1 00:00:01,000 --> 00:00:05,400 The following content is provided under 2 00:00:02,879 --> 00:00:07,519 a Creative Commons license. Your support 3 00:00:05,400 --> 00:00:09,320 will help MIT Open Courseware continue 4 00:00:07,519 --> 00:00:11,000 to offer high-quality educational 5 00:00:09,320 --> 00:00:13,000 resources for free. 6 00:00:11,000 --> 00:00:15,839 To make a donation or to view additional 7 00:00:13,000 --> 00:00:17,759 materials from hundreds of MIT courses, 8 00:00:15,839 --> 00:00:20,759 visit MIT Open Courseware at 9 00:00:17,760 --> 00:00:20,760 ocw.mit.edu. 10 00:00:22,640 --> 00:00:26,199 All right. So, like I told you guys, 11 00:00:24,559 --> 00:00:28,839 Friday marked the end of the hardest 12 00:00:26,199 --> 00:00:30,640 part of the course and Monday marked the 13 00:00:28,839 --> 00:00:32,200 end of the hardest P set. So, because 14 00:00:30,640 --> 00:00:34,000 the rest of your classes are going full 15 00:00:32,200 --> 00:00:35,120 throttle, this one's going to wind down 16 00:00:34,000 --> 00:00:37,039 a little bit. 17 00:00:35,119 --> 00:00:39,239 So, today I'd say sit back, relax, and 18 00:00:37,039 --> 00:00:41,600 enjoy a nuclear catastrophe. 19 00:00:39,240 --> 00:00:43,560 Because we are going to explain what 20 00:00:41,600 --> 00:00:46,439 happened at Chernobyl. Now that you've 21 00:00:43,560 --> 00:00:48,440 got the physics and uh intuitive 22 00:00:46,439 --> 00:00:50,199 background to understand the actual 23 00:00:48,439 --> 00:00:52,359 sequence of events. 24 00:00:50,200 --> 00:00:54,440 To kick it off, I want to show you guys 25 00:00:52,359 --> 00:00:56,600 some actual footage 26 00:00:54,439 --> 00:00:58,280 of the Chernobyl reactor as it was 27 00:00:56,600 --> 00:01:01,640 burning. So, this is the part that most 28 00:00:58,280 --> 00:01:01,640 folks know about. 29 00:01:09,079 --> 00:01:12,560 This is footage taken from a helicopter 30 00:01:10,840 --> 00:01:16,880 from folks that were either surveying or 31 00:01:12,560 --> 00:01:16,879 dropping materials onto the reactor. 32 00:01:25,840 --> 00:01:29,560 That was probably a bad idea. 33 00:01:29,680 --> 00:01:34,680 Over where the smoke is. We'll get into 34 00:01:31,519 --> 00:01:34,679 what the smoke was. 35 00:01:51,840 --> 00:01:54,520 So, that 36 00:01:52,840 --> 00:01:57,640 red stuff right there, that's actually 37 00:01:54,519 --> 00:01:59,479 glowing graphite amongst other materials 38 00:01:57,640 --> 00:02:02,319 from the graphite fire that resulted 39 00:01:59,480 --> 00:02:04,760 from the R the RBMK reactor burning 40 00:02:02,319 --> 00:02:07,439 after the Chernobyl accident caused by 41 00:02:04,760 --> 00:02:10,319 both flaws in the physical design of the 42 00:02:07,439 --> 00:02:12,680 RBMK reactor and absolute operator 43 00:02:10,319 --> 00:02:15,039 stupidity and neglect of any sort of 44 00:02:12,680 --> 00:02:16,640 safety systems or safety culture. We're 45 00:02:15,039 --> 00:02:18,519 lucky to live here in the US where our 46 00:02:16,639 --> 00:02:20,079 worst accident at Three Mile Island was 47 00:02:18,520 --> 00:02:22,760 not actually really that much of an 48 00:02:20,080 --> 00:02:24,440 accident. There was a partial meltdown. 49 00:02:22,759 --> 00:02:27,079 There was not that much of a release of 50 00:02:24,439 --> 00:02:28,400 radionuclides into the atmosphere 51 00:02:27,080 --> 00:02:31,040 because we do things like build 52 00:02:28,400 --> 00:02:32,920 containments on our reactors. If you 53 00:02:31,039 --> 00:02:35,079 think of what a typical reactor looks 54 00:02:32,919 --> 00:02:37,519 like, like if you consider the MIT 55 00:02:35,080 --> 00:02:39,960 reactor as a scaled-down version of a 56 00:02:37,520 --> 00:02:41,719 normal reactor, or I 57 00:02:39,960 --> 00:02:43,719 let's say a commercial power reactor, 58 00:02:41,719 --> 00:02:46,199 you've got the core here. You've got a 59 00:02:43,719 --> 00:02:48,000 bunch of shielding around it. 60 00:02:46,199 --> 00:02:51,119 And you've got a dome 61 00:02:48,000 --> 00:02:51,120 that's rather thick 62 00:02:52,159 --> 00:02:55,799 that comprises the containment. 63 00:02:57,360 --> 00:03:02,720 That would be the core. 64 00:02:59,479 --> 00:03:02,719 This would be some shielding. 65 00:03:03,520 --> 00:03:10,719 So, this is what you find in US and most 66 00:03:06,360 --> 00:03:14,200 other reactors. For the RBMK reactors, 67 00:03:10,719 --> 00:03:16,439 there was no containment. 68 00:03:14,199 --> 00:03:19,479 Because it was thought that nothing 69 00:03:16,439 --> 00:03:21,120 could happen. And boy, were they wrong. 70 00:03:19,479 --> 00:03:23,560 So, I want to walk you guys through a 71 00:03:21,120 --> 00:03:25,719 chronology of what actually happened at 72 00:03:23,560 --> 00:03:28,199 the Chernobyl reactor, which you guys 73 00:03:25,719 --> 00:03:30,280 can read on the NEA or Nuclear Energy 74 00:03:28,199 --> 00:03:32,280 Agency website, the same place that you 75 00:03:30,280 --> 00:03:34,000 find Janice. And we're going to refer to 76 00:03:32,280 --> 00:03:35,759 a lot of the Janice cross sections to 77 00:03:34,000 --> 00:03:36,879 explain why these sorts of events 78 00:03:35,759 --> 00:03:38,719 happened. 79 00:03:36,879 --> 00:03:41,719 So, the whole point of what happened at 80 00:03:38,719 --> 00:03:44,080 Chernobyl was it was desired to see if 81 00:03:41,719 --> 00:03:46,439 you could use the spinning-down turbine 82 00:03:44,080 --> 00:03:49,520 after you shut down the reactor to power 83 00:03:46,439 --> 00:03:50,919 the emergency systems at the reactor. 84 00:03:49,520 --> 00:03:53,920 Uh this would be following something 85 00:03:50,919 --> 00:03:55,799 what's called a a loss of offsite power. 86 00:03:53,919 --> 00:03:57,639 If the offsite power or the grid was 87 00:03:55,800 --> 00:03:59,920 disconnected from the reactor, the 88 00:03:57,639 --> 00:04:01,519 reactor automatically shuts down. But 89 00:03:59,919 --> 00:04:03,319 the turbine, like I showed you a couple 90 00:04:01,520 --> 00:04:06,480 weeks ago, is this enormous spinning 91 00:04:03,319 --> 00:04:08,479 hulk of metal and machinery that coasts 92 00:04:06,479 --> 00:04:10,799 down over a long period of let's say 93 00:04:08,479 --> 00:04:13,519 hours. And as it's spinning, the 94 00:04:10,800 --> 00:04:15,240 generator coils are still spinning and 95 00:04:13,520 --> 00:04:16,239 still producing electricity, or they 96 00:04:15,240 --> 00:04:18,120 could be. 97 00:04:16,238 --> 00:04:20,639 So, it was desired to find out can we 98 00:04:18,120 --> 00:04:22,199 use the spinning-down turbine to power 99 00:04:20,639 --> 00:04:23,519 the emergency equipment if we lose 100 00:04:22,199 --> 00:04:25,599 offsite power? 101 00:04:23,519 --> 00:04:27,959 So, they had to simulate this event. 102 00:04:25,600 --> 00:04:30,600 So, what they actually decided to do is 103 00:04:27,959 --> 00:04:32,959 coast down the reactor to a moderate 104 00:04:30,600 --> 00:04:35,280 power level, a very low power, and see 105 00:04:32,959 --> 00:04:37,439 what comes out of the turbine itself, or 106 00:04:35,279 --> 00:04:40,479 out of the generator, rather. 107 00:04:37,439 --> 00:04:42,839 Um now, there were a lot of flaws in the 108 00:04:40,480 --> 00:04:44,879 RBMK design. And I'd like to bring it up 109 00:04:42,839 --> 00:04:47,439 here so we can talk about what it looks 110 00:04:44,879 --> 00:04:50,279 like and what was wrong with it. 111 00:04:47,439 --> 00:04:52,240 So, the RBMKs, unlike any of the 112 00:04:50,279 --> 00:04:54,119 United States light water reactors that 113 00:04:52,240 --> 00:04:56,400 you may have seen before, many of the 114 00:04:54,120 --> 00:04:58,920 components are the same. There's still 115 00:04:56,399 --> 00:05:01,560 uh light water reactor coolant loop 116 00:04:58,920 --> 00:05:03,240 where a water flows around fuel rods, 117 00:05:01,560 --> 00:05:05,199 goes into a steam separator, better 118 00:05:03,240 --> 00:05:07,840 known as a big heat exchanger, and the 119 00:05:05,199 --> 00:05:09,959 steam drives a turbine 120 00:05:07,839 --> 00:05:11,599 which produces energy, and then this 121 00:05:09,959 --> 00:05:13,919 coolant pump keeps it going, and then 122 00:05:11,600 --> 00:05:15,879 the water circulates. Uh what makes it 123 00:05:13,920 --> 00:05:18,520 different, though, is that each of these 124 00:05:15,879 --> 00:05:21,920 fuel rods was inside its own pressure 125 00:05:18,519 --> 00:05:23,439 tube. So, the coolant was pressurized, 126 00:05:21,920 --> 00:05:25,439 and out here, 127 00:05:23,439 --> 00:05:27,639 this stuff right here was the moderator, 128 00:05:25,439 --> 00:05:29,719 composed of graphite. 129 00:05:27,639 --> 00:05:31,639 Unlike light water reactors in the US, 130 00:05:29,720 --> 00:05:33,040 the coolant was not the only moderator 131 00:05:31,639 --> 00:05:35,199 in the reactor. 132 00:05:33,040 --> 00:05:37,439 Graphite also existed, which meant that 133 00:05:35,199 --> 00:05:39,920 if the water went away, which would 134 00:05:37,439 --> 00:05:42,279 normally shut down a light water reactor 135 00:05:39,920 --> 00:05:44,759 from lack of moderation, graphite was 136 00:05:42,279 --> 00:05:46,959 still there to slow the neutrons down 137 00:05:44,759 --> 00:05:48,120 into the high fission cross section 138 00:05:46,959 --> 00:05:50,959 area. 139 00:05:48,120 --> 00:05:52,639 And I'd like to pull up Janice 140 00:05:50,959 --> 00:05:55,599 and show you what I mean with the 141 00:05:52,639 --> 00:05:58,919 uranium cross section. 142 00:05:55,600 --> 00:06:02,200 So, let's go again to uranium 235 143 00:05:58,920 --> 00:06:05,000 and pull up its fission cross section. 144 00:06:02,199 --> 00:06:05,000 Z fission. 145 00:06:08,519 --> 00:06:12,719 Can make it a little thicker, too. 146 00:06:10,879 --> 00:06:14,519 So, 147 00:06:12,720 --> 00:06:17,120 again, the goal of the moderator is to 148 00:06:14,519 --> 00:06:19,279 take neutrons from high energies, like 1 149 00:06:17,120 --> 00:06:21,519 to 10 MeV, where the fission cross 150 00:06:19,279 --> 00:06:23,679 section is relatively low, and slow them 151 00:06:21,519 --> 00:06:26,759 down into this region where fission is, 152 00:06:23,680 --> 00:06:28,920 let's say, a thousand times more likely. 153 00:06:26,759 --> 00:06:30,959 And in a light water reactor in the US, 154 00:06:28,920 --> 00:06:33,480 if the coolant goes away, so does the 155 00:06:30,959 --> 00:06:35,399 moderation, and there's nothing left to 156 00:06:33,480 --> 00:06:38,200 slow those neutrons down to make fission 157 00:06:35,399 --> 00:06:39,879 more likely. In the RBMK, 158 00:06:38,199 --> 00:06:41,079 that's not the case. The graphite's 159 00:06:39,879 --> 00:06:42,839 still there. 160 00:06:41,079 --> 00:06:44,879 The graphite is cooled by a 161 00:06:42,839 --> 00:06:46,759 helium-nitrogen mixture 162 00:06:44,879 --> 00:06:49,120 because the neutron interactions in the 163 00:06:46,759 --> 00:06:50,439 graphite, that's slowing down, 164 00:06:49,120 --> 00:06:52,319 we've always talked about what happens 165 00:06:50,439 --> 00:06:53,279 from the point of view of the neutron. 166 00:06:52,319 --> 00:06:54,879 But what about the point of view of the 167 00:06:53,279 --> 00:06:57,239 other material? 