uses of nuclear radiation, fission and fusion. figure 4.2: the penetrating power of radiation. ©...

Uses of Nuclear Radiation, Fission and

Fusion

Figure 4.2: The penetrating power of radiation.

© 2003 John Wiley and Sons Publishers

Figure 4.4: The components of α rays, β rays, and γ rays.

© 2003 John Wiley and Sons Publishers

Natural Background(cosmic rays, earth minerals) 81%

Medicineand Diagnostics 15%

Consumer Products(televisions sets,smoke detectors) 4%

Origins of radiation exposure

Human Exposure to Radiation

Uses of Nuclear Radiation/Energy

• Radioactive Dating• Medicine

– Chemotherapy – Power pacemakers– Diagnostic tracers

• Agriculture– Irradiate food– Pesticide– Fertilizer evaluation

• Energy – Fission– Fusion

22,920 years ago22,920 years ago

Carbon-14 dating

17,190 years ago17,190 years ago

11,460 years ago11,460 years ago

5730 years ago5730 years ago

PresentPresent

Radioisotopes in Medicine

Radioisotopes likeTc-99 can be used to detect bone cancer.The Tc-99 accumulatesin areas of abnormalbone metabolism and then detection of the nuclear radiation (gammarays) show the location ofthe cancer.

Radioisotopes in Agriculture

-Radioactive tracers used to determine the effectivenessof fertilizers.

- Cobalt-60 producesgamma rays that areused to irradiate food.

Fission

• Nuclear fission occurs when scientists bombard a large isotope with a neutron.

• This collision causes the larger isotope to break apart into two or more elements.

• These reactions release a lot of energy.

• You can calculate the amount of energy produced during a nuclear reaction using an equation developed by Einstein: E=mc2

Chain Reaction Figure

Nuclear Power Plants• If the neutrons can be controlled, then the

energy can be released in a controlled way. Nuclear power plants produce heat through controlled nuclear fission chain reactions.

• The fissionable isotope is contained in fuel rods in the reactor core. All the fuel rods together comprise the critical mass.

• Control rods, commonly made of boron and cadmium, are in the core, and they act like neutron sponges to control the rate of radioactive decay.

Nuclear Reactors• The reaction is kept in

check by the use of control rods.

• These block the paths of some neutrons, keeping the system from reaching a dangerous supercritical mass.

Nuclear Power Plants (cont)• In the U.S., there are approximately 100 nuclear reactors,

producing a little more than 20% of the country’s electricity.

• Advantages– No fossil fuels are burned.

– No combustion products (CO2, SO2, etc) to pollute the air and water.

• Disadvantages– Cost - expensive to build and operate.– Limited supply of fissionable Uranium-235.– Accidents (Three Mile Island & Chernobyl) – Disposal of nuclear wastes

Nuclear Reactors

In nuclear reactors the heat generated by the reaction is used to produce steam that turns a turbine connected to a generator.

What is Nuclear Fusion?

• Nuclear Fusion is the energy-producing process taking place in the core of the Sun and stars

• The core temperature of the Sun is about 15 million °C. At these temperatures hydrogen nuclei fuse to give Helium and Energy. The energy sustains life on Earth via sunlight

Energy from Fusion

H 2

1 +He 4

2+ n1

0H

3

1 +Energy

Nuclear Fusion• Fusion would be a superior

method of generating power.– The good news is that the

products of the reaction are

not radioactive.– The bad news is that in order to achieve fusion, the

material must be in the plasma state at several million kelvins.

– Tokamak apparati like the one shown at the right show promise for carrying out these reactions.

– They use magnetic fields to heat the material.