Applied Chemistry Nuclear Chemistry. When you think of the word NUCLEAR, what does it bring to mind?
-
Upload
jeffrey-benson -
Category
Documents
-
view
214 -
download
0
Transcript of Applied Chemistry Nuclear Chemistry. When you think of the word NUCLEAR, what does it bring to mind?
Radioactivity Discovery
In 1896, Henri Becquerel noticed that a piece of uranium ore, called pitchblende, exposed a piece of photographic film.
Uranium gave off invisible rays he called uranic rays.
Uranium is radioactive.
Marie & Pierre Curie: 1903
Shared the Nobel Prize in Chemistry with Becquerel.
They discovered 2 new radioactive elements, Radium and Polonium.
Marie called Radium the “radiant” element and Polonium she named for her native Poland.
How do you think Marie & Pierre died???
1867-1934
1859-1906
What happened to The Curies?
Pierre was run over by a horse-drawn wagon in Paris and killed in 1906. Marie was left alone with two daughters, aged 2 and 9.
In 1911 she went on to win a second Nobel Prize in chemistry.
In 1934, Marie died of leukemia brought on by radiation exposure one year before her daughter and son-in-law won the Nobel Prize for Chemistry.
Radioactivity
Radioactivity is the release of particles, energy, or both from the nucleus of an atom.
RadioactivityNatural radioactivity is found on the
earth.Everyone receives background radiation
at low levels from cosmic radiation, ground, building materials, and food.
Exposure to radiation does not make you or anything else radioactive.
Artificial radioactivity is produced in the lab.
Types of Radiation -EnergyNonionizing radiation is radiation with
low energy.Ex: radiowaves, infrared, and visible light
Ionizing radiation is radiation with high energy.Ex: ultraviolet, x-ray, and gamma
Types of Radiation - Energy
Particles released from the nucleus of an atom.
Examples: alpha and beta particles
Characteristics of Radiation
TypeSymb
olCompositi
onPenetra
tionStopped
by…
Alpha particle
Beta particle
Gamma ray
2 protons & 2 neutrons
Helium nucleiLow Sheet of
paper
An electronMediumAluminumFoil
High EnergyHighThick
concrete or lead
Exposure and Uses of Radiation - Radon
Radon is a decay product of uranium found in the soil or bedrock.
This is natural radioactivity.
Radon is a colorless, odorless gas.
Some radon produced in the soil dissolves in groundwater.
Radon
Many houses have cracks in the foundation and basement floors that permit radon to collect and concentrate.
Most radon enters your body by breathing.
Radon decays by alpha emission to produce heavy metals. These heavy metals are not exhaled and
produce damaging alpha particles in your body.
Exposure and Uses of RadiationRadon
Radon in your home can be checked by you.
Increased ventilation and sealing cracks in the floors are 2 ways you can reduce radon exposure.
External view of a Radon mitigation system from a home basement.
Below is a view of the fan inside which runs 24 hours a day pulling air from under the basement floor.
Exposure and Uses of RadiationSmoke Detectors
Smoke detectors use americium as the ionizing source.
Americium emits alpha particles.
Special disposal of smoke detectors is required.
Exposure and Uses of Radiation
Some EXIT signs use tritium or hydrogen-3 instead of electricity.Aircraft dialsLuminous paintsWrist watches
The tritium gas is contained in sealed glass tubes. The insides of the tubes are lined with a phosphor.
Low-energy Beta particles (electrons) emitted by the tritium bombard the phosphor, causing it to glow.
Exposure and Uses of RadiationAgricultural and Consumer Product
Many everyday products and food are treated to kill bacteria and insects.
Examples: fruits, poultry, cosmetics, band aids
Products are irradiated with gamma rays from cobalt-60.(used by CFC Logistics in its irradiator)
Irradiated products are not radioactive.
Medical Uses – Diagnostic Equipment
Computer-Axial Tomography scans or CAT scans use x-rays to produce cross-sectional images of the brain.
Magnetic Resonance Imaging or MRI uses radiowaves to “see through” bones to produce images of soft tissue.
Medical Uses – Diagnostic Equipment
Medical Uses – Diagnostic Tools using Radioisotope-Tracer studiesRadioisotopes prepared in a nuclear
reactor can be used to both treat and detect various medical conditions.
Tracers can be used to follow a particular isotope through its normal path in the body to show any abnormalities.
Tracers used in the body will typically have short half-lives.
Devices used to measure radioactivityIn the Lab:
Geiger Counter
In the Workplace: Film badge or
Dosimeter
Measurements of RadioactivityUnits
rad measures the absorbed radiation dose
rem measures the ionizing effect on living organisms.
In humans, ionizing radiation is measured in millirem, abbreviated mrem.
Radioactive Dating
Used for determining the age of previously living material.
For material up to 25,000 years old, carbon-14 is used.
For material over 25,000 years old, potassium-40 is used.
