Most atoms are _________________ - their atomic mass does not _________________ over time.

Some atoms' atomic mass does change - this is a result of an unstable _________________ .

These atoms change to produce different _________________ .

Radium --> Helium + _________________ + energy

_________________ - substances that have unstable nuclei.

Radioactive _________________ - the breakdown of the unstable nucleus.

_________________ radiation - the emitted particles and energy released due to radioactive decay

All objects gives off some type of electromagnetic _________________ (EMR)

The electromagnetic _________________ contains the different types of electromagnetic radiation from high energy to low energy.

Each type of EMR has several common properties:

• A Form Of Energy With No _________________

• Travels Speed Of _________________

• Emitted By "_________________ " Atoms And/Or Atomic Decay

• Move Through Space As Packets Of Energy Called _________________

• The Energy Of Photons Is Related To Their Frequency

The effects of radiation on living things

_________________ radiation - high energy EMR (X-rays, gamma rays) can cause damage to living things. Electrons are ejected from molecules.

_________________ radiation - low energy EMR (UV, visible light, etc.)

Causes electrons to move to higher energy levels or increases the vibration of molecules (microwave ovens)

Questions:

1. What are cathode rays and how are they produced?

2. What did the German physicist W.K. Roentgen discover while he was working with a cathode ray tube?

3. Where did the name X-rays come from?

4. List several substances that block X-rays?

5. Explain Henri Becquerel (a French physicist) experiment with X-rays.

6. What did he discover?

There are three major kinds of radiation:

Ernest Rutherford was the first to show that radiation consisted of different types of rays

In the late 1800's, Rutherford in an experiment, focused a beam of alpha particles at a thin sheet of gold foil.

What do you think happened?

If the atoms in the gold were solid spheres - what would happen to the alpha particles when they hit them.

If the atoms in the gold were mostly empty space - what would happen to the alpha particles when they hit them.

In this experiment, most of the alpha particles went right through the gold foil indicating that atoms are made of mostly empty space.

Rutherford observed - that an atom contains a massive nucleus surrounded mostly by _________________ space.

_________________ number = mass of protons and neutrons

# of Neutrons = Mass number - atomic number

Isotopes - atoms of the same elements having _________________ atomic masses

Some isotopes are radioactive - _________________

Atomic notation

Vocabulary Words

Of the 90 natural elements - there are _________________ isotopes.

About _________________ of these isotopes are radioactive.

As radioactive isotopes _________________ - they give off alpha or beta particles and gamma radiation.

Radiation _________________ be detected by human senses

Geiger counter - detects radioactive _________________ as they hit its detector.

Background radiation - a constant level of _________________ radioactivity.

_________________ particles - most massive ( contain 2 protons and 2 neutrons) can be blocked

_________________ particles - small mass - 8,000 times smaller than alpha particles, fast moving electrons - not very dangerous to living cells

_________________ rays - (caused by nuclei in excited state) high energy electromagnetic radiation - most penetrating

During a nuclear explosion, when a U-235 atom splits, it gives off energy in the form of heat and Gamma radiation, which is the most powerful form of radioactivity and the most lethal.

Nuclear Balancing

Mass numbers are _________________ in nuclear equations, and while elements may change in a nuclear reaction, the atomic numbers (which may include electrons) are also conserved.

The total number of the mass numbers and atomic number are conserved in nuclear equations.

Example

The decay of a Radium-226 nucleus

Ra ------> Rn + He

In the above reaction - atoms can be created and destroyed. However, the total mass is still conserved.

In beta decay - a neutron changes into a proton and an electron

n -----> p + e

Pb ---> Bi + e

Beta emission causes no change in mass number - but it does cause a change in atomic number.

Co ---> Ni + e

half-life - the rate of _________________ of radioisotopes

One half-life - the time it takes for one-half the atoms in a sample of radioactive material to decay.

If you have $1000 and were told that you can only spend 1/2 of it per year (half-life analogy) - how many years would it be before you have $31.25 left and how much would be left after 10 half-lives (that is 10 years).

