BNEN – Nuclear Energy Intro W. D’haeseleer What is Radioactivity? BNEN Nuclear Energy: Intro William D’haeseleer

BNEN – Nuclear Energy Intro W. D’haeseleer Chemical elements Periodic Table (Mendeleev)

BNEN – Nuclear Energy Intro W. D’haeseleer

Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

BNEN – Nuclear Energy Intro W. D’haeseleer Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

BNEN – Nuclear Energy Intro W. D’haeseleer Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

BNEN – Nuclear Energy Intro W. D’haeseleer Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

BNEN – Nuclear Energy Intro W. D’haeseleer Atoms vs Nuclei & Electron Cloud (neutral) atom = nucleus + Z electrons ion = ionized atom nucleus = Z protons + N neutrons = A nucleons Matter is basically “empty space”, but electrons move at very high speed

BNEN – Nuclear Energy Intro W. D’haeseleer Exited states in atoms Stationary states Hydrogen Mercury (simplified)

BNEN – Nuclear Energy Intro W. D’haeseleer Exited states in atoms Transitions in eV range Emitted e.m. radiation = UV or X rays 1 eV = Joule

BNEN – Nuclear Energy Intro W. D’haeseleer Transitions btwn shells in atoms

BNEN – Nuclear Energy Intro W. D’haeseleer Exited states in nuclei Nuclei vibrate & rotate

BNEN – Nuclear Energy Intro W. D’haeseleer Exited states in nuclei Nuclei vibrate & rotate

BNEN – Nuclear Energy Intro W. D’haeseleer Exited states in nuclei Stationary states Transitions in MeV range Emitted e.m. radiation = Gamma rays

BNEN – Nuclear Energy Intro W. D’haeseleer

Electromagnetic spectrum UV & X rays Gamma rays Common e.m. waves: Radio TV Micro-wave I.R. (heat) visible

BNEN – Nuclear Energy Intro W. D’haeseleer Elements vs Isotopes Chemical elements characterized by Z –Number of protons = Z –Number of electrons = Z If same Z but different N, particles called isotopes of chemical element –E.g., Hydrogen has three isotopes –Sometimes “isotope” used as generic name of all nuclei/atoms with all kinds of Z & A.

BNEN – Nuclear Energy Intro W. D’haeseleer Some light Isotopes proton neutron

BNEN – Nuclear Energy Intro W. D’haeseleer Pb last stable nucleus Rank all stable isotopes in (N,Z) plot Every stable isotope represented by a black dot

BNEN – Nuclear Energy Intro W. D’haeseleer Chart of Nuclides About 1400 isotopes known About 280 stable About 1220 unstable

BNEN – Nuclear Energy Intro W. D’haeseleer Chart of Nuclides Too many protons Too many neutrons

BNEN – Nuclear Energy Intro W. D’haeseleer Chart of Nuclides N Z 208 Pb last stable nucleus

BNEN – Nuclear Energy Intro W. D’haeseleer Tc 61 Pm Chart of Nuclides N Z

BNEN – Nuclear Energy Intro W. D’haeseleer Chart of Nuclides N Z Too many protons Too many neutrons

BNEN – Nuclear Energy Intro W. D’haeseleer Radioactive decay Beta - decay when too many neutrons: neutron  proton + electron (+ anti neutrino) A remains same Z  Z+1 & N  N-1

BNEN – Nuclear Energy Intro W. D’haeseleer Radioactive decay Beta + decay when too many protons: proton  neutron + positron (+ neutrino) A remains same Z  Z-1 & N  N+1

BNEN – Nuclear Energy Intro W. D’haeseleer Chart of Nuclides N Z Heavy unstable isotopes

BNEN – Nuclear Energy Intro W. D’haeseleer Chart of Nuclides N Z Heavy unstable isotopes Wish to move downward quickly

BNEN – Nuclear Energy Intro W. D’haeseleer Radioactive decay Emission two protons & two neutrons A  A – 4 & Z  Z – 2 N  N - 2

BNEN – Nuclear Energy Intro W. D’haeseleer Summary radioactive decay Alpha decay Beta decay beta- decay beta+ decay Energetic alpha Energetic electron Energetic positron

BNEN – Nuclear Energy Intro W. D’haeseleer Alpha energies Well defined energies of emitted alpha particles upon transition Typically ~ 4-10 MeV

BNEN – Nuclear Energy Intro W. D’haeseleer Beta energies Energy variable (because neutrino) Beta min = electronBeta plus = positron

BNEN – Nuclear Energy Intro W. D’haeseleer Beta energies Emitted energies vary considerably dependent on isotope

BNEN – Nuclear Energy Intro W. D’haeseleer And Gamma rays?