Half-Life
Half-Life is the time for half of the nuclei in a radioactive sample to decay.
Abbreviated: t1/2
Units can vary from milliseconds to thousands of years.
Half-Life
Example: Plutonium-239 has a half-life of 24,000 years. A sample of this plutonium today will be half gone in 24,000 years.
A 16-g sample today will have a mass of 8 g in 24,000 years.
After another 24,000 years, its mass will be only 4 g.
Half-life Problems(amount problem – how much)A radioactive element has a half-life of 64 years. You have a 48 g sample of this element. What is its mass in 192 years?
t1/2 = 64 yrs initial = 48 g
t = 192 yrs final = ?
1st determine the number of half-lives:
2nd divide original mass by 2. How many times? As many as the number of half-lives.
1/2
t 192 yrNumber of half-lives = = = 3
t 64 yr
1 2 348 g 24 g 12g 6 g
2 2 2
Half-life Problems(time problem – how long/old?)Another radioactive sample has a half-life
of 37.2 minutes. How long will it take for a 55g sample to decay to 3.4g?
t1/2 = 37.2 min initial = 55 g
t = ? final = 3.4 g1st - Divide sample by 2 until final mass is reached.
2nd - Multiply t1/2 by the number of half-lives.
37.2 min x 4 = 148.8 min
1 2 3 455 g 27.5 g 13.75g 6.875g 3.4375 g
2 2 2 2
Half-Life Practice Problems1. The half-life for fluorine-18 is 109.8 minutes. How long will it take a 3.60 g sample to decay to 0.225 g?
time problem
1st repeatedly cut your sample mass in half until you have 0.225 g.
3.60 g 1.80 g 0.90 g 0.45 g
0.225 g
2nd multiply the half-life by the number of times you cut the sample in half.
109.8 minutes x 4 = 439.2 minutes
2. The half-life for americium-241 is 432 years. How much of a 50 mg sample will remain after 1296 years?
amount problem
1st find the number of half-lives in 1296 years.
1296 years 432 years
= 3
2nd cut your sample mass in half 3 times.
50 mg 25 mg 12.5 mg 6.25 mg
1 2 3 4
1 2 3
t1/2 = 109.8 min initial = 3.60 g total time = ??? final = 0.225 g
t1/2 = 432 yrs initial = 50 mg total time = 1296 yrs final = ???
Nuclear Fission
Nuclear Fission is the splitting of a large nucleus in to smaller nuclei of similar size.
A small amount of mass is converted to a large amount of energy.
Nuclear Fission Examples
Atomic bomb uses U-235 or plutonium
1st military use of an atomic bomb was in Hiroshima, Japan on August 6, 1945 during WWII.
Nuclear Power Plants
Nuclear Fission
A chain reaction occurs when the material used to start the reaction is also produced until the fuel is used up.
In this fission reaction, the fuel is U-235 and the starter for the reaction is the neutron.
235 1 140 93 192 0 56 36 03U n Ba Kr n energy
Nuclear Chain Reaction - Fission
Fuel: U-235 or Pu-239
Critical mass for U is 110 lbs
Critical Mass is the minimum amount of fissionable material present (the fuel) to sustain a chain reaction.
A wooden house built 1km away from the test site…
The first Atomic Bomb is detonated at Trinity Site near Alamogordo, New Mexico on July 16, 1945.
A Monument stands at the test site today.
shows the result of the blast.
Video of 1st Atomic Bomb
“Little Boy”Uranium fission bomb dropped on Hiroshima,
Japan by the “Enola Gay” flown by Colonel Paul
Tibbets
Hiroshima - August 6, 1945
Distance fromGround Zero (km)
Killed Injured Population
0 -1.0 86% 10% 31,020
1.0 - 2.5 27% 37% 144,800
2.5 - 5.0 2% 25% 80,300
Total 27% 30% 256,300
Nagasaki - August 9, 1945
Distance fromGround Zero (km)
Killed Injured Population
0 -1.0 88% 6% 30,900
1.0 - 2.5 34% 29% 144,800
2.5 - 5.0 11% 10% 15,200
Total 22% 12% 173,800
“Fat Man” – Plutonium Fuel
Nuclear Fusion
Nuclear Fusion is the joining of smaller nuclei to form a larger nucleus.
A small amount of mass is converted into a large amount of energy that is 4-7 times more than a fission reaction.
1 2 4 11 1 2 12 2 2H H He H energy
Nuclear Fusion
Examples: SunHydrogen Bomb
We are currently unable to control fusion as an energy source
Temperatures of 100 million °F are required - thermonuclear
Fusion produces little waste. Helium is the waste product.
