

00:32:00.759 --> 00:32:04.879
You will need that data for problem set

00:32:02.400 --> 00:32:06.400
eight. So, do schedule it soon.

00:32:04.880 --> 00:32:08.040
Preferably before Thanksgiving so that

00:32:06.400 --> 00:32:09.920
you'll be able to take a look at it. Has

00:32:08.039 --> 00:32:12.319
anyone found anything interesting in

00:32:09.920 --> 00:32:14.160
your spectra?

00:32:12.319 --> 00:32:15.919
Good.

00:32:14.160 --> 00:32:18.000
Glad to hear that.

00:32:15.920 --> 00:32:20.480
But, you do see a potassium peak that

00:32:18.000 --> 00:32:22.440
you can probably integrate and do some

00:32:20.480 --> 00:32:24.759
problems with, right?

00:32:22.440 --> 00:32:27.200
Yeah, cuz you will. Okay.

00:32:24.759 --> 00:32:29.400
Anyway, yeah, it's the betas. That's the

00:32:27.200 --> 00:32:31.720
real killer. The gammas are going to

00:32:29.400 --> 00:32:33.679
leave the cesium, enter your body, and

00:32:31.720 --> 00:32:37.759
most likely come out the other side.

00:32:33.679 --> 00:32:41.280
Because the mass attenuation coefficient

00:32:37.759 --> 00:32:44.920
of six What is it? Water for 660 keV

00:32:41.279 --> 00:32:46.399
gammas, let's find that.

00:32:44.920 --> 00:32:51.440
Table three.

00:32:46.400 --> 00:32:51.440
Let's say you're made mostly of water.

00:32:53.279 --> 00:32:56.920
Water, liquid. That's pretty much

00:32:55.079 --> 00:32:59.919
humans.

00:32:56.920 --> 00:33:03.920
660 keV is right about here leading to

00:32:59.920 --> 00:33:06.240
about 0.1 cm squared per gram, and with

00:33:03.920 --> 00:33:08.880
a density of 1 g, that's a pretty low

00:33:06.240 --> 00:33:10.640
attenuation of gammas. So, this chart

00:33:08.880 --> 00:33:12.480
actually shows why most of the cesium

00:33:10.640 --> 00:33:13.880
gammas that would be produced from

00:33:12.480 --> 00:33:15.960
ingestion just get right out, but it's

00:33:13.880 --> 00:33:17.520
the betas that have an awfully short

00:33:15.960 --> 00:33:20.120
range.

00:33:17.519 --> 00:33:22.240
Anyone remember the formula for range

00:33:20.119 --> 00:33:23.479
in general?

00:33:22.240 --> 00:33:25.480
Cuz it's going to come back up in our

00:33:23.480 --> 00:33:28.079
discussion of dose and biological

00:33:25.480 --> 00:33:28.079
effects.

00:33:29.920 --> 00:33:33.840
Integral of

00:33:32.160 --> 00:33:36.160
Yep, of stopping power to the negative

00:33:33.839 --> 00:33:36.159
one.

00:33:36.599 --> 00:33:42.678
And that stopping power

00:33:38.679 --> 00:33:42.679
is this simple formula.

00:33:49.039 --> 00:33:54.559
Let's see. What did that come out as?

00:33:57.400 --> 00:34:01.960
log minus beta squared. Ah, simple

00:34:00.599 --> 00:34:03.119
little formula.

00:34:01.960 --> 00:34:05.039
Which I'm not going to expect you guys

00:34:03.119 --> 00:34:06.239
to memorize, so don't worry about it.

00:34:05.039 --> 00:34:07.879
But

00:34:06.240 --> 00:34:09.679
if you integrate this, you find out that

00:34:07.880 --> 00:34:11.878
the range of electrons, even 1 MeV

00:34:09.679 --> 00:34:14.559
electrons in water, is not very high.

00:34:11.878 --> 00:34:17.519
So, most of them are stopped near or by

00:34:14.559 --> 00:34:19.840
the cells that absorb them doing quite a

00:34:17.519 --> 00:34:21.840
bit of damage to the DNA, which is

00:34:19.840 --> 00:34:24.200
eventually what causes mutagenic

00:34:21.840 --> 00:34:25.800
effects, cancer, cell death what we're

00:34:24.199 --> 00:34:28.439
going to talk about for the whole third

00:34:25.800 --> 00:34:29.960
part of the course.

00:34:28.440 --> 00:34:32.320
There's also

00:34:29.960 --> 00:34:35.039
a worry about which organs actually

00:34:32.320 --> 00:34:38.080
absorb these radionuclides, and iodine

00:34:35.039 --> 00:34:39.639
in particular is preferentially absorbed

00:34:38.079 --> 00:34:40.799
by the thyroid.

00:34:39.639 --> 00:34:43.119
So, when we started looking at the

00:34:40.800 --> 00:34:44.760
amount of radioactive substances

00:34:43.119 --> 00:34:46.079
released, remember they said, "Okay, at

00:34:44.760 --> 00:34:48.280
the round

00:34:46.079 --> 00:34:50.918
26th of April or the 2nd of May or so,

00:34:48.280 --> 00:34:52.840
the release was stopped." Not according

00:34:50.918 --> 00:34:55.519
to our data. That's when the graphite

00:34:52.840 --> 00:34:58.680
fire picked up again. In addition, the

00:34:55.519 --> 00:35:01.400
core of Chernobyl which had undergone a

00:34:58.679 --> 00:35:04.358
mostly total meltdown

00:35:01.400 --> 00:35:07.559
was sitting in a pool

00:35:04.358 --> 00:35:09.440
on top of this concrete pad.