168 00:06:54,879 --> 00:06:59,519 Any energy lost by the neutrons is 169 00:06:57,240 --> 00:07:02,439 gained by the moderating material. So, 170 00:06:59,519 --> 00:07:04,919 the graphite gets really hot. And you 171 00:07:02,439 --> 00:07:07,160 have to flow some non-oxygen-containing 172 00:07:04,920 --> 00:07:09,040 gas mixture, like helium and nitrogen, 173 00:07:07,160 --> 00:07:10,840 which is pretty inert, to keep that 174 00:07:09,040 --> 00:07:12,319 graphite cool. 175 00:07:10,839 --> 00:07:15,159 And then in between the graphite 176 00:07:12,319 --> 00:07:17,800 moderator were control rods, about 200 177 00:07:15,160 --> 00:07:19,640 of them or so, 30 of which were required 178 00:07:17,800 --> 00:07:21,920 to be down in the reactor at any given 179 00:07:19,639 --> 00:07:24,959 time in order to control power. And that 180 00:07:21,920 --> 00:07:27,439 was a design rule that was broken during 181 00:07:24,959 --> 00:07:28,959 the actual experiment. And then on top 182 00:07:27,439 --> 00:07:31,639 of here, on top of this biological 183 00:07:28,959 --> 00:07:33,239 shield, you could walk on top of it. So, 184 00:07:31,639 --> 00:07:35,879 those the tops of those pressure tubes, 185 00:07:33,240 --> 00:07:37,160 despite being about 350 kilo chunks of 186 00:07:35,879 --> 00:07:38,759 concrete, 187 00:07:37,160 --> 00:07:40,439 you could walk on top of them. It's 188 00:07:38,759 --> 00:07:42,399 pretty cool. 189 00:07:40,439 --> 00:07:46,519 Kind of scary, too. 190 00:07:42,399 --> 00:07:48,759 So, what happened in chronological order 191 00:07:46,519 --> 00:07:51,560 was around midnight the decision was 192 00:07:48,759 --> 00:07:53,319 made to undergo this test and start 193 00:07:51,560 --> 00:07:55,680 spinning down the turbine. 194 00:07:53,319 --> 00:07:57,599 Uh but the grid operator came back and 195 00:07:55,680 --> 00:07:59,519 said, "No, you can't just cut the 196 00:07:57,600 --> 00:08:01,120 reactor power to nothing. You have to 197 00:07:59,519 --> 00:08:04,240 maintain it at a rather high power for a 198 00:08:01,120 --> 00:08:06,800 while." About 500 megawatts electric, or 199 00:08:04,240 --> 00:08:08,759 half the rated power of the reactor. And 200 00:08:06,800 --> 00:08:11,160 what that had the effect of doing is 201 00:08:08,759 --> 00:08:13,920 continuing to create fission products, 202 00:08:11,160 --> 00:08:16,520 including xenon 135. 203 00:08:13,920 --> 00:08:18,840 We haven't mentioned this one yet. 204 00:08:16,519 --> 00:08:20,639 You'll talk about it quite a lot 205 00:08:18,839 --> 00:08:22,399 in 2205 206 00:08:20,639 --> 00:08:24,120 in neutron physics. 207 00:08:22,399 --> 00:08:25,759 Black shirt really shows chalk well. 208 00:08:24,120 --> 00:08:27,800 Okay. 209 00:08:25,759 --> 00:08:29,719 What xenon 135 does is it just sits 210 00:08:27,800 --> 00:08:32,320 there. It's a noble gas. It has a 211 00:08:29,720 --> 00:08:34,158 half-life of a few days, so it decays on 212 00:08:32,320 --> 00:08:35,599 the slow side for, 213 00:08:34,158 --> 00:08:38,840 you know, fission as fission products 214 00:08:35,599 --> 00:08:41,120 go, but it also absorbs lots and lots 215 00:08:38,840 --> 00:08:42,879 and lots of neutrons. 216 00:08:41,120 --> 00:08:44,960 Let's see if I can find which one is the 217 00:08:42,879 --> 00:08:47,639 xenon one. There we go. 218 00:08:44,960 --> 00:08:51,080 So, here I've plotted the total cross 219 00:08:47,639 --> 00:08:52,399 section for xenon 135 and the absorption 220 00:08:51,080 --> 00:08:54,800 cross section. 221 00:08:52,399 --> 00:08:56,480 And notice how for low energies, pretty 222 00:08:54,799 --> 00:08:58,479 much the entire cross section of xenon 223 00:08:56,480 --> 00:09:00,000 is made up of absorption. Did you guys 224 00:08:58,480 --> 00:09:03,120 in your homework see anything that 225 00:09:00,000 --> 00:09:03,919 reached about 10 million barns? 226 00:09:03,120 --> 00:09:05,919 No. 227 00:09:03,919 --> 00:09:07,799 Xenon 135 is one of the best neutron 228 00:09:05,919 --> 00:09:10,199 absorbers there is, and reactors produce 229 00:09:07,799 --> 00:09:13,199 it constantly. So, as they're operating, 230 00:09:10,200 --> 00:09:15,879 you'll build up xenon 135 that you have 231 00:09:13,200 --> 00:09:17,879 to account for in your sigma absorption 232 00:09:15,879 --> 00:09:20,399 cross section. 233 00:09:17,879 --> 00:09:21,799 Cuz like you guys saw on the homework, 234 00:09:20,399 --> 00:09:24,279 if you want to write what's the sigma 235 00:09:21,799 --> 00:09:26,359 absorption cross section of the reactor, 236 00:09:24,279 --> 00:09:28,919 it's the sum 237 00:09:26,360 --> 00:09:31,039 of every single isotope in the reactor 238 00:09:28,919 --> 00:09:32,559 of its number density 239 00:09:31,039 --> 00:09:34,639 times 240 00:09:32,559 --> 00:09:36,559 its absorption cross section. 241 00:09:34,639 --> 00:09:37,679 And so, that would include everything 242 00:09:36,559 --> 00:09:39,239 for 243 00:09:37,679 --> 00:09:42,479 water 244 00:09:39,240 --> 00:09:44,039 and let's say the uranium and the xenon 245 00:09:42,480 --> 00:09:46,080 that you're building up. 246 00:09:44,039 --> 00:09:48,199 When the reactor starts up, the number 247 00:09:46,080 --> 00:09:50,680 density of xenon is zero cuz you don't 248 00:09:48,200 --> 00:09:52,440 have any anything to have produced it. 249 00:09:50,679 --> 00:09:55,519 When you start operating, you'll reach 250 00:09:52,440 --> 00:09:57,280 the xenon equilibrium level where it 251 00:09:55,519 --> 00:09:59,519 will build to a certain level that will 252 00:09:57,279 --> 00:10:00,839 counteract the reactivity of the 253 00:09:59,519 --> 00:10:03,159 reactor. 254 00:10:00,840 --> 00:10:06,360 And in your K effective expression 255 00:10:03,159 --> 00:10:07,519 where it's sources 256 00:10:06,360 --> 00:10:11,080 over 257 00:10:07,519 --> 00:10:13,240 absorption plus leakage 258 00:10:11,080 --> 00:10:15,400 this has the effect of rise at raising 259 00:10:13,240 --> 00:10:17,360 sigma absorption and lowering K 260 00:10:15,399 --> 00:10:18,720 effective. 261 00:10:17,360 --> 00:10:20,960 The trick is it doesn't last for very 262 00:10:18,720 --> 00:10:23,680 long. It both decays with a half-life of 263 00:10:20,960 --> 00:10:25,440 about 5 days and when you try and raise 264 00:10:23,679 --> 00:10:27,639 the reactor power you will also start to 265 00:10:25,440 --> 00:10:29,760 burn it out. So if you're operating at a 266 00:10:27,639 --> 00:10:32,679 fairly low power level, you'll both be 267 00:10:29,759 --> 00:10:33,840 decaying and burning xenon without 268 00:10:32,679 --> 00:10:35,879 really knowing what's going on and 269 00:10:33,840 --> 00:10:38,120 that's exactly what happened here. 270 00:10:35,879 --> 00:10:40,439 So an hour or so later 271 00:10:38,120 --> 00:10:42,039 let me pull up the chronology again. 272 00:10:40,440 --> 00:10:43,760 A little more than an hour later, so the 273 00:10:42,039 --> 00:10:45,879 reactor power stabilized at something 274 00:10:43,759 --> 00:10:47,639 like 30 MW. 275 00:10:45,879 --> 00:10:49,639 And they were like, "What is going on? 276 00:10:47,639 --> 00:10:51,439 Why is the reactor power so low? We need 277 00:10:49,639 --> 00:10:54,000 to increase the reactor power." So what 278 00:10:51,440 --> 00:10:55,800 did they do? Couple things. One was 279 00:10:54,000 --> 00:10:57,399 remove all but six or seven of the 280 00:10:55,799 --> 00:11:01,279 control rods. 281 00:10:57,399 --> 00:11:02,959 Going way outside the spec of the design 282 00:11:01,279 --> 00:11:05,279 uh because 30 were needed to actually 283 00:11:02,960 --> 00:11:07,400 maintain the reactor at a stable power. 284 00:11:05,279 --> 00:11:10,439 All the while the xenon that had been 285 00:11:07,399 --> 00:11:11,959 building up is still there keeping the 286 00:11:10,440 --> 00:11:13,680 reactor from going critical. It's what 287 00:11:11,960 --> 00:11:16,120 was the main reason that the reactor 288 00:11:13,679 --> 00:11:17,519 didn't even have very much power. 289 00:11:16,120 --> 00:11:18,679 But it was also burning out at the same 290 00:11:17,519 --> 00:11:20,960 time. 291 00:11:18,679 --> 00:11:23,399 So all the while 292 00:11:20,960 --> 00:11:25,800 let's say if we were to show a graph of 293 00:11:23,399 --> 00:11:29,000 two things, time 294 00:11:25,799 --> 00:11:31,838 xenon inventory and 295 00:11:29,000 --> 00:11:34,759 as a solid line and let's say control 296 00:11:31,839 --> 00:11:34,760 rod worth 297 00:11:35,679 --> 00:11:39,799 as a dotted line. 298 00:11:37,320 --> 00:11:42,000 The xenon inventory at full power would 299 00:11:39,799 --> 00:11:45,120 have been at some level and then it 300 00:11:42,000 --> 00:11:47,039 would start to decay and burn out. Well, 301 00:11:45,120 --> 00:11:49,600 at the same time the control rod worth 302 00:11:47,039 --> 00:11:51,319 as you remove control rods from the 303 00:11:49,600 --> 00:11:52,839 reactor 304 00:11:51,320 --> 00:11:55,680 every time you remove one you lose some 305 00:11:52,839 --> 00:11:56,839 control rod worth would continue to 306 00:11:55,679 --> 00:11:58,879 diminish. 307 00:11:56,839 --> 00:12:01,560 Leading to the point where that stuff 308 00:11:58,879 --> 00:12:01,559 was going to happen. 309 00:12:02,159 --> 00:12:06,959 Let me make sure I didn't lose my place. 310 00:12:04,639 --> 00:12:08,360 So at any rate as they started pulling 311 00:12:06,960 --> 00:12:10,080 the control rods out a couple of 312 00:12:08,360 --> 00:12:11,639 interesting quirks happened in terms of 313 00:12:10,080 --> 00:12:12,920 feedback. So let's look back at this 314 00:12:11,639 --> 00:12:14,759 design. 315 00:12:12,919 --> 00:12:16,279 Like any reactor 316 00:12:14,759 --> 00:12:18,919 this reactor had what's called a 317 00:12:16,279 --> 00:12:20,679 negative fuel temperature coefficient. 318 00:12:18,919 --> 00:12:22,479 What that means is that 319 00:12:20,679 --> 00:12:24,279 when you heat up the fuel 320 00:12:22,480 --> 00:12:26,680 two things happen. One, the 321 00:12:24,279 --> 00:12:28,879 cross-section for anything absorption or 322 00:12:26,679 --> 00:12:31,519 fission would go up but the number 323 00:12:28,879 --> 00:12:34,320 density would also go down. As the atoms 324 00:12:31,519 --> 00:12:36,559 physically spaced out in the fuel, their 325 00:12:34,320 --> 00:12:38,120 number density would go down lowering 326 00:12:36,559 --> 00:12:40,159 the macroscopic cross-section for 327 00:12:38,120 --> 00:12:41,159 fission. And that's arguably a good 328 00:12:40,159 --> 00:12:45,000 thing. 329 00:12:41,159 --> 00:12:46,559 The problem is at below about 20% power 330 00:12:45,000 --> 00:12:48,120 the reactor had what's called a positive 331 00:12:46,559 --> 00:12:50,719 void coefficient 332 00:12:48,120 --> 00:12:53,320 which meant that if you boil the coolant 333 00:12:50,720 --> 00:12:54,879 you increase the reactor power. 334 00:12:53,320 --> 00:12:56,560 Because the other thing that I think I 335 00:12:54,879 --> 00:13:00,000 mentioned this once 336 00:12:56,559 --> 00:13:03,119 and you calculated in the homework 337 00:13:00,000 --> 00:13:06,679 the absorption cross-section of hydrogen 338 00:13:03,120 --> 00:13:08,919 is not zero. It's small but fairly 339 00:13:06,679 --> 00:13:11,079 significant. Let's actually take a look 340 00:13:08,919 --> 00:13:12,719 at it cuz we can always see this in 341 00:13:11,080 --> 00:13:15,480 Janus. 342 00:13:12,720 --> 00:13:18,320 Go back down to hydrogen. 343 00:13:15,480 --> 00:13:18,320 Hydrogen one. 344 00:13:18,639 --> 00:13:23,240 And we look at the absorption 345 00:13:20,440 --> 00:13:23,240 cross-section. 