CHEM 418 quiz 2 2024

pdf

School

University of Washington *

*We aren’t endorsed by this school

Course

418

Subject

Chemistry

Date

Feb 20, 2024

Type

pdf

Pages

Uploaded by ProfEnergyKingfisher13

CHEM 418 Last Name:___________________________ Quiz 2 Assigned: 7-Feb-24 First Name:___________________________ 1 st Due Date: 13-Feb-24 2 nd Due Date: 16-Feb-24 Lecture 6: Gamma Decay Lecture 7: Fission Lecture 8: Nuclear Force and Nuclear Structure Lecture 9: Nuclear Reactions Lecture 10: Radiation Interactions Question Lectures 1 Lecture 6 Gamma Decay, Lecture 5 Beta Decay 2 Lecture 7 Fission, Lecture 1 Chart of the Nuclides 3 Lecture 8 Nuclear Force and Nuclear Structure, Lecture 1 Chart of the Nuclides 4 Lecture 9: Nuclear Reactions, Lecture 1 Chart of the Nuclides, Lecture 6 Gamma decay 5 Lecture 10: Radiation interactions 6 Lecture 8: Nuclear Structure 7 Lecture 8: Nuclear Structure, Lecture 2: Nuclear Properties Use lecture notes, textbooks, Chart of the Nuclides, Table of the Isotopes, and web pages. Use the chart of the nuclides as your primary dataset for isotope half-life. Show your work or references on a separate page and save electronically. Please use 3 significant digits for your answers. 1. (20 Points) Use the decay schemes for the following questions. 1.1. Provide the following data 1.1.1. 137 Cs half-life (years) 1.1.2. Half-life of 137m Ba (minutes) 1.1.3. Log ft value for the most likely beta decay branch of 137 Cs 1.1.4. Is there another stable isotope of A=137? 1.1.5. 137 Ba spin and parity 1.1.6. What is the gamma decay energy associated with 137 Cs in keV?

1.1.7. 137 Cs beta decay Q value (keV) 1.1.8. 137 La Electron capture Q value (keV) 1.2. What are the possible multipole radiations for the gamma decay shown above? 1.3. What is the actual multipole radiation for the gamma decay shown above? 1.4. Using the figure above provide the logft values for the ground state to ground decays of 137 Cs and 137 La. 1.4.1. 137 Cs logft 1.4.2. 137 La logft 1.5. The spin and parity of 137 La is the same as 137 Cs and both decay to 137 Ba. Yet 137 La does not decay to the 11/2- metastable state in the 137 Ba as does 137 Cs. Why? The questions above related to energy provide insight.

2. (15 Points) Use the chart of the nuclides data below for question 2. Consider the spontaneous fission of 250 Cf 1,2 . 2.1. Based on the data, what is the spontaneous fission half-life in years for 250 Cf? 2.2. Based on the spontaneous fission of 250 Cf, provide the data in the figure below. One fission product is provided. For the Coulomb barrier use ) ( 8 . 1 44 . 1 V 3 / 1 2 3 / 1 1 2 1 A A Z Z c + = Reaction # Fission Product 1 Fission Product 2 Vc (MeV) Q value (MeV) 1 88 Kr ___________ ___________ ___________ 2 99 Mo ___________ ___________ ___________ 3 110 Pd ___________ ___________ ___________ 4 134 Te ___________ ___________ ___________ 5 144 Ba ___________ ___________ ___________ 2.3. From the fissions shown in the table above which fission reaction is most likely? 2.4. Why did you select the fission product reactions from the question above? 2.5. What is the difference between spontaneous fission and neutron induced fission?

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

3. (20 Points) Consider the nucleus 99 Mo. This isotope is important for medical applications, as it is the parent of 99m Tc. These questions will explore why 99m Tc is the prominent progeny from the decay of 99 Mo rather than the ground state 99 Tc. 3.1. Provide the spin and parity of 99 Mo from the shell model 3.2. Provide the spin and parity from chart of the nuclides 3.3. Based on the actual spin and parity from the chart of the nuclides use the Nilsson diagram on the next page to answer the following questions. 3.3.1. Is 99 Mo a deformed nucleus? 3.3.2. Indicate which location on the Nilsson diagram (next page) would be occupied by the unpaired nucleon in 99 Mo. The red circle indicates the possible locations. 3.3.3. What is the shape of the 99 Mo nucleus?

A B C D E F

4. (20 Points) The isotope 225 Ac is of interest for medical applications 3 . The reactions of 232 Th with protons shown in the excitation function below is a means to indirectly produce 225 Ac 4 . Use the data to answer the questions below. A comparison of the experimental excitation functions for the 232 Th(p, 3n) 230 Pa reaction (blue diamonds), the 232 Th(p, 4n) 229 Pa reaction (red squares), and the 232 Th(p, 5n) 228 Pa reaction (black circles) with the theoretical PHITS (solid curves) and MCNP6 (dashed curves) excitation functions 4 .

