1. 1-1 CHEM 312 Radiochemistry Lecture 1: Introduction Readings: §Chart of the nuclides àClass handout §Table of the isotopes §Modern Nuclear Chemistry: Chapter 1 àAt http://radchem.nevada.edu/classes/chem312/readings.htmlhttp://radchem.nevada.edu/classes/chem312/readings.html Class organization §Outcomes §Grading History of radiation research Chart of the nuclides and Table of the isotopes §Description and use §Data Radiochemistry introduction §Atomic properties §Nuclear nomenclature §X-rays §Types of decays §Forces (limit of course instruction)

2. 1-2 Chart of the nuclides

3. 1-3 Chart of the nuclides

4. 1-4 Chart of the nuclides

5. 1-5 Chart of the Nuclide: Fission yields

6. 1-6 Fission yields

7. 1-7 Terms and decay modes: Utilization of chart of the nuclides Identify the isomer, isobars, isotones, and isotopes § 60m Co, 57 Co, 97 Nb, 58 Co, 57 Ni, 57 Fe, 59 Ni, 99m Tc Identify the daughter from the decay of the following isotopes § 210 Po (alpha decay, 206 Pb) § 196 Pb § 204 Bi (EC decay, 204 Pb) § 209 Pb § 222 At § 212 Bi (both alpha and beta decay) § 208 Pb (stable) How is 14 C naturally produced §Reactions with atmosphere ( 14 N as target) Identify 5 naturally occurring radionuclides with Z<84

8. 1-8 Chart of the Nuclides Questions How many stable isotopes of Ni? What is the mass and isotopic abundance of 84 Sr? Spin and parity of 201 Hg? Decay modes and decay energies of 212 Bi What are the isotopes in the 235 U decay series? What is the half-life of 176 Lu? What is the half-life of 176 Yb How is 238 Pu produced? How is 239 Pu made from 238 U Which actinide isotopes are likely to undergo neutron induced fission? Which isotopes are likely to undergo alpha decay? What is the half life of 130 Te §What is its decay mode? What cross section data is provided for 130 Te?

9. 1-9 Equation questions Calculate decay constant for the following § 75 Se example    ln(2)/119.78 day = 0.00579 d -1  = 0.00579 d -1 *1d/24 hr * 1 hr/3600 s =6.7E-8 s -1 Isotopet 1/2  (s -1 ) 75 Se119.78 days5.79E-3 d -1 6.78E-8 74m Ga10 seconds6.93E-2 s -1 6.93E-2 81 Zn0.32 seconds2.17 s -1 2.17 137 Cs30.07 years2.31E-2 a -1 7.30E-10 239 Pu2.41E4 years2.88E-5 a -1 9.11E-13

10. 1-10 Equation Questions What percentage of 66 As remains from a given amount after 0.5 seconds  Use N/N o =e - t  t 1/2 = 95.6 ms; =7.25 s -1  N/N o =e - t = N/N o =e -7.25(.5) = 0.0266 =2.66 % *After 5.23 half lives How long would it take to decay 90 % of 65 Zn?  Use N/N o =e - t §90 % decay means 10 % remains  Set N/N o =0.1, t 1/2 = 244 d, = 2.84E-3 d -1  0.1=e -2.84E-3t  ln(0.1)= -2.84E-3 d -1 t à=-2.30/-2.84E-3 d -1 = t =810 days

11. 1-11 Equation Questions If you have 1 g of 72 Se initially, how much remains in 12 days?  t 1/2 = 8.5 d, =8.15E-2 d -1  N=N o e - t  N=(1 g) e - 8.15E-2(12) §N=0.376 g What if you started with 10000 atoms of 72 Se, how many atoms after 12 days? §0.376 (37.6 %) remains §10000(0.376) = 3760 atoms

12. 1-12 Topic review History of nuclear physics research Discovery of the radioelements §Methods and techniques used Types of radioactive decay §Define X-rays and gamma decay Understand and utilize the data presented in the chart of the nuclides and table of the isotopes Utilize the fundamental decay equations Identify common fission products

13. 1-13 Study Questions What are the course outcomes? What were important historical moments in radiochemistry? Who were the important scientists in the investigation of nuclear properties? What are the different types of radioactive decay? What are some commonalities in the discovery of the actinides? Provide 5 radioelements Identify 6 naturally occurring radionuclides and their production routes What is the 59 keV gamma intensity in % for 241 Am

14. 1-14 Pop Quiz Provide 10 facts about 239 Pu using the chart of the nuclide or the table of the isotopes Send answers as e-mail or bring to next class meeting Provide comments in blog when complete

