Nuclear Energy Notes 18.2 & 18.3. 1.Nuclear Reactions : Change the composition of an atom’s...

Nuclear Energy Notes

18.2 & 18.3

1. Nuclear Reactions: Change the composition of an atom’s nucleus.

2. The strong nuclear force holds the nucleus together.

3. Most atoms are stable (equal number of p & n). These are the smaller

atoms which are NOT radioactive.

4. Unstable nuclei have more neutrons than

protons. These isotopes are radioactive.5. As the elements become larger they

become more unstable.6. All elements have at least 1 radioactive

isotope. All the isotopes of those elements with atomic numbers greater than 83 are radioactive.

7. The larger nuclei are radioactive because they have more neutrons than protons.

Unstable Nucleus

8. Characteristics of Subatomic Particles and

Rays:Particle Mass

(amu) ChargeSymbol

Stopped by

Proton1.00727647

Neutron1.00866490

Beta Particle

(electron)

0.00054858

Alpha Particle

(He nucleus)

4.00150617

Gamma Ray

0

+1

0

+2

0Several

centimeters of lead

paper

Heavy clothing/Al

foil

Few centimeters of

lead

paper

-1

p+ or n0

or

11H

10 n

0 01 -1e or β

4 42 2He or α

00 γ or E

Nuclear Radiation Penetrating Power

Nuclear Radiation Penetrating Power

9. Spontaneous Emission of Radiation:

A. Unstable nuclei will spontaneously emit 3 types of natural radiation, this is also called radioactive decay.

B. When an atom emits 1 kind of radiation the original nucleus decomposes or decays to form a new nucleus and releases radiation. This is written in a nuclear equation.

Alpha & Beta Decay

10. 3 Types of Spontaneous Radiation:

A. Alpha Decay – spontaneous emission of an alpha particle

from the nucleus.

B. Beta Decay – spontaneous emission of beta particle

from the nucleus

C. Gamma Decay – spontaneous emission of gamma

rays from the nucleus

18177Ir226 222 4

88 86 2Ra Rn α 185 479 2Au _________ α

14 06 1C ________ β

238 092 0U ________ γ

147 N

23892U

131 13153 54I Xe + _____

01β

Uranium Radioactive Decay Series

How Radon Gas Enters your House

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.

Testing Methods for Radon

U.S. Radon Zones

11. Transmutation (Nuclear Bombardment Reactions):

A. Process in which a new element is formed by bombarding a nucleus with small energetic particles.

B. The energetic particle hits the nucleus and forms an unstable compound nucleus, which is short-lived.

C. This nucleus can emit another particle to stabilize itself.

D. This is the process used in particle accelerators where artificial isotopes and transuranium elements have been produced.

Particle Accelerator in Switzerland with a 16.7 mile

circumference

Nuclear Bombardment Reaction

14 4 18 17 17 2 9 8 1[ ]N He F O H

target nucleus

projectile

new isotope (element)

ejected particle

Nuclear Fission

A. Process by which a heavy nucleus splits into two smaller nuclei.

B. Most fission reactions are induced.C. The energy yield for fission reactions are

very high.D. Fission reactions are the source of

energy used to generate electricity in nuclear power plants.

E. U-235 & Pu-239 are the radioisotopes used in reactors.

Nuclear Fission Reaction

235 1 236 93 140 192 0 92 36 56 0[ ] 3U n U Kr Ba n

Nuclear fuel

projectile – particle that starts the chain reaction

temporary unstable nuclei that immediately splits

into 2 approximately equal mass product nuclei

3 neutrons are produced which start additional fission reactions

F. In fission reactions, the product nuclei have far too

many neutrons, and are intensely radioactive. This

is considered radioactive waste.

G. The released neutrons can cause another reaction as

long as sufficient U-235 remains.

H. This is called a chain reaction.

I. The smallest amount (minimum volume) of fissionable material needed to sustain a chain reaction is called the critical mass.