346 00:13:24,399 --> 00:13:29,959 And of course it started us with a 347 00:13:25,879 --> 00:13:32,039 linear scale. Let's go logarithmic. Ah. 348 00:13:29,960 --> 00:13:33,560 So at low energies at you know, 10 to 349 00:13:32,039 --> 00:13:35,879 the minus eight to 10 to the minus seven 350 00:13:33,559 --> 00:13:37,799 it's around a barn. 351 00:13:35,879 --> 00:13:39,159 Not super high but absolutely not 352 00:13:37,799 --> 00:13:40,759 negligible. 353 00:13:39,159 --> 00:13:43,039 Which meant that part of the normal 354 00:13:40,759 --> 00:13:46,120 functionality of the RBMK depending on 355 00:13:43,039 --> 00:13:48,879 depended on the absorption of the water 356 00:13:46,120 --> 00:13:50,879 to help absorb some of those neutrons. 357 00:13:48,879 --> 00:13:53,120 With those neutrons gone, I'm sorry, 358 00:13:50,879 --> 00:13:54,519 with those with that water gone 359 00:13:53,120 --> 00:13:56,919 there was less absorption but there was 360 00:13:54,519 --> 00:13:58,919 still a ton of moderation 361 00:13:56,919 --> 00:14:00,319 in this graphite moderator. So they 362 00:13:58,919 --> 00:14:01,838 still could get slow but then there'd be 363 00:14:00,320 --> 00:14:03,960 more of them and that would cause the 364 00:14:01,839 --> 00:14:06,640 power to increase. And then that caused 365 00:14:03,960 --> 00:14:08,920 more of the water the coolant to boil 366 00:14:06,639 --> 00:14:10,480 which would cause less absorption which 367 00:14:08,919 --> 00:14:12,279 would cause the power to increase. Yeah, 368 00:14:10,480 --> 00:14:14,560 Charlie? So if they removed the water 369 00:14:12,279 --> 00:14:14,559 from 370 00:14:14,839 --> 00:14:18,360 They did not remove the water from the 371 00:14:16,399 --> 00:14:20,679 reactor. However, as the power started 372 00:14:18,360 --> 00:14:22,240 to rise some of the water started to 373 00:14:20,679 --> 00:14:23,838 boil. 374 00:14:22,240 --> 00:14:25,680 And so you can still have let's say 375 00:14:23,839 --> 00:14:27,120 steam flowing through 376 00:14:25,679 --> 00:14:29,039 and still remove some of the heat. 377 00:14:27,120 --> 00:14:31,720 However, you don't have that denser 378 00:14:29,039 --> 00:14:32,879 water to act as an absorber. 379 00:14:31,720 --> 00:14:35,200 And that's what really undid this 380 00:14:32,879 --> 00:14:38,240 reactor. In addition, they decided to 381 00:14:35,200 --> 00:14:39,879 disable the ECCS or the emergency core 382 00:14:38,240 --> 00:14:41,200 cooling system which you're just not 383 00:14:39,879 --> 00:14:42,360 supposed to do. 384 00:14:41,200 --> 00:14:43,600 So they shut down a bunch of these 385 00:14:42,360 --> 00:14:44,839 systems to see if you could power the 386 00:14:43,600 --> 00:14:46,000 other ones from the spinning down 387 00:14:44,839 --> 00:14:48,200 turbine. 388 00:14:46,000 --> 00:14:49,919 And then as they noticed that the 389 00:14:48,200 --> 00:14:53,079 reactor was getting less and less stable 390 00:14:49,919 --> 00:14:56,159 they had almost all the rods out. Some 391 00:14:53,078 --> 00:15:00,359 of these pressure tubes started to bump 392 00:14:56,159 --> 00:15:02,838 and jump. These 350 kg pressure tube 393 00:15:00,360 --> 00:15:05,039 caps were just rattling. I mean imagine 394 00:15:02,839 --> 00:15:08,200 something that weighs you know, 900 lb 395 00:15:05,039 --> 00:15:09,759 or so rattling around and there's a few 396 00:15:08,200 --> 00:15:11,839 hundred of them. So there was someone in 397 00:15:09,759 --> 00:15:14,159 the control room that said, "The caps 398 00:15:11,839 --> 00:15:16,120 are rattling. What the heck?" 399 00:15:14,159 --> 00:15:19,519 Uh didn't quite make it down the spiral 400 00:15:16,120 --> 00:15:21,480 staircase because about 10 seconds later 401 00:15:19,519 --> 00:15:22,799 everything went wrong. 402 00:15:21,480 --> 00:15:24,879 And so I want to pull up this actual 403 00:15:22,799 --> 00:15:27,199 timeline so you can see 404 00:15:24,879 --> 00:15:29,200 it splits from minutes to seconds 405 00:15:27,200 --> 00:15:33,120 because the speed at which this stuff 406 00:15:29,200 --> 00:15:35,759 started to go wrong was pretty striking. 407 00:15:33,120 --> 00:15:38,560 So for example, the control rods raised 408 00:15:35,759 --> 00:15:40,439 at 1:19 in the morning. 409 00:15:38,559 --> 00:15:42,319 2 minutes later 410 00:15:40,440 --> 00:15:43,920 when the power starts to become unstable 411 00:15:42,320 --> 00:15:47,000 the caps on the fuel channels which 412 00:15:43,919 --> 00:15:48,799 again are like 350 kg blocks start 413 00:15:47,000 --> 00:15:51,240 jumping in their sockets. 414 00:15:48,799 --> 00:15:53,240 And a lot of that was we go back to the 415 00:15:51,240 --> 00:15:55,799 RBMK reactor. 416 00:15:53,240 --> 00:15:57,720 As the coolant started to boil here, 417 00:15:55,799 --> 00:15:59,838 well that boiling force actually creates 418 00:15:57,720 --> 00:16:02,000 huge pressure instabilities which would 419 00:15:59,839 --> 00:16:04,120 cause the pressure tubes to jump up and 420 00:16:02,000 --> 00:16:06,480 down eventually rupturing almost every 421 00:16:04,120 --> 00:16:09,879 single one of them with enough force to 422 00:16:06,480 --> 00:16:10,920 shoot these 350 kilo caps 423 00:16:09,879 --> 00:16:14,639 and still what did they what did they 424 00:16:10,919 --> 00:16:16,559 say? I like the language that they used. 425 00:16:14,639 --> 00:16:17,480 Jumping in their sockets. 426 00:16:16,559 --> 00:16:19,759 So 427 00:16:17,480 --> 00:16:21,639 50 seconds later 428 00:16:19,759 --> 00:16:22,799 pressure fails in the steam drums which 429 00:16:21,639 --> 00:16:25,799 means there's been some sort of 430 00:16:22,799 --> 00:16:27,719 containment leak. So all the while 431 00:16:25,799 --> 00:16:30,519 the coolant was boiling, the absorption 432 00:16:27,720 --> 00:16:32,720 was going down, the power was going up 433 00:16:30,519 --> 00:16:34,600 repeat, repeat, repeat and the power 434 00:16:32,720 --> 00:16:37,759 jumped to about 100 times the rated 435 00:16:34,600 --> 00:16:39,800 power in something like 4 seconds. 436 00:16:37,759 --> 00:16:42,838 So it was normally a 1000 MW electric 437 00:16:39,799 --> 00:16:45,838 reactor which is about 3200 MW thermal. 438 00:16:42,839 --> 00:16:48,120 It was producing nearly 439 00:16:45,839 --> 00:16:50,600 yeah, half a terawatt of thermal power 440 00:16:48,120 --> 00:16:52,039 for a very short amount of time until it 441 00:16:50,600 --> 00:16:53,560 exploded. 442 00:16:52,039 --> 00:16:55,360 Now this is interesting. A lot of folks 443 00:16:53,559 --> 00:16:57,679 called Chernobyl a nuclear explosion. 444 00:16:55,360 --> 00:17:00,519 That's actually a misnomer. A nuclear 445 00:16:57,679 --> 00:17:02,279 explosion would be a nuclear weapon. 446 00:17:00,519 --> 00:17:05,319 Something set off by an enormous chain 447 00:17:02,279 --> 00:17:07,559 reaction principally heated by fission 448 00:17:05,319 --> 00:17:10,159 or fusion. That's not actually what 449 00:17:07,559 --> 00:17:11,838 happened at Chernobyl nor at Fukushima 450 00:17:10,160 --> 00:17:14,320 nor was that the worry at Three Mile 451 00:17:11,838 --> 00:17:16,519 Island. Not to say it wasn't a horrible 452 00:17:14,319 --> 00:17:17,799 thing but it wasn't an actual nuclear 453 00:17:16,519 --> 00:17:20,119 explosion. 454 00:17:17,799 --> 00:17:21,639 At first what happened was a pressure 455 00:17:20,119 --> 00:17:24,438 explosion. 456 00:17:21,640 --> 00:17:27,800 So there was an enormous release of 457 00:17:24,439 --> 00:17:30,200 steam as the power built up to 100 times 458 00:17:27,799 --> 00:17:32,279 normal operating power the steam force 459 00:17:30,200 --> 00:17:34,120 was so large that it actually blew the 460 00:17:32,279 --> 00:17:35,720 reactor lid 461 00:17:34,119 --> 00:17:37,519 up off of the thing. 462 00:17:35,720 --> 00:17:40,720 And I think I have a picture of that 463 00:17:37,519 --> 00:17:40,720 somewhere here too. 464 00:17:42,119 --> 00:17:46,239 Should be further down. Yeah. To give 465 00:17:44,200 --> 00:17:47,600 you a little sense of scale 466 00:17:46,240 --> 00:17:50,359 the reactor cover which weighed about 467 00:17:47,599 --> 00:17:52,359 1000 tons launched into the air 468 00:17:50,359 --> 00:17:54,279 and landed above the reactor 469 00:17:52,359 --> 00:17:56,599 sending most of the reactor components 470 00:17:54,279 --> 00:17:59,039 up to a kilometer up in the air. 471 00:17:56,599 --> 00:18:01,079 4 seconds later 472 00:17:59,039 --> 00:18:02,519 that was followed by a hydrogen 473 00:18:01,079 --> 00:18:05,039 explosion. 474 00:18:02,519 --> 00:18:07,359 Let me get back down to that chronology. 475 00:18:05,039 --> 00:18:10,399 So yeah. 476 00:18:07,359 --> 00:18:11,719 At 1:23 and 40 seconds in the morning. 477 00:18:10,400 --> 00:18:13,679 Oh yeah, so I should mention why this 478 00:18:11,720 --> 00:18:15,600 happened. Emergency insertion of all the 479 00:18:13,679 --> 00:18:17,400 control rods. 480 00:18:15,599 --> 00:18:19,119 The last part that this diagram doesn't 481 00:18:17,400 --> 00:18:21,320 mention is these control rods and I'll 482 00:18:19,119 --> 00:18:23,959 draw this up here were tipped with about 483 00:18:21,319 --> 00:18:26,359 6 in of graphite. 484 00:18:23,960 --> 00:18:29,240 So if these were two graphite channels, 485 00:18:26,359 --> 00:18:31,559 let's say these are carbon 486 00:18:29,240 --> 00:18:34,599 and this is your control rod the goal 487 00:18:31,559 --> 00:18:37,119 was to get this control rod 488 00:18:34,599 --> 00:18:39,158 all the way into the reactor. 489 00:18:37,119 --> 00:18:41,399 One part they didn't mention 490 00:18:39,159 --> 00:18:43,440 was they were tipped with about 6 in of 491 00:18:41,400 --> 00:18:46,040 graphite which only functions as 492 00:18:43,440 --> 00:18:48,559 additional moderator. Graphite is one of 493 00:18:46,039 --> 00:18:50,440 the lowest absorbing materials in the 494 00:18:48,559 --> 00:18:51,759 periodic table, second I think only to 495 00:18:50,440 --> 00:18:53,799 oxygen. 496 00:18:51,759 --> 00:18:56,799 And if we pull up graphite's 497 00:18:53,799 --> 00:18:56,799 cross-sections 498 00:18:57,079 --> 00:18:59,799 I've plotted here the total 499 00:18:58,440 --> 00:19:01,440 cross-section 500 00:18:59,799 --> 00:19:05,480 the elastic scattering cross-section and 501 00:19:01,440 --> 00:19:08,000 down here in the point 001 barn level is 502 00:19:05,480 --> 00:19:09,640 the absorption cross-section. About 1000 503 00:19:08,000 --> 00:19:11,240 times lower than water. So you're 504 00:19:09,640 --> 00:19:13,440 shoving more material in the reactor 505 00:19:11,240 --> 00:19:14,799 that slows down neutrons even more 506 00:19:13,440 --> 00:19:17,240 bringing them into the high fission 507 00:19:14,799 --> 00:19:19,879 region without absorbing anything and 508 00:19:17,240 --> 00:19:22,319 they jammed about halfway down, about 2 509 00:19:19,880 --> 00:19:24,760 and 1/2 ft down leaving the extra 510 00:19:22,319 --> 00:19:26,480 graphite right in the center of the core 511 00:19:24,759 --> 00:19:28,720 where it could do the most damage. And 512 00:19:26,480 --> 00:19:30,759 it didn't take that much time. Yeah? Um 513 00:19:28,720 --> 00:19:32,480 so my understanding is that also one of 514 00:19:30,759 --> 00:19:34,158 the designs was that the control rods 515 00:19:32,480 --> 00:19:36,519 didn't like immediately drop down but 516 00:19:34,159 --> 00:19:38,560 they were slowly lowered. Yep. Um so 517 00:19:36,519 --> 00:19:39,720 They took they took 7 to 10 seconds. 518 00:19:38,559 --> 00:19:41,200 Okay, if they had a system where they 519 00:19:39,720 --> 00:19:43,400 did drop them would that have possibly 520 00:19:41,200 --> 00:19:45,159 actually shut the system down properly? 