15. 1-15 CHEM 312: Lecture 2 Nuclear Properties Readings: §Modern Nuclear Chemistry: Chapter 2 Nuclear Properties §Nuclear and Radiochemistry: Chapter 1 Introduction, Chapter 2 Atomic Nuclei Nuclear properties §Masses §Binding energies §Reaction energetics àQ value §Nuclei have shapes

16. 1-16 Which are the 4 stable odd-odd nuclei? Simple example: Number of stable nuclei based on neutron and proton number Nevenoddevenodd Z even even odd odd Number 160 53 49 4 Simple property dictates nucleus behavior. Number of protons and neutron important

17. 1-17 Masses and Q value Atomic masses §From nuclei and electrons Nuclear mass can be found from atomic mass §m 0 is electron rest mass, B e (Z) is the total binding energy of all the electrons §B e (Z) is small compared to total mass Energy (Q) from mass difference between parent and daughter §Mass excess values can be used to find Q (in MeV) β - decay Q value  A Z  A (Z+1) + + β - +  + Q àConsider β - mass to be part of A (Z+1) atomic mass (neglect binding)  Q=  A Z-  A (Z+1)  14 C  14 N + + β - +  + Q àEnergy =Q= mass 14 C – mass 14 N *Use Q values (http://www.nndc.bnl.gov/wallet/wccurrent.html)http://www.nndc.bnl.gov/wallet/wccurrent.html àQ=3.0198-2.8634=0.156 MeV

18. 1-18 Q value Positron Decay  A Z  A (Z-1) - + β + +  + Q §Have 2 extra electrons to consider àβ + (positron) and additional atomic electron from Z-1 daughter *Each electron mass is 0.511 MeV, 1.022 MeV total from the electrons  Q=  A Z – (  A (Z-1) - + 1.022) MeV  90 Nb  90 Zr - + β + +  + Q  Q=  90 Nb – (  90 Zr + 1.022) MeV §Q=-82.6632-(-88.7742+1.022) MeV=5.089 MeV Electron Capture (EC) §Electron comes from parent orbital àParent can be designated as cation to represent this behavior  A Z + + e -  A (Z-1) +  + Q  Q=  A Z –  A (Z-1)  207 Bi  207 Pb +  + Q  Q=  207 Bi –  207 Pb MeV §Q= -20.0553- -22.4527 MeV=2.3947 MeV

19. 1-19 Q value Alpha Decay § A Z  (A-4) (Z-2) + 4 He + Q § 241 Am  237 Np + 4 He + Q àUse mass excess or Q value calculator to determine Q value  Q=  241 Am-(  237 Np+  4 He) §Q = 52.937-(44.874 + 2.425) §Q = 5.638 MeV §Alpha decay energy for 241 Am is 5.48 and 5.44 MeV

20. 1-20 Q value determination For a general reaction §Treat Energy (Q) as part of the equation àSolve for Q 56 Fe+ 4 He  59 Co+ 1 H+Q §Q= [M 56 Fe+M 4 He-(M 59 Co+M 1 H)]c 2 *M represents mass of isotope àQ=-3.241 MeV (from Q value calculator) Mass excess and Q value data can be found in a number of sources §Table of the Isotopes §Q value calculator àhttp://www.nndc.bnl.gov/qcalc/qcalcr.jsphttp://www.nndc.bnl.gov/qcalc/qcalcr.jsp §Atomic masses of isotopes àhttp://physics.nist.gov/cgi- bin/Compositions/stand_alone.plhttp://physics.nist.gov/cgi- bin/Compositions/stand_alone.pl

21. 1-21 Terms from Energy Binding energy §Difference between mass of nucleus and constituent nucleons àEnergy released if nucleons formed nucleus §Nuclear mass not equal to sum of constituent nucleons B tot (A,Z)=[ZM( 1 H)+(A-Z)M(n)-M(A,Z)]c 2 §average binding energy per nucleon àB ave (A,Z)= B tot (A,Z)/A àSome mass converted into energy that binds nucleus àMeasures relative stability Binding Energy of an even-A nucleus is generally higher than adjacent odd-A nuclei Exothermic fusion of H atoms to form He from very large binding energy of 4 He Energy released from fission of the heaviest nuclei is large §Nuclei near the middle of the periodic table have higher binding energies per nucleon Maximum in the nuclear stability curve in the iron-nickel region (A~56 through 59) §Responsible for the abnormally high natural abundances of these elements §Elements up to Fe formed in stellar fusion

22. 1-22 Mass Based Energetics Calculations Why does 235 U undergo neutron induced fission for thermal energies while 238 U doesn’t? Generalized energy equation § A Z + n  A+1 Z + Q For 235 U §Q=(40.914+8.071)-42.441 §Q=6.544 MeV For 238 U §Q=(47.304+8.071)-50.569 §Q=4.806 MeV For 233 U §Q=(36.913+8.071)-38.141 §Q=6.843 MeV Fission requires around 5-6 MeV §Does 233 U from thermal neutron?

