Nuclear Chemistry

1. Nuclear Chemistry Fuuuuuusiiiiioooon HA!

2. The Atom • Nuclear chemistry revolves around the nucleus of the atom • Electrons do not really matter for these reactions. • E=mc2

3. The nucleus • Composed of protons and neutrons • Atomic number is number of protons Ex. Sodium has an atomic number of 11, so it has 11 protons

4. Neutrons • Since they are neutrally charged, they do not impact reactivity of the element. • Protons + Neutrons = Atomic mass • Wait… • If sodium has 11 protons, and has a mass of 22.990… • Then it has 11.990 neutrons? What gives?

5. Isotopes • Not all atoms of an element are exactly the same • Isotopes are atoms of an element with different numbers of neutrons (and thusly different masses) • The mass on the periodic table is the weighted average of all the atoms of that element

6. Examples • Sodium has a mass of 22.990 this means… • Most sodium atoms have a mass of 23 • A very small number have a mass of 22 • Other isotopes will be extremely rare • Uranium has a mass of 238.029, meaning… • Most uranium atoms have a mass of 238 • Very few have the useful mass of 235

7. Stability • If protons are in the nucleus, and electrons are in the cloud around it, how can a nucleus be stable? • Answer is a little complex

8. Stability Cont. • When protons collide, they “stick” together to form a larger, positive charge. They quit behaving like single positive charges. • Neutrons aid in the “stick” together. • Scientists are still trying to figure out why this happens.

9. Instability • If there are not enough neutrons, the atom has an unstable nucleus. • Unstable nuclei can and will break down into nuclei of a different element. • Ex. Uranium-235 will spontaneously break down into thorium-231 • All elements on the periodic table after Uranium are radioactive for ALL isotopes

10. Fission • Fission is a natural process in which unstable nuclei break down. • Elements heavier than iron have energy released with break down.

11. Fission • But where does the mass go? • A very small part of the nucleus will be shot off will most of the “missing” mass and have much of the energy • This is known as radiation. • Not all of it is harmful

12. Radiation • 3 types of particles released • Alpha • Beta • Gamma • Not all 3 types are produced when they decay • Most elements only produce 1

13. Alpha • Helium-4 nucleus • +2 charge (zero electrons) • Nearly harmless • A few centimeters of air will effectively block • Used in smoke detectors • Polonium-210 breaks down into Lead-206 by alpha emission

14. Beta • Electron emitted from the nucleus • Stopped by glass • Used for medical purposes • Carbon releases this when breaking down into nitrogen.

15. Gamma • This is a high-energy electromagnetic wave • In English, this is essentially just energy • Will penetrate several meters through lead • Due to its high energy this is the big one for causing cancer. • Uranium emits this on its way to thorium

16. Radiation Poisoning

17. Radiation poisoning • I’d show you a picture, but I’d like to eat sometime today • It’s very difficult to measure exactly how much radiation is dangerous • Scientist cannot agree on how it should be measured.

18. mrem • We’ll be using millirem (mrem) for comparison purposes • Rem stands for “Roentgen equivalent in man” and is a function of radiation dosage and biological effectiveness of the radiation • 15-25mrem is typical for just living normally on Earth. • 1mrem will come from your TV • Living near a nuclear power plant will add a whopping 0.01 mrem (coal delivers 0.03 mrem) • A chest x-ray delivers 6 mrem • The average American receives 360mrem a year

19. Deadly amounts • 450,000 mrem will cause death in 50% of people… • Yeah, that nuclear plant is starting to sound much safer, isn’t it? • You’d have to live next to the plant for 45 million years to receive that much radiation.

20. More Deadly Amounts • The Chernobyl accident had a radiation spike of 3,000,000 mrem/hr • That hits the 50% fatality mark in under 10 minutes. • Severe illness would begin in minutes.

21. Symptoms of Radiation Poisoning • Hair loss • Skin lesions (open sores) • Teeth falling out • Nausea/vomiting • Diarrhea • Headache • Fever • Dizziness • Fatigue • Poor wound healing • Bloody vomit • Low blood pressure • Death in 2-6 days for high doses • And worst of all… • Your cable bill will be late

22. Media • Why is it the media over emphasizes amount of radioactive material?

23. Half-Lives No, not the video game series.

24. Half-Life • Fission happens randomly amongst unstable nuclei. • But it happens at a predictable rate. • So, we know how many will be lost in a given time, but not which ones. • For every half-life that passes, ½ of the remaining sample has decayed.

25. Half-Lives Starting with 100g: After 1 half life: 50g remain After 2: 25g remain After 3: 12.5g After 4: 6.25g After 5: 3.125g After 6: 1.5625g After 7: 0.78125g After 10: 0.09766g

26. Half-Lives • This is used to carbon-date objects. • 10 half-lives is considered safe for most radioactive samples. • For uranium-235, 1 half-life is 700 million years • 700million x10 for safety= 7billion years • The age of the Earth is around 4.5 billion years.