00:35:07.559 --> 00:35:11.279
So, let's just call this liquid stuff

00:35:09.440 --> 00:35:13.639
The actual word that we use in parlance

00:35:11.280 --> 00:35:15.960
is called corium.

00:35:13.639 --> 00:35:17.319
It's our tongue-in-cheek word for every

00:35:15.960 --> 00:35:19.039
element mixed together in a hot

00:35:17.320 --> 00:35:20.760
radioactive soup.

00:35:19.039 --> 00:35:22.599
It's First of all, it started to

00:35:20.760 --> 00:35:24.840
redistribute reacting with any water

00:35:22.599 --> 00:35:26.239
that was present, flashing it to steam,

00:35:24.840 --> 00:35:28.240
and the steam caused additional

00:35:26.239 --> 00:35:29.919
dispersion of radionuclides, and

00:35:28.239 --> 00:35:31.559
eventually

00:35:29.920 --> 00:35:32.720
it burrowed its way through and into the

00:35:31.559 --> 00:35:35.519
ground

00:35:32.719 --> 00:35:37.358
releasing more. You know, it's it's uh

00:35:35.519 --> 00:35:38.960
it's the worst nuclear thing that's ever

00:35:37.358 --> 00:35:40.759
happened in the history of nuclear

00:35:38.960 --> 00:35:42.000
things.

00:35:40.760 --> 00:35:44.359
Quite a mess.

00:35:42.000 --> 00:35:46.559
And luckily, it did sort of taper off

00:35:44.358 --> 00:35:48.759
after this.

00:35:46.559 --> 00:35:51.000
But, let's now look into

00:35:48.760 --> 00:35:53.080
what happens next. And this is the nice

00:35:51.000 --> 00:35:55.920
intro to the third part of the course.

00:35:53.079 --> 00:35:57.679
Iodine is is preferentially uptaken by

00:35:55.920 --> 00:35:58.680
the thyroid gland somewhere right about

00:35:57.679 --> 00:36:00.559
here.

00:35:58.679 --> 00:36:02.879
Um so, has anyone ever heard of the idea

00:36:00.559 --> 00:36:04.559
of taking iodine tablets in the case of

00:36:02.880 --> 00:36:07.760
a nuclear disaster?

00:36:04.559 --> 00:36:07.759
Anyone have any idea why?

00:36:09.480 --> 00:36:13.599
If you saturate your thyroid with

00:36:11.199 --> 00:36:15.000
iodine, then if you ingest radioactive

00:36:13.599 --> 00:36:18.239
iodine, it's less likely to be

00:36:15.000 --> 00:36:21.119
permanently uptaken by the thyroid. So,

00:36:18.239 --> 00:36:23.439
this actually provided some statistics

00:36:21.119 --> 00:36:26.079
on the probability of getting thyroid

00:36:23.440 --> 00:36:27.480
cancer from radioactive iodine

00:36:26.079 --> 00:36:29.519
ingestion.

00:36:27.480 --> 00:36:31.199
Luckily, the statistics were quite poor,

00:36:29.519 --> 00:36:34.320
which means that not many people were

00:36:31.199 --> 00:36:35.480
exposed. It was somewhere around 1,300

00:36:34.320 --> 00:36:38.200
or so.

00:36:35.480 --> 00:36:39.440
Not like millions. Yeah, 1,300 people

00:36:38.199 --> 00:36:42.119
total.

00:36:39.440 --> 00:36:44.840
But, what I want to jump to is the dose

00:36:42.119 --> 00:36:47.559
versus risk curve. And this is going to

00:36:44.840 --> 00:36:49.400
apply all of our discussion about the

00:36:47.559 --> 00:36:50.799
biological long-term effects of

00:36:49.400 --> 00:36:53.358
radioactivity.

00:36:50.800 --> 00:36:56.600
What's the most striking thing you see

00:36:53.358 --> 00:36:56.599
as part of this curve?

00:36:56.920 --> 00:37:00.358
That's That's right. That's the first

00:36:58.880 --> 00:37:03.079
thing I saw.

00:37:00.358 --> 00:37:05.000
There are six different models for how

00:37:03.079 --> 00:37:07.519
dose and increased risk of cancer

00:37:05.000 --> 00:37:09.800
proceeds, and they all fall within

00:37:07.519 --> 00:37:11.159
almost all the error bars of these

00:37:09.800 --> 00:37:13.160
measurements.

00:37:11.159 --> 00:37:15.119
I'll say again, thank God that the error

00:37:13.159 --> 00:37:17.480
bars are so high because that means that

00:37:15.119 --> 00:37:19.480
the sample size was so low.

00:37:17.480 --> 00:37:22.199
So, when folks say we don't really know

00:37:19.480 --> 00:37:24.519
how much radioactivity causes how much

00:37:22.199 --> 00:37:26.199
cancer, they're right because luckily,

00:37:24.519 --> 00:37:28.639
we don't have enough data from people

00:37:26.199 --> 00:37:29.879
being exposed to know that really,

00:37:28.639 --> 00:37:31.159
really well.

00:37:29.880 --> 00:37:33.400
So, some folks say we should be

00:37:31.159 --> 00:37:35.039
cautious. I kind of agree with them.

00:37:33.400 --> 00:37:37.639
Some folks say the jury's still out. I

00:37:35.039 --> 00:37:39.119
also agree with them.

