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

2. 1.1 The applications are myriad
very small size of radionuclide radiation sources
the great variety of available radionuclides
medical applications
industrial and research applications
everyday lives
defence
the consumption of isotopes in a country depends on the level of its economic development and industrialization

4. 1.2 Stable and Radioactive nuclides
Z = # of protons
Radioactive Nuclides:
2800
Natural: 238U、232Th、226Ra…
Man-made: 239Pu、239Np、131I
N = # of neutrons

5. Radioactivity - 238U radioactive decay series

6. Radioactive Series in Nature

7. Its activity decreases with time
Have different penetrating ability with materials of different thickness and densities
Kill cells
Cause cell mutation
Ionise molecules
Have the same chemical properties as non-radioactive isotopes of the same element
Its activity decreases with time

8. Chapter 8. Radioactive isotopes and Their Applications
Introduction
Production of Radioisotopes
Some Commonly Used Radionuclides
Tracer Applications
Thickness Gauging
Radioisotope Dating
Radioisotope Applications in Space Exploration

9. Select suitable nuclides
Produce
Select suitable nuclides
Radioactive nuclei
Nuclear reactor
accelerator
natural

10. 2. Production of Radioisotopes

11. 2.1 Nuclear Reactor Irradiation Neutron flux: 1010~1013 cm-2·s-1，
(n,α), (n,p), (n,f), (n,γ)
(n,α)、(n,p): En High, σ Small，Light nuclides
32S(n,p)32P, Li(n,α)3H 。
Parent and daughter is different
Chemical separation

12. (n,f) Fission products: > 500
233U、 235U 、 239Pu
decay by α emission or by spontaneous fission
I 3 7 Cs and 90Sr
almost always decay by β emission
(n,γ)
Parent and daughter are isotope
Chemical separation no
low ratio activities ?

13. Cross Sections and Rate
The cross section for neutron capture of cobalt is 17 b. Estimate the rate of nuclear reaction when 1.0 g of 59Co is irradiated by neutrons with an intensity of 1.0e15 n s-1 cm-2 in a reactor.
Solution: In a nuclear reactor, the entire sample is bathed in the neutron flux.
N = 6.022e23 *1.0 / 59 = 1.02e22 59Co rate =  N I = 17e-24 * 1.02e22 * 1.0e15 = 1.74e14 60Co s-1
Estimate the mass of 60Co, is irradiated 24 hours.
M = 1.74e14x24x60x60x60(g)/ 6.022e23 = 1.5 mg
Irradiation time: the longer, the better?

14. How to separate (n,α)、(n,p): 32S(n,p)32P, 6Li(n,α)3H 。
Parent and daughter is different
Chemical separation
(n,γ)
Parent and daughter are isotope
Chemical separation no
low ratio activities ?

15. 2.2 Accelerator Production
To produce radioisotopes that are proton rich and that generally decay by positron emission
(p,n)、(p,α)、(d,n)、(d,2n)、(d,α)、(α,n)、(α,2n)
65Cu(p,n)65Zn…
chemical extraction techniques possible
Low yields

16. (n,γ): （14C：5730a），（19O：26.9s）
Accelerator: 25Mg(p,α)22Na ，11C、13N…
Nevertheless, is less popular than reactor method
Only in the cases:
High ratio radioactivity
chemical extraction possible
suitable half lifetime

18. Commercial Isotope Production with cyclotrons ~30 MeV proton beam
201Tl: Tl (p,3n) 201Pb Tl most important SPECT isotope, commercialized by all radiopharmaceutical Co. The worldwide installed production capacity exceeds the demand
123I: 124Xe (p,2n) 123Cs I very important SPECT isotope, corresponding target design from Karlsruhe is installed worldwide. Batch size up to 10 Ci possible.
111In: 112Cd (p,2n) 111In important for certain SPECT techniques, expensive because of low demand
S 31: The (p;2n) process is the standard reaction in classical medical isotope production with cyclotrons. Most important are 123I, 111In and 67Ga. There are many other radionuclides of commercial interest that can be produced via this reaction. However, the 201Tl dictates the parameters of a production cyclotron:

19. Isotope Production with Cyclotrons (p,n) process with ~15 MeV protons
18F: 18O (p, n) 18F most important PET isotope, commercialized by many centers using dedicated small cyclotrons, however also done at 30 MeV or even at 65 MeV cyclotrons as well (Nice)
124I: 124Te (p,n) 124I
very important PET isotope with commercial interest (in-vivo dosimetry), large scale production technology not yet available, same technology could be used for medium scale 123I production based on 123Te target material
86Y: 86Sr (p,n) 86Y
very important PET isotope with commercial interest (in-vivo dosimetry)
64Cu: 64Ni (p,n) 64Gu
therapeutic isotope for RIT, PET allows the measurement of the biodistribution during therapy.
186Re: 186W(p,n) 186Re
186Re (3.7 d) is one of the two important therapeutic isotopes of Re. The advantage over 188Re (16 h) is the longer half-life, the advantage over the reactor based 185Re(n,g)186Re process is the carrier free quality.
Remark: The (p,n) process requires ~15 MeV only, and is performed normally at dedicated small PET cyclotrons. However, due to the high productivity of dedicated targets combined with a modern system for beam diagnosis allows to run these reaction under economical conditions at larger cyclotrons as well using only a small fraction of the available beam time.
S 33: As said before, today the highly developed standard in target technology for 18F production as well as modern diagnostic tools allow the production of 18F in a 10 Ci level within about 2 hours. Thus, one can practically obtain up to 5 Ci batches of [18F]FDG for a national clinical PET program. Due to the high productivity today transport times of up to 6 hours are accepted. The bottle neck in FDG utilization is not the productivity of a cyclotron center, it is clearly the scanning capacity and the patient flow. Under this consideration it is justified to day spending few hours beam time of a large cyclotron per day aiming producing large quantities of FDG for commercial purpose (done in Nice, France since many years using the 65 MeV cyclotron, see next slide)
Alternatively one can also consider other (p;n) processes to be performed with a large multipurpose cyclotron because of the following motivation: R&D, development of new technologies, education (university type) and training of personal. Results of those activities are qualified personal for the isotope work in the medical environment, new production technologies and new radiopharmaceuticals.

20. Production of other useful isotopes with the PET cyclotron
with < 20 MeV proton induced reactions
The irradiation of solid materials requires much better beam quality parameters than gas targets. Consequently, beam homogenisation and beam manipulation is needed, ussually not possible at the PET cyclotrons.
External beam lines, known from classical isotope production at cyclotrons, will take this function over.
The new generation of multi-purpose cyclotrons will be equipped with high-tech diagnostic tools and provide higher beam current than in the past.
Auger Therapy
20 GBq
nat
Ho (p,n)
165 Er
10.3 h
SPECT
10 GBq
123
Te (p,n) I
13.2 h
PET
1 GBq
124
4.15 d
Therapy
5 GBq
186
W (p,n) Re
90.6 h
120
1.35 h 5 -
110
Cd (p,n) In
69.1 m 94
Mo (p,n) Tc
4.9 h
PET, bioconjugates 90
Zr (p,n) Nb
14.6 h 89
Y (p,n) Zr
78.4 h 86
Sr (p,n) Y
14.7 h
Generator, SPECT
0.5 82
Kr (p,2n) 81 Rb
4.58 h
Rb/
81m Kr
2 GBq 76
Se (p,n) Br
16 h 66
Zn (p,n) Ga
9.4 h
therapy, bioconjugates 10 70
Zn (p, a ) 67 Cu
61.9 h
PET & therapy,
40 GBq 64
Ni (p,n)
12.7 h
PET, encymes, vitamines
Fe (p,2n) 55 Co
17.54 h
PET: bioconjugates
nat.
Sc (p,n) 45 Ti
3.08 h
Application
Batch size
Reaction T
1/2
Isotope
50 GBq
50GBq
100 GBq

21. 2.3 Principles of a Generator
The use of short-lived radionuclides has grown considerably, because larger dosages of these radionuclides can be administered to the patient with only minimal radiation dose and produce excellent image quality.
A generator is constructed on the principle of the decay-growth relationship between a long-lived parent radionuclide and its short-lived daughter radionuclide
The most widely used radionuclide generator is a 99Mo (T1/2 = 65.9 d) “cow" which can be ''milked'' to extract the short-lived 99mTc daughter (T1/2 = 6.01 h).

22. Three Component Decay Chains

23. daughter's decay rate is limited by the decay rate of the parent.
Daughter Decays Faster than the Parent
λI < λ2,
daughter's decay rate is limited by the decay rate of the parent.