521 00:19:43,400 --> 00:19:47,040 I'm not sure. I don't know whether 522 00:19:45,159 --> 00:19:49,280 lowering control rods into something 523 00:19:47,039 --> 00:19:51,119 that was undergoing steam explosions 524 00:19:49,279 --> 00:19:53,119 would have actually helped. I mean to me 525 00:19:51,119 --> 00:19:54,159 by this point it was all over. 526 00:19:53,119 --> 00:19:56,079 Um 527 00:19:54,160 --> 00:19:58,120 whether or not, you know, so the extra 528 00:19:56,079 --> 00:20:00,079 the extra abs- what is it? The extra 529 00:19:58,119 --> 00:20:01,679 moderator that was dumped in was the 530 00:20:00,079 --> 00:20:04,199 last kick in the pants this thing needed 531 00:20:01,680 --> 00:20:06,320 to go absolutely insane. 532 00:20:04,200 --> 00:20:08,720 And if we go back to the timeline on the 533 00:20:06,319 --> 00:20:12,639 second level, control rods inserted at 534 00:20:08,720 --> 00:20:16,120 1:23 and 40 seconds, explosion 4 seconds 535 00:20:12,640 --> 00:20:18,880 later. Ah, to 120 times full power. 536 00:20:16,119 --> 00:20:22,159 Getting towards a terawatt, so. 1 second 537 00:20:18,880 --> 00:20:24,560 later, the 1,000 ton lid launches off 538 00:20:22,160 --> 00:20:26,720 from the first explosion. 539 00:20:24,559 --> 00:20:29,519 Very shortly after that, second 540 00:20:26,720 --> 00:20:32,120 explosion. And that happened because of 541 00:20:29,519 --> 00:20:35,759 this reaction. 542 00:20:32,119 --> 00:20:38,199 Well, any- just about anything 543 00:20:35,759 --> 00:20:41,359 corroding with water will make pretty 544 00:20:38,200 --> 00:20:43,600 much anything oxide 545 00:20:41,359 --> 00:20:45,240 plus hydrogen. The same chemical 546 00:20:43,599 --> 00:20:47,559 explosion that was the undoing of 547 00:20:45,240 --> 00:20:49,039 Fukushima and was the worry at Three 548 00:20:47,559 --> 00:20:51,319 Mile Island that there was a hydrogen 549 00:20:49,039 --> 00:20:53,359 bubble building because of corrosion 550 00:20:51,319 --> 00:20:55,159 reactions with whatever happened to be 551 00:20:53,359 --> 00:20:57,079 in the core. This happens with zirconium 552 00:20:55,160 --> 00:20:58,680 pretty vigorously, but it happens with 553 00:20:57,079 --> 00:21:01,439 other materials, too. 554 00:20:58,680 --> 00:21:02,920 If you oxidize something with water, you 555 00:21:01,440 --> 00:21:05,400 leave behind the hydrogen, and the 556 00:21:02,920 --> 00:21:08,360 hydrogen in a very wide range of 557 00:21:05,400 --> 00:21:09,600 concentrations in the air is explosive. 558 00:21:08,359 --> 00:21:12,679 We're actually not allowed to use 559 00:21:09,599 --> 00:21:13,759 hydrogen at above 4% in any of the labs 560 00:21:12,680 --> 00:21:16,080 here because that reaches the 561 00:21:13,759 --> 00:21:18,119 flammability or explosive limit. 562 00:21:16,079 --> 00:21:20,599 So, we were doing some um for my PhD, we 563 00:21:18,119 --> 00:21:22,439 were doing these experiments corroding 564 00:21:20,599 --> 00:21:24,639 materials in liquid lead, and we wanted 565 00:21:22,440 --> 00:21:26,640 to dump in pure hydrogen to see what 566 00:21:24,640 --> 00:21:28,840 happens when there's no oxygen. We were 567 00:21:26,640 --> 00:21:30,160 told absolutely not. We had to drill a 568 00:21:28,839 --> 00:21:32,959 hole in the side of the wall so that the 569 00:21:30,160 --> 00:21:34,560 hydrogen would vent outside. And do some 570 00:21:32,960 --> 00:21:36,319 calculations to show if the entire 571 00:21:34,559 --> 00:21:38,480 bottle of hydrogen emptied into the lab 572 00:21:36,319 --> 00:21:40,599 at once, which it could do if the cap of 573 00:21:38,480 --> 00:21:42,920 the bottle breaks off, it would not 574 00:21:40,599 --> 00:21:44,240 reach 4% concentration. 575 00:21:42,920 --> 00:21:46,240 So, hydrogen explosions are pretty 576 00:21:44,240 --> 00:21:48,920 powerful things. Have you guys ever seen 577 00:21:46,240 --> 00:21:50,480 people making water from scratch? 578 00:21:48,920 --> 00:21:51,240 Mix hydrogen and oxygen in the bottle 579 00:21:50,480 --> 00:21:52,920 and 580 00:21:51,240 --> 00:21:54,160 light a match? 581 00:21:52,920 --> 00:21:56,039 We've got a video of it circulating 582 00:21:54,160 --> 00:21:58,080 somewhere around here because for RTC, 583 00:21:56,039 --> 00:22:00,159 for the reactor technology course, I do 584 00:21:58,079 --> 00:22:01,799 this in front of a bunch of CEOs. Watch 585 00:22:00,160 --> 00:22:03,519 them jump out of their chairs 586 00:22:01,799 --> 00:22:06,839 to teach basic chemical reactions, but 587 00:22:03,519 --> 00:22:08,839 it's pretty loud. Enough uh about enough 588 00:22:06,839 --> 00:22:10,480 hydrogen and oxygen 589 00:22:08,839 --> 00:22:12,159 to just fill this cup or fill a half 590 00:22:10,480 --> 00:22:13,920 liter water bottle makes a bang that 591 00:22:12,160 --> 00:22:16,600 gets your ears ringing. Not quite 592 00:22:13,920 --> 00:22:17,840 bleeding, but close enough. 593 00:22:16,599 --> 00:22:19,399 So, that's what happened here, except on 594 00:22:17,839 --> 00:22:22,199 a much more massive scale. So, there was 595 00:22:19,400 --> 00:22:24,840 a steam explosion followed seconds later 596 00:22:22,200 --> 00:22:26,759 by a hydrogen explosion from hydrogen 597 00:22:24,839 --> 00:22:28,199 liberated from the corrosion reaction of 598 00:22:26,759 --> 00:22:29,720 everything with the water that was 599 00:22:28,200 --> 00:22:33,039 already there. 600 00:22:29,720 --> 00:22:33,039 And that's when 601 00:22:33,519 --> 00:22:36,359 this happened. 602 00:22:54,679 --> 00:22:59,480 So, that smoke right there 603 00:22:57,400 --> 00:23:02,679 is from the graphite fire. 604 00:22:59,480 --> 00:23:02,679 Not normal smoke. 605 00:23:20,799 --> 00:23:23,879 Spoke too soon. 606 00:23:53,119 --> 00:23:56,599 This actually provides a perfect conduit 607 00:23:55,119 --> 00:23:58,599 to transition from the second to the 608 00:23:56,599 --> 00:23:59,799 third parts of this course. A lot of you 609 00:23:58,599 --> 00:24:01,000 have been waiting to find out what are 610 00:23:59,799 --> 00:24:02,720 the units of dose and what are the 611 00:24:01,000 --> 00:24:04,519 biological and chemical effects of 612 00:24:02,720 --> 00:24:06,480 radiation. Well, this is where you get 613 00:24:04,519 --> 00:24:09,279 them. From neutron physics, you can 614 00:24:06,480 --> 00:24:10,360 understand why Chernobyl went wrong. 615 00:24:09,279 --> 00:24:12,119 With honestly, you've just been doing 616 00:24:10,359 --> 00:24:13,759 this for three or four weeks, but with 617 00:24:12,119 --> 00:24:15,839 your knowledge of cross sections, 618 00:24:13,759 --> 00:24:17,599 reactor feedback, and criticality, you 619 00:24:15,839 --> 00:24:19,839 can start to understand why Chernobyl 620 00:24:17,599 --> 00:24:20,959 was flawed in its design. And what we're 621 00:24:19,839 --> 00:24:23,159 going to teach you in the rest of the 622 00:24:20,960 --> 00:24:25,000 course is what happens next. What 623 00:24:23,160 --> 00:24:27,440 happens when radionuclides are absorbed 624 00:24:25,000 --> 00:24:30,079 by animals and the human body? And what 625 00:24:27,440 --> 00:24:31,640 was the main fallout, let's say, in the 626 00:24:30,079 --> 00:24:34,159 in the uh 627 00:24:31,640 --> 00:24:37,320 colloquial sense and the actual sense 628 00:24:34,160 --> 00:24:38,600 from the Chernobyl reactor. 629 00:24:37,319 --> 00:24:40,919 Let's look a bit what they did next, 630 00:24:38,599 --> 00:24:40,919 though. 631 00:25:45,960 --> 00:25:50,039 That's not quite true. We'll see why. 632 00:25:58,960 --> 00:26:02,279 That actually did happen. 633 00:26:08,480 --> 00:26:11,920 I think that pretty much summarizes the 634 00:26:10,039 --> 00:26:13,920 state of things now. 635 00:26:11,920 --> 00:26:16,440 They uh they built a sarcophagus around 636 00:26:13,920 --> 00:26:18,120 this reactor, a gigantic tomb, which 637 00:26:16,440 --> 00:26:20,880 according to some reports is not that 638 00:26:18,119 --> 00:26:22,559 structurally sound and is in danger of 639 00:26:20,880 --> 00:26:24,400 partial collapse. 640 00:26:22,559 --> 00:26:27,240 So, yeah, more difficult efforts are 641 00:26:24,400 --> 00:26:29,720 ahead. But let's now talk about 642 00:26:27,240 --> 00:26:31,000 what happened next. 643 00:26:29,720 --> 00:26:33,440 I'm going to jump to the very end of 644 00:26:31,000 --> 00:26:35,039 this. The actual way that the accident 645 00:26:33,440 --> 00:26:37,519 was noticed 646 00:26:35,039 --> 00:26:41,799 was the spread of the radioactive cloud 647 00:26:37,519 --> 00:26:43,759 to not so close by Sweden. 648 00:26:41,799 --> 00:26:45,960 So, it was noticed that folks entering a 649 00:26:43,759 --> 00:26:47,119 reactor in Sweden had contaminants on 650 00:26:45,960 --> 00:26:48,400 them, which they thought was coming from 651 00:26:47,119 --> 00:26:50,199 their own reactor, good first 652 00:26:48,400 --> 00:26:51,880 assumption. When it was determined that 653 00:26:50,200 --> 00:26:54,200 nothing was amiss at the reactor in 654 00:26:51,880 --> 00:26:55,880 Sweden, folks started to analyze wind 655 00:26:54,200 --> 00:26:57,960 patterns and find out what happened, and 656 00:26:55,880 --> 00:26:59,440 then it was clear that the USSR had 657 00:26:57,960 --> 00:27:01,240 tried to cover up the Chernobyl 658 00:26:59,440 --> 00:27:04,400 accident. But you can't cover up 659 00:27:01,240 --> 00:27:05,880 fallout. And it eventually spread 660 00:27:04,400 --> 00:27:08,759 pretty wide 661 00:27:05,880 --> 00:27:11,240 covering most of Europe and Russia and 662 00:27:08,759 --> 00:27:13,640 surprisingly not Spain. Lucky them for 663 00:27:11,240 --> 00:27:14,720 the wind patterns that day or those few 664 00:27:13,640 --> 00:27:16,880 days. 665 00:27:14,720 --> 00:27:19,519 So, what happened is a few days after 666 00:27:16,880 --> 00:27:21,280 the actual accident, a graphite fire 667 00:27:19,519 --> 00:27:23,679 started to break out because graphite 668 00:27:21,279 --> 00:27:25,440 when exposed to air, well, you can do 669 00:27:23,679 --> 00:27:29,360 the chemistry. 670 00:27:25,440 --> 00:27:29,360 Add graphite plus oxygen, 671 00:27:29,720 --> 00:27:34,279 you start making carbon dioxide. 672 00:27:32,279 --> 00:27:37,559 So, graphite burns when it's hot. And as 673 00:27:34,279 --> 00:27:37,559 you could see from the video, 674 00:27:39,119 --> 00:27:44,119 where is that nice still of 675 00:27:42,240 --> 00:27:45,559 mol- burning graphite? Yeah. That 676 00:27:44,119 --> 00:27:48,079 graphite was pretty hot. So, a lot of 677 00:27:45,559 --> 00:27:50,039 that smoke included burning graphite and 678 00:27:48,079 --> 00:27:51,199 a lot of the materials from the reactor 679 00:27:50,039 --> 00:27:53,559 itself. 680 00:27:51,200 --> 00:27:55,160 Now, when you build up fission products 681 00:27:53,559 --> 00:27:57,039 in a reactor and they get volatilized 682 00:27:55,160 --> 00:27:58,400 like this, the ones that tend to get out 683 00:27:57,039 --> 00:28:00,879 first would be things like the noble 684 00:27:58,400 --> 00:28:03,080 gases. So, the whole xenon inventory of 685 00:28:00,880 --> 00:28:05,160 the reactor was released. It's estimated 686 00:28:03,079 --> 00:28:08,559 about 100%. 687 00:28:05,160 --> 00:28:10,480 And I can actually pull up those figures 688 00:28:08,559 --> 00:28:12,839 when we talk about how much of which 689 00:28:10,480 --> 00:28:14,720 radionuclide was released. 690 00:28:12,839 --> 00:28:17,119 Uh that's also a typo. If somebody wants 691 00:28:14,720 --> 00:28:20,559 to call in, there's no 33 isotope of 692 00:28:17,119 --> 00:28:21,919 xenon. It's supposed to be 133. 