00:37:37.639 --> 00:37:41.159
But, you can start to estimate these

00:37:39.119 --> 00:37:44.119
sorts of things by knowing how much

00:37:41.159 --> 00:37:45.519
radiation energy was absorbed and to

00:37:44.119 --> 00:37:47.159
what organ.

00:37:45.519 --> 00:37:49.159
So, I think the only technical thing I

00:37:47.159 --> 00:37:51.119
want to go over today

00:37:49.159 --> 00:37:52.639
is the different units of dose because

00:37:51.119 --> 00:37:54.319
as you start to read things in the

00:37:52.639 --> 00:37:55.920
reading, which I recommend you do if you

00:37:54.320 --> 00:37:57.760
haven't been doing yet, you're going to

00:37:55.920 --> 00:38:00.599
encounter a lot of different units of

00:37:57.760 --> 00:38:03.320
radiation dose ranging from things like

00:38:00.599 --> 00:38:03.319
the roentgen

00:38:04.400 --> 00:38:09.720
which responds to a number of

00:38:06.719 --> 00:38:09.719
ionizations.

00:38:10.320 --> 00:38:15.720
You won't usually see this one

00:38:12.760 --> 00:38:17.359
given in sort of biological parlance

00:38:15.719 --> 00:38:19.599
because it's the number of ionizations

00:38:17.358 --> 00:38:21.920
detected by some sort of gaseous

00:38:19.599 --> 00:38:23.880
ionization detector. So, the dosimeters

00:38:21.920 --> 00:38:25.358
that you all put on the Did you guys all

00:38:23.880 --> 00:38:27.200
bring these uh

00:38:25.358 --> 00:38:29.639
these like brass

00:38:27.199 --> 00:38:30.960
pen dosimeters into the reactor? Anyone

00:38:29.639 --> 00:38:33.519
look through them to see what the unit

00:38:30.960 --> 00:38:34.800
of dose was?

00:38:33.519 --> 00:38:37.679
It's going to be in roentgens cuz that's

00:38:34.800 --> 00:38:39.480
directly correlatable to the number of

00:38:37.679 --> 00:38:42.159
ionizations that that dosimeter has

00:38:39.480 --> 00:38:44.358
experienced. You'll also see four dose

00:38:42.159 --> 00:38:46.279
units, two of which are just factors of

00:38:44.358 --> 00:38:49.799
100 away from each other. There is

00:38:46.280 --> 00:38:52.840
what's called the rad and the gray

00:38:49.800 --> 00:38:55.880
and there's what's called the rem

00:38:52.840 --> 00:38:55.880
and the sievert.

00:38:57.760 --> 00:39:03.040
You'll see these approximated as gray.

00:39:00.400 --> 00:39:05.639
You'll see these as R, and these are

00:39:03.039 --> 00:39:08.920
just usually written as rem.

00:39:05.639 --> 00:39:10.358
So, a rad is simple.

00:39:08.920 --> 00:39:13.240
Let's see.

00:39:10.358 --> 00:39:15.440
100 rads

00:39:13.239 --> 00:39:17.358
is the same as 1 gray.

00:39:15.440 --> 00:39:20.800
And 100 rem

00:39:17.358 --> 00:39:23.440
is the same as 1 sievert. And for gamma

00:39:20.800 --> 00:39:26.120
for the case of gamma radiation

00:39:23.440 --> 00:39:28.639
these units are actually equal.

00:39:26.119 --> 00:39:30.199
I particularly like this set of units

00:39:28.639 --> 00:39:32.879
because

00:39:30.199 --> 00:39:34.679
this is the kind of SI of radiation

00:39:32.880 --> 00:39:36.880
units because it comes directly from

00:39:34.679 --> 00:39:38.639
measurable, calculatable quantities.

00:39:36.880 --> 00:39:40.119
Like the gray, for example, the actual

00:39:38.639 --> 00:39:42.679
unit of gray

00:39:40.119 --> 00:39:45.199
is joules absorbed

00:39:42.679 --> 00:39:47.480
per kilogram of absorber.

00:39:45.199 --> 00:39:49.359
It's a pretty simple unit to understand.

00:39:47.480 --> 00:39:52.039
If you know how many radioactive

00:39:49.360 --> 00:39:54.200
particles or gammas or whatever that you

00:39:52.039 --> 00:39:56.759
have absorbed, you can multiply that

00:39:54.199 --> 00:39:59.119
number by their energy, divide by the

00:39:56.760 --> 00:40:01.040
mass of the organ absorbing them, and

00:39:59.119 --> 00:40:02.920
you get its dose in gray.

00:40:01.039 --> 00:40:04.920
Sievert

00:40:02.920 --> 00:40:07.240
is gray

00:40:04.920 --> 00:40:09.960
times some quality factor for the

00:40:07.239 --> 00:40:09.959
radiation

00:40:10.960 --> 00:40:17.679
times some quality factor

00:40:14.159 --> 00:40:20.239
for the specific type of tissue.

00:40:17.679 --> 00:40:22.639
What this says is that some types of

00:40:20.239 --> 00:40:25.759
radiation are more effective at causing

00:40:22.639 --> 00:40:27.719
damage than others, and some organs are

00:40:25.760 --> 00:40:29.920
more susceptible to radiation damage

00:40:27.719 --> 00:40:31.359
than others. Does anyone happen to know

00:40:29.920 --> 00:40:35.519
some of the organs that are most

00:40:31.360 --> 00:40:35.519
susceptible to radiation damage?

00:40:38.079 --> 00:40:42.679
Soft tissues like what? Cuz there's lots

00:40:40.159 --> 00:40:42.679
of those.

00:40:43.760 --> 00:40:50.640
Stomach lining, yep. Yep. Huh?