27. C. Half-life mf:final mass mi:initial mass n:# of half-lives

28. C. Half-life • Fluorine-21 has a half-life of 5.0 seconds. If you start with 25 g of fluorine-21, how many grams would remain after 60.0 s? GIVEN: t½ = 5.0 s mi = 25 g mf = ? total time = 60.0 s n = 60.0s ÷ 5.0s =12 WORK: mf = mi (½)n mf = (25 g)(0.5)12 mf = 0.0061 g

29. Fusion

30. Fusion • combining of two nuclei to form one nucleus of larger mass • thermonuclear reaction – requires temp of 40,000,000 K to sustain • 1 g of fusion fuel = 20 tons of coal • occurs naturally in stars

31. Fusion • Elements after Uranium have been synthesized by fusing smaller elements • Ex. Synthesis of Einsteinium • Californium-249 is struck by hydrogen-2 • Products are einsteinium-248 and 3 neutrons

32. Practice • Pick three trans uranium elements • Predict a possible synthesis reaction for them.

33. 235U is limited danger of meltdown toxic waste thermal pollution fuel is abundant no danger of meltdown no toxic waste not yet sustainable C. Fission vs. Fusion FISSION FUSION

34. Nuclear Reactors

35. Main idea • chain reaction - self-propagating reaction • critical mass - mass required to sustain a chain reaction

36. Chain reactions • One nuclei breaks down and releases enough energy to trigger another break down. • If the mass is too small, the energy escapes without colliding with another nuclei.

37. Parts • Control Rod • Absorbs neutrons to keep decay under control • Too fast = meltdown • Too slow = shutdown • Fluid to absorb heat-sodium or pressurized water • Cooling tower • The part of the plant you’re probably most familiar with

38. Cooling Tower A. Nuclear Power • Fission Reactors

39. A. Nuclear Power • Fission Reactors

40. A. Nuclear Power • Fusion Reactors (not yet sustainable)

41. Fusion Plasma • What might be a potential issue with using plasmas in a fusion reactor?

42. Nuclear weapons Adding the “new clear” to nuclear And I’m so going to prison for this

43. Power vs. Weapon • In a power plant, the decay is tightly controlled. Not too fast nor too slow. • In a weapon, the decay is forced to happen at once. • A power plant CANNOT be turned into a weapon • Fuel is not pure enough • Not as simple as getting a lot of uranium together and flinging it at someone.

44. Timing • For a nuclear weapon to work, every atom must decay in unison. • If decay is not uniform, weapon will just be a really expensive bullet. • A hydrogen bomb uses a uranium or plutonium bomb to trigger the fusion reaction.

45. Timing continued • Step 1: keep sub critical (mass too small to maintain a chain reaction) masses apart • Step 2: Smash sub critical parts together without a neutron setting the whole thing off prematurely • Step 3: Introduce a neutron at peak time • Step 4: Climb into a 1950’s fridge

46. Adding the “nuke you” to nuclear

47. Destruction • A kiloton references how much TNT could be used for a similar effect. 1 kiloton=1,000 tons of TNT. • 1megaton=1,000,000 tons of TNT • The largest conventional weapon (non-nuclear) is 0.15kilotons. • Temperature of a typical explosive can reach temperatures of 1,000 degrees Celsius, while nuclear can exceed 1,000,000 degrees Celsius (temperatures on the order of the sun)

48. Destruction of a 15 kiloton nuclear weapon • .75mi • 500mph winds • Most buildings leveled • Zero survivors • 1.2 mi • 3rd degree burns • Death likely due to lack of medical response and capabilities. • 1.5 mi • 93mph winds • Severe injuries and casualties

49. Tsar Bomba • Largest yield nuclear weapon ever detonated (50megatons) • If dropped on Sugar Land… • Louisiana would feel the wind. • Katy would be history • 68 mi away, 45% of people would be injured, 5% killed • 170 miles away, the heat would be felt. • 560 miles away, windows would break. • Would be seen 620 miles away (Kansas would be able to see it) • Mushroom cloud would be 8 times higher that Mount Everest • Could cause an earthquake hitting 7.1 on the Richter scale (same as the earthquake responsible for Fukushima) • Anybody injured on our side of San Antonio and Louisiana would have a high chance of dying from otherwise treatable injuries due to inhibited medical response.

50. Warning Time • How much warning time would be necessary for you to get to a safe distance from the blast? • Assuming the flight from Cuba (they’re not really fond of us) is 2 hours, is there reason for alarm if such a weapon were to be found?