24. Important Radionuclide Generators
99Mo–99mTc Generator:-
The 99Mo radionuclide has a half-life of 66 hr and decays by β emission.
The radionuclide 99mTc has a half-life of 6 hr and decays to 99Tc by isomeric transition of 140 keV.
The extreme usefulness of this generator is due to the excellent radiation characteristics of 99mTc, namely its 6-hr half-life, very little electron emission, and a high yield of 140-keV γ rays (90%), which are nearly ideal for the current generation of imaging devices in nuclear medicine

25. The chemical property of the daughter nuclide must be distinctly deferent from that of the parent nuclide so that the former can be readily separated. In a generator, basically a long-lived parent nuclide is allowed to decay to its short-lived daughter nuclide and the latter is then chemically separated. The importance of radionuclide generators lies in the fact that they are easily transportable and serve as sources of short-lived radionuclides in institutions far from the site of a cyclotron or reactor facility.

26. A radionuclide generator consists of a glass or plastic column fitted at the bottom with a fritted disk. The column is filled with adsorbent material such as alumina, on which the parent nuclide is adsorbed.
the daughter activity is eluted in a carrier free state with an appropriate solvent, leaving the parent on the column.
A radionuclide generator consists of a glass or plastic column fitted at the bottom with a fritted disk. The column is filled with adsorbent material such as alumina, on which the parent nuclide is adsorbed. The daughter radionuclide grows as a result of the decay of the parent until equilibrium is reached. Because there are diferences in chemical properties, the daughter activity is eluted in a carrier free state with an appropriate solvent, leaving the parent on the column.

27. Production time
As long as possible?
After elution, the daughter activity starts to grow again in the column until an equilibrium is reached; the elution of activity can be made repeatedly.
the 99mTc is "milked" from the 90Mo "cow."

28. Desirable properties of radionuclide generator
should be simple, convenient, rapid to use, and give a high yield of the daughter nuclide repeatedly and reproducibly.
It should be properly shielded to minimize radiation exposure, and sturdy and compact for shipping.
The generator eluate should be free from the parent radionuclide and the adsorbent material.
Other extraneous radioactive contaminants should be absent in the eluate.
must be sterile and pyrogen-free. Elution or ‘‘milking’’ of the generator is also carried out under-aseptic-conditions

29. Radioisotope Processing
isotope extraction,
separation purification © 2009 QSA 9 Global Inc
separation, purification, containment
waste reduction, solidification, disposal

30. 2.4 Production requirements
keep the radiation dose to the patient as low as possible.
generally have a short half life and emit only gamma-rays preferred.
From an energy point of view, not be so low not too high : ~ 100 and 200 keV.
needs to be incorporated into some form of radiopharmaceuticale capable of being produced in a form which is amenable to chemical, pharmaceutical and sterile-processing.
GMP (Good Manufacture Practice for drugs)

31. Syntheses of Radioactive Isotopes
Over 1300 radioactive nuclides have been made by nuclear reactions. The most well known is the production of 60Co, by neutron capture,
59Co (100%) (n, g) 60mCo and 60Co - b and g emission t1/2 = 5.24 y
The sodium isotope for study of Na transport and hypertension is produced by
23Na (n, g) 24Na (b emission, t1/2 = 15 h)
For radioimmunoassay, 131I is prepared by
127I (n, ) 128I (b+, b- EC, t1/2 = 25 m)
There are many other production methods.

32. Syntheses of Transuranium Elements
From 1940 to 1962, about 11 radioactive transuranium elements (almost 100 nuclides) have been synthesized, about one every two years. Representative isotopes of the 11 elements are neptunium (Np93), plutonium (Pu94), americium (Am95), curium (Cm96), berklium (Bk97), californium (Cf98), einsteinium (Es99), fermium (Fm100), mendelevium (Md101), nobelium (No102), and lawrencium (Lw103).
La57 , Ce, Pr59, Nd, Pm61, Sm, Eu63 , Gd, Tb65 , Dy, Ho67, Er, Tm69, Yb, Lu71 Ac89, Th, Pa91, U92, Np93 , Pu , Am95, Cm, Bk97, Cf, Es99, Fm, Md, No, Lw103
Among these, tons of 239Np, and its decay products 239Pu have been made for weapon and reactor fuel. Successive neutron capture reactions are major methods, but accelerators are involved. . .

33. Syntheses of Transuranium Elements -continue
Very heavy elements are synthesized using accelerated nuclides,
246Cm + 12C  254No n,
252Cf + 10B  Lw n,
252Cf + 11B  247Lw n.
These syntheses completed the analogous of rare-earth elements. These elements were made during the cold war

34. Recovery of Fission Products:
Many useful radionuclides are produced copiously as fission products and can be obtained by chemically processing spent fuel from reactors.
These include 137Cs and 90Sr.
Spent nuclear fuel also contains important transuranic isotopes produced by (multiple) neutron absorption(s) and radioactive decay reactions. Important transuranic radionuclides include 238Pu, 244Cm and 252Cf. These heavy radionuclides usually decay by a emission or by spontaneous fission.