Carbon-14 has a half-life of 5,730 years

C ---> N + e

Radon-223 has a half-life of 3.28 days

AR ---> PO + He

Nuclear fission - the _________________ of an atom into various products

Uranium-235 usually splits into barium and krypton

U + n -------> Ba + Kr + n

The energy lies in the forces that hold the protons and neutrons together in the _________________ .

In nuclear reactions a small amount of mass is converted into _________________ causing a large amount of energy to be released.

Einstein's equation E=mc2 (Energy = mass loss X speed of light squared)

Conversion Of 1 Gram Of Uranium = 700,000 Gallons Of Petroleum

In a chain reaction, the release of _________________ keep a nuclear reaction going by splitting more nuclei.

Since most of the atom is empty space, the probability that a neutron formed in a fission reaction will split another nuclei depends on the amount of fissionable material available.

Certain amounts of fissionable material are needed for a chain reaction to occur - this is called the _________________ mass.

For the uranium used in the first atomic bomb about 110 lbs.. (50 kilograms) of pure U-235 was needed

Today, nuclear reactors are mostly used to produce _________________ . There are over _________________ commercial nuclear reactors in the United States generating 20% of our electricity.

There are over _________________ nuclear reactors in the world which produce over 15% of the world's electricity. Illustrate how a nuclear power plant works. Use overhead of power plant diagrams.

Worldwide Nuclear Power

Major parts of nuclear reactors

 

• Fuel Rods containing _________________ are placed in the reactor where the fission reaction occurs.

 

• Control Rods containing boron or cadmium, can _________________ neutrons. The movement of these rods can control the rate of nuclear fission.

 

• Moderator - usually heavy water (D2O) to help slow down high _________________ neutrons and transfer heat.

 

• Generator - the heat produced by the nuclear reactor turns water into steam which moves a turbine connected to a generator. The generator produces _________________ .

 

• Cooling System - so much heat is generated that the water used to _________________ ______ ___________also turns to steam which is condensed in the large cooling towers.

The white _________________ we see rising from the cooling towers is not smoke -- it is condensed steam (a cloud).

Nuclear fusion involves the formation of a new, more massive atom by forcing two less-massive nuclei to _________________ .

In nuclear fusion positrons are released. Positrons have almost no mass and carry a _________________ charge.

4 Hydrogen ------> He + 2 positrons

Nuclear fusion reactions have been used in the hydrogen bomb. The large amounts of heat needed to start a fusion reaction is ignited by a small fission bomb -- causing the fusion reaction to begin.

Today's technology does not permit us to use fusion reactions to produce electricity.

The power in a fusion reaction is the reaction that occurs on the _________________ , the ultimate source of energy.

Medical applications of radioactive substances:

Other applications:

Tracer substances are used to trace abnormalities in body functions.

Ionizing radiation can cause damage in human tissues.

How do we measure radiation exposure?

REM (Roentgen equivalent man) is a way of _________________ the impact of radiation on the human body.

It is currently difficult to assess small amounts of radiation exposure because it does not have noticeable immediate effects.

Small doses of radiation may affect the nucleic acids in _________________ : Minor damages causes mutations - changes in the structure of DNA

High doses can cause severe tissue _________________ .

We are all exposed to _________________ amounts of radiation.

There are natural and human sources of background radiation:

Natural sources include:

Human sources include:

Radon gas (an inert gas) can be produced as uranium-238 _________________ in the soil.

Rn then decays into polonium (Po), bismuth (Bi) and lead (Pb) - during each decay, alpha particles are released.

Radon can enter the basement and due to lack of air circulation - it can stay there.

54% of all background radiation is caused by radon gas _________________ .

A. Answer the following questions.

1. Define rem.

2. At what radiation dose (in rem) does a person start to vomit and lose hair.

3. At what radiation does a person become more sensitive to infections?

4. At what radiation will a person die?

5. In the film Fat Man And Little Boy -- what does did the scientist receive in the experimental accident? What happened to him?

