Nuclear Chemistry

Fuuuuuusiiiiioooon

HA!

The Atom

• Nuclear chemistry revolves around the nucleus of the atom

• Electrons do not really matter for these reactions.

• E=mc2

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

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?

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

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

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

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.

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

Fission

• Fission is a natural process in which unstable nuclei break down.

• Elements heavier than iron have energy released with break down.

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

Radiation

• 3 types of particles released– Alpha– Beta– Gamma

• Not all 3 types are produced when they decay

• Most elements only produce 1

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

Beta

• Electron emitted from the nucleus

• Stopped by glass

• Used for medical purposes

• Carbon releases this when breaking down into nitrogen.

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

Radiation Poisoning

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.

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

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.

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.

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

Media

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

Half-Lives

No, not the video game series.

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.

Half-Lives

Starting with 100g:After 1 half life: 50g remainAfter 2: 25g remainAfter 3: 12.5gAfter 4: 6.25gAfter 5: 3.125gAfter 6: 1.5625gAfter 7: 0.78125gAfter 10: 0.09766g

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.

C. Half-life

nif mm )( 2

1

mf: final massmi: initial massn: # of half-lives

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

Fusion

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

HH 31

21

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

Practice

• Pick three trans uranium elements

• Predict a possible synthesis reaction for them.

C. Fission vs. Fusion

• 235U is limited• danger of meltdown• toxic waste• thermal pollution

• fuel is abundant• no danger of meltdown• no toxic waste• not yet sustainable

FISSION

FUSION

Nuclear Reactors

Main idea• chain reaction - self-propagating reaction• critical mass -

mass required to sustain a chain reaction

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.

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

A. Nuclear Power

• Fission ReactorsCooling Tower

A. Nuclear Power

• Fission Reactors

A. Nuclear Power

• Fusion Reactors (not yet sustainable)

Fusion Plasma

• What might be a potential issue with using plasmas in a fusion reactor?

Nuclear weaponsAdding the “new clear” to nuclear

And I’m so going to prison for this

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.

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.

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

Adding the “nuke you” to nuclear

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)

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

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.

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?

Complications

• Random radiation from space can set off a critical mass

• Random radioactive decay can set off critical mass

• So, the entire process must be done extremely fast (faster than a single nuclei can decay ~4microseconds).

To complicate things even more…

• It is difficult to predict exactly how much damage such a weapon would do.

• Terrain and weather can impact the forces.

• Modern weapons now employ the “more is better” option– By setting off multiple warheads, the total destruction

area can be maximized.– Instead of “goodbye Houston,” it could be “goodbye

New York, Los Angeles, Houston, Washington D.C. and Seattle”

On Indiana Jones…

• Would it have been plausible for him to have survived in the lead lined refrigerator?

• Why or why not?

Hiroshima

15 kiloton atomic bomb

Before

After

Ground Zero

The first signs of these effects were visible four miles or so from the bomb’s dropping point. The roofs looked denuded, as their tiles had been blown off by the blast. In places, the grass was bleached, as if dried; the Japanese journalist explained to me that the plants, vegetables and rice up to five or six miles from the bomb's epicentre had lost their green colour immediately after the explosion. They only got their colour back three or four weeks later. However, some plants, obviously more sensitive, had died.   

At three miles from the bomb's epicentre, some houses had been flattened like cardboard. The roofs were completely caved in; the rafters stuck out all round. This was the familiar sight of cities destroyed by explosive bombs. At two and a half miles, there were only piles of beams and planks, but the stone houses seemed intact. At just over two miles from the town centre, all houses had been gutted by fire. All that remained was the outline of their foundations and heaps of rusty metal. This area looked like the towns of Tokyo, Osaka and Kobe, destroyed by incendiary bombs. At one mile or so everything had been torn apart, blasted and swept away as if by a supernatural power; houses and trees had disappeared.   Dr. Junod

Paint exposed to the radiation was burned away. Unexposed areas

left behind “shadows

Tsutomo Yamaguchi(Lucky?) Survivor of both bombs

Murphy and Nuclear Power

Why thousands can pay for a “nobody will know”

Chernobyl Accident in 1986

• Reactor near Pripyat Ukraine

• 30 people dead

Issues

• Control rods leave a space when being moved.

