663 A Selected Data on Radionuclides of Health Physics Interest A.1 Introduction Although there are over 2500 known radionuclides, it is important to become familiar with the fundamental characteristics of those systems commonly encountered in the radiation protection field. These characteristics include the decay mode, type of radiation, energy of the radiation, half-life, and production mode. Table A.1 outlines the fundamental characteristics of selected radionuclides. These radionuclides include those emphasized in the American Board of Health Physics Examination Preparation Guide. Nuclear systems move toward stability through a number of modes noted in Table A.1. These include alpha, beta, and gamma decay. Electron capture, internal conversion, positron emission, and spontaneous fission () are additional nuclear deexcitation mechanisms. A.2 Alpha Decay Almost all naturally occurring alpha emitters are heavy elements. Alpha decay becomes the dominant decay mode for proton (neutron)-rich nuclides with A 160 ( 211). This decay mode occurs preferentially in the 232 Th, 235 U, and 238 U natural decay series. In the heaviest known transuranic nuclear systems, alpha emission competes with spontaneous fission as the dominant decay mode. Other decay modes (e.g., beta decay) occur but are usually not the dominant decay mechanism. A.3 Beta Decay In beta decay, a nucleus emits an electron and an antielectron neutrino. These particles arise from the decay of a neutron into a proton in an unstable nuclear system. Health Physics: Radiation-Generating Devices, Characteristics, and Hazards, First Edition. Joseph John Bevelacqua. 2016 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2016 by Wiley-VCH Verlag GmbH & Co. KGaA.
664 A Selected Data on Radionuclides of Health Physics Interest Table A.1 Fundamental characteristics of commonly encountered radionuclides a) c). 3 H β 0.018591 (max) 12.32 years 2 H(n, γ) 3 H He(n, p) 3 H Li(n, α) 3 H B(n, 2α) 3 H Spallation of atmospheric nuclides induced by cosmic rays 7 Be γ 0.4776 53.3 days 10 B(p, α) 7 Be Spallation of atmospheric nuclides induced by cosmic rays 11 C β + 0.960 (max) 20.36 min 12 C(γ, n) 11 C γ 0.511 12 C(n, 2n) 11 C 14 N(p, α) 11 C 13 N β + 1.190 (max) 9.97 min 12 C(p, γ) 13 N γ 0.511 13 C(p, n) 13 N N(γ, n) 13 N N(n, 2n) 13 N O(p, α) 13 N 14 C β 0.157 (max) 5715 years 13 C(n, γ) 14 C N(n, p) 14 C O(n, α) 14 C 15 O β + 1.72 (max) 2.037 min 12 C(α, n) 15 O γ 0.511 14 N(p, γ) 15 O 16 O(γ, n) 15 O O(n, 2n) 15 O 16 N β 4.27 (max) 7.13 s 15 N(n, γ) 16 N 10.44 (max) 16 O(n, p) 16 N γ 6.129 19 F(n, α) 16 N 7.115 α 1.85 18 F β + 0.635 (max) 1.8293 h 18 O(p, n) 18 F γ 0.511 19 F(n, 2n) 18 F 16 O( 3 He, p) 18 F 22 Na β + 0.546 (max) 2.604 years 19 F(α, n) 22 Na γ 0.511 23 Na(n, 2n) 22 Na 1.2745 23 Na(γ, n) 22 Na
A.3 Beta Decay 665 Table A.1 (Continued) 24 Na β 1.391 (max) 14.97 h 23 Na(n, γ) 24 Na γ 1.3686 24 Mg(n, p) 24 Na 2.7540 27 Al(n, α) 24 Na 32 P β 1.709 (max) 14.28 days 31 P(n, γ) 32 P S(n, p) 32 P Cl(n, α) 32 P 35 S β 0.1674 (max) 87.2 days 34 S(n, γ) 35 S Cl(n, p) 35 S 40 K β 1.33 1.25 10 9 years Naturally occurring γ 1.4608 41 Ar β 1.198 (max) 1.83 h 40 Ar(n, γ) 41 Ar γ 1.2936 41 K(n, p) 41 Ar Ca(n, α) 41 Ar 55 Fe γ 0.126 2.75 years 54 Fe(n, γ) 55 Fe 58 Ni(n, α) 55 Fe Fe(γ, n) 55 Fe 58 Co β + 0.474 (max) 70.88 days 57 Co(n, γ) 58 Co γ 0.511 59 Co(n, 2n) 58 Co 0.8108 58 Ni(n, p) 58 Co 60 Co β 0.318 (max) 5.271 years 59 Co(n, γ) 60 Co γ 1.1732 60 Ni(n, p) 60 Co 1.3325 63 Cu(n, α) 60 Co 65 Zn β + 0.325 (max) 244.0 days 64 Zn(n, γ) 65 Zn γ 0.511 66 Zn(n, 2n) 65 Zn 1.1155 85 Kr β 0.687 (max) 10.76 years Fission product γ 0.514 84 Kr(n, γ) 85 Kr 90 Sr β 0.546 (max) 28.8 years Fission product Sr + n 89 Sr + n 90 Sr 90 Y β 2.281 (max) 2.669 days Fission product Sr daughter Y(n, γ) 90 Y Zr(n, p) 90 Y Nb(n, α) 90 Y (continued overleaf)
