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  1. 0:00:00.000,0:00:03.075
  2. Welcome to "Big Bang, outer space and life."
  3.  
  4. 0:00:03.080,0:00:05.300
  5. We continue the comment check
  6.  
  7. 0:00:05.300,0:00:09.740
  8. with Professor Dr. Hartmut Zohm of the Max Planck Institute for Plasma Physics
  9.  
  10. 0:00:09.920,0:00:12.080
  11. here in Garching.
  12.  
  13. 0:00:12.100,0:00:16.820
  14. He published a few nice videos on this channel about nuclear fusion.
  15.  
  16. 0:00:16.820,0:00:18.840
  17. We already discussed a few questions
  18.  
  19. 0:00:18.840,0:00:21.600
  20. and now continue with the topics "Environment characteristics"
  21.  
  22. 0:00:21.660,0:00:25.160
  23. "Sustainability" and "Dangers" of nuclear fusion.
  24.  
  25. 0:00:30.860,0:00:33.880
  26. We start with the first user question (Joba1?)
  27.  
  28. 0:00:33.880,0:00:37.240
  29. "Interesting presentation. I'd like to know how much Lithium and Deuterium
  30.  
  31. 0:00:37.240,0:00:40.580
  32. we'd have to "burn" to Helium each year
  33.  
  34. 0:00:40.580,0:00:42.380
  35. to cover the current global energy consumption.
  36.  
  37. 0:00:42.380,0:00:45.660
  38. Is there enough available and is it regenerative?"
  39.  
  40. 0:00:46.200,0:00:49.020
  41. So... It's not regenerative,
  42.  
  43. 0:00:49.020,0:00:51.540
  44. Lithium indeed is consumed.
  45.  
  46. 0:00:51.900,0:00:54.640
  47. We're talking about a nuclear reaction, not a chemical reaction.
  48.  
  49. 0:00:54.660,0:00:57.835
  50. The energy that is converted with each reaction
  51.  
  52. 0:00:57.840,0:01:02.240
  53. is higher by the factor of 1 million to 10 million.
  54.  
  55. 0:01:02.800,0:01:06.520
  56. Accordingly the consumption rate is 10 million times lower
  57.  
  58. 0:01:06.520,0:01:08.920
  59. compared to chemical reactions.
  60.  
  61. 0:01:09.220,0:01:12.780
  62. The number is huge and I trip over that every time I try to work it out in my head
  63.  
  64. 0:01:12.860,0:01:14.340
  65. so I wrote it down.
  66.  
  67. 0:01:14.640,0:01:17.100
  68. What i wrote down is:
  69.  
  70. 0:01:17.100,0:01:19.560
  71. If we want to cover the current global energy consumption
  72.  
  73. 0:01:19.620,0:01:24.140
  74. - which is roughly 500 exajoule (5 * 10^20 Joule) -
  75.  
  76. 0:01:24.140,0:01:28.640
  77. If we convert that in gigawatt-hours
  78.  
  79. 0:01:28.640,0:01:30.960
  80. how much would we consume?
  81.  
  82. 0:01:31.140,0:01:34.640
  83. That would be 45 thousand tons of Lithium consumed
  84.  
  85. 0:01:34.640,0:01:39.620
  86. to cover the global energy consumption for one year.
  87.  
  88. 0:01:40.060,0:01:43.460
  89. And to compare i looked up how much coal
  90.  
  91. 0:01:43.740,0:01:45.660
  92. we burn in a coal power plant.
  93.  
  94. 0:01:45.700,0:01:48.100
  95. We have one close to use, in Munich.
  96.  
  97. 0:01:48.200,0:01:52.515
  98. There they burn 800 thousand tons of coal each year
  99.  
  100. 0:01:52.520,0:01:55.600
  101. to cover a part of Munich,
  102.  
  103. 0:01:55.600,0:02:01.200
  104. which is 20 times more than you need Lithium to satisfy the energy thirst of the whole world.
  105.  
  106. 0:02:01.200,0:02:05.520
  107. And that is the answer to this questions, we can calculate all of these numbers
  108.  
  109. 0:02:05.600,0:02:08.080
  110. they are vanishingly small.
  111.  
  112. 0:02:08.160,0:02:11.040
  113. If we turn the calculation around and look how much Lithium is available
  114.  
  115. 0:02:11.040,0:02:12.920
  116. how much of the Lithium 6 we need
  117.  
