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1. Chapter 8. Radioactive isotopes and
Their Applications
1. Introduction
2. Production of Radioisotopes
3. Some Commonly Used Radionuclides
4. Tracer Applications
5. Thickness Gauging
6. Radioisotope Dating
7. Radioisotope Applications in Space Exploration

2. Produce

3. 4.1 Radioisotopes are ideal tracers( 示
踪）
The use of some easily detected material to tag or label some
bulk material allows the bulk material to be followed as it moves
through some complex process.
Fluorescent dyes, stable isotopes, radioisotopes …
Why radioisotopes?

4. The amount of tagging material needed
If a sample contains N atoms of the radionuclide, the observed
count rate (CR) is
ε: detection efficiency
To detect the presence of the radionuclide tag, this count rate must be greater than
some minimum count rate CRmin which is above the background count rate.
Then the minimum number of radioactive atoms in the sample needed to detect the
presence of the radionuclide is
If the atomic weight of the radionuclide is A, the minimum mass of radionuclides
in the sample is

5. A typically gamma-ray detector efficiency is ε ~ 0.1 and a
minimum count rate is CRmin ~ 30 min-1
= 0.5 s-1
Thus, for 14
C
(T1/2 = 5730 y = 1.18 x 1011
s), the minimum detectable mass
of 14
C in a sample is:
few atoms are needed!
How about 32
P (T1/2 = 14.26 d) ?
P is often used in plant studies to follow the uptake of
phosphorus by plants.

6. 6
4.2 Medical Applications
Radioisotopes with short half-lives
are used in nuclear medicine
because
• they have the same chemistry in
the body as the nonradioactive
atoms.
• in the organs of the body, they
give off radiation that exposes a
photographic plate (scan) giving
an image of an organ.
Thyroid scan

7. 4.3 Leak Detection
To find the location of a leak in a shallowly buried
pipe without excavation
This use of radionuclide tracers to find leaks or flow paths has
wide applications:
(1)finding the location of leaks in oil-well casings,
(2)determining the tightness of abandoned slate quarries for
the temporary storage of oil,
(3)Locating the positions of freon leaks in refrigeration coils,
(4)finding leaks in heat exchanger piping,
(5)locating leaks in engine seals.

8. Underground pipe leaks
Tracer will be added to the
liquid in the pipe
Detector is moved along the
pipe
The count rate will increase as
there is large amount of water
The radioactive source will be
a short half-life γ emitter

9. 4.4 Other applications
Pipeline Interfaces
Flow Patterns
Flow Rate Measurements
Surface Temperature Measurements
Oil from different producers is often
carried in the same pipeline.
measuring the spatial distribution of
the activity concentration
(1) ocean current movements, (2) atmospheric dispersion of airborne
pollutants, (3) flow of glass lubricants in the hot extrusion of stainless steel, (4)
dispersion of sand along beaches, (5) mixing of pollutant discharges into
receiving bodies or water, and (6) gas flow through a complex filtration system.
measurements of the activity concentrations
of a radioactive tag in the fluid medium
The time required for the radionuclide (and the flowing material) to travel to a
downstream location is given by the time for the activity to reach a maximum
at the downstream location.
krypton atoms are only released at certain high temperatures. remaining 85
Kr
kryptonated surface

10. Thickness gauging by
radiation transmission
Thickness gauging by
backscatter transmission
5. Thickness gauging
Thickness gauging using
stimulated fluorescence

11. Thickness control
The manufacture of aluminium foil

β emitter is placed above the foil and a
detector below it

Some β particle will penetrate the foil
and the amount of radiation is
monitored by the computer

The computer will send a signal to the
roller to make the gap smaller or
bigger based on the count rate

12. Chapter 8. Radioactive isotopes and
Their Applications
1. Introduction
2. Production of Radioisotopes
3. Some Commonly Used Radionuclides
4. Tracer Applications
5. Thickness gauging
6. Radioisotope Dating
7. Radioisotope Applications in Space Exploration

13. Carbon datingCarbon dating
Carbon has 3 isotopes:Carbon has 3 isotopes:
1212
C – stableC – stable
1313
C – stableC – stable
1212
C:C:1313
C = 98.89 : 1.11C = 98.89 : 1.11
1414
C – radioactiveC – radioactive
Abundance:Abundance:
6.1 Radiocarbon dating principles
By observing how much of a
long-lived naturally occurring
radionuclide in a sample
has decayed, it is possible to
infer the age of the sample.

14. Radiocarbon
Forms:Forms:
in the upper atmospherein the upper atmosphere
Decays:Decays:
tt ½½ = 5730 yr= 5730 yr..
pCnN +→+ 1414
−
+→ βNC 1414
Living Tissue 14
C/12
C, Tissue ratio
same as atmospheric ratio
Dead Tissue 14
C/12
C< 14
C/12
C
tissue atmosphere

15. t
t eCC ⋅−
⋅= λ
0
1414
MeasuredMeasured
ConstantConstant
CalculatedCalculated
??????
Clock starts when one dies

16. N ( t ) = N(0)exp(-λt)
we never know N(0).
the initial ratio N(0)/NS of the radionuclide and some stable
isotope of the same element can be estimated with reliability
This ratio also decays with the same radioactive decay
law as the radionuclide
It is usually easier to measure
the specific activity of 14C in a sample, i.e.,
A14 per gram of carbon

17. As a consequence, 14
C is no longer in equilibrium with its
atmospheric production rate. However, before humans upset
this ancient equilibrium, the ratio of 14C to all carbon atoms
in the environment was about , a value
that has remained constant for the last several tens of
thousand years. It is usually easier to measure
the specific activity of 14C in a sample, i.e., A14 per gram of
carbon. This specific activity is proportional to the N14/NC
ratio,

18. What is the age of an archaeological sample of charcoal
from an ancient fire that has a A14(t)/g(C) ratio of 1.2 pCi/g
of carbon?