BNEN – Nuclear Energy Intro W. D’haeseleer Gamma decay Gamma decay typically follows beta decay Beta decay often to excited state of daughter Excited daughter then decays very quickly to lower state

BNEN – Nuclear Energy Intro W. D’haeseleer Gamma decay (after beta decay)

BNEN – Nuclear Energy Intro W. D’haeseleer Beta - Gamma decay E.g., beta min decay

BNEN – Nuclear Energy Intro W. D’haeseleer Alpha - Beta - Gamma decay 212 Bi has all three decay modes

BNEN – Nuclear Energy Intro W. D’haeseleer Alpha - Beta - Gamma decay

BNEN – Nuclear Energy Intro W. D’haeseleer When radioactive decay? Start from N° radioactive isotopes λ = desintegration constant = probability for decay per second

BNEN – Nuclear Energy Intro W. D’haeseleer When radioactive decay? Half life = time that half of the isotopes has decayed Average life time isotope

BNEN – Nuclear Energy Intro W. D’haeseleer When radioactive decay? Activity = number of disintegrations per second = Becquerel = Bq = [1/s] Old unit = Curie = Ci ; 1 Ci = 37 GBq

BNEN – Nuclear Energy Intro W. D’haeseleer Radioactive chains Very often daughter also unstable  Radioactive chains N1N1 N2N2 N3N3 λ1λ1 λ2λ2

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

BNEN – Nuclear Energy Intro W. D’haeseleer Cosmogenic isotopes Interaction of cosmic radiation produces protons & neutrons which interact with with nuclei from atmosphere Produce radioactive isotopes Typical examples:

BNEN – Nuclear Energy Intro W. D’haeseleer Cosmogenic Example C-14

BNEN – Nuclear Energy Intro W. D’haeseleer Cosmogenic isotopes Tritium / pure Beta- decay T 1/2 = 12.3 year Carbon 14 / pure Beta- decay T 1/2 = 5715 year Phosphor 32 / pure Beta- decay T 1/2 = 14.3 days

BNEN – Nuclear Energy Intro W. D’haeseleer Cosmogenic isotopes Tritium  Global inventory ~ 1.3 EBq T 1/2 = 12.3 year Due to weapons tests in 60’s up to 260 EBq (already gone) Carbon 14  ~ 230 Bq/kg of Carbon in T 1/2 = 5715 year living tissue Phosphor 32  of minor importance for T 1/2 = 14.3 days living tissues

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

BNEN – Nuclear Energy Intro W. D’haeseleer Primordial radionuclides Very long lived – lighter than Pb Formed at time or before formation solar system Typical examples:

BNEN – Nuclear Energy Intro W. D’haeseleer Primordial radionuclides Potassium 40 89% Beta- decay to Ca-40 with E max =1.3 MeV 11% EC to Ar-40, with Gamma of 1.46 MeV Typically in human body ~ 50 Bq/kg T 1/2 = y

53 Primordial radionuclides Potassium 40 Decay products are Ca-40 or Ar-40 (both stable) Present for 2.1% (weight) earth crust and 0.044% sea water K-40 only % of natural K (mostly K-39) K present for about 0.15 kg in human body Further info from [Wade Alison, “Radiation and Reason”, 2009, p 51] T 1/2 = y BNEN – Nuclear Energy Intro W. D’haeseleer

Potassium β-β- EC γ 40 K 40 Ar 40 Ca 1.46 MeV E e,max 1,3 MeV BNEN – Nuclear Energy Intro W. D’haeseleer

Primordial radionuclides

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactive Chains

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactive Chains U-238 U-235 Th-232

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactive Chains The Thorium series (Th-232) Ref: Yang & Hamilton, 1996

BNEN – Nuclear Energy Intro W. D’haeseleer Th-232 natural series

BNEN – Nuclear Energy Intro W. D’haeseleer Th-232 natural series

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactive Chains The Actinium series (U-235) Ref: Yang & Hamilton, 1996

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactive Chains The Uranium series (U-238) Ref: Yang & Hamilton, 1996