35. Chapter 8. Radioactive isotopes and Their Applications
Introduction
Production of Radioisotopes
Some Commonly Used Radioisotopes
Tracer Applications
Thickness Gauging
Radioisotope Dating
Radioisotope Applications in Space Exploration

36. 一些放射性同位素 40K 1.28x108 a 39K (93.2%) 60Co 5.27 a 59Co 90Sr 28.8 a 88Sr
131I d
137Cs a
39K (93.2%)
59Co
88Sr
127I
133Cs

37. Some Radioisotopes Used in Nuclear Medicine

38. Chapter 8. Radioactive isotopes and Their Applications
Introduction
Production of Radioisotopes
Some Commonly Used Radionuclides
Tracer Applications
Thickness Gauging
Radioisotope Dating
Radioisotope Applications in Space Exploration

39. 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?

40. 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

41. A typically gamma-ray detector efficiency is ε ~ 0
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 14C (T1/2 = 5730 y = 1.18 x 1011 s), the minimum detectable mass of 14C in a sample is:
How about 32P (T1/2 = d) ?
P is often used in plant studies to follow the uptake of phosphorus by plants.
few atoms are needed!

42. 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

43. 4.3 Leak Detection
This use of radionuclide tracers to find leaks or flow paths has wide applications:
finding the location of leaks in oil-well casings,
determining the tightness of abandoned slate quarries for the temporary storage of oil,
Locating the positions of freon leaks in refrigeration coils,
finding leaks in heat exchanger piping,
locating leaks in engine seals.
To find the location of a leak in a shallowly buried
pipe without excavation

44. Tracer will be added to the liquid in the pipe
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 γemitter

45. 4.4 Other applications Pipeline Interfaces Flow Patterns
Tracer Dilution
Surface Temperature Measurements …

46. 5. Thickness gauging Thickness gauging by
backscatter transmission
Thickness gauging by radiation transmission

47. 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

48. Chapter 8. Radioactive isotopes and Their Applications
Introduction
Production of Radioisotopes
Some Commonly Used Radionuclides
Tracer Applications
Thickness gauging
Radioisotope Dating
Radioisotope Applications in Space Exploration

49. 6.1 Radiocarbon dating principles
Carbon has 3 isotopes:
12C – stable
13C – stable
12C:13C = : 1.11
14C – radioactive
Abundance:

50. t ½ = 5730 yr. Radiocarbon Forms: in the upper atmosphere Decays:
Living Tissue 14C/12C, Tissue ratio same as atmospheric ratio
Dead Tissue 14C/12C< 14C/12C
tissue atmosphere

51. Clock starts when one dies
Calculated
Measured
???
Constant
Clock starts when one dies

52. This ratio also decays with the same radioactive decay
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

53. Radiocarbon Measurements and Reporting
Radiocarbon dates are determined by measuring the ratio of 14C to 12C 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 “14C years BP”, where BP is 1950

54. First 14C 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 14C 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

55. The Shroud of Turin
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
Credit: The Image Works

56. Mummified remains found frozen in the Italian Alps
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.
At least 5000 years old
By carbon-14 dating

57. The Radiocarbon Calibration Curve (atmospheric 14C 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
data from:
corals (bright red)
lake varves (green)
marine varves (blue)
speleothems (orange)
tree rings (black)
Observation:
radiocarbon dates
are consistently younger than calendar ages
equiline
time
Hughen et al., 2004

58. Source of Error in 14C dating
Variations in geomagnetic flux. Geomagnetic field strength partly controls 14C production in the atmosphere because of attenuation affects on the cosmic flux with increasing magnetic field strength.
Modulation of the cosmic-ray flux by increased solar activity (e.g., solar flares) leads to attenuation of the cosmic-ray flux.
Influence of the ocean reservoir. Any change in exchange rate between ocean reservoir and atmospheric reservoir will affect the level of 14C in the atmosphere.
Industrial revolution (ratio of 14C to stable carbon decreased because of burning fossil fuels) and bomb effects (14C 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.

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

60. Blocking temperatures for some common minerals and decay series.
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 geologists cite.

61. Fission tracks in an apatite crystal.
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?)

62. 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

63. 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

64. Applications Summary

65. Disposal and Recycling

66. Chapter 8. Radioactive isotopes and Their Applications
Introduction
Production of Radioisotopes
Some Commonly Used Radionuclides
Tracer Applications
Thickness Gauging
Radioisotope Dating
Radioisotope Applications in Space Exploration