Hydrogen Induced Embrittlement on Zircaloy-4

1. Hydrogen Induced Embrittlement on Zircaloy-4 Doug Ogletree, Glen Rose I.S.D. Dr. Lin Shao, Texas A&M University, Department of Nuclear Engineering Dr. Wayne Kinnison, Texas A&M University—Kingsville, Department of Physics

2. Overview • My research project involves the cladding material that covers fuel rods in a nuclear reactor. The material of interest in this project is Zircaloy-4. • Oxidative reaction of zirconium with water releases hydrogen gas, which partly diffuses into the alloy and forms zirconium hydrides. • The hydrides are less dense and are weaker mechanically than the alloy; their formation results in blistering and cracking of the cladding – a phenomenon known as hydrogen embrittlement.

3. My Assignment • The project is interested in studying the effect of hydrogen accumulation in Zircaloy-4 and how it causes the material to become brittle over time and try to understand how to lengthen the material’s stability. • The samples were characterized using nano- and micro-indentation techniques. • A measure of the depth of the indentations as a function of the applied force helps provide some insight into the embrittlement of the alloy.

5. Conceptual Design of the Project • There will be one main area of concentration in this project: Oxidation-Reduction of Metals. • The AP Chemistry students will design protocolsand set-up and demonstrate their procedures to determine how a variety of common metals may be organized based on their ability to oxidize or reduce. • Once the students are familiar with oxidation-reduction and reduction potentials, they will have to begin applying some engineering design to perform their activities. This will give the instructor the opportunity to address some of the design ideas.

6. Anticipated Design Ideas • Metals reacting with Acid

7. Anticipated Design Ideas • Metals reacting with heated Hydrogen Peroxide

8. Anticipated Design Ideas • Metals reacting with other reagents.

9. Anticipated Design Ideas • Metals heated to high temperatures.

10. Timeline • Day 1: • A brief review of Redox, definitions and terms. An introduction to material safety will be presented (possibly a pre-test). • www.youtube.com/watch?v=e6Xxz-VBE6s • The students must first pass the material safety test (will allow two days for preparation for this test).

11. Timeline • Day 2: • Engineering Design lesson –In simple context, a brief overview of some of the basic engineering design concepts and principles will be presented. • The groups will be assigned (three to four students per group).

12. Timeline • Day 3: • Material safety test will be administered. • One or more redox demonstrations will be performed. Here, I plan to use single-replacement reactions such as aluminum reacting with hydrochloric acid and iron reacting with copper (II) chloride. • Students will begin collaboration with their teams. They will also be asked to design a laboratory set up in order to measure the changes they will observe.

13. Timeline • Day 4: • Student design time – The students will collaborate with their teams to find solutions, come up with design ideas to create protocols and set-up and demonstrate their procedures to determine how a variety of common metals may be organized based on their ability to oxidize or reduce. • The metals that will be used are magnesium, aluminum, zinc, iron, tin and lead. • Each group is expected to produce a different protocol.

14. Timeline • Day 5 and 6: • Design trial and re-design time. • Realistically, we will need two days for this phase. • Since each group will need some set-up time, we will need approximately 20 minutes for each group to set up and perform their demonstrations.

15. Timeline • Day 7: • Final design presentations – 15 minutes per team. • Day 8: • Post-test – terms, definitions, problems.

16. Sample Questions • _____ 1. Oxidation is ______. A)a gain of electrons. B)a loss of electrons. C)a gain of protons. D)a loss of protons.

17. Sample Questions • _____ 3. Given the redox reaction: 2I-(aq) + Br2(l) -> 2Br-(aq) + I2(s) What occurs during this reaction? A)The I- ion is oxidized, and its oxidation number increases. B)The I- ion is oxidized, and its oxidation number decreases. C) The I- ion is reduced, and its oxidation number increases. D)The I- ion is reduced, and its oxidation number decreases.

18. Relevant End-of-Course (EOC) Objectives • (C.4) Science concepts. The student knows the characteristics of matter and can analyze the relationships between chemical and physical changes and properties. The student is expected to • (A)  differentiate between physical and chemical changes and properties; • (B)  identify extensive and intensive properties; • (C.7)  • (D)  describe the nature of metallic bonding and apply the theory to explain metallic properties such as thermal and electrical conductivity, malleability, and ductility; • C.11) Science concepts. The student understands the energy changes that occur in • (A)chemical reactions. The student is expected to understand energy and its forms, including kinetic, potential, chemical, and thermal energies; • (C.10) • (H)  understand and differentiate among acid-base reactions, precipitation reactions, and oxidation-reduction reactions;

19. Relevant End-of-Course (EOC) Objectives • (C.1)  Scientific processes. The student, for at least 40% of instructional time, conducts laboratory and field investigations using safe, environmentally appropriate, and ethical practices. The student is expected to • (A)  demonstrate safe practices during laboratory and field investigations, including the appropriate use of safety showers, eyewash fountains, safety goggles, and fire extinguishers; • (B)  know specific hazards of chemical substances such as flammability, corrosiveness, and radioactivity as summarized on the Material Safety Data Sheets (MSDS); and • (C)  demonstrate an understanding of the use and conservation of resources and the proper disposal or recycling of materials. • C.2)  Scientific processes. The student uses scientific methods to solve investigative questions. • (C.3) Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions within and outside the classroom.

20. Acknowledgements • TAMU E3 Program • National Science Foundation • Nuclear Power Institute • Dr. Lin Shao • Dr. Wayne Kinnison • Michael Martin • Richard Vega • Josey Wallace • Michael General