693 00:28:20,559 --> 00:28:23,279 Um that would be interesting if someone 694 00:28:21,920 --> 00:28:24,480 wants to call in and say the NAA's got a 695 00:28:23,279 --> 00:28:27,279 mistake. 696 00:28:24,480 --> 00:28:28,640 So, 100% of the inventory released. That 697 00:28:27,279 --> 00:28:30,200 should be pretty obvious because it's a 698 00:28:28,640 --> 00:28:31,200 noble gas and it just kind of floats 699 00:28:30,200 --> 00:28:33,440 away. 700 00:28:31,200 --> 00:28:35,799 The real dangers, though, came from 701 00:28:33,440 --> 00:28:37,600 iodine 131, 702 00:28:35,799 --> 00:28:41,200 about 50% 703 00:28:37,599 --> 00:28:43,599 of a three exabecquerel activity. 704 00:28:41,200 --> 00:28:45,200 So, we're talking like megacuries or 705 00:28:43,599 --> 00:28:47,559 might be giga. I can't do that math in 706 00:28:45,200 --> 00:28:49,679 my head. Lot a lot of radiation. And the 707 00:28:47,559 --> 00:28:52,918 problem with that is iodine behaves just 708 00:28:49,679 --> 00:28:54,519 like any other halogen. It forms salts. 709 00:28:52,919 --> 00:28:57,320 It's rather volatile. Have any of you 710 00:28:54,519 --> 00:28:59,279 guys played with iodine before? 711 00:28:57,319 --> 00:29:01,559 Uh no one does Oh, you have. Okay. What 712 00:28:59,279 --> 00:29:02,319 happens when you play with it? I mean, 713 00:29:01,559 --> 00:29:04,799 it just 714 00:29:02,319 --> 00:29:07,039 absorbs the stuff like 715 00:29:04,799 --> 00:29:10,399 for instance, everything 716 00:29:07,039 --> 00:29:12,440 and it just reacts with like acids and 717 00:29:10,400 --> 00:29:13,720 stuff. I haven't done very much with it, 718 00:29:12,440 --> 00:29:15,360 so. Okay. 719 00:29:13,720 --> 00:29:17,039 I happen to have extensive practice 720 00:29:15,359 --> 00:29:18,119 playing with iodine in my home cuz I did 721 00:29:17,039 --> 00:29:19,759 all the stuff you're not supposed to do 722 00:29:18,119 --> 00:29:21,479 as a kid. Going to build your own 723 00:29:19,759 --> 00:29:22,559 chemistry stuff, things that somehow, 724 00:29:21,480 --> 00:29:24,360 you know, leak out of your local high 725 00:29:22,559 --> 00:29:27,039 school, somehow. 726 00:29:24,359 --> 00:29:29,918 Iodine's pretty neat. 727 00:29:27,039 --> 00:29:31,480 Yeah, it happens sometimes. Um if you 728 00:29:29,919 --> 00:29:33,600 put iodine in your hand, it actually 729 00:29:31,480 --> 00:29:35,880 sublimes. The heat from your hand is 730 00:29:33,599 --> 00:29:39,119 enough to directly go from solid to 731 00:29:35,880 --> 00:29:40,880 vapor. And so, the iodine was also quite 732 00:29:39,119 --> 00:29:42,399 volatile. Some of it may have been in 733 00:29:40,880 --> 00:29:44,280 the form of other compounds, some of it 734 00:29:42,400 --> 00:29:45,759 may have been elemental, probably not 735 00:29:44,279 --> 00:29:47,799 likely, but there was certainly some 736 00:29:45,759 --> 00:29:50,400 iodine vapor, and about half of that was 737 00:29:47,799 --> 00:29:53,839 released. The problem is then it 738 00:29:50,400 --> 00:29:56,280 condenses out and falls on anything 739 00:29:53,839 --> 00:29:57,839 green, anything with surface area. So, 740 00:29:56,279 --> 00:30:01,599 the biggest danger to the folks living 741 00:29:57,839 --> 00:30:03,519 nearby was from eating leafy vegetables 742 00:30:01,599 --> 00:30:05,559 because the the leaves that leaves got 743 00:30:03,519 --> 00:30:07,639 lots of surface area, iodine deposits on 744 00:30:05,559 --> 00:30:10,440 them, and it's intensely radioactive for 745 00:30:07,640 --> 00:30:12,280 a month or so or depositing on the grass 746 00:30:10,440 --> 00:30:14,080 that cows eat, which led to the problem 747 00:30:12,279 --> 00:30:16,119 of radioactive milk. 748 00:30:14,079 --> 00:30:17,839 And so, that's why milk in the Soviet 749 00:30:16,119 --> 00:30:19,000 Union was banned for such a long time 750 00:30:17,839 --> 00:30:22,079 because this was one of the major 751 00:30:19,000 --> 00:30:23,759 sources of iodine contamination. 752 00:30:22,079 --> 00:30:27,679 The other one which we're worrying about 753 00:30:23,759 --> 00:30:29,480 now from Fukushima as well is cesium 754 00:30:27,680 --> 00:30:31,840 which has similar chemistry to sodium 755 00:30:29,480 --> 00:30:33,079 and potassium, again a rather salty 756 00:30:31,839 --> 00:30:34,879 compound 757 00:30:33,079 --> 00:30:37,079 or rather salty element, but it's got a 758 00:30:34,880 --> 00:30:38,560 half-life of 30 years. 759 00:30:37,079 --> 00:30:40,279 And if we look it up in the table of 760 00:30:38,559 --> 00:30:42,799 nuclides 761 00:30:40,279 --> 00:30:45,319 we'll see what it actually releases. Oh, 762 00:30:42,799 --> 00:30:47,159 good. It's back online. 763 00:30:45,319 --> 00:30:48,879 Anyone else notice this broken couple 764 00:30:47,160 --> 00:30:50,240 days ago? 765 00:30:48,880 --> 00:30:52,080 Yeah. 766 00:30:50,240 --> 00:30:54,599 Well, luckily Brookhaven National Lab 767 00:30:52,079 --> 00:30:57,759 has a good version up, too. But, let's 768 00:30:54,599 --> 00:31:00,000 grab cesium. 769 00:30:57,759 --> 00:31:02,240 Yeah, there's plenty out there. 770 00:31:00,000 --> 00:31:04,359 Cesium 137 771 00:31:02,240 --> 00:31:07,720 beta decays to barium, but also gives 772 00:31:04,359 --> 00:31:10,079 off gamma rays, and most of the decays 773 00:31:07,720 --> 00:31:13,440 end up giving off one of those gamma 774 00:31:10,079 --> 00:31:15,639 rays. Let's say a 660 keV gamma ray. So, 775 00:31:13,440 --> 00:31:17,360 it's both a beta and a gamma emitter. 776 00:31:15,640 --> 00:31:18,840 Now, which of those types of radiation 777 00:31:17,359 --> 00:31:20,919 do you think is more damaging to 778 00:31:18,839 --> 00:31:24,119 biological organisms? 779 00:31:20,920 --> 00:31:24,120 The beta or the gamma? 780 00:31:24,319 --> 00:31:28,960 You say the gamma. Why do you say so? 781 00:31:27,119 --> 00:31:30,719 Doesn't beta get stopped by like skin or 782 00:31:28,960 --> 00:31:33,440 clothing? It does. 783 00:31:30,720 --> 00:31:35,400 But, if cesium is better known as 784 00:31:33,440 --> 00:31:37,960 Yes. 785 00:31:35,400 --> 00:31:39,519 That's right. So Did I get to tell you 786 00:31:37,960 --> 00:31:41,920 guys this question, the four cookies 787 00:31:39,519 --> 00:31:42,759 question? 788 00:31:41,920 --> 00:31:44,440 Yeah. 789 00:31:42,759 --> 00:31:46,079 You eat the gamma cookie because most 790 00:31:44,440 --> 00:31:47,440 gammas that are emitted by the cookie 791 00:31:46,079 --> 00:31:48,879 simply leave you and irradiate your 792 00:31:47,440 --> 00:31:51,160 friend, which is going to be the topic 793 00:31:48,880 --> 00:31:52,560 of piece at number eight. 794 00:31:51,160 --> 00:31:54,600 You'll see. That's why you guys are 795 00:31:52,559 --> 00:31:56,079 getting your whole body counts. Speaking 796 00:31:54,599 --> 00:31:58,839 of, who's who's gotten their whole body 797 00:31:56,079 --> 00:32:00,759 counts at DHS? 798 00:31:58,839 --> 00:32:02,399 Awesome. So, that's almost everybody. 799 00:32:00,759 --> 00:32:04,879 You will need that data for problem set 800 00:32:02,400 --> 00:32:06,400 eight. So, do schedule it soon. 801 00:32:04,880 --> 00:32:08,040 Preferably before Thanksgiving so that 802 00:32:06,400 --> 00:32:09,920 you'll be able to take a look at it. Has 803 00:32:08,039 --> 00:32:12,319 anyone found anything interesting in 804 00:32:09,920 --> 00:32:14,160 your spectra? 805 00:32:12,319 --> 00:32:15,919 Good. 806 00:32:14,160 --> 00:32:18,000 Glad to hear that. 807 00:32:15,920 --> 00:32:20,480 But, you do see a potassium peak that 808 00:32:18,000 --> 00:32:22,440 you can probably integrate and do some 809 00:32:20,480 --> 00:32:24,759 problems with, right? 810 00:32:22,440 --> 00:32:27,200 Yeah, cuz you will. Okay. 811 00:32:24,759 --> 00:32:29,400 Anyway, yeah, it's the betas. That's the 812 00:32:27,200 --> 00:32:31,720 real killer. The gammas are going to 813 00:32:29,400 --> 00:32:33,679 leave the cesium, enter your body, and 814 00:32:31,720 --> 00:32:37,759 most likely come out the other side. 815 00:32:33,679 --> 00:32:41,280 Because the mass attenuation coefficient 816 00:32:37,759 --> 00:32:44,920 of six What is it? Water for 660 keV 817 00:32:41,279 --> 00:32:46,399 gammas, let's find that. 818 00:32:44,920 --> 00:32:51,440 Table three. 819 00:32:46,400 --> 00:32:51,440 Let's say you're made mostly of water. 820 00:32:53,279 --> 00:32:56,920 Water, liquid. That's pretty much 821 00:32:55,079 --> 00:32:59,919 humans. 822 00:32:56,920 --> 00:33:03,920 660 keV is right about here leading to 823 00:32:59,920 --> 00:33:06,240 about 0.1 cm squared per gram, and with 824 00:33:03,920 --> 00:33:08,880 a density of 1 g, that's a pretty low 825 00:33:06,240 --> 00:33:10,640 attenuation of gammas. So, this chart 826 00:33:08,880 --> 00:33:12,480 actually shows why most of the cesium 827 00:33:10,640 --> 00:33:13,880 gammas that would be produced from 828 00:33:12,480 --> 00:33:15,960 ingestion just get right out, but it's 829 00:33:13,880 --> 00:33:17,520 the betas that have an awfully short 830 00:33:15,960 --> 00:33:20,120 range. 831 00:33:17,519 --> 00:33:22,240 Anyone remember the formula for range 832 00:33:20,119 --> 00:33:23,479 in general? 833 00:33:22,240 --> 00:33:25,480 Cuz it's going to come back up in our 834 00:33:23,480 --> 00:33:28,079 discussion of dose and biological 835 00:33:25,480 --> 00:33:28,079 effects. 836 00:33:29,920 --> 00:33:33,840 Integral of 837 00:33:32,160 --> 00:33:36,160 Yep, of stopping power to the negative 838 00:33:33,839 --> 00:33:36,159 one. 839 00:33:36,599 --> 00:33:42,678 And that stopping power 840 00:33:38,679 --> 00:33:42,679 is this simple formula. 841 00:33:49,039 --> 00:33:54,559 Let's see. What did that come out as? 842 00:33:57,400 --> 00:34:01,960 log minus beta squared. Ah, simple 843 00:34:00,599 --> 00:34:03,119 little formula. 844 00:34:01,960 --> 00:34:05,039 Which I'm not going to expect you guys 845 00:34:03,119 --> 00:34:06,239 to memorize, so don't worry about it. 846 00:34:05,039 --> 00:34:07,879 But 847 00:34:06,240 --> 00:34:09,679 if you integrate this, you find out that 848 00:34:07,880 --> 00:34:11,878 the range of electrons, even 1 MeV 849 00:34:09,679 --> 00:34:14,559 electrons in water, is not very high. 850 00:34:11,878 --> 00:34:17,519 So, most of them are stopped near or by 851 00:34:14,559 --> 00:34:19,840 the cells that absorb them doing quite a 852 00:34:17,519 --> 00:34:21,840 bit of damage to the DNA, which is 853 00:34:19,840 --> 00:34:24,200 eventually what causes mutagenic 854 00:34:21,840 --> 00:34:25,800 effects, cancer, cell death what we're 855 00:34:24,199 --> 00:34:28,439 going to talk about for the whole third 856 00:34:25,800 --> 00:34:29,960 part of the course. 857 00:34:28,440 --> 00:34:32,320 There's also 858 00:34:29,960 --> 00:34:35,039 a worry about which organs actually 859 00:34:32,320 --> 00:34:38,080 absorb these radionuclides, and iodine 860 00:34:35,039 --> 00:34:39,639 in particular is preferentially absorbed 861 00:34:38,079 --> 00:34:40,799 by the thyroid. 