23. 1-23 Liquid-Drop Binding Energy: c 1 =15.677 MeV, c 2 =18.56 MeV, c 3 =0.717 MeV, c 4 =1.211 MeV, k=1.79 and  =11/A 1/2 1st Term: Volume Energy §dominant term àin first approximation, binding energy is proportional to the number of nucleons §(N-Z) 2 /A represents symmetry energy àbinding E due to nuclear forces is greatest for the nucleus with equal numbers of neutrons and protons

24. 1-24 Liquid drop model 2nd Term: Surface Energy §Nucleons at surface of nucleus have unsaturated forces §decreasing importance with increasing nuclear size 3rd and 4 th Terms: Coulomb Energy §3rd term represents the electrostatic energy that arises from the Coulomb repulsion between the protons àlowers binding energy §4th term represents correction term for charge distribution with diffuse boundary  term: Pairing Energy §binding energies for a given A depend on whether N and Z are even or odd àeven-even nuclei, where  =11/A 1/2, are the most stable §two like particles tend to complete an energy level by pairing opposite spins àNeutron and proton pairs

25. 1-25 Magic Numbers: Data comparison Certain values of Z and N exhibit unusual stability §2, 8, 20, 28, 50, 82, and 126 Evidence from different data §masses, §binding energies, §elemental and isotopic abundances Concept of closed shells in nuclei §Similar to electron closed shell Demonstrates limitation in liquid drop model Magic numbers demonstrated in shell model §Nuclear structure and model lectures

26. 1-26 Mass Parabolas Method of demonstrating stability for given mass constructed from binding energy §Values given in difference, can use energy difference For odd A there is only one  -stable nuclide §nearest the minimum of the parabola Friedlander & Kennedy, p.47

27. 1-27 Even A mass parabola For even A there are usually two or three possible  -stable isobars §Stable nuclei tend to be even-even nuclei àEven number of protons, even number of neutron for these cases

28. 1-28 R=r o A 1/3 Nuclear Shapes: Radii Nuclear volumes are nearly proportional to nuclear masses §nuclei have approximately same density nuclei are not densely packed with nucleons §Density varies r o ~1.1 to 1.6 fm for equation above Nuclear radii can mean different things §nuclear force field §distribution of charges §nuclear mass distribution

29. 1-29 Nuclear potentials Scattering experimental data have has approximate agreement the Square-Well potential Woods-Saxon equation better fit §V o =potential at center of nucleus §A=constant~0.5 fm §R=distance from center at which V=0.5V o (for half- potential radii) §or V=0.9V o and V=0.1V o for a drop- off from 90 to 10% of the full potential r o ~1.35 to 1.6 fm for Square- Well r o ~1.25 fm for Woods-Saxon with half-potential radii, r o ~2.2 fm for Woods-Saxon with drop-off from 90 to 10% Nuclear skin thickness

30. 1-30 Nuclear Skin Nucleus Fraction of nucleons in the “skin” 12 C 0.90 24 Mg 0.79 56 Fe 0.65 107 Ag 0.55 139 Ba 0.51 208 Pb 0.46 238 U 0.44

31. 1-31 Topic review Understand role of nuclear mass in reactions §Use mass defect to determine energetics §Binding energies, mass parabola, models Determine Q values How are nuclear shapes described and determined §Potentials §Nucleon distribution Quantum mechanical terms §Used in description of nucleus

32. 1-32 Study Questions What do binding energetics predict about abundance and energy release? Determine and compare the alpha decay Q values for 2 even and 2 odd Np isotopes. Compare to a similar set of Pu isotopes. What are some descriptions of nuclear shape? Construct a mass parabola for A=117 and A=50 What is the density of nuclear material? Describe nuclear spin, parity, and magnetic moment

33. 1-33 Pop Quiz Using the appropriate mass excess data calculate the following Q values for 212 Bi. Show the reaction     decay     decay §EC §Alpha decay Which decay modes are likely? Send answers as e-mail or bring to next class meeting Provide comments in blog when complete