Nuclear Chemistry Chapter 21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

핵화학 1. 핵반응 2. 핵의 안정성 3. 자연방사능 4. 핵변환 5. 핵분열 6. 핵융합 7. 동위원소의 이용 8. 방사선의 생물학적 영향

X A Z Mass Number Atomic Number Element Symbol Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons A Z 1p1p 1 1H1H 1 or proton 1n1n 0 neutron 0e0e 00 or electron 0e0e +1 00 or positron 4 He 2 44 2 or  particle

Balancing Nuclear Equations 1.Conserve mass number (A). The sum of protons plus neutrons in the products must equal the sum of protons plus neutrons in the reactants. 1n1n 0 U Cs Rb n1n = x1 2.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. 1n1n 0 U Cs Rb n1n = x0

212 Po decays by alpha emission. Write the balanced nuclear equation for the decay of 212 Po. 4 He 2 44 2 or alpha particle Po 4 He + A X 84 2Z 212 = 4 + AA = = 2 + ZZ = Po 4 He Pb

Nuclear Stability and Radioactive Decay Beta decay 14 C 14 N + 0  K 40 Ca + 0  n 1 p + 0  Decrease # of neutrons by 1 Increase # of protons by 1 Positron decay 11 C 11 B + 0  K 38 Ar + 0  p 1 n + 0  Increase # of neutrons by 1 Decrease # of protons by 1 and have A = 0 and Z = 0

Electron capture decay Nuclear Stability and Radioactive Decay 37 Ar + 0 e 37 Cl Fe + 0 e 55 Mn Increase # of neutrons by 1 Decrease # of protons by 1 1 p + 0 e 1 n Alpha decay Decrease # of neutrons by 2 Decrease # of protons by Po 4 He Pb Spontaneous fission 252 Cf In n

RadioisotopenpHalf-lifestable isotopes 11 C min 12 C, 13 C 13 N67<10 minutes 14 N, 15 N, 13 N 15 O78122 seconds 16 O, 17 O, 18 O 18 F min 19 F 40 K(+ EC, beta) ×10 9 a 39 K, 41 K 121 I h 127 I, 121 I Positron emission

RadioisotopenpHalf-lifestable isotopes 7 Be d 9 Be 37 Ar d 36 Ar, 38 Ar, 40 Ar 41 Ca E5 a 40 Ca, 42 Ca, 43 Ca, 44 Ca, 46 Ca 44 Ti2252 a 46 Ti, 47 Ti, 48 Ti, 49 Ti, 50 Ti 49 V23337 d 51 V 51 Cr d 50 Cr, 52 Cr, 54 Cr 53 Mn253.7E6 a 55 Mn 57 Co d 59 Co 56 Ni d 58 Ni, 60 Ni, 61 Ni, 62 Ni, 64 Ni 67 Ga d 69 Ga, 71 Ga 68 Ge d 70 Ge, 72 Ge, 73 Ge, 74 Ge 72 Se348.5 d 74 Se, 76 Se, 77 Se, 78 Se, 80 Se Electron capture

Band of Stability and Radioactive Decay n/p too large n/p too small

Stability of Nuclei Out of > 300 stable isotopes: Even Odd Even Z N P F m Ta has not yet been observed to decay despite experimental attempts

Nuclear Stability Certain numbers of neutrons and protons are extra stable n or p = 2, 8, 20, 50, 82 and 126 Like extra stable numbers of electrons in noble gases (e - = 2, 10, 18, 36, 54 and 86) Nuclei with even numbers of both protons and neutrons are more stable than those with odd numbers of neutron and protons All isotopes of the elements with atomic numbers higher than 83 are radioactive All isotopes of Tc and Pm are radioactive

Nuclear binding energy (BE) is the energy required to break up a nucleus into its component protons and neutrons. BE + 19 F 9 1 p n E = mc 2 BE = 9 x (p mass) + 10 x (n mass) – 19 F mass BE (amu) = 9 x x – BE = amu 1 amu = 1.49 x J BE = 2.37 x J binding energy per nucleon = binding energy number of nucleons = 2.37 x J 19 nucleons = 1.25 x J

