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В© 2003 John Wiley and Sons Publishers
Chapter 5: Harnessing the Secrets of the
Nucleus
Courtesy Roger
Ressmeyer/Corbis Images
Nuclear Energy, Nuclear Medicine, and a
Nuclear Calendar
В© 2003 John Wiley and Sons Publishers
Courtesy University of
Chicago/AIP Neils Bohr Library
Enrico Fermi built the first atomic pile and produced the first controlled chain reaction on
December 2, 1942.
В© 2003 John Wiley and Sons Publishers
“Birth of the Atomic Age by Gary Sheahan/Chicago Historical Society.
A depiction of the dawn of nuclear power as the first chain reaction begins beneath
Stagg Field, Chicago.
В© 2003 John Wiley and Sons Publishers
Figure 5.1: Schematic diagram of a nuclear power plant.
В© 2003 John Wiley and Sons Publishers
Courtesy David Bartruff/Corbis Images
Cooling towers of a nuclear power plant.
В© 2003 John Wiley and Sons Publishers
Courtesy Sipa Press
The nuclear power plant at Chernobyl, after the accident of April 16, 1986.
В© 2003 John Wiley and Sons Publishers
Courtesy Matthew Neal McVay/Stone/Getty
Images
Disposal of radioactive wastes by burial in a shallow pit.
В© 2003 John Wiley and Sons Publishers
Figure 5.2: Graphical representation of the disappearance of a radioisotope.
Half-Life
Half-life is
the time for
the radiation
level to
decrease
(decay) to
one-half of
the original
value.
decay curve
Half-Lives of Some Radioisotopes
Half-Life Calculations
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
Initial
40 mg
1 half-life
20 mg
2 half-lives
10 mg
Learning Check
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
Solution
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
64 mg
13 hrs
32 mg
16 mg
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.
Radioisotopes in Medicine
•
1 out of every 3 hospital patients will undergo a nuclear
medicine procedure
•
24Na,
•
131I,
tВЅ = 14.8 hr, b emitter, thyroid gland activity
•
123I,
tВЅ = 13.3 hr, g-ray emitter, brain imaging
•
18F,
tВЅ = 1.8 hr, b+ emitter, positron emission tomography
•
99mTc,
tВЅ = 14.8 hr, b emitter, blood-flow tracer
tВЅ = 6 hr, g-ray emitter, imaging agent
Brain images
with 123I-labeled
compound
23.6
В© 2003 John Wiley and Sons Publishers
Courtesy Custom Medical
Stock Photo
An image of a thyroid gland obtained through the use of radioactive iodine.
В© 2003 John Wiley and Sons Publishers
Courtesy CNRI/Phototake
Images of human lungs obtained from a Оі-ray scan.
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
В© 2003 John Wiley and Sons Publishers
Courtesy Yucca Mountain Project
Construction of a tunnel that will be used for burial of radioactive wastes deep within
Yucca Mountain, Nevada.
В© 2003 John Wiley and Sons Publishers
Youtube.com
Courtesy Kelley Culpepper/Transparencies, Inc.
A cancer patient receiving radiation therapy.
В© 2003 John Wiley and Sons Publishers
Figure 5.4: Positron emission by fluorine-18.
В© 2003 John Wiley and Sons Publishers
Courtesy Patrick Mesner/Liaison Agency, Inc.
/Getty Images
The image on the Shroud of Turin.
В© 2003 John Wiley and Sons Publishers
Courtesy Yoav Levy/Phototake
A medical worker wearing a film badge.
В© 2003 John Wiley and Sons Publishers
Figure 5.6: The Geiger counter.
11.8 Detecting Radiation
• A Geiger counter
detects radioactive
radiations.
• Ions produced by
radiation create an
electrical current.
27
Geiger counter
28
• 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.
29
Chapter 22
Slide 29
Biological Effects of Radiation
• The penetrating power of radiation is a function of
its mass: g-rays > b-particles >> пЃЎ-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.
30
Chapter 22
Slide 30
Radiation Measurement
• The Curie measures the number of atoms that
decay in one second. Curie: 1 Ci = 3.7 x 1010
disintegrations
• 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.
31
В© 2003 John Wiley and Sons Publishers
Courtesy AP/Wide World Photos
Girl being scanned with a Geiger counter after a nuclear accident.
В© 2003 John Wiley and Sons Publishers
Courtesy PhotoDisc, Inc./Getty Images
Receiving radiation from a dental X-ray.
Background Radiation
• A person is exposed to
radiation from
naturally occurring
radioisotopes and
medical X rays.
34
Effects of Radiation
35
QUESTION
В© 2003 John Wiley and Sons Publishers
(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
В© 2003 John Wiley and Sons Publishers
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
В© 2003 John Wiley and Sons Publishers
Describe one advantage of a breeder reactor
over a conventional nuclear reactor. Describe
one disadvantage.
QUESTION
В© 2003 John Wiley and Sons Publishers
What is the ultimate fate of every radioactive
atom now in existence?
QUESTION
В© 2003 John Wiley and Sons Publishers
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
В© 2003 John Wiley and Sons Publishers
(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
В© 2003 John Wiley and Sons Publishers
Name and describe two types of biological
damage caused by ionizing radiation.
QUESTION
В© 2003 John Wiley and Sons Publishers
How is each of the following used in medical
diagnosis and/or therapy? (a) I-131; (b) Tc99m; (c) Co-60.
QUESTION
В© 2003 John Wiley and Sons Publishers
Into what element is an atom of nitrogen-13
transformed when it emits a positron?
QUESTION
В© 2003 John Wiley and Sons Publishers
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
В© 2003 John Wiley and Sons Publishers
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
В© 2003 John Wiley and Sons Publishers
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
В© 2003 John Wiley and Sons Publishers
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?
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