00:40:46.880 --> 00:40:50.640
Lungs? Yep. What else?

00:40:51.199 --> 00:40:55.599
Thyroid. Yep, there there is definitely

00:40:53.519 --> 00:40:57.519
one for thyroid.

00:40:55.599 --> 00:41:00.519
Bone marrow.

00:40:57.519 --> 00:41:00.519
What other ones?

00:41:00.639 --> 00:41:05.440
Y'all,

00:41:01.719 --> 00:41:07.319
brain actually not so much. Eyes.

00:41:05.440 --> 00:41:10.720
And where else do you find rapidly

00:41:07.320 --> 00:41:14.519
dividing cells in your body?

00:41:10.719 --> 00:41:14.519
Skin? Yep, the dermis.

00:41:14.559 --> 00:41:17.759
I don't know about the liver. I would

00:41:16.159 --> 00:41:19.079
assume so. Yeah, it's a pretty active

00:41:17.760 --> 00:41:20.720
organ.

00:41:19.079 --> 00:41:22.440
But when folks are worried about birth

00:41:20.719 --> 00:41:24.559
defects

00:41:22.440 --> 00:41:26.760
reproductive organs.

00:41:24.559 --> 00:41:28.079
The link here that for some reason is

00:41:26.760 --> 00:41:30.240
not said in the reading and I've never

00:41:28.079 --> 00:41:33.159
figured out why is the more often a cell

00:41:30.239 --> 00:41:35.559
is dividing the more susceptible it is

00:41:33.159 --> 00:41:38.679
to gaining cancer risk because every

00:41:35.559 --> 00:41:41.239
cell division is a copy of its DNA.

00:41:38.679 --> 00:41:44.079
And anytime that radiation goes in and

00:41:41.239 --> 00:41:45.719
damages or changes that DNA by either

00:41:44.079 --> 00:41:47.759
causing what's called a thymine bridge

00:41:45.719 --> 00:41:49.759
where two thymine bases get linked

00:41:47.760 --> 00:41:52.360
together or damaging the structure in

00:41:49.760 --> 00:41:54.120
some other way, that gene is then

00:41:52.360 --> 00:41:56.360
replicated and the faster they're

00:41:54.119 --> 00:41:59.440
replicating the more likely cancer is

00:41:56.360 --> 00:42:01.200
going to become apparent.

00:41:59.440 --> 00:42:03.480
I guess that this brings up a question,

00:42:01.199 --> 00:42:05.319
when does a rapidly dividing cell become

00:42:03.480 --> 00:42:07.519
cancer? Is it division number one or is

00:42:05.320 --> 00:42:08.600
it when you notice it?

00:42:07.519 --> 00:42:10.079
I guess I'll leave that question to the

00:42:08.599 --> 00:42:12.239
biologists.

00:42:10.079 --> 00:42:13.519
But if you notice in the reading you'll

00:42:12.239 --> 00:42:15.839
see a bunch of different tissue

00:42:13.519 --> 00:42:17.519
equivalency factors.

00:42:15.840 --> 00:42:19.760
And you'll just see them tabulated and

00:42:17.519 --> 00:42:21.400
say there they are, memorize them. I

00:42:19.760 --> 00:42:23.640
want you to try and think of the pattern

00:42:21.400 --> 00:42:26.200
between them. The tissues that basically

00:42:23.639 --> 00:42:29.759
don't matter like the non-marrow part of

00:42:26.199 --> 00:42:31.719
the bone, dead skin cells, muscles,

00:42:29.760 --> 00:42:33.960
things that basically aren't listed that

00:42:31.719 --> 00:42:35.639
much, they're not dividing very fast.

00:42:33.960 --> 00:42:38.079
But anywhere where you find stem cells,

00:42:35.639 --> 00:42:40.119
the lining of your intestine, your lungs

00:42:38.079 --> 00:42:42.519
which undergo a lot of environmental

00:42:40.119 --> 00:42:44.799
damage need to be replenished, gonads,

00:42:42.519 --> 00:42:46.840
dermis, what was the other one that we

00:42:44.800 --> 00:42:47.920
said? Eyes.

00:42:46.840 --> 00:42:49.840
These are places that are either

00:42:47.920 --> 00:42:51.760
sensitive tissues or they're rapidly

00:42:49.840 --> 00:42:54.400
dividing.

00:42:51.760 --> 00:42:57.360
And so the sievert is kind of an a unit

00:42:54.400 --> 00:42:59.639
of increased equivalent risk. So that if

00:42:57.360 --> 00:43:03.079
you were to absorb one gray of gamma

00:42:59.639 --> 00:43:05.799
rays versus one gray of alphas, you'd be

00:43:03.079 --> 00:43:07.880
about 20 times more likely to incur

00:43:05.800 --> 00:43:09.680
cancer from the alphas than the gammas

00:43:07.880 --> 00:43:10.880
because the amount of localized damage

00:43:09.679 --> 00:43:13.679
that they do to cells. And we'll be

00:43:10.880 --> 00:43:15.960
doing all this in detail pretty soon.

00:43:13.679 --> 00:43:18.159
And then for tissue equivalency factor,

00:43:15.960 --> 00:43:20.760
if you absorb one gray in your whole

00:43:18.159 --> 00:43:22.839
body, which means one joule per kilogram

00:43:20.760 --> 00:43:24.960
of average body mass

00:43:22.840 --> 00:43:27.360
versus one gray directly to the lining

00:43:24.960 --> 00:43:29.280
of your intestine by let's say drinking

00:43:27.360 --> 00:43:32.320
polonium-laced tea

00:43:29.280 --> 00:43:34.519
like happened to a poor ex was it

00:43:32.320 --> 00:43:35.840
current or ex-KGB guy? One of the

00:43:34.519 --> 00:43:37.320
Russian fellows?