6. What type of cancer is associated with radiation exposure?

7. Recently, in Tom River, New Jersey, there was a high incidence of leukemia - scientists are currently analyzing the areas food and water - what do you believe they should look for?

8. List two sources of natural and human sources of background radiation.

9. List in order from highest to lowest, the sources of background radiation. What percent of the background radiation is caused by human sources?

10. What is considered a safe level of radiation exposure? Note 1 rem = 1000 mrem

11. What things can you do to reduce your exposure to radiation?

12. Radon is an inert or noble gas. What does this mean?

13. When did the public first become aware of the presence of this gas in some U.S. homes?

14. How does radon enter the house and why does it stay there?

15. Explain the threat of inhaling radon gas.

16. Why is the threat of radon gas greater in new and modern homes?

17. How can we test for radon gas?

 

 

 

 

 

 

 

 

 

 

B. Complete Your Turn on p. 326-327.

1. Answer the questions

1. What is the Greek myth about Pandora's Box?

2. What is the problem with the garbage in the home discussed in the 1st paragraph?

3. In an average nuclear reactor, how many fuel rods must be replaced each year?

4. What is the problem with the used or spent fuel rods taken from a nuclear reactor?

5. List some of the isotopes left over in spent Uranium-235 fuel rods.

6. What is the current federal law concerning nuclear power plant reactor waste?

7. How may sites has the USA government opened to accept radioactive waste for disposal?

8. Which volume of waste is greater, commercial (power plant) or military?

9. Where is the USA government considering to set up waste disposal sites?

10. How will this waste be dealt with once a site is opened for nuclear waste?

11. How does vitrification fit into the disposal methods?

12. What is vitrification?

13. How many countries in the world now have permanent burial sites for nuclear waste?

14. How much nuclear waste does an average American nuclear reactor produce each year?

15. Besides military and nuclear reactors, what other source produces radioactive waste? Explain your answer.

16. Out of the two sites chosen, the most promising USA permanent disposal site seems to be Yucca mountain. Where is Yucca mountain located?

17. The term NIMBY has now come into the debate over Yucca mountain. What does NIMBY mean and how would that affect people living in that area of the world?

18. What kind of container is used now to store nuclear wastes? Is it crash proof?

19. Where does Limerick nuclear power plant store its nuclear waste?

20. How is nuclear waste disposal like "Pandora's box"?

 

Please answer these questions after the video

 

11. Why did the government and power plant officials wait 36 hours before telling the people living in the area about the disaster?

12. List some techniques used to clean up the damages and contaminated area around the plant.

13. What happened to the town nearest to the power plant?

14. What is the name of our nearest nuclear power plant?

15. What happened at TMI (Three Mile Island) nuclear power plant?

16. Can a nuclear power plant in the United States explode like a nuclear bomb?

 

17. Summarize the damage caused at the power plant that lasted ten years.

18. Does the area appear to be safe to live in?

19. What precautions still need to be taken at the nuclear power plant?

20. How does the design of the Chernobyl nuclear power plant differ from a typical nuclear power plant made in the United States?

 

 

 

 

Nuclear Issues

1. Briefly list some other aspects of modern life that involve both risks and benefits.

2. Why would radon gas concentration tend to be higher in a basement than in an upstairs room.

3. Why do radon daughter products pose a greater health risk than radon itself?

4. One proposal for solving the nuclear waste problem is to use rockets or the space shuttle to shoot the wastes out into space. What are some problems with this idea?

5. Even if all nuclear power plants were phased out in the next five years, nuclear energy disposal would remain a controversial issue that still needed attention. Why is this so?

6. Why do you think other countries are using nuclear power to a much greater extent than we are in the United States?

7. Should the United States continue to use nuclear power to generate electricity?

8. About 20% of our electricity is made by nuclear power, what will happen if we abruptly discontinue using nuclear energy?

9. Where will we get other energy sources and what might happen to air and water quality?

10. What should we do with our high level nuclear waste?