Presentation on theme: "Chapter 8. Radioactive isotopes and Their Applications"— Presentation transcript:
1 Chapter 8. Radioactive isotopes and Their Applications IntroductionProduction of RadioisotopesSome Commonly Used RadionuclidesTracer ApplicationsThickness GaugingRadioisotope DatingRadioisotope Applications in Space Exploration
2 1.1 The applications are myriad very small size of radionuclide radiation sourcesthe great variety of available radionuclidesmedical applicationsindustrial and research applicationseveryday livesdefencethe consumption of isotopes in a country depends on the level of its economic development and industrialization
7 Its activity decreases with time 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
8 Chapter 8. Radioactive isotopes and Their Applications IntroductionProduction of RadioisotopesSome Commonly Used RadionuclidesTracer ApplicationsThickness GaugingRadioisotope DatingRadioisotope Applications in Space Exploration
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 nuclides32S(n,p)32P, Li(n,α)3H 。Parent and daughter is differentChemical separation
12 (n,f) Fission products: > 500 233U、 235U 、 239Pudecay by α emission or by spontaneous fissionI 3 7 Cs and 90Sralmost always decay by β emission(n,γ)Parent and daughter are isotopeChemical separation nolow 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-1Estimate the mass of 60Co, is irradiated 24 hours.M = 1.74e14x24x60x60x60(g)/ 6.022e23 = 1.5 mgIrradiation 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 differentChemical separation(n,γ)Parent and daughter are isotopeChemical separation nolow 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 possibleLow yields
16 (n,γ): （14C：5730a），（19O：26.9s）Accelerator: 25Mg(p,α)22Na ，11C、13N…Nevertheless, is less popular than reactor methodOnly in the cases:High ratio radioactivitychemical extraction possiblesuitable 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 demand123I: 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 demandS 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) 124Ivery 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 material86Y: 86Sr (p,n) 86Yvery 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,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 reactionsThe 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 Therapy20 GBqnatHo (p,n)165Er10.3 hSPECT10 GBq123Te (p,n)I13.2 hPET1 GBq1244.15 dTherapy5 GBq186W (p,n)Re90.6 h1201.35 h5-110Cd (p,n)In69.1 m94Mo (p,n)Tc4.9 hPET, bioconjugates90Zr (p,n)Nb14.6 h89Y (p,n)Zr78.4 h86Sr (p,n)Y14.7 hGenerator, SPECT0.582Kr (p,2n)81Rb4.58 hRb/81mKr2 GBq76Se (p,n)Br16 h66Zn (p,n)Ga9.4 htherapy, bioconjugates1070Zn (p,a)67Cu61.9 hPET & therapy,40 GBq64Ni (p,n)12.7 hPET, encymes, vitaminesFe (p,2n)55Co17.54 hPET: bioconjugatesnat.Sc (p,n)45Ti3.08 hApplicationBatch sizeReactionT1/2Isotope50 GBq50GBq100 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 radionuclideThe 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).
23 daughter's decay rate is limited by the decay rate of the parent. Daughter Decays Faster than the ParentλI < 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 timeAs 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
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 yThe sodium isotope for study of Na transport and hypertension is produced by23Na (n, g) 24Na (b emission, t1/2 = 15 h)For radioimmunoassay, 131I is prepared by127I (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, Lw103Among 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 IntroductionProduction of RadioisotopesSome Commonly Used RadioisotopesTracer ApplicationsThickness GaugingRadioisotope DatingRadioisotope 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 d137Cs a39K (93.2%)59Co88Sr127I133Cs
38 Chapter 8. Radioactive isotopes and Their Applications IntroductionProduction of RadioisotopesSome Commonly Used RadionuclidesTracer ApplicationsThickness GaugingRadioisotope DatingRadioisotope 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) isε: detection efficiencyTo 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 isIf the atomic weight of the radionuclide is A, the minimum mass of radionuclidesin 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 ApplicationsRadioisotopes with short half-lives are used in nuclear medicine becausethey 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 DetectionThis 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 buriedpipe without excavation
44 Tracer will be added to the liquid in the pipe 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
45 4.4 Other applications Pipeline Interfaces Flow Patterns Tracer DilutionSurface Temperature Measurements…
46 5. Thickness gauging Thickness gauging by backscatter transmissionThickness gauging by radiation transmission
47 Thickness control The manufacture of aluminium foil β 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
48 Chapter 8. Radioactive isotopes and Their Applications IntroductionProduction of RadioisotopesSome Commonly Used RadionuclidesTracer ApplicationsThickness gaugingRadioisotope DatingRadioisotope Applications in Space Exploration
49 6.1 Radiocarbon dating principles Carbon has 3 isotopes:12C – stable13C – stable12C:13C = : 1.1114C – radioactiveAbundance:
50 t ½ = 5730 yr. Radiocarbon Forms: in the upper atmosphere Decays: Living Tissue 14C/12C, Tissue ratio same as atmospheric ratioDead Tissue 14C/12C< 14C/12Ctissue atmosphere
51 Clock starts when one dies CalculatedMeasured???ConstantClock 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 reliabilityThis ratio also decays with the same radioactive decaylaw as the radionuclideIt is usually easier to measurethe 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 wood14C 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 BPRadiocarbon age:3979±350 BPSecond 14C date: wood from Hellenistic coffinHistoric 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 yearsCarbon-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 TurinReputed as the burial cloth of Jesus Christ. C-14 dating by 3 independent labs report the Cloth originated during the Medieval times, between A.DCredit: 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 oldBy carbon-14 dating
57 The Radiocarbon Calibration Curve (atmospheric 14C history) Principle: compare radiocarbon dates with independent datesExamples of independent dating: tree-ring counting, coral dates, varve counting,correlation of climate signals in varves with ice coredata from:corals (bright red)lake varves (green)marine varves (blue)speleothems (orange)tree rings (black)Observation:radiocarbon datesare consistently younger than calendar agesequilinetimeHughen 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 elementsNot all elements are radioactive. Those are the most useful for geologic dating are:U-238 Half-life = 4.5 ByK-40 Half-life = 1.25 ByAlso, 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. 5.9Fission 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 loopIn 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” junctionhigh 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
66 Chapter 8. Radioactive isotopes and Their Applications IntroductionProduction of RadioisotopesSome Commonly Used RadionuclidesTracer ApplicationsThickness GaugingRadioisotope DatingRadioisotope Applications in Space Exploration