Nuclear Binding Energy 1. Ni-62 ( Mev/nucleon) 2. Fe-58 (8.7Mev/nucleon) 3. Fe-56 (8.7Mev/nucleon)

Kinetics of Radioactive Decay N daughter rate = - dN dtdt = NN = N 0 exp(- t) N : the number of atoms at time t N 0 : the number of atoms at t = 0 : the decay constant(s -1 ) ln2 = t½t½

Radiocarbon Dating 14 N + 1 n 14 C + 1 H C 14 N + 0  t ½ = 5730 years Uranium-238 Dating 238 U 206 Pb   t ½ = x 10 9 years

Nuclear Transmutation Cyclotron Particle Accelerator 14 N + 4  17 O + 1 p Al + 4  30 P + 1 n N + 1 p 11 C + 4 

Nuclear Transmutation

Nuclear Fission Energy = [mass 235 U + mass n – (mass 90 Sr + mass 143 Xe + 3 x mass n )] x c 2 Energy = 3.3 x J per 235 U = 2.0 x J per mole 235 U Combustion of 1 ton of coal = 5 x 10 7 J

Nuclear Fission 235 U + 1 n 90 Sr Xe n + Energy Representative fission reaction

Non-critical Critical Nuclear Fission Nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions. The minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction is the critical mass.

Nakasaki, 1945

Schematic Diagram of a Nuclear Reactor

Annual Waste Production 35,000 tons SO x 10 6 tons CO 2 1,000 MW coal-fired power plant 3.5 x 10 6 ft 3 ash 1,000 MW nuclear power plant 70 ft 3 vitrified waste Nuclear Fission

Diagram of a nuclear power plant

The Oklo Fossil Fission Reactors, natural Fission Reactors Natural Uranium % U % U-238 Measured at Oklo % U-235

Geological situation in Gabon leading to natural nuclear fission reactors 1. Nuclear reactor zones 2. Sandstone 3. Uranium ore layer 4. Granite self-sustaining nuclear fission reactions. The Gabon Reactor

Up for a half-hour, and down for 2.5 hrs for > 150,000 yrs. approximately 2 billion years ago, when U-235 was ~ 3%. ran for > 150,000 years, averaging 100 kW of power output during that time.

Nuclear Fission Hazards of the radioactivities in spent fuel compared to uranium ore From “Science, Society and America’s Nuclear Waste,” DOE/RW-0361 TG

Nuclear Fusion Fusion - Hydrogen Burning 1 H + 1 H → 2 H + e 2 H + 1 H → 3 He 3 He + 3 He → 4 He H H → 4 He + 2 e : 26.7 MeV Occurs in the sun and other stars Energy

Candidates for terrestrial reactions (1) D+T→ 4 He(3.5 MeV)+ n(14.1 MeV) (2i) D+D→ T(1.01 MeV)+ p(3.02 MeV) 50% (2ii) → 3 He(0.82 MeV)+ n(2.45 MeV) 50% (3) D+ 3 He→ 4 He(3.6 MeV)+ p(14.7 MeV) (4) T+T→ 4 He +2 n MeV (5) 3 He+ 3 He→ 4 He +2 p MeV (6i) 3 He+T→ 4 He + p +n MeV 51% (6ii) → 4 He(4.8 MeV)+ D(9.5 MeV) 43% (6iii) → 4 He(0.5 MeV)+ n(1.9 MeV)+p(11.9 MeV) 6% (7) D+ 6 Li→2 4 He MeV (8) p+ 6 Li→ 4 He(1.7 MeV)+ 3 He(2.3 MeV) (9) 3 He+ 6 Li→2 4 He + p MeV (10) p+ 11 B→3 4 He+ 8.7 MeV Nuclear Fusion in the Sun

Nuclear Fusion 2 H + 2 H 3 H + 1 H Fusion ReactionEnergy Released 2 H + 3 H 4 He + 1 n Li + 2 H 2 4 He x J 2.8 x J 3.6 x J Tokamak magnetic plasma confinement