862 00:34:39,639 --> 00:34:43,119 So, when we started looking at the 863 00:34:40,800 --> 00:34:44,760 amount of radioactive substances 864 00:34:43,119 --> 00:34:46,079 released, remember they said, "Okay, at 865 00:34:44,760 --> 00:34:48,280 the round 866 00:34:46,079 --> 00:34:50,918 26th of April or the 2nd of May or so, 867 00:34:48,280 --> 00:34:52,840 the release was stopped." Not according 868 00:34:50,918 --> 00:34:55,519 to our data. That's when the graphite 869 00:34:52,840 --> 00:34:58,680 fire picked up again. In addition, the 870 00:34:55,519 --> 00:35:01,400 core of Chernobyl which had undergone a 871 00:34:58,679 --> 00:35:04,358 mostly total meltdown 872 00:35:01,400 --> 00:35:07,559 was sitting in a pool 873 00:35:04,358 --> 00:35:09,440 on top of this concrete pad. 874 00:35:07,559 --> 00:35:11,279 So, let's just call this liquid stuff 875 00:35:09,440 --> 00:35:13,639 The actual word that we use in parlance 876 00:35:11,280 --> 00:35:15,960 is called corium. 877 00:35:13,639 --> 00:35:17,319 It's our tongue-in-cheek word for every 878 00:35:15,960 --> 00:35:19,039 element mixed together in a hot 879 00:35:17,320 --> 00:35:20,760 radioactive soup. 880 00:35:19,039 --> 00:35:22,599 It's First of all, it started to 881 00:35:20,760 --> 00:35:24,840 redistribute reacting with any water 882 00:35:22,599 --> 00:35:26,239 that was present, flashing it to steam, 883 00:35:24,840 --> 00:35:28,240 and the steam caused additional 884 00:35:26,239 --> 00:35:29,919 dispersion of radionuclides, and 885 00:35:28,239 --> 00:35:31,559 eventually 886 00:35:29,920 --> 00:35:32,720 it burrowed its way through and into the 887 00:35:31,559 --> 00:35:35,519 ground 888 00:35:32,719 --> 00:35:37,358 releasing more. You know, it's it's uh 889 00:35:35,519 --> 00:35:38,960 it's the worst nuclear thing that's ever 890 00:35:37,358 --> 00:35:40,759 happened in the history of nuclear 891 00:35:38,960 --> 00:35:42,000 things. 892 00:35:40,760 --> 00:35:44,359 Quite a mess. 893 00:35:42,000 --> 00:35:46,559 And luckily, it did sort of taper off 894 00:35:44,358 --> 00:35:48,759 after this. 895 00:35:46,559 --> 00:35:51,000 But, let's now look into 896 00:35:48,760 --> 00:35:53,080 what happens next. And this is the nice 897 00:35:51,000 --> 00:35:55,920 intro to the third part of the course. 898 00:35:53,079 --> 00:35:57,679 Iodine is is preferentially uptaken by 899 00:35:55,920 --> 00:35:58,680 the thyroid gland somewhere right about 900 00:35:57,679 --> 00:36:00,559 here. 901 00:35:58,679 --> 00:36:02,879 Um so, has anyone ever heard of the idea 902 00:36:00,559 --> 00:36:04,559 of taking iodine tablets in the case of 903 00:36:02,880 --> 00:36:07,760 a nuclear disaster? 904 00:36:04,559 --> 00:36:07,759 Anyone have any idea why? 905 00:36:09,480 --> 00:36:13,599 If you saturate your thyroid with 906 00:36:11,199 --> 00:36:15,000 iodine, then if you ingest radioactive 907 00:36:13,599 --> 00:36:18,239 iodine, it's less likely to be 908 00:36:15,000 --> 00:36:21,119 permanently uptaken by the thyroid. So, 909 00:36:18,239 --> 00:36:23,439 this actually provided some statistics 910 00:36:21,119 --> 00:36:26,079 on the probability of getting thyroid 911 00:36:23,440 --> 00:36:27,480 cancer from radioactive iodine 912 00:36:26,079 --> 00:36:29,519 ingestion. 913 00:36:27,480 --> 00:36:31,199 Luckily, the statistics were quite poor, 914 00:36:29,519 --> 00:36:34,320 which means that not many people were 915 00:36:31,199 --> 00:36:35,480 exposed. It was somewhere around 1,300 916 00:36:34,320 --> 00:36:38,200 or so. 917 00:36:35,480 --> 00:36:39,440 Not like millions. Yeah, 1,300 people 918 00:36:38,199 --> 00:36:42,119 total. 919 00:36:39,440 --> 00:36:44,840 But, what I want to jump to is the dose 920 00:36:42,119 --> 00:36:47,559 versus risk curve. And this is going to 921 00:36:44,840 --> 00:36:49,400 apply all of our discussion about the 922 00:36:47,559 --> 00:36:50,799 biological long-term effects of 923 00:36:49,400 --> 00:36:53,358 radioactivity. 924 00:36:50,800 --> 00:36:56,600 What's the most striking thing you see 925 00:36:53,358 --> 00:36:56,599 as part of this curve? 926 00:36:56,920 --> 00:37:00,358 That's That's right. That's the first 927 00:36:58,880 --> 00:37:03,079 thing I saw. 928 00:37:00,358 --> 00:37:05,000 There are six different models for how 929 00:37:03,079 --> 00:37:07,519 dose and increased risk of cancer 930 00:37:05,000 --> 00:37:09,800 proceeds, and they all fall within 931 00:37:07,519 --> 00:37:11,159 almost all the error bars of these 932 00:37:09,800 --> 00:37:13,160 measurements. 933 00:37:11,159 --> 00:37:15,119 I'll say again, thank God that the error 934 00:37:13,159 --> 00:37:17,480 bars are so high because that means that 935 00:37:15,119 --> 00:37:19,480 the sample size was so low. 936 00:37:17,480 --> 00:37:22,199 So, when folks say we don't really know 937 00:37:19,480 --> 00:37:24,519 how much radioactivity causes how much 938 00:37:22,199 --> 00:37:26,199 cancer, they're right because luckily, 939 00:37:24,519 --> 00:37:28,639 we don't have enough data from people 940 00:37:26,199 --> 00:37:29,879 being exposed to know that really, 941 00:37:28,639 --> 00:37:31,159 really well. 942 00:37:29,880 --> 00:37:33,400 So, some folks say we should be 943 00:37:31,159 --> 00:37:35,039 cautious. I kind of agree with them. 944 00:37:33,400 --> 00:37:37,639 Some folks say the jury's still out. I 945 00:37:35,039 --> 00:37:39,119 also agree with them. 946 00:37:37,639 --> 00:37:41,159 But, you can start to estimate these 947 00:37:39,119 --> 00:37:44,119 sorts of things by knowing how much 948 00:37:41,159 --> 00:37:45,519 radiation energy was absorbed and to 949 00:37:44,119 --> 00:37:47,159 what organ. 950 00:37:45,519 --> 00:37:49,159 So, I think the only technical thing I 951 00:37:47,159 --> 00:37:51,119 want to go over today 952 00:37:49,159 --> 00:37:52,639 is the different units of dose because 953 00:37:51,119 --> 00:37:54,319 as you start to read things in the 954 00:37:52,639 --> 00:37:55,920 reading, which I recommend you do if you 955 00:37:54,320 --> 00:37:57,760 haven't been doing yet, you're going to 956 00:37:55,920 --> 00:38:00,599 encounter a lot of different units of 957 00:37:57,760 --> 00:38:03,320 radiation dose ranging from things like 958 00:38:00,599 --> 00:38:03,319 the roentgen 959 00:38:04,400 --> 00:38:09,720 which responds to a number of 960 00:38:06,719 --> 00:38:09,719 ionizations. 961 00:38:10,320 --> 00:38:15,720 You won't usually see this one 962 00:38:12,760 --> 00:38:17,359 given in sort of biological parlance 963 00:38:15,719 --> 00:38:19,599 because it's the number of ionizations 964 00:38:17,358 --> 00:38:21,920 detected by some sort of gaseous 965 00:38:19,599 --> 00:38:23,880 ionization detector. So, the dosimeters 966 00:38:21,920 --> 00:38:25,358 that you all put on the Did you guys all 967 00:38:23,880 --> 00:38:27,200 bring these uh 968 00:38:25,358 --> 00:38:29,639 these like brass 969 00:38:27,199 --> 00:38:30,960 pen dosimeters into the reactor? Anyone 970 00:38:29,639 --> 00:38:33,519 look through them to see what the unit 971 00:38:30,960 --> 00:38:34,800 of dose was? 972 00:38:33,519 --> 00:38:37,679 It's going to be in roentgens cuz that's 973 00:38:34,800 --> 00:38:39,480 directly correlatable to the number of 974 00:38:37,679 --> 00:38:42,159 ionizations that that dosimeter has 975 00:38:39,480 --> 00:38:44,358 experienced. You'll also see four dose 976 00:38:42,159 --> 00:38:46,279 units, two of which are just factors of 977 00:38:44,358 --> 00:38:49,799 100 away from each other. There is 978 00:38:46,280 --> 00:38:52,840 what's called the rad and the gray 979 00:38:49,800 --> 00:38:55,880 and there's what's called the rem 980 00:38:52,840 --> 00:38:55,880 and the sievert. 981 00:38:57,760 --> 00:39:03,040 You'll see these approximated as gray. 982 00:39:00,400 --> 00:39:05,639 You'll see these as R, and these are 983 00:39:03,039 --> 00:39:08,920 just usually written as rem. 984 00:39:05,639 --> 00:39:10,358 So, a rad is simple. 985 00:39:08,920 --> 00:39:13,240 Let's see. 986 00:39:10,358 --> 00:39:15,440 100 rads 987 00:39:13,239 --> 00:39:17,358 is the same as 1 gray. 988 00:39:15,440 --> 00:39:20,800 And 100 rem 989 00:39:17,358 --> 00:39:23,440 is the same as 1 sievert. And for gamma 990 00:39:20,800 --> 00:39:26,120 for the case of gamma radiation 991 00:39:23,440 --> 00:39:28,639 these units are actually equal. 992 00:39:26,119 --> 00:39:30,199 I particularly like this set of units 993 00:39:28,639 --> 00:39:32,879 because 994 00:39:30,199 --> 00:39:34,679 this is the kind of SI of radiation 995 00:39:32,880 --> 00:39:36,880 units because it comes directly from 996 00:39:34,679 --> 00:39:38,639 measurable, calculatable quantities. 997 00:39:36,880 --> 00:39:40,119 Like the gray, for example, the actual 998 00:39:38,639 --> 00:39:42,679 unit of gray 999 00:39:40,119 --> 00:39:45,199 is joules absorbed 1000 00:39:42,679 --> 00:39:47,480 per kilogram of absorber. 1001 00:39:45,199 --> 00:39:49,359 It's a pretty simple unit to understand. 1002 00:39:47,480 --> 00:39:52,039 If you know how many radioactive 1003 00:39:49,360 --> 00:39:54,200 particles or gammas or whatever that you 1004 00:39:52,039 --> 00:39:56,759 have absorbed, you can multiply that 1005 00:39:54,199 --> 00:39:59,119 number by their energy, divide by the 1006 00:39:56,760 --> 00:40:01,040 mass of the organ absorbing them, and 1007 00:39:59,119 --> 00:40:02,920 you get its dose in gray. 1008 00:40:01,039 --> 00:40:04,920 Sievert 1009 00:40:02,920 --> 00:40:07,240 is gray 1010 00:40:04,920 --> 00:40:09,960 times some quality factor for the 1011 00:40:07,239 --> 00:40:09,959 radiation 1012 00:40:10,960 --> 00:40:17,679 times some quality factor 1013 00:40:14,159 --> 00:40:20,239 for the specific type of tissue. 1014 00:40:17,679 --> 00:40:22,639 What this says is that some types of 1015 00:40:20,239 --> 00:40:25,759 radiation are more effective at causing 1016 00:40:22,639 --> 00:40:27,719 damage than others, and some organs are 1017 00:40:25,760 --> 00:40:29,920 more susceptible to radiation damage 1018 00:40:27,719 --> 00:40:31,359 than others. Does anyone happen to know 1019 00:40:29,920 --> 00:40:35,519 some of the organs that are most 1020 00:40:31,360 --> 00:40:35,519 susceptible to radiation damage? 1021 00:40:38,079 --> 00:40:42,679 Soft tissues like what? Cuz there's lots 1022 00:40:40,159 --> 00:40:42,679 of those. 1023 00:40:43,760 --> 00:40:50,640 Stomach lining, yep. Yep. Huh? 1024 00:40:46,880 --> 00:40:50,640 Lungs? Yep. What else? 1025 00:40:51,199 --> 00:40:55,599 Thyroid. Yep, there there is definitely 1026 00:40:53,519 --> 00:40:57,519 one for thyroid. 1027 00:40:55,599 --> 00:41:00,519 Bone marrow. 1028 00:40:57,519 --> 00:41:00,519 What other ones? 1029 00:41:00,639 --> 00:41:05,440 Y'all, 1030 00:41:01,719 --> 00:41:07,319 brain actually not so much. Eyes. 1031 00:41:05,440 --> 00:41:10,720 And where else do you find rapidly 1032 00:41:07,320 --> 00:41:14,519 dividing cells in your body? 1033 00:41:10,719 --> 00:41:14,519 Skin? Yep, the dermis. 1034 00:41:14,559 --> 00:41:17,759 I don't know about the liver. I would 1035 00:41:16,159 --> 00:41:19,079 assume so. Yeah, it's a pretty active 1036 00:41:17,760 --> 00:41:20,720 organ. 1037 00:41:19,079 --> 00:41:22,440 But when folks are worried about birth 1038 00:41:20,719 --> 00:41:24,559 defects 1039 00:41:22,440 --> 00:41:26,760 reproductive organs. 1040 00:41:24,559 --> 00:41:28,079 The link here that for some reason is 1041 00:41:26,760 --> 00:41:30,240 not said in the reading and I've never 1042 00:41:28,079 --> 00:41:33,159 figured out why is the more often a cell 1043 00:41:30,239 --> 00:41:35,559 is dividing the more susceptible it is 1044 00:41:33,159 --> 00:41:38,679 to gaining cancer risk because every 1045 00:41:35,559 --> 00:41:41,239 cell division is a copy of its DNA. 1046 00:41:38,679 --> 00:41:44,079 And anytime that radiation goes in and 1047 00:41:41,239 --> 00:41:45,719 damages or changes that DNA by either 1048 00:41:44,079 --> 00:41:47,759 causing what's called a thymine bridge 1049 00:41:45,719 --> 00:41:49,759 where two thymine bases get linked 1050 00:41:47,760 --> 00:41:52,360 together or damaging the structure in 1051 00:41:49,760 --> 00:41:54,120 some other way, that gene is then 1052 00:41:52,360 --> 00:41:56,360 replicated and the faster they're 1053 00:41:54,119 --> 00:41:59,440 replicating the more likely cancer is 1054 00:41:56,360 --> 00:42:01,200 going to become apparent. 