ACADs (08-006) Covered Keywords

1. Basic Reactor Physics - Radioactive Decay ACADs (08-006) Covered Keywords Radioactivity, radioactive decay, half-life, nuclide, alpha, beta, positron. Description Supporting Material

2. OBJECTIVES • Define the following terms associated with radioactive decay: • radioactivity • radiation • radioactive decay • half-life • State the difference between radioactivity and radiation. FEN-BET-I764 Rev. 0

3. OBJECTIVES • Using the Chart of the Nuclides and given a stable nuclide, determine the following: • Element Name • Atomic Number (A) • Atomic Mass (Z) • Isotopic Mass • Atom Percent Abundance (%) FEN-BET-I764 Rev. 0

4. OBJECTIVES • Using the Chart of the Nuclides and given a man-made radioactive nuclide, determine the following: • Element Name • Atomic Number (A) • Atomic Mass (Z) • Half-Life FEN-BET-I764 Rev. 0

5. OBJECTIVES • Describe the following types of decay in terms of the requirements for and mode of occurrence, the resulting products, and emissions: • Alpha • Beta • Positron • Electron capture FEN-BET-I764 Rev. 0

6. PRESENTATION

7. RADIOACTIVE DECAY TERMS • Radioactivity is defined as “that ability of an unstable nucleus to spontaneously emit particles and/or energy to achieve a more stable state.” • Radiation is defined as “energy or particles propagated through space.” FEN-BET-I764 Rev. 0

8. RADIOACTIVE DECAY TERMS • Radioactive decay is defined as “that process in which an unstable nucleus spontaneously emits particles and/or energy to achieve a more stable state.” • Half Life (t1/2), is defined as “the time required for one-half of the nuclei of a given radioactive material to undergo radioactive decay.” Half Life is unique to each nuclide and is expressed in seconds, minutes, hours, days, or years. FEN-BET-I764 Rev. 0

9. RADIOACTIVITY v.s. RADIATION Radioactivity The spontaneous nuclear transformation that usually results in the formation of a different nuclide. Radiation Energy or particles propagated through space. Be sure you know the difference between these two. They are not the same!! FEN-BET-I764 Rev. 0

10. RADIOACTIVE DECAY • As mass numbers of nuclei become larger, the neutron to proton ratio becomes larger for the stable nuclei. • Non-stable nuclei may have an excess or deficiency of neutrons and undergo various decay processes such as beta (- or +), alpha (), neutron (n), or proton (p) decay. • The result of these decay processes provides a more stable configuration. FEN-BET-I764 Rev. 0

11. RADIOACTIVE DECAY CHART OF THE NUCLIDES

12. Chart of the Nuclides The Vertical Column of Numbers lists the Atomic Number or “Z Number” for each associated row. It describes how many protons are in that row Z FEN-BET-I764 Rev. 0

13. Chart of the Nuclides The Horizontal Row of Numbers lists the “N Number” for each associated column. It describes how many neutrons are in that column. N FEN-BET-I764 Rev. 0

14. Chart of the Nuclides Each box in the chart contains information about that particular nuclide. Let’s look at some examples. FEN-BET-I764 Rev. 0

15. Chemical Element H - Symbol 1.00794 - Atomic Weight (Carbon -12 Scale) Hydrogen - Element Name a .333,.150 - Thermal Neutron Absorption Cross-Section in Barns Followed by Resonance Integral, in Barns Chart of the Nuclides These are the heavily bordered Squares at the end of each row. Atomic weight It contains the chemical symbol and properties of the element as found in nature. These properties include: Thermal neutron absorption cross-section FEN-BET-I764 Rev. 0

16. Stable Nuclides - Symbol, Mass Number Atom Percent Abundance - This box contains the following information: Thermal Neutron Capture Cross-Sections in Barns Leading to (Isomeric + Ground State), Followed by Resonance Integrals Leading to (Isomeric + Ground State). Isotopic Mass (Carbon - 12 Scale) - Chemical symbol with atomic mass number. Thermal neutron absorption cross section A stable nuclide is naturally stable and found in nature. Isotopic abundance (%) Isotopic mass of neutral atom on C12 scale FEN-BET-I764 Rev. 0

17. Naturally Occurring or Otherwise Available but Radioactive La 138 5+ Symbol, Mass Number - 0.090 1.05e11 a - Atom Percent Abundance - Half-Life Modes of Decay in Order of Prominence with Energy of Radiation in MeV for Alpha and Beta; keV for Gammas. , -.25  1435.8, 788.7  ~57,4E2 - Beta Disintegration Energy Followed by Isotopic Mass E 1.04 137.90711 Thermal Neutron Capture Cross-Section, Followed by Resonance Integral. Long-Lived, Naturally Occurring Radioactive Nuclides Squares with both black rectangles and gray represent naturally occurring isotopes with a very long half life. The black rectangle indicates that the isotope is radioactive and found in nature. FEN-BET-I764 Rev. 0

