Radioactive decay

1. is the process by which an unstable atomic nucleus loses energy by emitting ionizing particles or radiation. The emission is spontaneous in that the nucleus decnt nuclide, transforming to an atom of ays without collision with another particle. This decay, or loss of energy, results in an atom of one type, called the parea different type, named the daughter nuclide, 14C ------- 15N Radioactive decay

2. Radioactive Decay • Atom (nuclei) yang mempunyai rasio • proton – neutron berada di luar Belt of • stability secara langsung akan mengalami • radioactive decay secara Spontan • Tipe Decay tergantung dimana posisi • atom berada relative terhadap band of stability • Radioactive particle are emitted with • different kinetic energy • - Energy change is related to the change • in binding energy from reactant to product

3. Band Stability and radioactive Decay

5. CONTOH NATURAL DECAY An example is the natural decay chain of 238U which is as follows: decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234 which decays, through beta-emission, with a half-life of 24 days to protactinium-234 which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234 which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230 which decays, through alpha-emission, with a half-life of 77 thousand years to radium-226 which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon-222 which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218 which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214 which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214 which decays, through beta-emission, with a half-life of 20 minutes to polonium-214 which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210 which decays, through beta-emission, with a half-life of 22 years to bismuth-210 which decays, through beta-emission, with a half-life of 5 days to polonium-210 which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a stable nuclide.

13. 14C 14N + 0b + n 6 7 -1 40K 40Ca + 0b + n 19 -1 20 1n 1p + 0b + n 0 1 -1 11C 11B + 0b + n 6 5 +1 38K 38Ar + 0b + n 19 18 +1 1p 1n + 0b + n 1 0 +1 n and n have A = 0 and Z = 0 Nuclear Stability and Radioactive Decay Beta decay Decrease # of neutrons by 1 Increase # of protons by 1 Positron decay Increase # of neutrons by 1 Decrease # of protons by 1

14. 37Ar + 0e 37Cl + n 18 17 -1 55Fe + 0e 55Mn + n 26 25 -1 1p + 0e 1n + n 1 -1 0 212Po 4He + 208Pb 2 82 84 252Cf 2125In + 21n 98 49 0 Nuclear Stability and Radioactive Decay Electron capture decay Increase # of neutrons by 1 Decrease # of protons by 1 Alpha decay Decrease # of neutrons by 2 Decrease # of protons by 2 Spontaneous fission HITUNG PERUBAHAN ENERGI BINDING PADA PROSES DECAY DIATAS ? 23.2

15. HALF-LIFE is the time that it takes for 1/2 a sample to decompose. • The rate of a nuclear transformation depends only on the “reactant” concentration. Half-Life

16. Half-Life Decay of 20.0 mg of 15O. What remains after 3 half-lives? After 5 half-lives?

17. 263Sg ----> 259Rf + 4He

18. Terjadi pada Solar Energi dan Proses terjadinya alam semesta Terjadi pada proses bom nuklir dan reaktor nuklir kini

21. For each duration (half-life), one half of the substance decomposes. For example: Ra-234 has a half-life of 3.6 daysIf you start with 50 grams of Ra-234 Kinetics of Radioactive Decay After 3.6 days > 25 grams After 7.2 days > 12.5 grams After 10.8 days > 6.25 grams

23. The probability of decay (−dN/N) is proportional to dt: The solution to this first-order differential equation is the following function: Dimana, The half life is related to the decay constant as follows:

31. N daughter DN rate = - Dt DN - = lN Dt Ln 2 = l t½ Kinetics of Radioactive Decay rate = lN lnN = lnN0 - lt N = N0e(-lt) N = the number of atoms at time t N0 = the number of atoms at time t = 0 l is the decay constant (sometimes called k) k = 23.3

32. ACTIVITY CALCULATION N = N0e(-lt) UNTUK HALF LIFE 2,303 Log 0,5/1 = -λ t½ λ = 0,693/t½ A = A0e(-l t ) ECERCISE : Hitung sisa aktifitas Tritium setela tersimpan 26 tahun dari aktifitas semula 15 Ci, t1/2 tritium = 12,34 th