  118. 0:02:12.920,0:02:15.600
  119. - not even the Lithium 7 we need for the laptop batteries -
  120.  
  121. 0:02:15.740,0:02:17.600
  122. then the result is a few thousand years.
  123.  
  124. 0:02:17.760,0:02:20.260
  125. Only taking the Lithium reserves in account
  126.  
  127. 0:02:20.620,0:02:23.920
  128. that can be mined easily - If we look at how much Lithium
  129.  
  130. 0:02:24.120,0:02:27.240
  131. is evenly spread in rocks, how much is available there
  132.  
  133. 0:02:27.240,0:02:30.380
  134. then the result is many hundreds of thousands of years.
  135.  
  136. 0:02:30.380,0:02:32.880
  137. So i think that is not a problem we have.
  138.  
  139. 0:02:33.220,0:02:38.000
  140. From the nuclear fission reactions we know that the result are radio active elements
  141.  
  142. 0:02:38.020,0:02:41.680
  143. which unfortunately have high half-life periods, they radiate very long
  144.  
  145. 0:02:41.680,0:02:43.640
  146. and are a long time environmental burden.
  147.  
  148. 0:02:43.880,0:02:46.120
  149. So one question that came up frequently
  150.  
  151. 0:02:46.160,0:02:48.780
  152. for example from the user "acidfreak"
  153.  
  154. 0:02:49.240,0:02:52.020
  155. or also from - now i have to take a look for that
  156.  
  157. 0:02:53.260,0:02:56.860
  158. It wasn't (Joba?), right, it was "Wardragon"
  159.  
  160. 0:02:56.860,0:02:59.180
  161. "What about radioactivity?
  162.  
  163. 0:02:59.180,0:03:00.500
  164. How long does it radiate?
  165.  
  166. 0:03:00.520,0:03:03.560
  167. In the presentation it was talked about a few years."
  168.  
  169. 0:03:03.740,0:03:06.240
  170. Can you quantify that a bit?
  171.  
  172. 0:03:06.240,0:03:07.980
  173. So...
  174.  
  175. 0:03:07.980,0:03:11.320
  176. First, we differentiate between
  177.  
  178. 0:03:11.320,0:03:15.180
  179. the radioactivity of the fuels we use
  180.  
  181. 0:03:15.180,0:03:17.380
  182. because we can't avoid those
  183.  
  184. 0:03:17.380,0:03:20.360
  185. and then the radioactivity of the structure materials
  186.  
  187. 0:03:20.360,0:03:23.640
  188. that surround the fuels, so the walls.
  189.  
  190. 0:03:23.960,0:03:27.960
  191. For the fuels it's indeed the Tritium which is radioactive
  192.  
  193. 0:03:27.960,0:03:30.340
  194. it has a half-life period of 12 years.
  195.  
  196. 0:03:30.700,0:03:34.740
  197. So after 12 years there's half of it left, after another 12 years the half of the half, etc.
  198.  
  199. 0:03:34.800,0:03:39.680
  200. So Tritium is something that can be considered as rare ressource
  201.  
  202. 0:03:39.680,0:03:43.220
  203. which has to be processed and what you can't find a lot on earth.
  204.  
  205. 0:03:44.080,0:03:47.500
  206. And we already addressed it earlier
  207.  
  208. 0:03:47.500,0:03:50.460
  209. those are really low amounts that are used
  210.  
  211. 0:03:50.460,0:03:53.040
  212. One gigawatt power plant would use 500g
  213.  
  214. 0:03:53.180,0:03:56.080
  215. Tritium each day, so consume it.
  216.  
  217. 0:03:56.080,0:03:57.700
  218. That is not a lot.
  219.  
  220. 0:03:58.260,0:04:02.340
  221. I think more of a thing we have to adress
  222.  
  223. 0:04:02.400,0:04:04.900
  224. are the walls and the structure materials.
  225.  
  226. 0:04:05.380,0:04:10.440
  227. And there we can chose the materials by their half-life period
  228.  
  229. 0:04:10.900,0:04:15.340
  230. A typical mix of materials we could use to build right now
  231.  
  232. 0:04:15.680,0:04:20.220
  233. currently could be recycled after 100 years of buffer storage.
  234.  
  235. 0:04:20.220,0:04:24.820
  236. So actually recycle it and use it again to build the next power plant.
  237.  
  238. 0:04:25.420,0:04:29.535
  239. That means - and 100 years typically is where you say "I leave it where it is" -
  240.  