00:43:35.840 --> 00:43:38.559
No, it's the KGB guys that poisoned him,

00:43:37.320 --> 00:43:40.559
right?

00:43:38.559 --> 00:43:41.440
Yeah, you guys remember back in 2010 or

00:43:40.559 --> 00:43:43.519
so?

00:43:41.440 --> 00:43:46.240
There was a Russian

00:43:43.519 --> 00:43:49.519
Was he a journalist?

00:43:46.239 --> 00:43:51.759
Ex-KGB. So the current KGB somehow got

00:43:49.519 --> 00:43:55.599
into London and slipped polonium into

00:43:51.760 --> 00:43:55.600
his tea at a Japanese restaurant.

00:43:56.880 --> 00:44:00.079
Uh, really?

00:44:01.280 --> 00:44:04.560
What was his name?

00:44:04.880 --> 00:44:08.000
Let's see.

00:44:08.760 --> 00:44:14.960
Then polonium

00:44:12.000 --> 00:44:19.039
poisoning. Did he actually die?

00:44:14.960 --> 00:44:19.039
Poisoning of Alexander Litvinenko.

00:44:23.679 --> 00:44:26.759
He's not doing too well.

00:44:27.639 --> 00:44:32.480
Illness and poisoning, death and last

00:44:29.679 --> 00:44:32.480
statement.

00:44:32.599 --> 00:44:37.358
At the hospital in London. So, yeah.

00:44:37.800 --> 00:44:42.000
Well

00:44:39.840 --> 00:44:44.680
interesting. That probably has something

00:44:42.000 --> 00:44:44.679
to do with it.

00:44:44.960 --> 00:44:48.039
Yeah? Well

00:44:46.840 --> 00:44:49.880
all right, we're not going to comment on

00:44:48.039 --> 00:44:53.679
the politics, but the the radiation

00:44:49.880 --> 00:44:55.640
effect worked clearly, unfortunately. So

00:44:53.679 --> 00:44:58.279
polonium is an alpha emitter and that

00:44:55.639 --> 00:45:00.799
caused a massive dose of alphas to his

00:44:58.280 --> 00:45:02.720
entire gastrointestinal tract. And that

00:45:00.800 --> 00:45:04.720
caused a whole lot of damage to those

00:45:02.719 --> 00:45:06.799
cells. No time for cancer. It actually

00:45:04.719 --> 00:45:08.319
killed off a lot of those stem cells.

00:45:06.800 --> 00:45:10.200
And the way that radiation poisoning

00:45:08.320 --> 00:45:12.280
would work is that if you kill off the

00:45:10.199 --> 00:45:14.279
stem cells, the villi in your intestine

00:45:12.280 --> 00:45:17.400
die which are responsible for absorbing

00:45:14.280 --> 00:45:19.320
nutrition. You can't uptake nutrition.

00:45:17.400 --> 00:45:22.079
You basically starve. Doesn't matter

00:45:19.320 --> 00:45:24.240
what you eat. It's messed up.

00:45:22.079 --> 00:45:26.079
Yeah.

00:45:24.239 --> 00:45:27.599
That's a really bad way to go. It's

00:45:26.079 --> 00:45:30.559
called gastrointestinal syndrome. And

00:45:27.599 --> 00:45:33.239
we'll be talking about the progressive

00:45:30.559 --> 00:45:35.279
effects of acute radiation exposure

00:45:33.239 --> 00:45:38.639
where you have immediate effects mostly

00:45:35.280 --> 00:45:40.519
relating to the death of some organ that

00:45:38.639 --> 00:45:43.119
is responsible for either cell division

00:45:40.519 --> 00:45:45.119
to keep you alive or in extreme cases

00:45:43.119 --> 00:45:46.559
your neurological system and nerve

00:45:45.119 --> 00:45:48.920
function just stops at the highest

00:45:46.559 --> 00:45:53.000
levels of dose. And that corresponds to

00:45:48.920 --> 00:45:56.200
doses of around 4 to 6 gray. 4 to 6

00:45:53.000 --> 00:45:59.039
joules per kilogram of villi or body

00:45:56.199 --> 00:46:00.759
mass will kill you pretty quickly with

00:45:59.039 --> 00:46:02.079
very little chance of survival as what

00:46:00.760 --> 00:46:03.720
happened here.

00:46:02.079 --> 00:46:06.559
And so this was the problem with all the

00:46:03.719 --> 00:46:09.919
folks living around and near Chernobyl

00:46:06.559 --> 00:46:11.400
and Ukraine and Belarus and everywhere

00:46:09.920 --> 00:46:14.760
was the contamination was pretty

00:46:11.400 --> 00:46:16.519
extensive. Uh, about 4,000 people are

00:46:14.760 --> 00:46:18.280
estimated to have died or contracted

00:46:16.519 --> 00:46:20.559
cancer from this. I can't believe how

00:46:18.280 --> 00:46:22.440
low that number is, but it's still 4,000

00:46:20.559 --> 00:46:25.199
people that it should never happen to.