• The negative space allows steam to form

• Neutrons that would have been absorbed by liquid water strike the reactor rods

• Reactor output actually increased as the control rods were inserted

• Government was slow to order evacuation

The Test

• A test was to be run on the reactor to see how it performed if it lost power.

• Automatic shutdown feature was DISABLED• Due to some human error, the people trained to

conduct the test were NOT present• Combined with the issue of control rods briefly

INCREASING the power of the reactor…

Reactor after explosion

Graphite moderator. Notice the control rod channel

Reactor today with concrete containment structure over reactor

I talked to some scientists. One told me: “I could lick your helicopter with my tongue and nothing would happen to me.” Another said: “You’re flying without protection? You don’t want to live too long? Big mistake! Cover yourselves!”

Eduard Borisovich Korotkov

Red Forest-Trees killed from radiation

Warning Sign

Bumper cars left behind

Some 3,600 soldiers worked on the roofof the ruined reactor. They slept on the ground in tents. They were young guys. These people don’t exist any more, just the documents in our museum, with their names.

Sergei Vasilyevich Sobolev

Control Room-Where so many mistakes were made

We buried trash heaps and gardens. The women in the villages watched us and crossed themselves.

One of the poets says somewhere that animals are a different people. I killed them (animals) by the ten, by the hundred, thousand, not even knowing what they were called. I destroyed their houses, their secrets. And buried them. Buried them.

Arkady Filin

I took my daughter and my wife to the hospital. They had black spots all over their bodies. These spots would appear, then disappear.

I want to bear witness: my daughter died from Chernobyl. And they want us to forget about it.

Nikolai Fomich Kalugin

The only thing that saved me was it happened so fast; there wasn’t any time to think, there wasn’t any time to cry. It was a hospital for people with serious radiation poisoning. Fourteen days. In 14 days a person dies.

I tell the nurse: “He’s dying.” And she says to me: “What did you expect? He got 1,600 roentgen. Four hundred is a lethal dose. You’re sitting next to a nuclear reactor.”

They buried him barefoot. My love.

We were newlyweds. We still walked around holding hands, even if we were just going to the store. I would say to him, “I love you.” But I didn’t know then how much. I had no idea.

Lyudmilla Ignatenko

I’m 12 years old and I’m an invalid. The mailman brings two pension cheques to our house – for me and my grandad.

When the girls in my class found out that I had cancer of the blood, they were afraid to sit next to me. They didn’t want to touch me.

The doctors said that I got sick because my father worked at Chernobyl. And after that I was born. I love my father.

Vanya Kovarov

Chemistry Classroom

Fukushima Diichi Nuclear Disaster

Issues

• Falsification of safety records

• Major design flaws ignored

• Tsunami study ignored

• Reactors 4,5,6 were shut down at the time

• Reactors 1,2,3 were immediately shut down during earthquake

Myth vs. Fact

• There was a lot of radiation released, but sources vary—and may not ever agree (same for just about every other radiation issue)

• Nobody was killed (hundreds exposed to radiation, and projected deaths from cancer is 100)

• On a scale of 0-7, Fukushima ranks in at a 7 (same as Chernobyl) due to the reactor explosion

• Sources STILL disagree on exactly how far the radiation distance compares to Chernobyl

Comparison

• Which was worse, Chernobyl or Fukushima?

• How do they compare to Hiroshima?

Common Misconceptions

Radiation

• It is not green.– It’s actually blue– Cherenkov radiation

• Blue glow from electrons exceeding the speed of light in water

• Speed of light in water is .75c

• Will not generate new species overnight– Remember evolution? Still takes a long time.

• Not necessarily dangerous (alpha is harmless)

Cherenkov Radiation

Nuclear Power

• Far safer than most power types.• Most news stories over-hype the dangers• Reactors now cannot sustain themselves without

power• The uranium used is not the same as in

weapons.• Don’t always have cooling towers looking like

the ones you are familiar with• Lesson was learned from Chernobyl. New

safety regulations and understanding of nuclear reactors prevent it from ever happening again.

Weapons

• Not an easy thing to build

• You’ve got a billion things to do within 4 microseconds.

• Conventional weapons cannot cause one to go critical. Worst case scenario is the radiation kills everyone in the room.

• President Obama does not have a big red button. (It’s a briefcase)

AAAAND

• No, dragon ball z has nothing to do with real world fusion.

• Quit asking.

• And yes, the power output of a nuclear reactor is over 9,000.