  241. 0:04:29.540,0:04:32.980
  242. or even "I don't have to lock that away"
  243.  
  244. 0:04:33.460,0:04:36.260
  245. These long half-life periods we have at nuclear fission
  246.  
  247. 0:04:36.260,0:04:38.340
  248. that go into hundreds of thousands of years
  249.  
  250. 0:04:38.860,0:04:41.600
  251. just don't exist for nuclear fusion if it's done correctly.
  252.  
  253. 0:04:41.600,0:04:43.360
  254. I consider that as huge advantage.
  255.  
  256. 0:04:43.600,0:04:45.420
  257. Because for me
  258.  
  259. 0:04:45.420,0:04:50.260
  260. the accident hazard for a nuclear fission isn't that high either if it's built correctly
  261.  
  262. 0:04:51.260,0:04:54.820
  263. - it's more about that we don't know how to permanently store the waste.
  264.  
  265. 0:04:55.100,0:05:00.060
  266. Like where we burden generations of people
  267.  
  268. 0:05:00.780,0:05:04.820
  269. not only today and tomorrow
  270.  
  271. 0:05:06.000,0:05:09.200
  272. Neither you or me know what it'll be like in thousand years - god beware -
  273.  
  274. 0:05:09.205,0:05:11.755
  275. and we don't want to bequeath that I think
  276.  
  277. 0:05:13.180,0:05:16.600
  278. Good - The next question is from "Bob Tronexy" (?)
  279.  
  280. 0:05:16.600,0:05:20.040
  281. "I don't understand the cooling of the plasma from the carbon sheets.
  282.  
  283. 0:05:20.260,0:05:22.320
  284. How does such a discharge work?
  285.  
  286. 0:05:22.500,0:05:25.460
  287. The plasma doesn't have direct contact with the surrounding
  288.  
  289. 0:05:25.920,0:05:29.040
  290. in case of an accident. How can I picture that?"
  291.  
  292. 0:05:29.300,0:05:35.120
  293. Ok, so first: There is no direct contact of the hot plasma in the centre
  294.  
  295. 0:05:35.160,0:05:37.340
  296. and the wall, that's what the magnetic field is used for
  297.  
  298. 0:05:37.340,0:05:40.820
  299. As the plasma particles are charged they are bound to the magnetic field.
  300.  
  301. 0:05:41.500,0:05:47.260
  302. The plasma at the edge comes into contact with the surrounding material when it cooled down
  303.  
  304. 0:05:47.460,0:05:49.900
  305. that is where the energy is discharged
  306.  
  307. 0:05:50.285,0:05:53.145
  308. There we have to take care a bit
  309.  
  310. 0:05:53.145,0:05:55.375
  311. the plasma still is very hot.
  312.  
  313. 0:05:55.375,0:05:57.395
  314. When it recombines from plasma to neutral gas
  315.  
  316. 0:05:57.395,0:05:59.145
  317. and then comes to the wall it still has around
  318.  
  319. 0:05:59.640,0:06:03.380
  320. 10.000 degrees if we measure the temperature of it.
  321.  
  322. 0:06:03.380,0:06:07.740
  323. In another episode of "comment check" we already discussed
  324.  
  325. 0:06:07.880,0:06:10.840
  326. that the density of the plasma is very low - 10^20 particles in one cubic metre
  327.  
  328. 0:06:10.840,0:06:15.440
  329. which is one millions times less particles than it would be in one cubic metre of air
  330.  
  331. 0:06:15.440,0:06:18.660
  332. And that leads to the result that the energy density is very low in the end.
  333.  
  334. 0:06:18.660,0:06:20.880
  335. And what heats up the plasma at the edge
  336.  
  337. 0:06:21.040,0:06:24.200
  338. for example where the wall comes into contact with the plasma
  339.  
  340. 0:06:24.200,0:06:29.080
  341. is about the energy density, not so much about the temperature.
  342.  
  343. 0:06:29.920,0:06:32.660
  344. And that is the part
  345.  
  346. 0:06:32.980,0:06:35.380
  347. which is confusing a bit
  348.  
  349. 0:06:35.460,0:06:38.020
  350. the amount of energy that is actually stored is not that high.
  351.  
  352. 0:06:38.320,0:06:42.055
  353. For an accident that also means
  354.  
  355. 0:06:42.060,0:06:45.720
  356. if the kinecic energy, the temperature, the thermal energy in the plasma is set free
  357.  