00:46:22.440 --> 00:46:27.358
And effects were felt far away in towns

00:46:25.199 --> 00:46:29.719
like Gomel and I can't read that one cuz

00:46:27.358 --> 00:46:32.079
there's not enough pixels. Um, because

00:46:29.719 --> 00:46:34.519
of the way that let's say rainwater

00:46:32.079 --> 00:46:36.079
whisked or let's say um, the vapor cloud

00:46:34.519 --> 00:46:37.719
from the reactor was whisked away,

00:46:36.079 --> 00:46:40.279
rainwater caused it to fall on certain

00:46:37.719 --> 00:46:42.879
places which still to this day can have

00:46:40.280 --> 00:46:44.560
a really large contamination area.

00:46:42.880 --> 00:46:46.039
And this brings me a little bit into

00:46:44.559 --> 00:46:48.519
what should we be worried about from

00:46:46.039 --> 00:46:51.039
Fukushima? A whole lot less than

00:46:48.519 --> 00:46:53.039
Chernobyl. And the reason why is

00:46:51.039 --> 00:46:55.920
Fukushima did undergo a hydrogen

00:46:53.039 --> 00:46:59.320
explosion and did and still continues to

00:46:55.920 --> 00:47:01.960
release cesium 137 into the ocean.

00:46:59.320 --> 00:47:04.039
Luckily for us the ocean is big.

00:47:01.960 --> 00:47:05.840
And except for fish caught right near

00:47:04.039 --> 00:47:08.039
around Fukushima, even though

00:47:05.840 --> 00:47:10.160
concentrations can be measured at

00:47:08.039 --> 00:47:12.079
hundreds to thousands of times normal

00:47:10.159 --> 00:47:14.239
concentrations, they can still be

00:47:12.079 --> 00:47:17.639
hundreds to thousands of times lower

00:47:14.239 --> 00:47:20.000
than the safe consumption. So a lot of

00:47:17.639 --> 00:47:21.400
the problems you see in the news today,

00:47:20.000 --> 00:47:23.519
I'm not going to call them lies, but I'm

00:47:21.400 --> 00:47:26.440
going to call them half-truths. Folks

00:47:23.519 --> 00:47:28.960
will show the radiation plume of cesium

00:47:26.440 --> 00:47:31.720
137 escaping from Fukushima and that's

00:47:28.960 --> 00:47:34.240
true. There is radiation escaping. The

00:47:31.719 --> 00:47:38.399
question is is it high enough to cause a

00:47:34.239 --> 00:47:40.039
noticeable increased risk of cancer?

00:47:38.400 --> 00:47:42.000
That's the question that reporters

00:47:40.039 --> 00:47:43.358
should be asking themselves. When they

00:47:42.000 --> 00:47:45.159
only tell the half of the story that

00:47:43.358 --> 00:47:46.920
gets them viewers and they don't tell

00:47:45.159 --> 00:47:47.920
the half of the story to complete the

00:47:46.920 --> 00:47:49.800
story

00:47:47.920 --> 00:47:52.639
and tell you should you be afraid or not

00:47:49.800 --> 00:47:54.800
cuz unfortunately fear brings viewers.

00:47:52.639 --> 00:47:56.519
This is the problem and I'm happy to go

00:47:54.800 --> 00:47:58.760
on camera saying this. This is the

00:47:56.519 --> 00:48:00.519
problem with the media today

00:47:58.760 --> 00:48:03.080
is with a half-truth and with a

00:48:00.519 --> 00:48:05.559
half-story you can incite real panic

00:48:03.079 --> 00:48:08.279
over non-physical issues that may not

00:48:05.559 --> 00:48:10.480
actually exist. And so it's important

00:48:08.280 --> 00:48:12.800
that the media tell the whole story.

00:48:10.480 --> 00:48:15.599
Yes, it's true that Fukushima's leasing

00:48:12.800 --> 00:48:17.120
releasing cesium 137.

00:48:15.599 --> 00:48:18.920
How much though is the question that

00:48:17.119 --> 00:48:20.199
people and the media should be asking

00:48:18.920 --> 00:48:21.440
themselves.

00:48:20.199 --> 00:48:23.159
And in the rest of this course we're

00:48:21.440 --> 00:48:25.000
going to answer the question how much is

00:48:23.159 --> 00:48:26.679
too much.

00:48:25.000 --> 00:48:28.760
So I'm going to stop here

00:48:26.679 --> 00:48:30.639
since it's 2 of 5 of and ask you guys if

00:48:28.760 --> 00:48:31.960
you have any questions on

00:48:30.639 --> 00:48:35.079
the whole second part of the course or

00:48:31.960 --> 00:48:35.079
what happened in Chernobyl.

00:48:37.159 --> 00:48:41.719
Yeah. Yeah, uh, could you explain the

00:48:39.039 --> 00:48:43.840
quality factor or determine how you find

00:48:41.719 --> 00:48:45.480
that? Yep, the quality factor Well,

00:48:43.840 --> 00:48:47.960
there's two quality factors. There's the

00:48:45.480 --> 00:48:49.840
quality factor for radiation which will

00:48:47.960 --> 00:48:52.480
tell you how much let's say how much

00:48:49.840 --> 00:48:54.160
more cell damage a given amount of a

00:48:52.480 --> 00:48:57.440
given type of radiation of the same

00:48:54.159 --> 00:49:00.000
energy will deposit into a cell.

00:48:57.440 --> 00:49:03.400
And the tissue equivalency factor tells

00:49:00.000 --> 00:49:05.400
you, well, what's the added risk of some

00:49:03.400 --> 00:49:07.720
sort of defect leading to cell death or

00:49:05.400 --> 00:49:10.200
cancer or some other defect

00:49:07.719 --> 00:49:12.599
from that radiation absorption.

