chapter 8. radioactive isotopes and their applications 1.introduction 2.production of radioisotopes...

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

1.1 The applications are myriad

very small size of radionuclide radiation sources

the great variety of available radionuclides

medical applicationsindustrial and research applicationseveryday livesdefence

the consumption of isotopes in a country depends on the level of its economic development and industrialization

1.2 Stable and Radioactive nuclides

N = # of neutrons

Z = # of protons

Radioactive Nuclides:2800

Natural: 238U 、 232Th 、 226Ra…

Man-made: 239Pu 、 239Np 、 131I

The Decay Path of 4n + 2 or 238U Family 238U234U234Pa

234Th230Th

226Ra

222Rn 218At

218Po214Po214Bi

214Pb

210Po 210Bi206Pb 210Pb 206Tl 210Tl 206Hg

Minor route

Major route

decay

decay

Radioactivity - 238U radioactive decay series

Radioactive Series in Nature

Have different penetrating ability with materials of different thickness and densitiesKill cellsCause cell mutationIonise moleculesHave the same chemical properties as non-radioactive isotopes of the same elementIts activity decreases with time


1.Introduction




5.Thickness Gauging



Produce

nPHeAl 10

3015

42

2713

eSiP 01

3014

3015

2. Production of Radioisotopes

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, 6Li(n,α)3H 。

Parent and daughter is different

Chemical separation

(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 ?

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?

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 ?

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)

chemical extraction techniques possibleLow yields

65Cu(p,n)65Zn…

(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

Commercial Isotope Production

with cyclotrons ~30 MeV proton beam

• 201Tl: 203Tl (p,3n) 201Pb 201Tl most important SPECT isotope, commercialized by all radiopharmaceutical Co. The worldwide installed production capacity exceeds the demand

• 123I: 124Xe (p,2n) 123Cs 123I very important SPECT isotope, corresponding target design from Karlsruhe is installed worldwide. Batch size up to 10 Ci possible.

• 111In: 112Cd (p,2n) 111Inimportant for certain SPECT techniques, expensive because of low demand

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) 64Gutherapeutic isotope for RIT, PET allows the measurement of the biodistribution during therapy.

• 186Re: 186W(p,n) 186Re186Re (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,)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.

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.

Production of other useful isotopes with the PET cyclotron

Production of other useful isotopes

Auger Therapy20 GBqnatHo (p,n) 165Er10.3 h165Er

SPECT10 GBq123Te (p,n) 123I13.2 h123I

PET1 GBq124Te (p,n) 124I4.15 d124I

Therapy5 GBq186W (p,n) 186Re90.6 h186Re

PET10 GBq120Te (p,n) 120I1.35 h120I

PET5-10 GBq110Cd (p,n) 110In69.1 m110In

PET10 GBq94Mo (p,n) 94Tc4.9 h94Tc

PET, bioconjugates10 GBq90Zr (p,n) 90Nb14.6 h90Nb

PET, bioconjugates10 GBq89Y (p,n) 89Zr78.4 h89Zr

PET, bioconjugates5-10 GBq86Sr (p,n) 86Y14.7 h86Y

Generator, SPECT0.5-1 GBq82Kr (p,2n) 81Rb4.58 h81Rb/81mKr

PET2 GBq76Se (p,n) 76Br16 h76Br

PET10 GBq66Zn (p,n) 66Ga9.4 h66Ga

therapy, bioconjugates10-20 GBq70Zn (p,) 67Cu61.9 h67Cu

PET & therapy, 40 GBq64Ni (p,n) 64Cu12.7 h64Cu

PET, encymes, vitamines0.5-1 GBqnatFe (p,2n) 55Co17.54 h55Co

PET: bioconjugates10-20 GBqnat.Sc (p,n) 45Ti3.08 h45Ti

ApplicationBatch sizeReactionT 1/2Isotope

Auger Therapy40 GBqnatHo (p,n) 165Er10.3 h165Er

SPECT20 GBq123Te (p,n) 123I13.2 h123I

PET2 GBq124Te (p,n) 124I4.15 d124I

Therapy20 GBq186W (p,n) 186Re90.6 h186Re

PET10 GBq120Te (p,n) 120I1.35 h120I

PET20 GBq110Cd (p,n) 110In69.1 m110In

PET20 GBq94Mo (p,n) 94Tc4.9 h94Tc

PET, bioconjugates20 GBq90Zr (p,n) 90Nb14.6 h90Nb

PET, bioconjugates20 GBq89Y (p,n) 89Zr78.4 h89Zr

PET, bioconjugates50 GBq86Sr (p,n) 86Y14.7 h86Y

Generator, SPECT20 GBq82Kr (p,2n) 81Rb4.58 h81Rb/81mKr

PET10 GBq76Se (p,n) 76Br16 h76Br

PET50GBq66Zn (p,n) 66Ga9.4 h66Ga

therapy, bioconjugates50 GBq70Zn (p,) 67Cu61.9 h67Cu

PET & therapy, 100 GBq64Ni (p,n) 64Cu12.7 h64Cu

PET, encymes, vitamines50 GBqnatFe (p,2n) 55Co17.54 h55Co

PET: bioconjugates100 GBqnat.Sc (p,n) 45Ti3.08 h45Ti

ApplicationBatch sizeReactionT 1/2Isotope

with < 20 MeV proton induced reactions

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).