Nuclear Chain Reaction

Fuel: U-235 or Pu-239

Critical mass for U is 110 lbs

16. Nuclear Fusion:A. This is a thermonuclear reaction - requires high

temperatures.B. Occurs when two small nuclei fuse, or join, to form larger, more stable nuclei.C. Releases a large amount of energy.D. Process that occurs on the sun and in a hydrogen bomb.E. If fusion reactions are going to be practical, they need to produce more energy than they require to get started. F. In a fusion reaction, the starting materials are in a form of plasma. G. The biggest problem is obtaining the high temperatures necessary for a fusion reaction to occur.

H. A “magnetic bottle” is used to hold plasma at high temperatures.

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

neutron

U-235 Energy

Krypton-92

3 neutrons

Barium-141

21H

21H

11H

11H

11H

11H

42 He

Energy

Fission

Fusion

Nuclear Power Plants/A-bomb

The Sun/

H-bomb

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.

“Little Boy” Uranium fission bomb dropped on Hiroshima,

Japan by the “Enola Gay” flown by

Colonel Paul Tibbets

Hiroshima - August 6, 1945Distance 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

Hiroshima 1945 & Today

Nagasaki - August 9, 1945Distance 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

U.S. Nuclear Testing• Large craters pockmark Frenchman Flats,

Nevada, a former test site for U.S. nuclear weapons. The US conducted more than 1050 tests here and in Alaska, Colorado, Mississippi, New Mexico between 1945 and 1992.

• The Soviet Union, UK, France, China, India and Pakistan had a similar total number of tests over the same time period.

Fusion Bombs• The first thermonuclear weapon (hydrogen

bomb), code-named Mike, was detonated at Enewetak atoll in the Marshall Islands, Nov. 1, 1952. The photograph was taken at an altitude of 12,000 feet over 50 miles from the detonation site.

• Only 6 countries have detonated a hydrogen bomb – US, UK, Soviet Union, France, China and India.

• To obtain temperatures in the millions of degrees Celsius a fission reaction is set off first to start the fusion reaction.

Nuclear ReactorsA. There are currently 111 commercial nuclear power plants in the U.S. They provide 20% of our country’s electricity, but 80% of the

electricity used in southeastern PA.

B. There are 530 nuclear reactors in 30 nations around the world that provide 1/6 of the

world’s electricity. To produce electricity you need to turn a turbine. This can be accomplished by wind or water, must most commonly by steam. The only difference between a nuclear power plant and a conventional fossil fuel plant is the method used to produce boiling water.

14. Parts of a Nuclear Reactor

A.Fuel Rods: Composed of 97% U-238 and 3% U-235 (the fissionable isotope). Chalk- sized

pellets are arranged in long steel cylinders in the reactor core. When the fuel has given up most of its energy it is called spent. It will be reloaded every 1 to 3 years. There can be 10,000,000 pellets in 1 plant.

B. Control Rods control the rate of a nuclear reaction. Without them the reaction would occur too fast for it to be effective.

C. Moderator is usually heavy water (D2O). Without sufficient cooling of the core a meltdown could occur. This water also shields workers.

View of fuelrods andcontrol rodsimmersed in“heavy water.”

D. Generator produces electricity by turning a steam turbine from the boiling water.

E. Cooling System: Water from outside is used to cool the steam (it does not come into contact with the cooling water in the core). Excess steam rises up in the cooling tower, condenses and falls back.

14. Parts of a Nuclear Reactor con’t.

Cooling Towers

Limerick, PA

Nuclear Power Plant Diagram

Pressurized-Water Reactor

Boiling Water ReactorBoiling-Water Reactor

France 42.6

Sweden 36.2

Lithuania 31.9

Armenia 27.7

Slovakia 24.8

Bulgaria 24.3

Switzerland 22.5

Belgium 21.9

Slovenia 21

Korea (Republic of) 17.9

Finland 17.3

Ukraine 16.1

Japan 15

Czech Republic 14.3

Hungary 13

Germany 12.3

Spain 10.3

United Kingdom 9.1

United States 9

Canada 8.8

Russian Federation 6.1

Romania 3.8

Argentina 2.8

South Africa 2.3

Mexico 1.6

Netherlands 1.3

Brazil 1.2

China 0.8

India 0.8

Pakistan 0.8

Nuclear power (% of total primary energy supply) IEA (International Energy Agency) 2007

15. 15. Radioactive Radioactive Waste:Waste:

A. Spent fuel rods have been accumulating for about 40 years. Spent fuel rods are highly radioactive,

with some isotopes remaining active for thousands of years. By federal law reactor waste must be

stored on site. The U.S. Government has not yet opened any permanent storage sites, but one called

Yucca Mountain in Nevada is currently being negotiated. On-site storage is only a temporary

measure, as tanks require too much maintenance to be safe for long term storage.