19. Radiocarbon Measurements and Reporting
 Radiocarbon dates are determined by measuring the
ratio of 14
C to 12
C in a sample, relative to a standard,
usually in an accelerator mass spectrometer.
standard = oxalic acid that represents activity of 1890
wood
14C ages are reported as “14
C years BP”, where BP is 1950

20.  First 14
C date: wood from tomb of
Zoser (Djoser), 3rd Dynasty
Egyptian king (July 12, 1948).
Historic age: 4650±75 BP
Radiocarbon age:
3979±350 BP
 Second 14
C date: wood from
Hellenistic coffin
Historic age: 2300±200 BP
Radiocarbon age: (C-?)
Modern! Fake!
 First “Curve of Knowns”:
6 data points (using seven
samples) spanning AD 600 to
2700 BC.
Half life used: 5720± 47 years
Carbon-14 dating lends itself to age determination of carbon-
containing objects that are between 1,000 and 40,000 years old

21. 21
The Shroud of Turin
Credit: The Image Works
Reputed as the burial cloth of
Jesus Christ. C-14 dating by 3
independent labs report the Cloth
originated during the Medieval
times, between A.D. 1260-1390.

22. 22
Mummified remains found frozen in the
Italian Alps
At least 5000 years old
By carbon-14 dating
In 1991,hikers discovered the body of a
prehistoric hunter that had been entombed in
glacial ice until the ice recently moved and
melted.
pathologists also examined his well-preserved
remains, he died from a fatal wound in the back
—most likely delivered during his prolonged
struggle with at least two other prehistoric
hunters.

23. data from:
corals (bright red)
lake varves (green)
marine varves (blue)
speleothems (orange)
tree rings (black)
The Radiocarbon Calibration Curve (atmospheric 14
C history)
Principle: compare radiocarbon dates with independent dates
Examples of independent dating: tree-ring counting, coral dates, varve counting,
correlation of climate signals in varves with ice core
Hughen et al., 2004
equiline
Observation:
radiocarbon dates
are consistently
younger than
calendar ages
time

24. Source of Error in 14
C dating
1. Variations in geomagnetic flux. Geomagnetic field strength partly
controls 14
C production in the atmosphere because of attenuation
affects on the cosmic flux with increasing magnetic field strength.
2. Modulation of the cosmic-ray flux by increased solar activity (e.g.,
solar flares) leads to attenuation of the cosmic-ray flux.
3. Influence of the ocean reservoir. Any change in exchange rate
between ocean reservoir and atmospheric reservoir will affect the
level of 14
C in the atmosphere.
4. Industrial revolution (ratio of 14
C to stable carbon decreased because
of burning fossil fuels) and bomb effects (14
C to stable carbon
increased because of increased neutron production from detonation
of nuclear bombs in the atmosphere) have made modern organic
samples unsuitable for as reference samples.

25. Radioactive elements
• Not all elements are radioactive. Those are the
most useful for geologic dating are:
• U-238 Half-life = 4.5 By the age of the earth
• K-40 Half-life = 1.25 By rocks
•
• Also, Sm-147, Rb 87, Th-232, U-235

26. The blocking temperature
is the temperature above
which a mineral or rock no
longer behaves as a
closed system and the
parent/daughter ratios may
be altered from that due to
pure radioactive
disintegration.
This can result in resetting
the isotopic clock and/or
give what are called
discordant dates.
These types of problems
have given opponents of
the radiometric dating of
the Earth ammunition to
attack the 4.5 By age
Blocking temperatures for some common minerals and decay series.

27. Fig. 5.9
Fission tracks in an
apatite crystal.
They are produced
when an atom of U-238
disintegrates emitting
an alpha particle, a
Helium nucleus (He-4).
This massive atomic
particle causes massive
structural damage in
the crystal that can be
revealed by etching.
The number of tracks in
a given area is
proportional to the age
of the mineral.
(Why not just use the
U-238 to Pb-206
method directly in such
cases?)

28. 7. Radioisotope Applications in Space
Exploration
Radioisotope Thermoelectric Generator (RTG)
if two dissimilar metals were joined at two locations
that were maintained at different temperatures, an
electric current would flow in a loop
In an RTG, the decay of a radioisotope fuel provides
heat to the “hot” junction, while the other junction
uses radiation heat transfer to outer space to
maintain itself as the “cold” junction
high degree of reliability

29. an RTG loaded with 1 kilogram of plutonium (238) dioxide fuel
would generate between 21 and 29 watts of electric power for
the spacecraft. After five years of travel through space, this
plutonium-fueled RTG would still have approximately 96
percent of its original thermal power level available for the
generation to electric power

30. Applications Summary

31. Alternative Technologies

32. Disposal and Recycling

34. Chapter 8. Radioactive isotopes
and Their Applications
1.Introduction
2.Production of Radioisotopes
3.Some Commonly Used Radionuclides
4.Tracer Applications
5.Thickness Gauging
6.Radioisotope Dating
7.Radioisotope Applications in Space Exploration