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

4.1. What is the primary gamma decay energy for 225 Ac and its associated gamma yield in %? 4.2. For the reaction with the highest experimental cross section at 22.5 MeV, provide the following: 4.2.1. Reaction notation 4.2.2. Reaction Q-values (MeV) 4.2.3. Threshold Reaction Energy (MeV) 4.2.4. Coulomb Barrier in MeV using the equation ) ( 8 . 1 44 . 1 V 3 / 1 2 3 / 1 1 2 1 A A Z Z c + = 4.3. Consider the calculations for the Q-value, Threshold Reaction Energy, and Coulomb Barrier. Provide the laboratory reaction energy necessary for producing the reaction. 4.4. Which is the reaction that will indirectly produce the medical isotope 225 Ac? 4.5. Describe how the 225 Ac is eventually produced from this reaction. 4.6. Which proton energies would eventually produce an isotope with an alpha decay energy at 5.6855 MeV? 4.7. A foil of 232 Th is irradiated with protons. Immediately after the end of bombardment the sample is measured in a gamma detector. The following gamma activity is found:

Gamma Energy (keV) 911.2 463.02 Activity (counts per second) 1025 1500 Select the proton energy in MeV used in the reaction. 4.8. What is the activity for the gamma energies in counts per second 24 hours after the end of bombardment? 4.9. An irradiation is performed with a 30 MeV proton. The sample is measured 21 days after the end of bombardment. Select the Pa isotope(s) present in the sample. 4.10. To maximize the production of 225 Ac, what proton energy on target in MeV should be used?

5. (20 Points) The generation of the medical isotope 225 Ac can use 229 Th as a parent. There is 229 Th available which has a significant amount of 228 Th. An isotope from the decay of 228 Th produces a gamma ray with an energy of 2.6 MeV. A generator with this 228 Th requires shielding to limit dose. The mass attenuation coefficient ( µ/ρ ) of a 2.6 MeV photon in Pb is 4.38E-2 cm 2 g -1 5 . The attenuation of the photon is found through: I f =I o e- (( µ/ρ )x ρ ) where the density of Pb ( ρ) is 11.35 g mL -1 . The thickness of Pb is cm is x. 5.1. What is the half-thickness of Pb for a 2.6 MeV gamma ray? 5.2. How thick of a Pb layer is needed to reduce the dose from the 2.6 MeV gamma ray to 5 % of the initial dose? 5.3. At the edge of a glovebox containing a 225 Ac generator with 229 Th and 228 Th, the measured dose is 40 mrem/hr. You wish to have a dose of 5 mrem/hr at the edge of the glovebox. What thickness of Pb shielding in cm should be used? 5.4. What is the isotope from the 228 Th decay chain that is the source of the 2.6 MeV photon? 5.5. Why not separate the 228 Th from the 229 Th to remove the source of the dose? 5.6. The figure below shows the cross sections for the different photon interaction with Pb. Which is the primary interaction for the photon of concern for the progeny of 228 Th discussed above.?

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

6. (5 Points). Discuss the relationship between fission and criticality . 7. (5 Points) A recent article postulates an extremely dense asteroid may contain superheavy elements 6 . An estimated density of an element with Z=162 is between 36.0 4 g cm -3 and 68.4 g cm -3 . For this element to be reasonable to exist, say with a long half-life, estimate its atomic mass A. 8. (Bonus 5 Points) What name would you give this element? References (1) Flynn, K. F.; Gindler, J. E.; Glendenin, L. E. Mass Distributions for the Spontaneous Fission of 248Cm and 250Cf. Journal of Inorganic and Nuclear Chemistry 1977 , 39 (5), 759–762. https://doi.org/10.1016/0022-1902(77)80149-8. (2) Hoffman, D. C.; Ford, G. P.; Balagna, J. P. Kinetic Energy Distributions in the Spontaneous Fission of Cm250 and Cf250. Phys Rev C 1973 , 7 (1), 276–279. https://doi.org/10.1103/PhysRevC.7.276. (3) Thiele, N. A.; Wilson, J. J. Actinium- 225 for Targeted α Therapy: Coordination Chemistry and Current Chelation Approaches. Cancer Biother Radiopharm 2018 , 33 (8), 336–348. https://doi.org/10.1089/cbr.2018.2494. (4) Griswold, J. R.; Jost, C. U.; Stracener, D. W.; Bruffey, S. H.; Denton, D.; Garland, M.; Heilbronn, L.; Mirzadeh, S. Production of 229Th for Medical Applications: Excitation Functions of Low-Energy Protons on 232Th Targets. Phys Rev C 2018 , 98 (4), 044607. https://doi.org/10.1103/PhysRevC.98.044607. (5) X-Ray Mass Attenuation Coefficients . https://physics.nist.gov/PhysRefData/XrayMassCoef/chap2.html (accessed 2024-02-06). (6) LaForge, E.; Price, W.; Rafelski, J. Superheavy Elements and Ultradense Matter. Eur Phys J Plus 2023 , 138 (9). https://doi.org/10.1140/epjp/s13360-023-04454-8.