00:49:10.199 --> 00:49:14.639
So to me the tissue equivalency factor

00:49:12.599 --> 00:49:17.039
is roughly but not completely

00:49:14.639 --> 00:49:20.079
approximated by the cell division rate

00:49:17.039 --> 00:49:21.719
and the radiation quality factor is

00:49:20.079 --> 00:49:23.920
going to be quite proportional to the

00:49:21.719 --> 00:49:27.159
stopping power.

00:49:23.920 --> 00:49:29.680
You'll see a term called the linear

00:49:27.159 --> 00:49:32.358
energy transfer or LET.

00:49:29.679 --> 00:49:34.519
This is the stopping power unit used in

00:49:32.358 --> 00:49:36.440
the biology community. It's stopping

00:49:34.519 --> 00:49:38.159
power. And luckily the Turner reading

00:49:36.440 --> 00:49:41.800
actually says it somewhere buried in a

00:49:38.159 --> 00:49:43.279
paragraph. LET is stopping power. So, if

00:49:41.800 --> 00:49:44.480
you start plotting these two together,

00:49:43.280 --> 00:49:45.720
you might find some striking

00:49:44.480 --> 00:49:47.719
similarities.

00:49:45.719 --> 00:49:49.959
I saw two other questions up here.

00:49:47.719 --> 00:49:51.719
Yeah. Can I ask uh

00:49:49.960 --> 00:49:53.559
Why is Chernobyl still considered like

00:49:51.719 --> 00:49:55.039
off-limits if most of the half-lives of

00:49:53.559 --> 00:49:57.159
these things were like

00:49:55.039 --> 00:49:59.360
on the range of like days to

00:49:57.159 --> 00:50:01.839
like 2 years? I mean, it happened in

00:49:59.360 --> 00:50:03.559
Let's answer that with numbers. So, most

00:50:01.840 --> 00:50:05.480
of the half-lives were on the range of

00:50:03.559 --> 00:50:08.279
days to hours.

00:50:05.480 --> 00:50:10.639
But, still, cesium 137 with a half-life

00:50:08.280 --> 00:50:12.800
of 30 years released a third of an

00:50:10.639 --> 00:50:14.440
exabecquerel. That's one of the major

00:50:12.800 --> 00:50:16.480
sources of contamination still out

00:50:14.440 --> 00:50:19.159
there. In addition, if we scroll down a

00:50:16.480 --> 00:50:20.880
little more,

00:50:19.159 --> 00:50:23.480
there was quite a bit of plutonium

00:50:20.880 --> 00:50:24.559
inventory with a half-life of 24,000

00:50:23.480 --> 00:50:26.280
years.

00:50:24.559 --> 00:50:28.279
So, on on Friday, we're going to have

00:50:26.280 --> 00:50:29.880
Jake Heckler come in and give his

00:50:28.280 --> 00:50:32.480
Chernobyl travelogue, cuz one of our

00:50:29.880 --> 00:50:34.160
seniors has actually been to Chernobyl.

00:50:32.480 --> 00:50:36.280
And his boots were so contaminated with

00:50:34.159 --> 00:50:37.639
pluto- with plutonium that he can never

00:50:36.280 --> 00:50:39.840
use them again. They got to stay wrapped

00:50:37.639 --> 00:50:42.719
up in plastic. So, some of these things

00:50:39.840 --> 00:50:44.240
last tens of thousands of years. And

00:50:42.719 --> 00:50:47.079
even though there weren't a lot of

00:50:44.239 --> 00:50:48.839
petabecquerels of plutonium released,

00:50:47.079 --> 00:50:51.279
they're alpha emitters. And they're

00:50:48.840 --> 00:50:52.640
extremely dangerous when ingested.

00:50:51.280 --> 00:50:54.920
So,

00:50:52.639 --> 00:50:56.960
uh greens and things that uptake

00:50:54.920 --> 00:50:59.200
radionuclides from the soil, like moss

00:50:56.960 --> 00:51:02.199
and mushrooms, are totally off-limits in

00:50:59.199 --> 00:51:04.159
a large range of this area.

00:51:02.199 --> 00:51:06.159
You will find a video online, if you

00:51:04.159 --> 00:51:07.440
look, of a mayor from a nearby town

00:51:06.159 --> 00:51:09.839
saying, "Oh, they're perfectly safe to

00:51:07.440 --> 00:51:11.000
eat. Look, I eat them right here." And I

00:51:09.840 --> 00:51:13.039
just say read the comments for what

00:51:11.000 --> 00:51:14.440
people have to say about that.

00:51:13.039 --> 00:51:16.519
Not too smart.

00:51:14.440 --> 00:51:18.559
Yeah. So, what what's like the process

00:51:16.519 --> 00:51:19.960
now for like taking care of Chernobyl?

00:51:18.559 --> 00:51:21.079
Like, what do they

00:51:19.960 --> 00:51:22.679
do there?

00:51:21.079 --> 00:51:24.199
The so so the sarcophagus around the

00:51:22.679 --> 00:51:26.079
reactor has got to be shored up to make

00:51:24.199 --> 00:51:28.399
sure that nothing else gets out, cuz

00:51:26.079 --> 00:51:29.960
most of the reactor is still there.

00:51:28.400 --> 00:51:31.920
And let's say rainwater comes in and

00:51:29.960 --> 00:51:33.159
starts washing away more stuff into the

00:51:31.920 --> 00:51:36.079
ground or whatever. We don't want that

00:51:33.159 --> 00:51:39.079
to happen. Soil replacement and disposal

00:51:36.079 --> 00:51:40.960
as nuclear waste is still going on.

