chapter 5: harnessing the secrets of the nucleus nuclear energy, nuclear medicine, and a nuclear...

Chapter 5: Harnessing the Secrets of the Nucleus

Nuclear Energy, Nuclear Medicine, and a Nuclear Calendar

© 2003 John Wiley and Sons Publishers

Courtesy Roger Ressmeyer/Corbis Images

http://www.youtube.com/watch?v=d9iOxMFmPlA&feature=share&list=PL20Zb2E-V6NNvY-MjIk68Vc_7P6ih6fuk

Enrico Fermi built the first atomic pile and produced the first controlled chain reaction on December 2, 1942.


Courtesy University of Chicago/AIP Neils Bohr Library

A depiction of the dawn of nuclear power as the first chain reaction begins beneath Stagg Field, Chicago.


“Birth of the Atomic Age by Gary Sheahan/Chicago Historical Society.

Figure 5.1: Schematic diagram of a nuclear power plant.


Cooling towers of a nuclear power plant.


Courtesy David Bartruff/Corbis Images

The nuclear power plant at Chernobyl, after the accident of April 16, 1986.


Courtesy Sipa Press

Disposal of radioactive wastes by burial in a shallow pit.


Courtesy Matthew Neal McVay/Stone/Getty Images

Figure 5.2: Graphical representation of the disappearance of a radioisotope.


Half-life is the time for the radiation level to decrease (decay) to one-half of the original value.

Half-Life

decay curve

Half-Lives of Some Radioisotopes

After one half-life, 40 mg of a radioisotope will decay to 20 mg. After two half-lives, 10 mg of radioisotope remain.

40 mg x 1 x 1 = 10 mg 2 2

1 half-life 2 half-lives

Initial40 mg

20 mg10 mg

Half-Life Calculations

The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?

1) 32 mg

2) 16 mg

3) 8 mg

Learning Check

2) 16 mg

Half life = 13 hrs

Number of half lives = 2

Amount remaining = 64 mg x 1 x 1 = 16 mg 2 2

13 hrs 13 hrs

64 mg 32 mg 16 mg

Solution

Medical Applications

Radioisotopes with short half-lives• Are used in nuclear medicine.• Have the same chemistry in the body as the

nonradioactive atoms.• In the body give off radiation that exposes a

photographic plate (scan), which gives an image of an organ.

23.6

Radioisotopes in Medicine• 1 out of every 3 hospital patients will undergo a nuclear

medicine procedure

• 24Na, t½ = 14.8 hr, emitter, blood-flow tracer

• 131I, t½ = 14.8 hr, emitter, thyroid gland activity

• 123I, t½ = 13.3 hr, ray emitter, brain imaging

• 18F, t½ = 1.8 hr, emitter, positron emission tomography

• 99mTc, t½ = 6 hr, ray emitter, imaging agent

Brain images with 123I-labeled compound

An image of a thyroid gland obtained through the use of radioactive iodine.


Courtesy Custom Medical Stock Photo

Images of human lungs obtained from a γ-ray scan.


Courtesy CNRI/Phototake

http://youtu.be/75MgpuWFzXU

Some Radioisotopes Used in Nuclear Medicine

Learning Check

Which of the following radioisotopes are most likely to be used in nuclear medicine?

1) 40K half-life 1.3 x 109 years

2) 42K half-life 12 hours

3) 131I half-life 8 days

Solution

Which of the following radioisotopes are most likely to be used in nuclear medicine?

Radioisotopes with short half-lives are used in nuclear medicine.

2) 42K half-life 12 hours

3) 131I half-life 8 days

Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain, Nevada.


Courtesy Yucca Mountain Project

A cancer patient receiving radiation therapy.


Courtesy Kelley Culpepper/Transparencies, Inc.

Youtube.com

http://youtu.be/VyoCUWxqcNQ

Figure 5.4: Positron emission by fluorine-18.


The image on the Shroud of Turin.