  358. 0:06:45.720,0:06:47.460
  359. uncontrolled
  360.  
  361. 0:06:47.580,0:06:49.180
  362. - the wall can't be destroyed.
  363.  
  364. 0:06:49.360,0:06:53.800
  365. The first wall might melt by 1mm or so
  366.  
  367. 0:06:54.000,0:06:56.520
  368. more can't happen because of the thermal energy
  369.  
  370. 0:06:56.900,0:07:00.215
  371. It's also a bit about "What is the worst case scenario?"
  372.  
  373. 0:07:00.220,0:07:03.540
  374. that also has been a user question from "acidfreak"
  375.  
  376. 0:07:03.540,0:07:06.500
  377. There always is a worst case scenario
  378.  
  379. 0:07:07.380,0:07:10.840
  380. That is a serious problem for the operator as the machine will be broken
  381.  
  382. 0:07:10.840,0:07:13.320
  383. and he can't earn money with it after that
  384.  
  385. 0:07:13.320,0:07:15.200
  386. - but it won't lead to the destruction of the facility.
  387.  
  388. 0:07:15.480,0:07:19.440
  389. For an accident from inside we can calulate that the energy densities aren't high enough
  390.  
  391. 0:07:19.440,0:07:23.880
  392. - a much higher energy density is used for the magnetic field than for the plasma itself
  393.  
  394. 0:07:23.880,0:07:26.600
  395. With that you can destroy components
  396.  
  397. 0:07:26.600,0:07:30.780
  398. but not let it explode, bust it, etc.
  399.  
  400. 0:07:31.300,0:07:33.420
  401. In fact the accident scenarios we have to talk about
  402.  
  403. 0:07:33.420,0:07:36.720
  404. are about "Where will what kind of material be released?"
  405.  
  406. 0:07:37.040,0:07:42.140
  407. There are scenarios we have to consider, like a crashing plane
  408.  
  409. 0:07:42.640,0:07:47.260
  410. and it falls right into the reactor - the worst place - and something is released
  411.  
  412. 0:07:47.440,0:07:51.420
  413. And there the inventories that could be released are relatively low
  414.  
  415. 0:07:51.700,0:07:54.420
  416. Then of course the machinery is broken
  417.  
  418. 0:07:54.420,0:07:59.600
  419. and you probably don't want to stay at the power plant area
  420.  
  421. 0:08:00.260,0:08:04.200
  422. But in fact you don't have to evacuate the people that are outside of the fence of the facility
  423.  
  424. 0:08:04.200,0:08:05.900
  425. even in this case
  426.  
  427. 0:08:05.900,0:08:09.180
  428. And if you can handle the worst case scenario like that
  429.  
  430. 0:08:09.260,0:08:12.200
  431. and that it doesn't lead to the evacuation of the surrounding people
  432.  
  433. 0:08:12.200,0:08:14.580
  434. as it for example was at Fukushima
  435.  
  436. 0:08:14.580,0:08:16.800
  437. I consider that as a huge advantage
  438.  
  439. 0:08:17.165,0:08:19.235
  440. of nuclear fusion compared to fission too.
  441.  
  442. 0:08:19.720,0:08:24.000
  443. In a fission power plant there are Cadmium rods that drop in when there's an emergency
  444.  
  445. 0:08:24.000,0:08:27.860
  446. which intercept the neutrons immediately and the reaction stops
  447.  
  448. 0:08:27.860,0:08:31.980
  449. Is there a similar process in a fusion power plant where something drops in
  450.  
  451. 0:08:31.980,0:08:35.260
  452. or someone who has to push a button or something that happens automatically?
  453.  
  454. 0:08:35.260,0:08:37.340
  455. You don't have to press the button
  456.  
  457. 0:08:37.360,0:08:39.920
  458. We always need intervention and active control
  459.  
  460. 0:08:39.920,0:08:42.800
  461. otherwise the reaction stops itself.
  462.  
  463. 0:08:42.800,0:08:45.620
  464. As soon as there is wall material in the plasma
  465.  
  466. 0:08:45.620,0:08:48.640
  467. which happens as soon as the plasma comes into contact with the wall
  468.  
  469. 0:08:48.640,0:08:51.680
  470. the plasma will be poluted and it stops to burn.
  471.  
  472. 0:08:53.000,0:08:55.660
  473. And the fuel supply in the container is depleted after 3 seconds
  474.  
