R adiations & Radioactivity

Radiations & Radioactivity Kyoung Won Jang Bio Optics Lab, School of Biomedical Engineering, Konkuk University

Atom and Nucleus 1. Atom : a (can’t) + tomos (divide); basic unit of matter  origins of electro-magnetic waves and radiations • electron Radiations • nucleus

Atom and Nucleus • Discovery of electron (Thomson’s experiment) + • electron • - minus • - mass • - particle • cathode ray (-) - I’m Thomson

Atom and Nucleus • Discovery of nucleus (Rutherford’s experiment) • alpha ray (+) • nucleus • - atom is almost empty • - plus • - dense • - relative heavy

Atom and Nucleus • Electron shell • : atom has discrete electron shells •  each shell has different energy level • energy level • N > M > L > K … • electron binding energy • K > L > M > N … • ※Coulomb’s law  • nucleus • K • L • M • N

Atom and Nucleus • Ionization and excitation radiation (characteristic x-rays) ionization - • N excitation • M - - • L - - • N - • M E ground state • L • K • K • nucleus

Atom and Nucleus 2. Nucleus : consist of nucleons  nucleon: proton and neutron • Proton • - mass: 1.673 ×10-27 kg • - charge: 1.6 ×10-19 C • Neutron • - mass: 1.675 ×10-27 kg • - charge: non • cf) electron • - mass: 9.11 ×10-31 kg • - charge: -1.6 ×10-19 C • nucleus • neutron • neutron • proton • proton nucleon

Atom and Nucleus • Notation of nuclide • X: elementary symbol • A: mass number (proton + neutron) • Z: atomic number (proton) • Type of nuclide • - isotope: same Z  1H, 2H • - isobar: same A  3H, 3He • - isotone: same N (A - Z)  3H, 4He • - isomer: all same but excited or not  99Tc, 99mTc

Atom and Nucleus • Energy level of nucleus radiation (α, β, γ) E • excited • nucleus • stable • nucleus • nucleus 60Co β γ energy level γ 60Ni

Atom and Nucleus • Nuclear force • - forces between nucleons •  nuclear force (attractive force ) •  electrical force (repulsive force ) d • nucleon • nucleon • d < 10-15m •  nuclear force • d > 10-15m •  electrical force

Atom and Nucleus • Atomic mass unit • - 1 amu = 1.66 × 10-27 kg = 931.48 MeV • Mass defect and binding energy • - mass of nucleus < sum of nucleons • - ∆M = [Z·Mp + N·Mn + Z·Me] - M • 1/12 of 12C • “amu” or “u” binding energy E = Δmc2 nucleons nucleus

Radiation • 1. Definition of radiation • : all particles and electro-magnetic waves •  here, we treat only ionizing radiations • Characters of the ionizing radiation? • - tasteless, odorless, intangible, invisible, inaudible… • energy transmission, ionization • Although we can’t sense with our sensing organs, the radiation interacts with our body!! • Therefore the radiation is very dangerous!!

Radiation • 10 CFR 20 (radiation standard in USA) • : title 10 of the code of federal regulations in section 20 • α-ray, β-ray, γ-ray, x-ray, high-speed electron, neutron, proton, other atomic particle • not including: radio wave, visible, infrared, ultraviolet • Korean nuclear law in section 6 • - α-ray, β-ray, γ-ray, x-ray, over 1MeV electron, neutron, proton, other atomic particle

Radiation • Radiations from atom x-ray electron - E α-ray ±β-ray ± n p proton E p n p neutron n γ-ray

Radiation • 2. Classification of radiation • natural or artificial? • natural radiation: radiations existing in natural • from concrete to our body • radiations from radioactive isotope (α, β, γ-ray ) • cosmic-ray (proton: 87%, α-ray: 12%, etc. particles) • artificial radiation: made radiations by artificially • medical x-ray • radiations from artificial radioactive isotope

Radiation • ionizing or non-ionizing? • ionizing radiation: radiations ionizing air or materials • direct ionizing radiation: charged particles • ·α-ray, β-ray, electron, proton • non-direct ionizing radiation: high-energy photon or non-charged particle • · γ-ray, x-ray, neutron • non-ionizing radiation: radiations except ionizing radiations •  visible light, infrared, ultraviolet, microwave …

Radiation • electro-magnetic or particle? • electro-magnetic radiation • : radiations having electro-magnetic character • x-ray, γ-ray • ·“wave” • : interference • : diffraction • ·“photon” • : photoelectric effect

Radiation • ※ electro-magnetic waves

Radiation • particle radiation • : radiations having kinetic energy with mass •  direct ionizing particle •  indirect ionizing particle electron - n p α-ray ±β-ray ± p n proton p n neutron

Radiation • 3. Radiation source • Radioactive isotope • - spontaneous radioactive isotope •  238U, 60Co … • - artificial radioactive isotope •  99mTc, 252Cf … • Accelerator high-energy particle beam ± ± accelerate charged particle target high-energy photon beam

Radiation • 4. Actions of radiations • Penetration • : radiations loss their energy by penetrating some • materials •  each radiation has different penetration depth • according to its energy and type & density of material • - α-ray: large charge, mass ○  penetration↓ • - β-ray: ½ charge of α-ray, mass ○ penetration↓ • - x or γ-ray: no charge, mass X  penetration↑ • - neutron: no charge, mass ○ penetration↑

Radiation • Ionization • : if the radiations are irradiated on some materials, • electrons or charged particles are ejected from atoms •  basic principle of radiation detector α-ray β-ray x-ray, γ-ray neutron paper aluminum lead water or paraffin

