Sources radioactives artificielles

Présentation au sujet: "Sources radioactives artificielles"— Transcription de la présentation:

1 Sources radioactives artificielles
Production d’Isotopes scellées et non scellés Jour 4 – Leçon 1

2 Discuter les sources radioactives artificielle
Objectifs Discuter les sources radioactives artificielle les caractéristiques des sources scellées et non scellées et comment les isotopes sont produits

3 Contenus Echantillons de Sources de Radionucléide
Sources Alpha, Beta, Gamma, X et Neutron Sources scellées et non scellées Production des isotopes radioactifs Générateurs d’isotopes

4 Radioactivité Relative
Exemple Unités Spéciales Unités SI (37x) Echantillon de l’environnement picocurie millibequerel 10-3 Laboratoire standard nanocurie 10-9 bécquerel 100 Traceur in-vitro microcurie 10-6 kilobequerel 103 Médicine Nucléaire millicurie 10-3 meéabequerel 106 Source de calibration curie 100 gigabequerel 109 Source télétherapie kilocurie 103 terabequerel 1012 Irradiateur mégacurie 106 pétabequerel 1015 The activity of sources varies widely depending on the application.

5 Où trouver les Radionucléides
Réacteur Combustible Produits de Fission Produits d’Activation Hors Réacteur Médical Industrie Militaire Aviation Support Recherche Commercial In reactor applications, there are basically 3 sources of radionuclides. The fuel itself, the radionuclides produced by fission of the uranium and activation products (stable materials made radioactive by bombardment with neutrons from the fission process). In materials applications, there are many areas where radionuclides are employed. The radionuclides are obtained either from a nuclear reactor or from particle accelerators. Some sources result from Naturally Occurring Radioactive Material sometimes referred to as NORM.

6 Sources de Radionucléides
Exemples de Sources de Radionucléides Médical Usage Humain (MBq-TBq) Médecine Nucléaire Diagnostique (99mTc, 131I, 153Gd, 125I, 201Tl) Thérapeutique (131I, 32P, 89Sr) Radiothérapie Télé thérapie (60Co) Curiethérapie (137Cs, 192Ir, 198Au, 125I, 109Pd) Usage Non-Humain (KBq) Laboratoire In-Vitro (125I, 51Cr, 59Co) This and the next few slides attempt to list some of the non-reactor uses for radioactive material. The range of activities for each group is listed along with some of the more common isotopes. This is not a complete list but serves to indicate the diversity of applications and sources.

7 Sources de Radionucléides
Echantillons de Sources de Radionucléides Industrie (GBq-PBq) Radiographie (192Ir, 60Co, 137Cs) Exploitation des mines (241Am, 137Cs, 60Co, 238U, 131I, 3H) Irradiateurs (60Co, 137Cs) Jauges Fixes (137Cs, 60Co, 147Pm) Portables (241Am, 137Cs) Cycle du combustible (U)

8 Sources de Radionucléides
Echantillons de Sources de Radionucléides Support (KBq ou moins) Calibration/ Sources de contrôle (60Co, 137Cs, 239Pu, 241Am, 252Cf, 238U, 90Sr, 232Th) Laboratoires Standards (plusieurs) Recherche (MBq) Chromatographies (63Ni) Formation (plusieurs)

9 Sources de Radionucléides
Echantillons de Sources de Radionucléides Commercial (variables – typiquement MBq ou moins) Person el Montre-bracelet(3H, 147Pm) Vaisselle (U) Loisirs manteaux Lanterne(232Th) Sûreté Détecteurs de fumée (241Am) Avertissement/ Signe d’Exit (3H) Blindage (238U) Service Dispositifs antistatiques (210Po)

10 Sources de Radionucléides
Echantillons de Sources de Radionucléides Militaire (MBq) Armes Non-Nucléaires Projectiles performants (238U) Survie Boussoles à lentilles (3H, 147Pm) Détection d’agents chimiques (63Ni, 241Am, 3H)

11 Sources de Radionucléides
Echantillons de Sources de Radionucléides Aviation (Bq-MBq) Opérationel Aéronefs à voilure fixe Indicateur du niveau d’huile (85Kr) aileron Contrepoids (238U) Panneaux de revêtement/Nickel de Magnésium(232Th) Éclateurs / Allumeurs(60Co) Hélicopter Contrôle de l’intégrité et la détection de glace(90Sr)

12 Sources de Radionucléides
Echantillons de Sources de Radionucléides Aviation (MBq-TBq) Affichages historiques / Aéronefs d’époque (226Ra) Articles de sûreté Feux de piste, marqueurs et les panneaux de sortie (3H)

13 Echantillon de sources Alpha, Bêta,
Gamma Some sources emit alpha, beta and gamma radiation. Some of these sources are used for calibration of instruments. Others are selected because they are pure, alpha, beta or gamma emitters. A source which emits alpha, beta and gamma can be converted to a virtually pure gamma emitter by the use of shielding.