1055 00:41:59,440 --> 00:42:03,480 I guess that this brings up a question, 1056 00:42:01,199 --> 00:42:05,319 when does a rapidly dividing cell become 1057 00:42:03,480 --> 00:42:07,519 cancer? Is it division number one or is 1058 00:42:05,320 --> 00:42:08,600 it when you notice it? 1059 00:42:07,519 --> 00:42:10,079 I guess I'll leave that question to the 1060 00:42:08,599 --> 00:42:12,239 biologists. 1061 00:42:10,079 --> 00:42:13,519 But if you notice in the reading you'll 1062 00:42:12,239 --> 00:42:15,839 see a bunch of different tissue 1063 00:42:13,519 --> 00:42:17,519 equivalency factors. 1064 00:42:15,840 --> 00:42:19,760 And you'll just see them tabulated and 1065 00:42:17,519 --> 00:42:21,400 say there they are, memorize them. I 1066 00:42:19,760 --> 00:42:23,640 want you to try and think of the pattern 1067 00:42:21,400 --> 00:42:26,200 between them. The tissues that basically 1068 00:42:23,639 --> 00:42:29,759 don't matter like the non-marrow part of 1069 00:42:26,199 --> 00:42:31,719 the bone, dead skin cells, muscles, 1070 00:42:29,760 --> 00:42:33,960 things that basically aren't listed that 1071 00:42:31,719 --> 00:42:35,639 much, they're not dividing very fast. 1072 00:42:33,960 --> 00:42:38,079 But anywhere where you find stem cells, 1073 00:42:35,639 --> 00:42:40,119 the lining of your intestine, your lungs 1074 00:42:38,079 --> 00:42:42,519 which undergo a lot of environmental 1075 00:42:40,119 --> 00:42:44,799 damage need to be replenished, gonads, 1076 00:42:42,519 --> 00:42:46,840 dermis, what was the other one that we 1077 00:42:44,800 --> 00:42:47,920 said? Eyes. 1078 00:42:46,840 --> 00:42:49,840 These are places that are either 1079 00:42:47,920 --> 00:42:51,760 sensitive tissues or they're rapidly 1080 00:42:49,840 --> 00:42:54,400 dividing. 1081 00:42:51,760 --> 00:42:57,360 And so the sievert is kind of an a unit 1082 00:42:54,400 --> 00:42:59,639 of increased equivalent risk. So that if 1083 00:42:57,360 --> 00:43:03,079 you were to absorb one gray of gamma 1084 00:42:59,639 --> 00:43:05,799 rays versus one gray of alphas, you'd be 1085 00:43:03,079 --> 00:43:07,880 about 20 times more likely to incur 1086 00:43:05,800 --> 00:43:09,680 cancer from the alphas than the gammas 1087 00:43:07,880 --> 00:43:10,880 because the amount of localized damage 1088 00:43:09,679 --> 00:43:13,679 that they do to cells. And we'll be 1089 00:43:10,880 --> 00:43:15,960 doing all this in detail pretty soon. 1090 00:43:13,679 --> 00:43:18,159 And then for tissue equivalency factor, 1091 00:43:15,960 --> 00:43:20,760 if you absorb one gray in your whole 1092 00:43:18,159 --> 00:43:22,839 body, which means one joule per kilogram 1093 00:43:20,760 --> 00:43:24,960 of average body mass 1094 00:43:22,840 --> 00:43:27,360 versus one gray directly to the lining 1095 00:43:24,960 --> 00:43:29,280 of your intestine by let's say drinking 1096 00:43:27,360 --> 00:43:32,320 polonium-laced tea 1097 00:43:29,280 --> 00:43:34,519 like happened to a poor ex was it 1098 00:43:32,320 --> 00:43:35,840 current or ex-KGB guy? One of the 1099 00:43:34,519 --> 00:43:37,320 Russian fellows? 1100 00:43:35,840 --> 00:43:38,559 No, it's the KGB guys that poisoned him, 1101 00:43:37,320 --> 00:43:40,559 right? 1102 00:43:38,559 --> 00:43:41,440 Yeah, you guys remember back in 2010 or 1103 00:43:40,559 --> 00:43:43,519 so? 1104 00:43:41,440 --> 00:43:46,240 There was a Russian 1105 00:43:43,519 --> 00:43:49,519 Was he a journalist? 1106 00:43:46,239 --> 00:43:51,759 Ex-KGB. So the current KGB somehow got 1107 00:43:49,519 --> 00:43:55,599 into London and slipped polonium into 1108 00:43:51,760 --> 00:43:55,600 his tea at a Japanese restaurant. 1109 00:43:56,880 --> 00:44:00,079 Uh, really? 1110 00:44:01,280 --> 00:44:04,560 What was his name? 1111 00:44:04,880 --> 00:44:08,000 Let's see. 1112 00:44:08,760 --> 00:44:14,960 Then polonium 1113 00:44:12,000 --> 00:44:19,039 poisoning. Did he actually die? 1114 00:44:14,960 --> 00:44:19,039 Poisoning of Alexander Litvinenko. 1115 00:44:23,679 --> 00:44:26,759 He's not doing too well. 1116 00:44:27,639 --> 00:44:32,480 Illness and poisoning, death and last 1117 00:44:29,679 --> 00:44:32,480 statement. 1118 00:44:32,599 --> 00:44:37,358 At the hospital in London. So, yeah. 1119 00:44:37,800 --> 00:44:42,000 Well 1120 00:44:39,840 --> 00:44:44,680 interesting. That probably has something 1121 00:44:42,000 --> 00:44:44,679 to do with it. 1122 00:44:44,960 --> 00:44:48,039 Yeah? Well 1123 00:44:46,840 --> 00:44:49,880 all right, we're not going to comment on 1124 00:44:48,039 --> 00:44:53,679 the politics, but the the radiation 1125 00:44:49,880 --> 00:44:55,640 effect worked clearly, unfortunately. So 1126 00:44:53,679 --> 00:44:58,279 polonium is an alpha emitter and that 1127 00:44:55,639 --> 00:45:00,799 caused a massive dose of alphas to his 1128 00:44:58,280 --> 00:45:02,720 entire gastrointestinal tract. And that 1129 00:45:00,800 --> 00:45:04,720 caused a whole lot of damage to those 1130 00:45:02,719 --> 00:45:06,799 cells. No time for cancer. It actually 1131 00:45:04,719 --> 00:45:08,319 killed off a lot of those stem cells. 1132 00:45:06,800 --> 00:45:10,200 And the way that radiation poisoning 1133 00:45:08,320 --> 00:45:12,280 would work is that if you kill off the 1134 00:45:10,199 --> 00:45:14,279 stem cells, the villi in your intestine 1135 00:45:12,280 --> 00:45:17,400 die which are responsible for absorbing 1136 00:45:14,280 --> 00:45:19,320 nutrition. You can't uptake nutrition. 1137 00:45:17,400 --> 00:45:22,079 You basically starve. Doesn't matter 1138 00:45:19,320 --> 00:45:24,240 what you eat. It's messed up. 1139 00:45:22,079 --> 00:45:26,079 Yeah. 1140 00:45:24,239 --> 00:45:27,599 That's a really bad way to go. It's 1141 00:45:26,079 --> 00:45:30,559 called gastrointestinal syndrome. And 1142 00:45:27,599 --> 00:45:33,239 we'll be talking about the progressive 1143 00:45:30,559 --> 00:45:35,279 effects of acute radiation exposure 1144 00:45:33,239 --> 00:45:38,639 where you have immediate effects mostly 1145 00:45:35,280 --> 00:45:40,519 relating to the death of some organ that 1146 00:45:38,639 --> 00:45:43,119 is responsible for either cell division 1147 00:45:40,519 --> 00:45:45,119 to keep you alive or in extreme cases 1148 00:45:43,119 --> 00:45:46,559 your neurological system and nerve 1149 00:45:45,119 --> 00:45:48,920 function just stops at the highest 1150 00:45:46,559 --> 00:45:53,000 levels of dose. And that corresponds to 1151 00:45:48,920 --> 00:45:56,200 doses of around 4 to 6 gray. 4 to 6 1152 00:45:53,000 --> 00:45:59,039 joules per kilogram of villi or body 1153 00:45:56,199 --> 00:46:00,759 mass will kill you pretty quickly with 1154 00:45:59,039 --> 00:46:02,079 very little chance of survival as what 1155 00:46:00,760 --> 00:46:03,720 happened here. 1156 00:46:02,079 --> 00:46:06,559 And so this was the problem with all the 1157 00:46:03,719 --> 00:46:09,919 folks living around and near Chernobyl 1158 00:46:06,559 --> 00:46:11,400 and Ukraine and Belarus and everywhere 1159 00:46:09,920 --> 00:46:14,760 was the contamination was pretty 1160 00:46:11,400 --> 00:46:16,519 extensive. Uh, about 4,000 people are 1161 00:46:14,760 --> 00:46:18,280 estimated to have died or contracted 1162 00:46:16,519 --> 00:46:20,559 cancer from this. I can't believe how 1163 00:46:18,280 --> 00:46:22,440 low that number is, but it's still 4,000 1164 00:46:20,559 --> 00:46:25,199 people that it should never happen to. 1165 00:46:22,440 --> 00:46:27,358 And effects were felt far away in towns 1166 00:46:25,199 --> 00:46:29,719 like Gomel and I can't read that one cuz 1167 00:46:27,358 --> 00:46:32,079 there's not enough pixels. Um, because 1168 00:46:29,719 --> 00:46:34,519 of the way that let's say rainwater 1169 00:46:32,079 --> 00:46:36,079 whisked or let's say um, the vapor cloud 1170 00:46:34,519 --> 00:46:37,719 from the reactor was whisked away, 1171 00:46:36,079 --> 00:46:40,279 rainwater caused it to fall on certain 1172 00:46:37,719 --> 00:46:42,879 places which still to this day can have 1173 00:46:40,280 --> 00:46:44,560 a really large contamination area. 1174 00:46:42,880 --> 00:46:46,039 And this brings me a little bit into 1175 00:46:44,559 --> 00:46:48,519 what should we be worried about from 1176 00:46:46,039 --> 00:46:51,039 Fukushima? A whole lot less than 1177 00:46:48,519 --> 00:46:53,039 Chernobyl. And the reason why is 1178 00:46:51,039 --> 00:46:55,920 Fukushima did undergo a hydrogen 1179 00:46:53,039 --> 00:46:59,320 explosion and did and still continues to 1180 00:46:55,920 --> 00:47:01,960 release cesium 137 into the ocean. 1181 00:46:59,320 --> 00:47:04,039 Luckily for us the ocean is big. 1182 00:47:01,960 --> 00:47:05,840 And except for fish caught right near 1183 00:47:04,039 --> 00:47:08,039 around Fukushima, even though 1184 00:47:05,840 --> 00:47:10,160 concentrations can be measured at 1185 00:47:08,039 --> 00:47:12,079 hundreds to thousands of times normal 1186 00:47:10,159 --> 00:47:14,239 concentrations, they can still be 1187 00:47:12,079 --> 00:47:17,639 hundreds to thousands of times lower 1188 00:47:14,239 --> 00:47:20,000 than the safe consumption. So a lot of 1189 00:47:17,639 --> 00:47:21,400 the problems you see in the news today, 1190 00:47:20,000 --> 00:47:23,519 I'm not going to call them lies, but I'm 1191 00:47:21,400 --> 00:47:26,440 going to call them half-truths. Folks 1192 00:47:23,519 --> 00:47:28,960 will show the radiation plume of cesium 1193 00:47:26,440 --> 00:47:31,720 137 escaping from Fukushima and that's 1194 00:47:28,960 --> 00:47:34,240 true. There is radiation escaping. The 1195 00:47:31,719 --> 00:47:38,399 question is is it high enough to cause a 1196 00:47:34,239 --> 00:47:40,039 noticeable increased risk of cancer? 1197 00:47:38,400 --> 00:47:42,000 That's the question that reporters 1198 00:47:40,039 --> 00:47:43,358 should be asking themselves. When they 1199 00:47:42,000 --> 00:47:45,159 only tell the half of the story that 1200 00:47:43,358 --> 00:47:46,920 gets them viewers and they don't tell 1201 00:47:45,159 --> 00:47:47,920 the half of the story to complete the 1202 00:47:46,920 --> 00:47:49,800 story 1203 00:47:47,920 --> 00:47:52,639 and tell you should you be afraid or not 1204 00:47:49,800 --> 00:47:54,800 cuz unfortunately fear brings viewers. 1205 00:47:52,639 --> 00:47:56,519 This is the problem and I'm happy to go 1206 00:47:54,800 --> 00:47:58,760 on camera saying this. This is the 1207 00:47:56,519 --> 00:48:00,519 problem with the media today 1208 00:47:58,760 --> 00:48:03,080 is with a half-truth and with a 1209 00:48:00,519 --> 00:48:05,559 half-story you can incite real panic 1210 00:48:03,079 --> 00:48:08,279 over non-physical issues that may not 1211 00:48:05,559 --> 00:48:10,480 actually exist. And so it's important 1212 00:48:08,280 --> 00:48:12,800 that the media tell the whole story. 1213 00:48:10,480 --> 00:48:15,599 Yes, it's true that Fukushima's leasing 1214 00:48:12,800 --> 00:48:17,120 releasing cesium 137. 