  475. 0:08:55.820,0:08:58.000
  476. if you don't resupply it actively
  477.  
  478. 0:08:58.460,0:09:01.820
  479. Such a power plant has supplies stored for half a year or a year
  480.  
  481. 0:09:02.000,0:09:04.560
  482. There is no chain reaction
  483.  
  484. 0:09:04.560,0:09:07.440
  485. where it consumes all of its fuel supplies
  486.  
  487. 0:09:07.440,0:09:11.460
  488. There's just not enough of that and also the fusion always has to be controlled actively, otherwise it stops.
  489.  
  490. 0:09:14.880,0:09:17.280
  491. Then there are questions from "Tina Tiet" (?)
  492.  
  493. 0:09:17.300,0:09:22.520
  494. "I didn't understand yet what is considered the advantage compared to the fission power plants.
  495.  
  496. 0:09:22.740,0:09:25.840
  497. Which advantage does the fusion have compared to the fission
  498.  
  499. 0:09:25.845,0:09:28.675
  500. - both is radioactivity as we already discussed -
  501.  
  502. 0:09:29.255,0:09:31.895
  503. and what is the sustainability there for mankind?"
  504.  
  505. 0:09:32.520,0:09:34.220
  506. Partially we already discussed it before
  507.  
  508. 0:09:34.220,0:09:37.620
  509. Yes, we already discussed sustainability before a bit
  510.  
  511. 0:09:37.620,0:09:40.500
  512. it is not regenerative by the meaning that we transform something
  513.  
  514. 0:09:40.500,0:09:42.580
  515. but in fact we burn something.
  516.  
  517. 0:09:42.880,0:09:44.620
  518. But it's not much
  519.  
  520. 0:09:45.960,0:09:48.895
  521. That is a big advantage for sustainability
  522.  
  523. 0:09:48.900,0:09:52.160
  524. If you're running a fission power plant with uranium
  525.  
  526. 0:09:52.160,0:09:54.945
  527. you'll come to the point after a few hundred years where you have to use different
  528.  
  529. 0:09:54.945,0:09:59.600
  530. and not so favored fission products
  531.  
  532. 0:09:59.640,0:10:03.820
  533. If you replace that with nuclear fusion you have a relatively sustainable process
  534.  
  535. 0:10:04.100,0:10:07.360
  536. as deuterium and lithium are commonly available
  537.  
  538. 0:10:07.520,0:10:10.645
  539. One thing i believe is very good too
  540.  
  541. 0:10:10.645,0:10:14.680
  542. is deuterium from sea water and lithium from rocks
  543.  
  544. 0:10:14.680,0:10:19.320
  545. so it's not geograhically located and concentrated
  546.  
  547. 0:10:20.200,0:10:23.560
  548. There won't be a "lithium sheik"
  549.  
  550. 0:10:23.600,0:10:27.780
  551. someone who holds the monopoly for that
  552.  
  553. 0:10:28.000,0:10:29.880
  554. as it's relatively accessible for everyone
  555.  
  556. 0:10:30.660,0:10:31.660
  557. Very good
  558.  
  559. 0:10:32.360,0:10:35.900
  560. As i see it, we addressed all the important questions now
  561.  
  562. 0:10:35.900,0:10:40.940
  563. I hope you had fun and for the end I'd say we show our fine t-shirts
  564.  
  565. 0:10:41.820,0:10:45.020
  566. As always, if you liked the video give it a thumbs up
  567.  
  568. 0:10:45.060,0:10:49.720
  569. Comments are always welcome and if you liked the answers you're welcome to write that too
  570.  
  571. 0:10:49.880,0:10:50.860
  572. Thank you a lot
  573.  
  574. 0:10:51.100,0:10:51.600
  575. Thank you a lot too
  576.  
  577. 0:10:51.600,0:10:56.280
  578. If we have to discuss more I'll be content to join
  579.  
  580. 0:10:56.640,0:11:01.380
  581. If we have further questions, when interesting new questions emerge we didn't answer yet
  582.  
  583. 0:11:01.380,0:11:05.360
  584. we can talk about nuclear fusion again with pleasure.
  585.  
  586. 0:11:05.600,0:11:08.540
  587. Great, thanks a lot for the offer, we surely will need an update
  588.  
  589. 0:11:08.540,0:11:11.800
  590. and we will contact you again - thanks again Hartmut
  591.  
  592. 0:11:11.800,0:11:13.120
  593. With pleasure!
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