18. Naturally Occuring or Otherwise Available but Radioactive - Spin and Parity La 138 5+ Symbol, Mass Number - 0.090 1.05e11 a - Atom Percent Abundance - Half-Life Modes of Decay in Order of Prominence with Energy of Radiation in MeV for Alpha and Beta; keV for Gammas. , -.25  1435.8, 788.7  ~57,4E2 - Beta Disintegration Energy Followed by Isotopic Mass E 1.04 137.90711 Thermal Neutron Capture Cross-Section, Followed by Resonance Integral. Long-Lived, Naturally Occurring Radioactive Nuclides (more) Chemical symbol with atomic mass number. Isotopic abundance (%) Decay modes and decay energies in MeV for ,; keV for . Half-Life Isotopic mass of neutral atom on C12 scale FEN-BET-I764 Rev. 0

19. Man-Made Radionuclides Artificially Radioactive S38 - Symbol, Mass Number - Half-Life 2.84 h - .99, ...  1941.9 ... Modes of Decay with Energy of Radiation in MeV for Alpha and Beta; keV for Gammas. E 2.94 - Beta Disintegration Energy in MeV. Chemical symbol with atomic mass number. Decay modes in MeV for ,; keV for . Half-Life Emax of Beta Energy FEN-BET-I764 Rev. 0

20. LINE OF STABILITY Note that there is a line of stable atoms (gray boxes) that run diagonally through the entire Chart of the Nuclides. This is known as the “Line of Stability”. It is where all radioactive isotopes will eventually come to rest after one or more decay events. FEN-BET-I764 Rev. 0

21. Radioactive Decay ACADs (08-006) Covered Keywords Description Supporting Material

22. TYPES OF RADIOACTIVE DECAY • There are many types of Radioactive Decay. We will discuss the following: • Alpha particle emission • Beta emission (both - and +); • Gamma emission • Electron capture FEN-BET-I764 Rev. 0

23. ALPHA EMISSION DECAY • A large, loosely packed nuclei will decay by alpha emission. An alpha particle () is released from its nucleus. • An alpha particle () is a Helium (He) nucleus (a Helium atom minus its two electrons). FEN-BET-I764 Rev. 0

24. ALPHA DECAY In Alpha decay 2 neutrons and 2 protons are emitted forming an  particle.  FEN-BET-I764 Rev. 0

25. ALPHA EMISSION DECAY • The Helium nucleus has two (2) protons, and two (2) neutrons. • When released from the original nucleus, the new nucleus will have an Atomic Number two less than its original and an Atomic mass of four less than its original. • Let’s look at a couple of graphic demonstrations of this type of decay on the Chart of the Nuclides. FEN-BET-I764 Rev. 0

26. Old Isotope New Isotope ALPHA DECAY N -2 N -1 N N +1 N +2 FEN-BET-I764 Rev. 0

27. EXAMPLE Americium 242 emits an  and transforms into Neptunium 238 FEN-BET-I764 Rev. 0

28. BETA MINUS DECAY • In a beta minus (-) decay, a nuclei emits a negative charge from the nucleus. • A - is identical in charge and mass of an electron. • In - decay, a neutron is converted to a proton, causing the nuclide’s Atomic Number to increase by one (1), but the Atomic Mass to stay the same. FEN-BET-I764 Rev. 0

29. BETA MINUS DECAY In Beta minus decay a neutron changes to a proton with the emission of a -. - FEN-BET-I764 Rev. 0

30. BETA MINUS DECAY • - decay is the primary emission mode of radioactive nuclides that are born below the Line of Stability. • Let’s look at a couple of graphic demonstrations of this type of decay on the Chart of the Nuclides. FEN-BET-I764 Rev. 0

31. Old Isotope New Isotope - DECAY N -2 N -1 N N +1 N +2 FEN-BET-I764 Rev. 0

32. EXAMPLE OF - DECAY Cesium 137 emits a - and transforms into Barium 137 FEN-BET-I764 Rev. 0

33. POSITRON (+) DECAY In Positron decay, a proton changes to a neutron with the emission of a + . Besides the emission of a +, the Atomic Number (A number) of the nucleus goes down by 1 and the Atomic Mass (Z number) stays the same. + FEN-BET-I764 Rev. 0

34. ELECTRON CAPTURE () In Electron Capture an electron is captured by the nucleus, changing a proton to a neutron with the emission of a characteristic X-Ray and a +. The end results are the same as a + decay discussed previously. The A number goes down by 1 and the Z number stays the same. X-ray + FEN-BET-I764 Rev. 0

35. EXAMPLE OF + AND  DECAY Lanthanum 136 captures an electron or emits a + and transforms into Barium 137 FEN-BET-I764 Rev. 0

36. + or ELECTRON CAPTURE DECAY Old Isotope New Isotope  N -2 N -1 N N +1 N +2 FEN-BET-I764 Rev. 0

37. SUMMARY • Summarize Objectives with students. FEN-BET-I764 Rev. 0