33. A sample of C14, whose half life is 5730 years, has a decay rate of 14 disintegration per minute (dpm) per gram of natural C. An artifact is found to have radioactivity of 4 dpm per gram of its present C, how old is the artifact? Using the above equation, we have: Where: years years

34. [N] ln [N] Kinetics of Radioactive Decay [N] = [N]0exp(-lt) ln[N] = ln[N]0 - lt 23.3

35. Arithmetically, melalui term half life kemudiandapatdihitungperubahan jumlah/aktivitaszatradioaktiveselamawaktutertentu • Graphycally, MengunakangrafiksemilogantaraAktivitaradioaktiv Vs waktu • Radioactive Equilibrium - Ratio Nomor atom padaprosesreaksi decay zatradioaktivesepertidibawahini, 238U λu 234Th λTh 234Pa NTh / NU = λU / λTh N Th / N U = t½ Th / t½ U - Hal yang samauntukatome decay dengannomor atom yang kostan , Ratio Massa ebandingdengan ratio half life nya, Massa X / Massa Y = t½ X . A X / t½ Y . A Y Dari perhitungan ratio nomor atom danmassaada decay reaction makadapat dihitung ratio dari ratio nomor atom dan mass darihasil decay tersebut Quantitative Aspect of Radiactive 238U Decay

36. Nuclear Reaction

37. + + + + + 2 + 2 1n 1n 1n 1n 96 96 0 0 0 0 Rb Rb 37 37 138 235 138 235 Cs Cs U U 92 55 92 55 Balancing Nuclear Equations • Conserve mass number (A). The sum of protons plus neutrons in the products must equal the sum of protons plus neutrons in the reactants. 235 + 1 = 138 + 96 + 2x1 • Conserve atomic number (Z) or nuclear charge. The sum of nuclear charges in the products must equal the sum of nuclear charges in the reactants. 92 + 0 = 55 + 37 + 2x0 23.1

38. Alpha emission Nuclear Reactions Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2. Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved

39. Beta emission Nuclear Reactions Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.

40. 207 207 Positron (0+1b): a positive electron Other Types of Nuclear Reactions Electron capture: the capture of an electron

41. New elements or new isotopes of known elements are produced by bombarding an atom with a subatomic particle such as a proton or neutron -- or even a much heavier particle such as 4He and 11B. Reactions using neutrons are called g reactions because a g ray is usually emitted. Radioisotopes used in medicine are often made by g reactions. Artificial Nuclear Reactions

42. Nuclear Bombardment Reactions Cyclotron or accelerator Nuclear reactor

44. ARTIFICIAL TRANSMUTATION TROUGH ACCELERATOR

45. Is the probability that a bombarding particle (neutron) will produce a nuclear reaction Cross section Unit is Barn (1 barn = 1024 cm-2) Formula ; N = Φ x σ x nX Where, N = Total number of reaction Φ = Flux neutron σ = nuclear cross section n = number of nuclei in Cm3 X= is thickness of target in Cm CROSS SECTION

46. Nuclear Cross Section

47. Example of a g reaction is production of radioactive 31P for use in studies of P uptake in the body. 3115P + 10n ---> 3215P + g Artificial Nuclear Reactions

48. Elements beyond 92 (transuranium) made starting with an g reaction 23892U + 10n ---> 23992U + g 23992U ---> 23993Np + 0-1b 23993Np ---> 23994Pu + 0-1b Transuranium Elements

49. Nuclear Fission

50. Fission is the splitting of atoms These are usually very large, so that they are not as stable Fission chain has three general steps: 1. Initiation. Reaction of a single atom starts the chain (e.g., 235U + neutron) 2. Propagation. 236U fission releases neutrons that initiate other fissions 3. ___________ . Nuclear Fission EXCERCISE , REACTION FISSION RANTAI URANIUM