1215 00:48:15,599 --> 00:48:18,920 How much though is the question that 1216 00:48:17,119 --> 00:48:20,199 people and the media should be asking 1217 00:48:18,920 --> 00:48:21,440 themselves. 1218 00:48:20,199 --> 00:48:23,159 And in the rest of this course we're 1219 00:48:21,440 --> 00:48:25,000 going to answer the question how much is 1220 00:48:23,159 --> 00:48:26,679 too much. 1221 00:48:25,000 --> 00:48:28,760 So I'm going to stop here 1222 00:48:26,679 --> 00:48:30,639 since it's 2 of 5 of and ask you guys if 1223 00:48:28,760 --> 00:48:31,960 you have any questions on 1224 00:48:30,639 --> 00:48:35,079 the whole second part of the course or 1225 00:48:31,960 --> 00:48:35,079 what happened in Chernobyl. 1226 00:48:37,159 --> 00:48:41,719 Yeah. Yeah, uh, could you explain the 1227 00:48:39,039 --> 00:48:43,840 quality factor or determine how you find 1228 00:48:41,719 --> 00:48:45,480 that? Yep, the quality factor Well, 1229 00:48:43,840 --> 00:48:47,960 there's two quality factors. There's the 1230 00:48:45,480 --> 00:48:49,840 quality factor for radiation which will 1231 00:48:47,960 --> 00:48:52,480 tell you how much let's say how much 1232 00:48:49,840 --> 00:48:54,160 more cell damage a given amount of a 1233 00:48:52,480 --> 00:48:57,440 given type of radiation of the same 1234 00:48:54,159 --> 00:49:00,000 energy will deposit into a cell. 1235 00:48:57,440 --> 00:49:03,400 And the tissue equivalency factor tells 1236 00:49:00,000 --> 00:49:05,400 you, well, what's the added risk of some 1237 00:49:03,400 --> 00:49:07,720 sort of defect leading to cell death or 1238 00:49:05,400 --> 00:49:10,200 cancer or some other defect 1239 00:49:07,719 --> 00:49:12,599 from that radiation absorption. 1240 00:49:10,199 --> 00:49:14,639 So to me the tissue equivalency factor 1241 00:49:12,599 --> 00:49:17,039 is roughly but not completely 1242 00:49:14,639 --> 00:49:20,079 approximated by the cell division rate 1243 00:49:17,039 --> 00:49:21,719 and the radiation quality factor is 1244 00:49:20,079 --> 00:49:23,920 going to be quite proportional to the 1245 00:49:21,719 --> 00:49:27,159 stopping power. 1246 00:49:23,920 --> 00:49:29,680 You'll see a term called the linear 1247 00:49:27,159 --> 00:49:32,358 energy transfer or LET. 1248 00:49:29,679 --> 00:49:34,519 This is the stopping power unit used in 1249 00:49:32,358 --> 00:49:36,440 the biology community. It's stopping 1250 00:49:34,519 --> 00:49:38,159 power. And luckily the Turner reading 1251 00:49:36,440 --> 00:49:41,800 actually says it somewhere buried in a 1252 00:49:38,159 --> 00:49:43,279 paragraph. LET is stopping power. So, if 1253 00:49:41,800 --> 00:49:44,480 you start plotting these two together, 1254 00:49:43,280 --> 00:49:45,720 you might find some striking 1255 00:49:44,480 --> 00:49:47,719 similarities. 1256 00:49:45,719 --> 00:49:49,959 I saw two other questions up here. 1257 00:49:47,719 --> 00:49:51,719 Yeah. Can I ask uh 1258 00:49:49,960 --> 00:49:53,559 Why is Chernobyl still considered like 1259 00:49:51,719 --> 00:49:55,039 off-limits if most of the half-lives of 1260 00:49:53,559 --> 00:49:57,159 these things were like 1261 00:49:55,039 --> 00:49:59,360 on the range of like days to 1262 00:49:57,159 --> 00:50:01,839 like 2 years? I mean, it happened in 1263 00:49:59,360 --> 00:50:03,559 Let's answer that with numbers. So, most 1264 00:50:01,840 --> 00:50:05,480 of the half-lives were on the range of 1265 00:50:03,559 --> 00:50:08,279 days to hours. 1266 00:50:05,480 --> 00:50:10,639 But, still, cesium 137 with a half-life 1267 00:50:08,280 --> 00:50:12,800 of 30 years released a third of an 1268 00:50:10,639 --> 00:50:14,440 exabecquerel. That's one of the major 1269 00:50:12,800 --> 00:50:16,480 sources of contamination still out 1270 00:50:14,440 --> 00:50:19,159 there. In addition, if we scroll down a 1271 00:50:16,480 --> 00:50:20,880 little more, 1272 00:50:19,159 --> 00:50:23,480 there was quite a bit of plutonium 1273 00:50:20,880 --> 00:50:24,559 inventory with a half-life of 24,000 1274 00:50:23,480 --> 00:50:26,280 years. 1275 00:50:24,559 --> 00:50:28,279 So, on on Friday, we're going to have 1276 00:50:26,280 --> 00:50:29,880 Jake Heckler come in and give his 1277 00:50:28,280 --> 00:50:32,480 Chernobyl travelogue, cuz one of our 1278 00:50:29,880 --> 00:50:34,160 seniors has actually been to Chernobyl. 1279 00:50:32,480 --> 00:50:36,280 And his boots were so contaminated with 1280 00:50:34,159 --> 00:50:37,639 pluto- with plutonium that he can never 1281 00:50:36,280 --> 00:50:39,840 use them again. They got to stay wrapped 1282 00:50:37,639 --> 00:50:42,719 up in plastic. So, some of these things 1283 00:50:39,840 --> 00:50:44,240 last tens of thousands of years. And 1284 00:50:42,719 --> 00:50:47,079 even though there weren't a lot of 1285 00:50:44,239 --> 00:50:48,839 petabecquerels of plutonium released, 1286 00:50:47,079 --> 00:50:51,279 they're alpha emitters. And they're 1287 00:50:48,840 --> 00:50:52,640 extremely dangerous when ingested. 1288 00:50:51,280 --> 00:50:54,920 So, 1289 00:50:52,639 --> 00:50:56,960 uh greens and things that uptake 1290 00:50:54,920 --> 00:50:59,200 radionuclides from the soil, like moss 1291 00:50:56,960 --> 00:51:02,199 and mushrooms, are totally off-limits in 1292 00:50:59,199 --> 00:51:04,159 a large range of this area. 1293 00:51:02,199 --> 00:51:06,159 You will find a video online, if you 1294 00:51:04,159 --> 00:51:07,440 look, of a mayor from a nearby town 1295 00:51:06,159 --> 00:51:09,839 saying, "Oh, they're perfectly safe to 1296 00:51:07,440 --> 00:51:11,000 eat. Look, I eat them right here." And I 1297 00:51:09,840 --> 00:51:13,039 just say read the comments for what 1298 00:51:11,000 --> 00:51:14,440 people have to say about that. 1299 00:51:13,039 --> 00:51:16,519 Not too smart. 1300 00:51:14,440 --> 00:51:18,559 Yeah. So, what what's like the process 1301 00:51:16,519 --> 00:51:19,960 now for like taking care of Chernobyl? 1302 00:51:18,559 --> 00:51:21,079 Like, what do they 1303 00:51:19,960 --> 00:51:22,679 do there? 1304 00:51:21,079 --> 00:51:24,199 The so so the sarcophagus around the 1305 00:51:22,679 --> 00:51:26,079 reactor has got to be shored up to make 1306 00:51:24,199 --> 00:51:28,399 sure that nothing else gets out, cuz 1307 00:51:26,079 --> 00:51:29,960 most of the reactor is still there. 1308 00:51:28,400 --> 00:51:31,920 And let's say rainwater comes in and 1309 00:51:29,960 --> 00:51:33,159 starts washing away more stuff into the 1310 00:51:31,920 --> 00:51:36,079 ground or whatever. We don't want that 1311 00:51:33,159 --> 00:51:39,079 to happen. Soil replacement and disposal 1312 00:51:36,079 --> 00:51:40,960 as nuclear waste is still going on. 1313 00:51:39,079 --> 00:51:42,480 Uh removal of any moss, lichen, 1314 00:51:40,960 --> 00:51:44,440 mushrooms, or anything with a sort of 1315 00:51:42,480 --> 00:51:47,480 radiation exposure has got to keep 1316 00:51:44,440 --> 00:51:49,639 going. But, this the area that it covers 1317 00:51:47,480 --> 00:51:51,639 is enormous. I don't know if we're ever 1318 00:51:49,639 --> 00:51:53,119 going to get rid of all of it. The 1319 00:51:51,639 --> 00:51:55,440 question is, how much do we have to get 1320 00:51:53,119 --> 00:51:57,519 rid of to lower our risk of cancer in 1321 00:51:55,440 --> 00:51:59,559 the area to an acceptable rate? There 1322 00:51:57,519 --> 00:52:01,320 will likely be parts of this that are 1323 00:51:59,559 --> 00:52:03,360 inaccessible for thousands to tens of 1324 00:52:01,320 --> 00:52:05,080 thousands of years, unless we hopefully 1325 00:52:03,360 --> 00:52:06,880 get smarter about how to contain and 1326 00:52:05,079 --> 00:52:08,719 dispose of this kind of stuff. 1327 00:52:06,880 --> 00:52:09,960 We're not there yet. So, right now, the 1328 00:52:08,719 --> 00:52:12,519 methods are 1329 00:52:09,960 --> 00:52:14,000 kind of simple. Get rid of the soil. 1330 00:52:12,519 --> 00:52:16,719 Fence off the area. 1331 00:52:14,000 --> 00:52:18,519 Some folks have been returning, and they 1332 00:52:16,719 --> 00:52:20,000 do get compensation and free medical 1333 00:52:18,519 --> 00:52:23,360 visits because the background levels 1334 00:52:20,000 --> 00:52:25,280 there are elevated, but not that high. 1335 00:52:23,360 --> 00:52:27,480 So, folks have started to move back to 1336 00:52:25,280 --> 00:52:28,680 some of these areas, 1337 00:52:27,480 --> 00:52:30,880 but there's a lot that are still 1338 00:52:28,679 --> 00:52:33,599 off-limits. 1339 00:52:30,880 --> 00:52:36,360 Any other questions? 1340 00:52:33,599 --> 00:52:38,519 Yeah. It's like way worse than the 1341 00:52:36,360 --> 00:52:40,480 atomic bombs dropped on Hiroshima and 1342 00:52:38,519 --> 00:52:43,000 Nagasaki, because those are like fully 1343 00:52:40,480 --> 00:52:45,240 functioning cities at at this point. 1344 00:52:43,000 --> 00:52:47,719 Yeah, the number of deaths from the 1345 00:52:45,239 --> 00:52:49,279 atomic bombs way outweighed the number 1346 00:52:47,719 --> 00:52:50,759 of deaths that will ever happen from 1347 00:52:49,280 --> 00:52:54,040 Chernobyl. But, like, why is the 1348 00:52:50,760 --> 00:52:55,560 radiation from those bombs not 1349 00:52:54,039 --> 00:52:57,880 Oh, not that much of an issue? Yeah. 1350 00:52:55,559 --> 00:52:59,279 There wasn't that much material. The not 1351 00:52:57,880 --> 00:53:00,960 There wasn't that much nuclear material 1352 00:52:59,280 --> 00:53:02,240 in an atomic bomb. 1353 00:53:00,960 --> 00:53:04,400 What did you guys get for the radius of 1354 00:53:02,239 --> 00:53:06,239 the critical sphere of plutonium? 1355 00:53:04,400 --> 00:53:06,960 4.7 1356 00:53:06,239 --> 00:53:08,879 cm. 1357 00:53:06,960 --> 00:53:10,519 Centimeters? Yeah. Yeah. 1358 00:53:08,880 --> 00:53:14,160 Doesn't take a lot. It takes, you know, 1359 00:53:10,519 --> 00:53:16,119 10, 20 kilos to make a weapon. 1360 00:53:14,159 --> 00:53:18,000 Now, we're talking about tons or 1361 00:53:16,119 --> 00:53:20,359 thousands of tons of material released. 1362 00:53:18,000 --> 00:53:23,760 So, an atomic weapon doesn't kill by 1363 00:53:20,360 --> 00:53:25,240 radiation. It kills by pressure wave, 1364 00:53:23,760 --> 00:53:27,720 the heat wave. 1365 00:53:25,239 --> 00:53:29,039 The fallout is not as much of a concern. 1366 00:53:27,719 --> 00:53:31,279 And we'll actually be looking at the 1367 00:53:29,039 --> 00:53:33,800 data from Hiroshima and Nagasaki 1368 00:53:31,280 --> 00:53:36,400 survivors to see who got what dose, what 1369 00:53:33,800 --> 00:53:37,840 increased cancer risk did they get, and 1370 00:53:36,400 --> 00:53:39,760 is this the 1371 00:53:37,840 --> 00:53:41,960 is the idea that every little bit of 1372 00:53:39,760 --> 00:53:44,800 radiation is a bad thing actually true? 1373 00:53:41,960 --> 00:53:46,440 The answer is, you can't say yes or no. 1374 00:53:44,800 --> 00:53:48,560 No one can say yes or no, because we 1375 00:53:46,440 --> 00:53:49,800 don't have good enough data. 1376 00:53:48,559 --> 00:53:51,440 The error bars support either 1377 00:53:49,800 --> 00:53:52,920 conclusion. 1378 00:53:51,440 --> 00:53:54,679 So, I'm not going to go on record and 1379 00:53:52,920 --> 00:53:56,119 say a little bit of radiation is okay. 1380 00:53:54,679 --> 00:53:59,079 The data's not out yet. 1381 00:53:56,119 --> 00:53:59,079 Hopefully, it never will be. 1382 00:54:00,719 --> 00:54:03,599 Any other questions? 1383 00:54:03,800 --> 00:54:07,840 All right. I'll see you guys on 1384 00:54:05,358 --> 00:54:07,840 Thursday.