Courtesy Patrick Mesner/Liaison Agency, Inc. /Getty Images

http://youtu.be/WNJPJ4JwHeE

A medical worker wearing a film badge.


Courtesy Yoav Levy/Phototake

Figure 5.6: The Geiger counter.


27

11.8 Detecting Radiation

• A Geiger counter detects radioactive radiations.

• Ions produced by radiation create an electrical current.

28

Geiger counter

29Chapter 22 Slide 29

• A Geiger counter determines the amount of ionization by detecting an electric current.

• A thin window is penetrated by the radiation and causes the ionization of Ar gas.

• The ionized gas carried a charge and so current is produced.

• The current pulse generated when the radiation enters is amplified and counted.

30Chapter 22 Slide 30

Biological Effects of Radiation• The penetrating power of radiation is a function of

its mass: -rays > -particles >> -particles.

• When ionizing radiation passes through tissue it removes an electron from water to form H2O+ ions.

• The H2O+ ions react with another water molecule to produce H3O+ and a highly reactive •OH radical.

• Free radicals generally undergo chain reactions, producing many radicals in the biomolecules.

31

Radiation Measurement

• The Curie measures the number of atoms that decay in one second. Curie: 1 Ci = 3.7 x 10Curie: 1 Ci = 3.7 x 101010 disintegrationsdisintegrations

• The rad (radiation absorbed dose) measures the radiation absorbed by the tissues of the body.

• The rem (Roentgen equivalent for man (rem) ) measures the biological damage.

Girl being scanned with a Geiger counter after a nuclear accident.


Courtesy AP/Wide World Photos

Receiving radiation from a dental X-ray.


Courtesy PhotoDisc, Inc./Getty Images

34

Background Radiation

• A person is exposed to radiation from naturally occurring radioisotopes and medical X rays.

35

Effects of RadiationEffects of Radiation


(a) What percentage of the world’s nuclear power plants are located in the United States? (b) Rank the countries of Table 5.1 in terms of the percentage of electric power produced from nuclear plants. Where in this ranking does the United States stand?

QUESTION


What is the most serious form of damage that could occur if a natural disaster such as a hurricane, a tornado, or an earthquake struck a nuclear power plant? Explain.

QUESTION


Describe one advantage of a breeder reactor over a conventional nuclear reactor. Describe one disadvantage.

QUESTION


What is the ultimate fate of every radioactive atom now in existence?

QUESTION


If each of the radioisotopes of Table 5.3 were stored at the Yucca Mountain site, which would still be present after 10,000 years at a level of 10% or more of the original amount?

QUESTION


(a) What is one cost of electric power production by nuclear power that is not a factor in the use of coal, petroleum, or natural gas? (b) What is one cost of electric power production by these fuels that is not a factor in the use of nuclear power?

QUESTION


Name and describe two types of biological damage caused by ionizing radiation.

QUESTION


How is each of the following used in medical diagnosis and/or therapy? (a) I-131; (b) Tc-99m; (c) Co-60.

QUESTION


Into what element is an atom of nitrogen-13 transformed when it emits a positron?

QUESTION


What would the ratio of Pb-206 to U-238 atoms be if the sample of meteorite in the exercise were 18.0 x 109 years old?

QUESTION


Which of the following can be dated by radiocarbon techniques: (a) a rock; (b) a leather slipper; (c) a wooden boat; (d) a mummified body; (e) a silver spoon. Describe your reasoning.

QUESTION


Which one or more of the detection devices described in this Section would you use if you wished to determine immediately whether the residue left by a spilled chemical is radioactive? Which would you use if you wanted to determine the total, cumulative amount of radiation you might be exposed to in the course of an entire month?

QUESTION


Assign the data of each of the sources of Table 5.6 into one of two categories: (a) originates in human activities; (b) natural, not dependent on human activities. What total percentage of exposure is associated with each of the two categories?

QUESTION

chapter 5: harnessing the secrets of the nucleus nuclear energy, nuclear medicine, and a nuclear...

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