14 Echantillon de sources Alpha
Americium-241is used in smoke detectors while mantles used for kerosene or propane heating units or lamps contain Thorium These devices are readily available and are often used to demonstrate the presence of radioactive material in commercially available items. There are very few pure alpha emitters. Most also emit betas and gamma radiation. Polonium-210 is one of the few which is almost a pure alpha emitter (it actually emits a gamma ray but with a very low yield).

15 Echantillon de sources Bêta
Beta sources are probably the most commonly used for commercially available items. When combined with a phosphor they can emit light which is useful for night illumination. In this slide we see some compasses, markers, exit signs and airport runway markers all containing beta emitting radioactive material, usually tritium (hydrogen-3). The item in the lower right hand corner of the slide is a beta applicator for medical treatment of abnormalities of the eye. It uses strontium-90. Promethium-147 is also commonly used.

16 Echantillon de sources Gamma
Sealed sources are almost always gamma sources since the characteristic of being sealed acts to shield beta and alpha radiation. Most high energy gamma emitters such as cobalt-60 and caesium-137 are also beta emitters. Encapsulating the source results in shielding the beta radiation but permitting the gamma radiation to escape.

17 Echantillon de sources de Neutron
There are very few neutron radioactive sources. Most neutrons are generated by particle accelerators, nuclear reactors or alpha-beryllium sources. The only radioisotope commonly used for neutron calibration and neutron radiography is californium-252. The alpha beryllium source on the right is housed in a metal drum containing paraffin which is used to slow down the neutrons emitted from the beryllium. Il existe plusieurs sources de neutron alpha-beryllium (Pu-Be, Am-Be, Ra-Be, Po-Be etc) ou Californium-252

18 Echantillon de sources de Ray-X
X-ray sources are plentiful. Most medical facilities have numerous x-ray machines for diagnosis. Treatment centers usually have linear accelerators which accelerate electrons. The electron beam can be used directly or it can be converted to x-rays by using a target. X-ray units are also used in dentistry and in veterinary practice. X-ray machines are also used for scanning inanimate objects such as in airport baggage scanners.

19 Sources scellées A sealed source is one that prevents the radioactive material from being released to the environment. A sealed source is not a safe source. Significant quantities of radiation can be emitted from a sealed source. It is only the physical material that is sealed, not necessarily the radiation that it emits. Sealed sources are typically used when the material inside is dispersible. This means the material inside is typically in powder or gaseous form or it can be composed of solid particles small enough so that if the encapsulation were to fail, the particles could disperse and cause a serious health problem. In the image here, the source is in the form of ceramic microspheres. Liquids are usually not used in sealed sources. Sealed sources are typically doubly encapsulated. This affords a measure of double protection. Should one of the two capsules fail, the second should be able to contain the material.

20 Sources scellées This is an example of a typical high energy gamma sealed source such as a cobalt-60 teletherapy source. The arrow indicates the threaded portion on the source and the schematic.

21 Sources scellées Although the source itself may appear outwardly to be solid, it can, in fact, contain many tiny sources. If the encapsulation were to be breached, the tiny sources could easily disperse. Being so small they could remain in unshielded locations without detection for extended periods. Although each tiny source emits much less radiation than the encapsulated source, the small size means they can expose people for long periods of time without detection. The source on the right is a one-piece solid source. Although still rather small (approximately 2 x 3 cm) it is clearly visible which affords some degree of protection in that it can be avoided if the individual knows that the object is hazardous. 18 mm 19 mm

22 Sources scellées 19 mm Sealed sources do not all look like the ones in the previous slides. In medical therapy, sealed sources shaped like needles, seeds and wires are not uncommon. As is evident in this slide, the seed pictured in the schematic is less than 1 mm in diameter and only 5 mm long. The seeds in the plastic wire are even smaller. Such sources can easily be misplaced resulting in the potential for serious exposures.

23 Sources scellées Most industrial sources are sealed sources with durable encapsulation. The source on the left is used in well-logging and must withstand tremendous temperatures and pressures when lowered thousands of meters underground. The source on the right is a Category IV pool type irradiator source. The radioactive material generates considerable heat and the sources must withstand numerous cycling from water to air as the sources are lowered for storage and raised for use.

24 Sources scellées This is a schematic of an alpha-beryllium neutron emitting sealed source.

25 Source non scellées Unsealed sources are very commonly used in some areas. Nuclear Medicine is a classic example. During diagnostic Nuclear Medicine procedures, liquid radioactive material is injected into a patient to study internal organs. For therapeutic procedures, as in this image, the patient may be required to drink the radioactive material through a straw or in some cases swallow a capsule containing the radioactive material. Obviously, the prime concern for unsealed sources is dispersal. Spills are common and can cause widespread contamination and exposures. If the half life of the material is short and the location can be isolated and is not needed for some other use, decontamination can be postponed until the radioactive material decays to safe levels. However, if the location must be available for use, decontamination must be accomplished taking into consideration the safety of the decontamination crew relative to the hazard posed to others from the contamination.