Radioisotopes in Medicine 1 out of every 3 hospital patients will undergo a nuclear medicine procedure 24 Na, t ½ = 14.8 hr,  emitter, blood-flow tracer 131 I, t ½ = 14.8 hr,  emitter, thyroid gland activity 123 I, t ½ = 13.3 hr,  ray emitter, brain imaging 18 F, t ½ = 1.8 hr,   emitter, positron emission tomography 99m Tc, t ½ = 6 hr,  ray emitter, imaging agent Brain images with 123 I-labeled compound

PET(positron Emission Tomography) 18 O + 1 p 18 F + n Production of 18 F t ½ = 1.8 hours H 18 F + glucose → FDG + H 2 O 18 F → 18 O + + β + β + - β → 511 keV PET sources: C-11 (~20 m), N-13 (~10 m), O-15 (~2 m), and F-18 (~110 m) Synthesis of FDG(Fludeoxyglucose)

Radioisotopes in Medicine 98 Mo + 1 n 99 Mo U + 1 n 99 Mo + other fission products m Tc 99 Tc +  -ray Mo 99m Tc + 0  Research production of 99 Mo Commercial production of 99 Mo t ½ = 66 hours t ½ = 6 hours Bone Scan with 99m Tc

Geiger-Müller Counter

Biological Effects of Radiation Radiation absorbed dose (rad) 1 rad = 1 x J/g of material Roentgen equivalent for man (rem) 1 rem = 1 rad x Q Quality Factor  -ray = 1  = 1 n=10  = 20 SI unit 100 rad = gray 100 rem = 1 sievert (Sv) SI unit 1 gray = 1 J/kg of material 1 sievert = 1 gray x Q

EffectDose Blood count changes50 rem Vomiting (threshold)100 rem Mortality (threshold)150 rem LD 50/60 * (with minimal supportive care)320 – 360 rem LD 50/60 (with supportive medical treatment)480 – 540 rem 100% mortality (with best available treatment)800 rem (Adapted from NCRP Report No. 98 "Guidance on Radiation Received in Space Activities, NCRP, Bethesda, MD (1989)) Prompt Effects High doses delivered to the whole body of healthy adults within short periods of time can produce effects such as blood component changes, fatigue, diarrhea, nausea and death. These effects will develop within hours, days or weeks, depending on the size of the dose. The larger the dose, the sooner a given effect will occur. Effects of Radiation

Annual Exposure to Average U.S. Citizen Exposure Source Average Annual Effective Dose Equivalent(mrems) Natural: Radon200 Other100 Occupational0.9 Nuclear Fuel Cycle0.05 Consumer Products: Tobacco?* Other5-13 Environmental Sources0.06 Medical: Diagnostic X-rays39 Nuclear Medicine14 Approximate Total360

Radiation in Human Body – 40 K 40 K + -1 β → 40 Ar (EC) or 40 K → 40 Ar + +1 β (PE): 11.2% 40 K → 40 Ca + -1 β : 88.8% 40 K has a half-life of 1.250×10 9 years. 40 K represents the largest source of radioactivity, greater even than 14 C. 40 K concentration is 1.17×10 -4 in all potassium, In a human body of 70 kg mass, 140 g is potassium, and about 4,400 nuclei of 40 K decay per second. The activity of natural potassium is 31 Bq/g.

Radiation in Human Body – 14 C 14 C → 14 N + -1 β; half-life = 5730 years. 14 C represents the second largest source of radioactivity, much smaller than 40 K. 14 C concentration in C is about 1.18× the second largest source of radioactivity in human body, but much smaller than that of 40 K 14 N + 1 n 14 C + 1 H C 14 N + 0  + 6 7

Chemistry In Action: Food Irradiation DosageEffect Up to 100 krads Inhibits sprouting of potatoes, onions, garlics. Inactivates trichinae in pork. Kills or prevents insects from reproducing in grains, fruits, and vegetables. 100 – 1000 krads Delays spoilage of meat poultry and fish. Reduces salmonella. Extends shelf life of some fruit to 10,000 krads Sterilizes meat, poultry and fish. Kills insects and microorganisms in spices and seasoning.