666 A Selected Data on Radionuclides of Health Physics Interest Table A.1 (Continued) 99m Tc e 0.0022 6.008 h 98 Tc(n, γ) 99m Tc 0.1427 γ 0.1405 98 Mo(n, γ) 99 Mo β Tc 125 I γ 0.03549 59.4 days Fission product 124 Xe + n 125 Xe β+ I e 129 I β 0.15 (max) 1.57 10 7 years Fission product γ 0.0396 128 Te + n 129 Te β I 131 I β 0.606 (max) 8.023 days Fission product γ 0.3645 130 Te + n 131 Te β I 133 Xe β 0.346 (max) 5.243 days Fission product γ 0.08099 132 Xe(n, γ) 133 Xe 137 Cs β 0.514 (max) 30.07 years Fission product γ 0.6617 136 Xe + n 137 Xe β Cs 201 Tl γ 0.1353 3.043 days 203 Tl(p, 3n) 201 Pb β+ Tl 0.1674 214 Pb β 0.67 (max) 27 min 238 U decay series 0.73 (max) γ 0.242 0.2952 0.3519 214 Bi β 1.51 (max) 19.9 min 238 U decay series 1.54 (max) 3.27 (max) γ 0.6093 1.1203 1.7645 α 5.450 5.513 214 Po γ 0.799 163.7 μs 238 U decay series α 7.6869 218 Po γ 0.510 3.10 min 238 U decay series α 6.0024
A.3 Beta Decay 667 Table A.1 (Continued) 220 Rn γ 0.5497 55.6 s 232 Th decay series α 6.2882 222 Rn γ 0.510 3.8235 days 238 U decay series α 5.4895 226 Ra γ 0.1862 1599 years 238 U decay series α 4.602 4.7844 232 Th γ 0.06381 1.4 10 10 years Naturally occurring 0.14088 α 3.947 4.012 238 U γ 0.0496 4.468 10 9 years Naturally occurring α 4.147 4.197 239 Pu γ 0.0516 2.41 10 4 years 238 U + n α 5.105 239 Np 239 Pu 5.144 5.156 241 Am γ 0.0595409 432.7 years 239 Pu + n 240 Pu + n 0.0263 0.955 241 Pu β Am α 5.4430 5.4857 252 Cf γ 0.0434 2.646 years Multiple neutron capture from a 0.1002 α 6.0756 6.1181 a) Baum et al. (2010). b) Electron capture (). c) Conversion electron (e ). 239 U β β varietyofnuclides(e.g., 238 U, 239 Pu, and 244 Cm) Beta decay predominates in systems with excess neutrons (e.g., fission products). This decay mode is an efficient method to move the unstable nucleus toward the line of stability.
668 A Selected Data on Radionuclides of Health Physics Interest A.4 Gamma Emission Gamma emission is a common nuclear decay mode. The emission of photons reduces the energy of an excited nucleus and permits it to reach its ground state or facilitates its decay to a more stable nuclear system. A.5 Internal Conversion Internal conversion is a process that transfers the energy of an excited nuclear system to an atomic electron. The electron, usually in the K or L shell, is ejected from the atom. This process competes with gamma emission. A.6 Electron Capture Orbital electron capture competes with positron emission to move a nucleus with excess protons toward the line of stability. A nucleus with excess protons captures an orbital electron, usually from the K shell. The result of this capture is the conversion of a proton into a neutron and the emission of an electron neutrino. A.7 Positron Emission Positron emission occurs in systems with excess protons (e.g., accelerator products). The decay results in the conversion of the proton into a neutron within the nucleus with the emission of a positron and electron neutrino. Competition between positron emission and electron capture is governed by the specific nuclear systems and their energy level structures. A.8 Spontaneous Fission Spontaneous fission is a decay mode of some heavy nuclear systems that splits the nucleus into two intermediate mass fragments and several neutrons. Because the maximum in the binding energy per nucleon curve occurs near A = 56 ( 56 Fe), nuclides with A greater than about 100 are theoretically unstable with respect to spontaneous fission. However, measurable spontaneous fission rates are only observed in nuclei with A > 230. This occurs because higher energies are required for fission product emission through the Coulomb barrier. For very heavy nuclei,
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