Chapter 2. Radiation 1. Radioactivity 2. Radiation interaction with matter 3. Radiation doses and hazard assessment
Chapter 2. Radiation 1.Radioactivity 2.Radiation interaction with Matter 3.Radiation Doses and hazard Assessment
2. 1 Radioactivit 1)Overview 2) Types of radioactive decay 3) Energetics of Radioactive Decay 4)Characteristics of Radioactive Decay 5)Decay Dynamics 6) Naturally occurring Radionuclides
1) Overview 2) Types of Radioactive Decay 3) Energetics of Radioactive Decay 4) Characteristics of Radioactive Decay 5) Decay Dynamics 6) Naturally Occurring Radionuclides 2.1 Radioactivity
c)Beta Decay Spectra and Neutrino A Beta Decay Scheme A Typical Beta Spectrum β ity #of阝 E β- decay:2P→[z+D]++-e+v Pauli: Neutrino with spin 1 2 is emitted simultaneously with beta, carrying the missing energy
3 c) Beta Decay Spectra and Neutrino Pauli: Neutrino with spin 1 /2 is emitted simultaneously with beta, carrying the missing energy. A Typical Beta Spectrum Intensity or # of Energy of E max A Beta Decay Scheme P Z → DZ+1 + – + v ?
c B-decay: Ap -[z+AD]*+-ie+v QB-/c2=M(EP)-[M(z+4D1*)+mB-+my M(2p)-[(M(Z+D)-me]+mB-+mi M(aP)-M(+AD) The mass of the neutrino is negligibly small eB-/c2=M(2P)-M(z+1D)-E /c2 Cl(3724m) B max B 1(319% -3810 kev 2(105%)7619%) 2167 65(576%)Y(424%) 、=4917 Ar(stable)
c) The mass of the neutrino is negligibly small
d)Positron Decay Energy B+ decay: 2P=_1D]++ie+v Positron emission Rp+/c2=M(2P)-[M(2-AD12)+m(+ie)+my M(2P)-IOM(Z-AD)+me)+mg++my M(P)-M(Z-AD)-2me oQ Qe+/c2=M(2P)-M(z-1D)-2me-E'/c2 B)max Q B
5 d) Positron Decay Energy Positron Emission + –
3)36Ci decays into 36S(35.967081 u)and 36Ar. If the energy release is 1. 142 Mev to 36S and 0.709 Mev to 36 Ar calculate the masses of 36CI and 36Ar. Describe the modes of decay 5)The radionuclide 41Ar decays by B emission to an excited level of 41K that is 1.293 Mev above the ground state. What is the maximum kinetic energy of the emitted B particle?
3）36CI decays into 36S (35.967081 u) and 36Ar. If the energy release is 1.142 MeV to 36S and 0.709 MeV to 36Ar, calculate the masses of 36CI and 36Ar. Describe the modes of decay. 5) The radionuclide 41Ar decays by β - emission to an excited level of 41K that is 1.293 MeV above the ground state. What is the maximum kinetic energy of the emitted β - particle?
Radioactive Decay Kinetics -exponential Variation of n as a function of time t Number of radioactive nuclei decrease exponentially with time N=N e as indicated by the graph here Also a=a e 九t As a result. the radioactivity vary in the same manner Note N=A 入N6=A
Variation of N as a function of time t N No t N = No e - t Also A = Ao e - t Radioactive Decay Kinetics -exponential Number of radioactive nuclei decrease exponentially with time as indicated by the graph here. As a result, the radioactivity vary in the same manner. Note N = A No = Ao
6) The activity of a radioisotope is found to decrease by 30% in one week. What are the values of its(a) decay constant,(b) half- life and(c)mean life?
6) The activity of a radioisotope is found to decrease by 30% in one week. What are the values of its (a) decay constant, (b) halflife, and (c) mean life?
b) Three Component Decay Chains X1+ X2 X3( stable) dN,(t) dt M,N1(t) N1(t)=M1(0)e-41t dN,(t dt =-2N2(t)+A1N1(t) (t)=N2(- m2 A1N1(0) λ1t e dN3(t) 2N2(t) at
b) Three Component Decay Chains
Daughter Decays Faster than the Parent l 2 2(t)=A1(0) 2 入1t (入2-入1)t 入2-入1 42()→410)x2-x1 入1t transient equilibrium: daughter's decay rate is limited by the decay rate of the parent N<<A2, A(t)→A、N82-A 2 Ait c A1(0) 入1t The activity of the daughter approaches that of the parent. This extreme case is known as secular equilibriun(久期平衡)
Daughter Decays Faster than the Parent λI < λ2, transient equilibrium: daughter's decay rate is limited by the decay rate of the parent. λI << λ2, The activity of the daughter approaches that of the parent. This extreme case is known as secular equilibrium(久期平衡)