Radioactive Waste

• Radioactive waste is stored under water until it decays to lower levels.

Radioactive Warning Symbol

• Waste is transferred to storage casks and stored on-site at each power plant.

Temporary Radioactive Waste Storage

• If permanent storage is opened, it would be transported to a location where it would be placed ½ mile underground in mine shafts drilled in rock that is above the water table and free from seismic activity.

Permanent Radioactive Waste Storage

Current Waste Storage Locations

Nuclear Accidents• Three Mile Island

March 28, 1979 on the Susquehanna River near Harrisburg, PA. The worst nuclear accident in U.S. history was caused by technical failures and human error. About 2 million people were exposed to 1mrem of radiation which led to no deaths or injuries.

• Chernobyl April 26, 1986 in the northern Ukraine. The core melt meltdown caused radioactive materials to spread over a wide area of Europe. Officials at a Sweden Nuclear Power Plant 1st noticed that radioactive particles were on their clothes and thought their own plant was malfunctioning. The worst nuclear accident in the world was caused by a flawed reactor design and inadequately trained operators.

Nuclear Accidents

• 57 immediate deaths with 4000 additional cancer deaths long term. Over 360,000 people were evacuated permanently from the area which remains closed. The initial cover-up of the incident made clean up worse.

17. Uses for Nuclear Chemistry:

A. Half life 1. The time required for ½ of the atoms

of a radioactive isotope to decay. 2. Using radioactive isotopes to

determine the age of an object is called radio carbon dating.

Ex. If I have 1.00 mg of , which has a ½ life of 8.04 days, how much will be left after 1 half-life? After 2? After 3?

13153 I

B. Radioactive Isotopes and Dating

1. All animals and plants contain carbon-14.2. Even though carbon-14 undergoes

radioactive decay, it is constantly replenished during a lifespan.

3. The half-life of carbon-14 is 5730 years.4. The ratio of C-12 to C-14 is compared to another object of a similar age.5. Cannot use carbon-14 dating with objects that never lived.

6. After 4 half lives, the amount of carbon-14 remaining is too small to give reliable data.

7. Carbon-14 is not useful for specimens over 25,000 years old, so Potassium-40

is used instead. It has a half-life of 1.28 billion years.

Radioactive Decay of Strontium-90

What is the ½ Life of Strontium-90???

28 years

How long until no more Strontium-90 remains?

What is the ½ Life of this Radioactive Sample?

2 days

C. Smoke Detectors: 1. Smoke detectors emit a small amount of

alpha particles.2. When smoke particles mix with the gas, they

slow the current flow setting off the alarm.

D. Medical Uses

1. CAT SCAN – the body is analyzed using X-rays.

2. MRI and NMR – detects body’s absorption of radio waves.

3. PET – Measures gamma rays from certain part of the brain.

4. Radioisotopes 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.

Ex) Upper and Lower GI uses

radioactive Barium to detect stomach and intestinal problems. An IVP measures the bodies absorption of radioactive iodine to detect kidney stones.

5. Irradiation can be used as an energy source to treat cancer. The diseased area is exposed to ionizing radiation to kill cancerous cells.

Ex) Ingest large amounts of I-131 kills thyroid cancer, External beam of Co-60 can be directed at a cancerous spot. Irradiation can also be used to sterilize medical instruments and preserve food.

Food Irradiation Symbol

• Radioisotopes found in various parts of the body

18. Exposure to Radioactivity:

A. Continued exposure to radiation is dangerous; therefore, people working in these conditions must monitor their exposure to radiation.

B. People working with radiation wear film badges to monitor their exposure.

C. A dosimeter measures radiation in people, a

Geiger Counter measures radiation of objects.

D. Radiation is usually measured in units of mrems. Higher doses for a longer period of time over a large area cause the most damage, especially for rapidly dividing cells like sex cells and blood cells.

Sources of Our Radiation Exposure