Fission vs. Fusion
FissionSplitting of a large
nucleiNuclear power
plants Solid radioactive waste
Atomic Bomb
FusionJoining 2 or more
smaller nucleiSun and stars
Very little waste Requires high temps to
maintain
Hydrogen Bomb
Fission vs. Fusion Videoclip
Nuclear Power Plants
1st plant in the US - Shippingport, PA in 1957
1st plant in the world Obninsk, Russia in 1954
In the US, there are 104 units in 34 states to generates 20% of our electricity.
Nuclear Power Plants
There are 5 plants in PA.Limerick Generating Plant is the
closest nuclear power plant to NPHS.
Nuclear Power Plant (Boiling Water Reactor Plant)
Overall process at a nuclear power plant:Fission reaction → produces heat → to heat
water into steam →the stream drives turbines in a generator → the generator produces electricity
Nuclear Reactors
The chain reaction of a fission reaction takes place in the nuclear reactor or reactor core.The reactor is made up of a fuel, control
rods, a moderator, and a coolant.US nuclear reactors are housed within a
concrete containment structure.
Fission Reaction: The fuel is U-235
Nonfissionable uranium is U-238.
Uranium ore (pitchblend) contains 0.7% U-235.
The enriched fuel is packed as pellets of 3% U-235 and 97% U-238. a centrifuge is used to enrich the fuel.
Weapons-grade uranium is at least 90% U-235.
Fission Reaction: The fuel is U-235
The pellets are packed into long steel cylinders called fuel rods that are 12-14 feet in length.
Fuel rods are replaced every 24 months.
Used fuel rods are known as spent fuel rods.
Nuclear Power PlantsControl Rods
Control rods are used to absorb the neutrons resulting in slowing down or stopping the chain reaction.
View of fuel rods and control rods immersed in water.
Nuclear Power PlantsModerator
A moderator is used to slow down the high-speed neutrons for more fission reactions to occur.
A common material used as a moderator is water.
Nuclear Power PlantsCooling System
A cooling system is used to cool the steam.
Water outside of the reactor is used to cool the steam.At Limerick Generating Plant, the cooled
water is discharged into the Schuykill River.
The cooled steam condenses into water and is reused inside the reactor.
Water in the cooling tower does not come in contact with the reactor core.
Advantages of Nuclear Power Plants
Large amounts of energy
Low operating costs
No CO2 emissions to produce acid rain
Disadvantages of Nuclear Power Plants
High construction costs
Waste from spent fuel rods
Safety
Location (NIMBY)
Nuclear Waste - Types
High-level nuclear waste is radioactive waste products with high levels of radioactivity.
Low-level nuclear waste is radioactive waste products with low levels of radioactivity.
Nuclear Waste - Sources
High-level nuclear wasteSpent fuel rodsMilitary weapons
Low-level nuclear wasteNuclear laboratory protective clothing Medical nuclear waste Supplies from nuclear power plants
Nuclear Waste
Spent fuel rods are still highly radioactive for thousands of years.
About 3,100 tons of commercial high-level nuclear waste are produced annually in the U.S.
There is no permanent storage place for nuclear waste in the U.S.
Nuclear Waste
Federal law mandates the spent fuel rods are stored on-site, usually in steel-lined storage tanks or pools of water.
Some plants are keeping the spent fuel rods in dry cask concrete vaults on the surface. (Limerick received approval in 2007)
Nuclear WasteUS government is developing a
permanent storage site in Yucca Mountain in Nevada.
The waste will be buried at least 1 km below the surface in vaults.
Progress for completion has been delayed from 1998 to 2017 at the earliest.
Delays are due to legal, environmental, and development concerns.
Yucca Mountain - More than five miles of tunnels, cross drifts and alcoves have been drilled. Another 60 miles of tunnels branching off the main one will store the hot waste.
http://blog.longnow.org/2002/03/03/yucca-mountains-future/
1. Canisters of waste, sealed in special casks, are shipped to the site by truck or train.
2. Shipping casks are removed, and the inner tube with the waste is placed in a steel, multilayered storage container.
3. An automated system sends storage containers underground to the tunnels.
4. Containers are stored along the tunnels, on their side.
http://www.nrc.gov/waste/hlw-disposal/design.html
Nuclear AccidentsThree-Mile IslandDate: March 28, 1979
Location: Susquehanna River near Harrisburg, PA
Technical failures and human errors lead to the worst nuclear accident in U.S.
https://www.youtube.com/watch?v=eGI7VymjSho
Nuclear Accidents - ChernobylDate: April 26, 1986
Location: northern Ukraine
Flawed reactor design and inadequately trained operators resulted in the worst nuclear accident in the world.
56 deaths to date due to radiation: 28 firefighters within 4 months with 19 later, and 9 thyroid cancer deaths (4000 children with thyroid cancer)
Nuclear AccidentsFukushima Nuclear Power Plant, Japan
Date: March 11, 2011
Location: East Coast of Japan
A massive tsunami following a major earthquake knocked out power to the reactors, causing multiple explosions and in some cases, core meltdowns.