26 Production des Isotopes
La plupart des isotopes disponibles dans le commerce utilisés en médecine et l'industrie sont produites par bombardement à l’aide de neutrons dans les réacteurs ou par bombardement à l’aide de particules chargées dans des accélérateurs(NARM). Certains isotopes sont obtenus à partir de la désintégration d'autres isotopes qui ont été produits par les procédés énumérés ci-dessus. Un des exemples de ce type d'isotope est le 99mTc qui est obtenu sous forme de la désintégration de 99Mo qui est lui-même issu de la fission (sous-produit). These processes were discussed in detail in other presentations.

27 Production de Radionucléides
Part 2. Radiation Physics Production de Radionucléides Radiation Protection in Nuclear Medicine Cible Réaction Radionucléide Cr-50 (n,γ) Cr-51 Mo (n, γ) Mo-99 Xe (n, γ) Xe-125 => I-125 Te (n, γ) Te-131 => I-131 Zn-68 (p,2n) Ga-67 Cd (p,n) In-111 Tl (p,3n) Pb-201 => Tl-201 Te (p,2n) I-123 I-127 (p,5n) Xe-123 => I-123 U (n,f) Zr-99 => Nb-99 => Mo-9

28 Part 2. Radiation Physics
CYCLOTRON Part 2. Radiation Physics Radiation Protection in Nuclear Medicine This is an image of the research cyclotron in Uppsala, Sweden Uppsala, Sweden

29 Générateurs d’Isotopes
In some cases the material is eluted from an isotope generator. In this device, a relatively long lived source such as molybdenum-99 is bound to some material so that it is immobile. However, it is not a sealed source. The molybdenum-99 decays to technetium-99m. A fluid is passed over the molybdenum and captures the technetium, washing it away into a vial. The remaining molybdenum stays bound in the device producing more technetium as it decays still further. The newly formed technetium can be extracted at some later time. This slide shows two different types of molybdenum-technetium generators. The 99Mo/99mTc radioisotope generator developed during the late nineteen fifties revolutionized the practice of diagnostic nuclear medicine. Since then, many other radionuclide generator systems have been investigated, although none has turned out to be as widely used or successful.

30 Générateurs d’Isotopes
Père fils 52Fe 52mMn 62Zn 62Cu 68Ge 68Ga 72Se 72As 82Sr 82Rb 118Te 118Sb 122Xe 122I Père Fils 128Ba 128Cs 191Os 191mIr 195mHg 195mAu 81Rb 81mKr 178W 178Ta 188W 188Re 115Cd 115mIn Recent advances in molecular biology, PET imaging, monoclonal antibody technology, radionuclide therapy, and many new areas of research in nuclear medicine have stimulated interest in readily available sources for various radionuclides. Generators for PET and SPECT radionuclides continue to be investigated. Some of the possibilities are shown here. Generators can be used to produce other radionuclides. For example, a source of radium-226 can be used to produce radon Since the half life of the initial radionuclide is much longer than the half life of the daughter radionulcide, a secular equilibrium situation exists. Equilibrium was discussed in a previous lecture. Many radionuclides decay to other radionuclides. The question is whether the daughter radionuclide is useful for some purpose and if it can be easily isolated from the parent.

31 Générateurs d’Isotopes
Père Dem-vie fils Demi-vie 66Ni 2.3j 66Cu 5.1m 69mZn 0.6j 69Zn 55m 112Pd 0.9j 112Ag 3.2h 115Cd 2.2j 115mIn 4.5h 128Ba 2.4j 128Cs 3.6m 132Te 3.2j 132I 2.3h 188W 69.4j 188Re 17h 224Ra/212Pb 3.7j 212Bi 1h 225Ra 14.8j 213Bi 46m For maximum convenience and wide acceptance of their clinical use, sufficient quantities of relatively short-lived radionuclides need to be readily available at the site of use. A number of these can possibly be obtained from long-lived parents through generator systems including those listed here One could also use the approach of labeling an intermediate half life radionuclide that decays in-vivo to a much shorter half life daughter with high beta emission. Since the daughter will be in equilibrium with the parent, it will exert an in-situ cytotoxic effect over a prolonged period, essentially as an "in-vivo generator".

32 Où trouver plus d’Information
Cember, H., Johnson, T. E, Introduction to Health Physics, 4th Edition, McGraw-Hill, New York (2009) International Atomic Energy Agency, Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources (PGEC), Training Course Series 18, IAEA, Vienna (2002)