BNEN – Nuclear Energy Intro W. D’haeseleer U-238 natural series

BNEN – Nuclear Energy Intro W. D’haeseleer Radioactive chains U-238t 1/2 = years U-235t 1/2 = years Th-232t 1/2 = years

BNEN – Nuclear Energy Intro W. D’haeseleer Radioactive chains

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

BNEN – Nuclear Energy Intro W. D’haeseleer Transuranics & Np decay series A fourth radioactive decay chain has existed in the past, called Np-237 series But T 1/2 = year too small Mother isotope was actually Pu-241 T 1/2 = 14 year Only surviving member Bi-209 T 1/2 = year; nearly stable

BNEN – Nuclear Energy Intro W. D’haeseleer Natural Radioactive Chains The Neptunium series (Np-237) Ref: Yang & Hamilton, 1996 Bi-209

BNEN – Nuclear Energy Intro W. D’haeseleer Transuranics & Np decay series Plutonium 239 does exist occur naturally in very small quantities: –From spontaneous fission U-235 & U-238 and then n-absorption in U-238 –In OKLO Gabon, natural fission reactor, naturally produced long time ago (but in mean time almost disappeared)

BNEN – Nuclear Energy Intro W. D’haeseleer Long lived isotopes in nature

BNEN – Nuclear Energy Intro W. D’haeseleer Long lived isotopes in nature Natural uranium –NU consist of 99.3% U-238 & 0.7% U-235 –Density soil ~1 à kg/m 3 –Make pit/hole of 20m x 20m x 10m in yard  Leads to about 6 to 10 kg natural uranium

BNEN – Nuclear Energy Intro W. D’haeseleer Long lived isotopes in nature

BNEN – Nuclear Energy Intro W. D’haeseleer Some orders of magnitude Natural Radioactivity in oceans: –U Bq (x 14 because progeny) –K Bq Natural Radioactivity in earth crust: –Contiguous states US, 1 km deep; about Bq Natural Radioactivity body (70kg) –About 8000 Bq (~ 55% from Ka-40, 40% from C-14) Rn-222 Radioactivity in buildings in Belgium –About 50 Bq/m 3 (Flanders ~20-30; Ardennes ~70-80)

BNEN – Nuclear Energy Intro W. D’haeseleer Artificial Radioactivity From isotopes –Produced in laboratories & industries for medical purposes, measuring techniques –Produced in nuclear reactors –Released in nature by atomic weapons tests No distinction btwn natural & artificial radioactivity –Also alpha, beta, gamma, neutrons –Energetic ionizing particles

BNEN – Nuclear Energy Intro W. D’haeseleer Artificial Radioactivity Examples Th-233  β T 1/2 = 22 min U-239  β T 1/2 = 23.2 min Pu-239  α T 1/2 = year

BNEN – Nuclear Energy Intro W. D’haeseleer Rare “decay” modes Two other occurring decay modes –Spontaneous break up / spontaneous fission –Neutron emission (in stead of gamma emiss)

BNEN – Nuclear Energy Intro W. D’haeseleer Spontaneous fission U-238 undergoes spontaneous breakup in large fragments = fission Process in “parallel” with alpha decay Probab fission = probab alpha decay (0.5 ppm) 238 U Example: 1 g U-238 undergoes 20 fissions/h Leads to 2-3 neutrons per fission Note: also heavier elements undergo sf

BNEN – Nuclear Energy Intro W. D’haeseleer Spontaneous fission U-238 undergoes spontaneous breakup in large fragments = fission 238 U Example: 1 g U-238 undergoes 20 fissions/h Leads to 2-3 neutrons per fission Recall: in yard pit/hole of 20m x 20m x 10m  à f/h  or 33 à 56 f/s

BNEN – Nuclear Energy Intro W. D’haeseleer Neutron emission after β decay After β decay, if energy excited state of daughter larger than “virtual energy” (binding energy weakest bound neutron) in neighbor: Then n emission rather than γ emission Called “delayed neutrons”

BNEN – Nuclear Energy Intro W. D’haeseleer Ionizing particles Alpha, beta, gamma Fission fragments Neutrons  Interaction of these energetic particles with matter  May lead to biological damage  But to be considered quantitatively!

BNEN – Nuclear Energy Intro W. D’haeseleer References Some basic examples (a.o.)