Radiation • Photography • : if the radiation is irradiated on a photographic plate, • the plate becomes dark  used as film badge radiation beam radiation beam photographic plate photographic plate

Radiation • ※ Radiation detectors • - ionization chamber • - scintillation detector electrometer gas or air current - radiation + photomultiplier tube (PMT) scintillating light radiation scintillator

Radiation • 5. Uses of radiations • Tracer • - material + radioactive isotope • - detecting the radiations from radioactive isotope •  we can trace the material by measuring radiation • Radiotherapy • - radio-sensitivity of tumor↑ • - ionization → electron → cutoff the DNA chain •  we can remove the tumor by irradiation of radiation

Radiation • Breeding • - irradiation → change the DNA •  we can breed the race with upgraded character by • changing of DNA • Non-destructive inspection • - radiation penetrates matters with different absorption • coefficient • - x-ray in medical, inspection in air port •  we can inspect the inside of our body or matter • without any destruction

Radiation • 6. Energies of radiations • Energy of x- or γ-ray

Radiation • Energy of charged-particle • - α-ray (v = 1.8× 107 [m/s])

Radioactivity 1. Definition of radioactivity : rate of ‘spontaneous’ nuclear transformation  # of transformations/sec γ-ray • A • B α-ray n p p ±β-ray n ± 1/sec transformation × 10 transformation × 10 transformation × 10 transformation • B • A mother daughter 30/sec

Radioactivity ※ Stability of atom • - in small Z • stable atom: P = N • # of P & N • even  stable • one is odd  stable • odd  unstable

Radioactivity • 2. Type of radioactivity • Natural or artificial? • - Natural radioactivity • : radio-isotope in natural •  Ra, Po, K-40, C-14, … , Z (atomic number) > 82 • - Artificial radioactivity • : radio-isotope by artificial •  fission products, activation products, trans-uramic • elements

Radioactivity • Decay mode • - α-decay • : number of nucleon ∝nucleus binding E () • but Coulomb’s F () ∝ Z2 • Z(atomic number) > 82  eject α-particle for stability α-particle n p p n

Radioactivity • - β-decay • : to eject β±-particle for stability • in unstable ratio of proton vs neutron • · β--decay (eject electron) •  in unstable ratio (P vs N) by over-neutron β--particle neutrino - ν

Radioactivity • · β+-decay (eject positron) •  in unstable ratio (P vs N) by over-proton • mother E > daughter E •  over than 1.02 MeV (0.511MeV × 2) β+-particle neutrino + ν

Radioactivity • - γ-decay • : to eject γ-ray for stability • after α- or β-decay, unstable daughter nuclei eject • electro-magnetic waves (γ-ray  photon) 60Co β 60Ni γ-ray γ γ 60Ni

Radioactivity • 3. Radioactive decay • Transformation (=decay) constant • λ : the rate of transformation of nuclide X is • proportional to the number of nuclide X •  independent of physical and chemical state • where, NX: atom # of nuclide X, λ : decay constant [1/sec]

Radioactivity • Unit of radioactivity • - Becquerel [Bq] = transition per sec [tps] • = decay per sec [dps] • - Curie [Ci] : activity of 226Ra (1g) • 1Ci = 3.7 ⅹ1010 dps = 3.7 ⅹ1010 Bq

Radioactivity • Radioactive series • : Some radioactive nuclei decay to unstable nuclei • ※ Naturally occurring radioactivity • 70 out of 340 naturally occurring nuclides are • radioactive •  Heavy elements (Z > 82 (Pb)) are almostradioactive A B C … decay decay decay

Radioactivity - Terrestrial origin ( by earth) · Uranium series (4n+2) · Thorium series (4n) 238U 232Th α-decay α-decay 206Pb 208Pb … … T(1/2) = 4.5 × 109yr T(1/2) = 1.4 × 1010yr stable stable

Radioactivity · Actinium series (4n+3) · Neptunium series (4n+1) 235U 241Pu α-decay α-decay 207Pb 205Pb … … T(1/2) = 7.1 × 108yr T(1/2) = 2 × 1010yr stable stable

Radioactivity · Radon gas 222Rn radon (uranium series)  220Rn radon (thorium series) 219Rn radon (actinium series) · K-40 (neutron: 21, proton: 19) beta-decay, T(1/2) = 1.3 × 109yr  abundance: 0.0118%

Radioactivity - Cosmic-ray · proton (87%) · alpha particle (12%) · etc particle (1%) - Radioactivity produced by cosmic-ray : H-3, Be-7, C-14, Na-21, Na-24, Cl-36 … interaction with air · electron · gamma · neutron · mesons

Radioactivity • ※ Exposure from natural radiation • (whole body equivalent on the ground) • - cosmic-ray at sea level : 44 mrem/yr (※ 1 Sv = 100 rem) •  add 1 mrem for every 100 ft elevation (1ft = 30cm) • ex) Denver in USA : 5285 ft •  44 mrem/yr + 52.8 = 96.8 mrem/yr • - home construction (3/4 occupancy  18 hr in home) •  brick or concrete : 45 mrem/yr • wood : 35 mrem/yr • stone : 50 mrem/yr

Radioactivity • - ground (1/4 occupancy  6 hr in outdoor) • : 15 mrem/yr • - drink water, food, air : 25 mrem/yr • total : 129 mrem/yr (120 ~ 200 mrem generally) • - x-ray diagnostic : chest x-ray  9 mrem/shot • - jet travel : 0.5 mrem/1000 km flight • ex) to Atlanta  12000 km  6mrem • - color TV viewing : 0.5 mrem/yr per 1hr/d viewing

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R adiations & Radioactivity