Applied Chemistry

Nuclear Chemistry

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

Nuclear Radiation Penetrating Power

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.

How Radon Gas Enters your House

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.

Testing Methods for Radon

Ways to Remove Radon Gas from Your Home

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.

U.S. Radon Zones

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.

Irradiated Ground Beef

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.

Radioisotopes found in various parts of the body

Exposure to Radiation

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.

235 1 140 93 192 0 56 36 03U n Ba Kr n energy

Nuclear Fission

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

Hiroshima 1945 & Today

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

3 2 4 1 121 1 2 0H H He n 1.7x10 J/mol

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

Fusion ReactorTokamak

http://jammit.com.au/20080115/china-pins-big-14b-hopes-on-nuclear-fusion/

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 Plants with Operating License

Nuclear Power Plant Diagram

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.

Fuel Pellets

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.

Nuclear Power Plant Diagram

Boiling-Water Reactor

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

Entrance into Yucca Mountain

http://blog.longnow.org/2002/03/03/yucca-mountains-future/

Nuclear AccidentsThree-Mile Island

Date: March 28, 1979

Location: Susquehanna River near Harrisburg, PA

Technical failures and human errors lead to the worst nuclear accident in U.S.

Three Mile Island

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)

Map of Chernobyl

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.