00:51:39.079 --> 00:51:42.480
Uh removal of any moss, lichen,

00:51:40.960 --> 00:51:44.440
mushrooms, or anything with a sort of

00:51:42.480 --> 00:51:47.480
radiation exposure has got to keep

00:51:44.440 --> 00:51:49.639
going. But, this the area that it covers

00:51:47.480 --> 00:51:51.639
is enormous. I don't know if we're ever

00:51:49.639 --> 00:51:53.119
going to get rid of all of it. The

00:51:51.639 --> 00:51:55.440
question is, how much do we have to get

00:51:53.119 --> 00:51:57.519
rid of to lower our risk of cancer in

00:51:55.440 --> 00:51:59.559
the area to an acceptable rate? There

00:51:57.519 --> 00:52:01.320
will likely be parts of this that are

00:51:59.559 --> 00:52:03.360
inaccessible for thousands to tens of

00:52:01.320 --> 00:52:05.080
thousands of years, unless we hopefully

00:52:03.360 --> 00:52:06.880
get smarter about how to contain and

00:52:05.079 --> 00:52:08.719
dispose of this kind of stuff.

00:52:06.880 --> 00:52:09.960
We're not there yet. So, right now, the

00:52:08.719 --> 00:52:12.519
methods are

00:52:09.960 --> 00:52:14.000
kind of simple. Get rid of the soil.

00:52:12.519 --> 00:52:16.719
Fence off the area.

00:52:14.000 --> 00:52:18.519
Some folks have been returning, and they

00:52:16.719 --> 00:52:20.000
do get compensation and free medical

00:52:18.519 --> 00:52:23.360
visits because the background levels

00:52:20.000 --> 00:52:25.280
there are elevated, but not that high.

00:52:23.360 --> 00:52:27.480
So, folks have started to move back to

00:52:25.280 --> 00:52:28.680
some of these areas,

00:52:27.480 --> 00:52:30.880
but there's a lot that are still

00:52:28.679 --> 00:52:33.599
off-limits.

00:52:30.880 --> 00:52:36.360
Any other questions?

00:52:33.599 --> 00:52:38.519
Yeah. It's like way worse than the

00:52:36.360 --> 00:52:40.480
atomic bombs dropped on Hiroshima and

00:52:38.519 --> 00:52:43.000
Nagasaki, because those are like fully

00:52:40.480 --> 00:52:45.240
functioning cities at at this point.

00:52:43.000 --> 00:52:47.719
Yeah, the number of deaths from the

00:52:45.239 --> 00:52:49.279
atomic bombs way outweighed the number

00:52:47.719 --> 00:52:50.759
of deaths that will ever happen from

00:52:49.280 --> 00:52:54.040
Chernobyl. But, like, why is the

00:52:50.760 --> 00:52:55.560
radiation from those bombs not

00:52:54.039 --> 00:52:57.880
Oh, not that much of an issue? Yeah.

00:52:55.559 --> 00:52:59.279
There wasn't that much material. The not

00:52:57.880 --> 00:53:00.960
There wasn't that much nuclear material

00:52:59.280 --> 00:53:02.240
in an atomic bomb.

00:53:00.960 --> 00:53:04.400
What did you guys get for the radius of

00:53:02.239 --> 00:53:06.239
the critical sphere of plutonium?

00:53:04.400 --> 00:53:06.960
4.7

00:53:06.239 --> 00:53:08.879
cm.

00:53:06.960 --> 00:53:10.519
Centimeters? Yeah. Yeah.

00:53:08.880 --> 00:53:14.160
Doesn't take a lot. It takes, you know,

00:53:10.519 --> 00:53:16.119
10, 20 kilos to make a weapon.

00:53:14.159 --> 00:53:18.000
Now, we're talking about tons or

00:53:16.119 --> 00:53:20.359
thousands of tons of material released.

00:53:18.000 --> 00:53:23.760
So, an atomic weapon doesn't kill by

00:53:20.360 --> 00:53:25.240
radiation. It kills by pressure wave,

00:53:23.760 --> 00:53:27.720
the heat wave.

00:53:25.239 --> 00:53:29.039
The fallout is not as much of a concern.

00:53:27.719 --> 00:53:31.279
And we'll actually be looking at the

00:53:29.039 --> 00:53:33.800
data from Hiroshima and Nagasaki

00:53:31.280 --> 00:53:36.400
survivors to see who got what dose, what

00:53:33.800 --> 00:53:37.840
increased cancer risk did they get, and

00:53:36.400 --> 00:53:39.760
is this the

00:53:37.840 --> 00:53:41.960
is the idea that every little bit of

00:53:39.760 --> 00:53:44.800
radiation is a bad thing actually true?

00:53:41.960 --> 00:53:46.440
The answer is, you can't say yes or no.

00:53:44.800 --> 00:53:48.560
No one can say yes or no, because we

00:53:46.440 --> 00:53:49.800
don't have good enough data.

00:53:48.559 --> 00:53:51.440
The error bars support either

00:53:49.800 --> 00:53:52.920
conclusion.

00:53:51.440 --> 00:53:54.679
So, I'm not going to go on record and

00:53:52.920 --> 00:53:56.119
say a little bit of radiation is okay.

00:53:54.679 --> 00:53:59.079
The data's not out yet.

00:53:56.119 --> 00:53:59.079
Hopefully, it never will be.

00:54:00.719 --> 00:54:03.599
Any other questions?

00:54:03.800 --> 00:54:07.840
All right. I'll see you guys on

00:54:05.358 --> 00:54:07.840
Thursday.