Three Component Decay Chains

Daughter Decays Faster than the Parent λI < λ2,

daughter's decay rate is limited by the decay rate of the parent.

Important Radionuclide Generators99Mo–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

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.

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.

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."

Production timeAs long as possible?

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

Radioisotope Processing

isotope extraction,separation purification © 2009 QSA 9 Global Incseparation, purification, containmentwaste reduction, solidification, disposal

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)

Syntheses of Radioactive IsotopesOver 1300 radioactive nuclides have been made by nuclear reactions. The most well known is the production of 60Co, by neutron capture,

59Co (100%) (n, ) 60mCo and 60Co - and emission t1/2 = 5.24 y

The sodium isotope for study of Na transport and hypertension is produced by

23Na (n, ) 24Na ( emission, t1/2 = 15 h)

For radioimmunoassay, 131I is prepared by

127I (n, ) 128I ( EC, t1/2 = 25 m)

There are many other production methods.

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. . .

Syntheses of Transuranium Elements -continue

Very heavy elements are synthesized using accelerated nuclides,

246Cm + 12C 254No102 + 4 n,

252Cf + 10B 247Lw103 + 5 n,

252Cf + 11B 247Lw103 + 6 n.

These syntheses completed the analogous of rare-earth elements. These elements were made during the cold war

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.


1.Introduction


3.Some Commonly Used Radioisotopes


5.Thickness Gauging



• 39K (93.2%)

• 59Co

• 88Sr

• 127I

• 133Cs

一些放射性同位素40K 1.28x108 a

60Co 5.27 a

90Sr 28.8 a

131I 8.04 d

137Cs 30.12 a

Some Radioisotopes Used in Nuclear Medicine


1.Introduction




5.Thickness Gauging



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?

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 thepresence of the radionuclide is

If the atomic weight of the radionuclide is A, the minimum mass of radionuclidesin the sample is

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:

few atoms are needed!

How about 32P (T1/2 = 14.26 d) ?

P is often used in plant studies to follow the uptake of phosphorus by plants.

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

4.3 Leak Detection

To find the location of a leak in a shallowly buriedpipe 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.

Underground pipe leaksTracer will be added to the liquid in the pipeDetector is moved along the pipeThe count rate will increase as there is large amount of waterThe radioactive source will be a short half-life γemitter

4.4 Other applications

Pipeline Interfaces

Flow Patterns

Tracer Dilution

Surface Temperature Measurements

…

Thickness gauging by radiation transmission

Thickness gauging bybackscatter transmission

5. Thickness gauging

Thickness control

The manufacture of aluminium foilβ emitter is placed above the foil and a detector below itSome β particle will penetrate the foil and the amount of radiation is monitored by the computerThe computer will send a signal to the roller to make the gap smaller or bigger based on the count rate


1.Introduction




5.Thickness gauging



Carbon datingCarbon dating

Carbon has 3 Carbon has 3 isotopes:isotopes:

1212C – stableC – stable1313C – stableC – stable

1212C:C:1313C = 98.89 : 1.11C = 98.89 : 1.11

1414C – radioactiveC – radioactive

Abundance: Abundance:

6.1 Radiocarbon dating principles

Radiocarbon

Forms:Forms: in the upper atmospherein the upper atmosphere

Decays:Decays:

tt ½ ½ = 5730 = 5730 yryr..

pCnN 1414

NC 1414

Living Tissue 14C/12C, Tissue ratio same as atmospheric ratio

Dead Tissue 14C/12C< 14C/12C

tissue atmosphere

tt eCC

01414

MeasuredMeasured

ConstantConstant

CalculatedCalculated

??????

Clock starts when one dies

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 reliabilityThis ratio also decays with the same radioactive decaylaw as the radionuclide

It is usually easier to measurethe specific activity of 14C in a sample, i.e., A14 per gram of carbon

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

• First 14C date: wood from tomb of Zoser (Djoser), 3rd Dynasty Egyptian king (July 12, 1948).

Historic age: 4650±75 BPRadiocarbon age: 3979±350 BP

• Second 14C date: wood from Hellenistic coffin

Historic age: 2300±200 BPRadiocarbon 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

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.

56

Mummified remains found frozen in the Italian Alps

At least 5000 years oldBy 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.

data from:corals (bright red)lake varves (green)marine varves (blue)speleothems (orange)tree rings (black)

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

Hughen et al., 2004

equiline

Observation:radiocarbon datesare consistently younger than calendar ages

time

Source of Error in 14C dating

1. 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.

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 14C in the atmosphere.

4. 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.

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

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.

Blocking temperatures for some common minerals and decay series.

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?)

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

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

Applications Summary

Disposal and Recycling


1.Introduction




5.Thickness Gauging



chapter 8. radioactive isotopes and their applications 1.introduction 2.production of radioisotopes...

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