Please sit together in pairs: Mike A. and Joe Serruto Barney and Yiran Thomas and Steve T.

1. Arielle and Grant • Mikhail and Evan • Valerie and Rebecca • Kevin and Katherine • Ally and Joe Sebek • Matt M. and Quanbiao • Morgan and Charlie • Laura and Lu • Lauren and Ashkan • Mikey O. and Naichen • Hannah and Dale • Jim and Disha • Nick and Efrain • Ben and Da • Nik and Heran • Please sit together in pairs: • Mike A. and Joe Serruto • Barney and Yiran • Thomas and Steve T. • Glenn and Joey B. • Ann and Johnny • Meaghan and Stephen H. • Korey and Qihan • Will and Nicole • Michael W. and Ed • Zach and Zhenmin • Casey and Taehoon • Audrey and Shenheng • Lisette and Matt R. • Erica and Andrea Phys 150 Lecture 10

2. Announcements • Exam 1 is Thursday, October 4, in class. Multiple choice and written-answer questions (like homework). Exam covers Chapters 1-5. • Practice Exam is posted on the web page. • There is no reading assignment for next week and no Quiz on Tuesday, October 2. • Homework 5 is due on Monday, October 1, at midnight. Phys 150 Lecture 10

3. i>clicker question A thermonuclear bomb (H bomb) may contain • Deuterium and Tritium • Deuterium and Lithium • 238U • All of the above Phys 150 Lecture 10

4. i>clicker question A thermonuclear bomb (H bomb) may contain • Deuterium and Tritium – D + T  He + n + Energy • Deuterium and Lithium – n + Li  T +He • 238U – Surrounds the bomb to increase the yield • All of the above • D = 2H = pn • T = 3H = pnn - H bomb ignited by a fission (239Pu) bomb Phys 150 Lecture 10

5. i>clicker question The 238U bomb that destroyed Hiroshima had a yield of 13 kilotons of TNT equivalent. The largest thermonuclear bomb (H bomb) ever tested had a yield of • 50 kilotons • 500 kilotons • 5 Megatons • 50 Megatons Phys 150 Lecture 10

6. i>clicker question The 238U bomb that destroyed Hiroshima had a yield of 13 kilotons of TNT equivalent. The largest thermonuclear bomb (H bomb) ever tested had a yield of • 50 kilotons • 500 kilotons • 5 Megatons • 50 Megatons Enewetak Atoll Tsar Bomba 1961 Phys 150 Lecture 10

7. Nuclear Reactors and Bombs • Chain reaction • n + 235U  2 fission fragments + 2 n + Energy • Basic reaction for a nuclear bomb or a nuclear reactor • Bomb: explosive chain reaction • Reactor: controlled chain reaction Phys 150 Lecture 10

8. i>clicker question 235U is more likely to fission when it is hit with • a slow neutron • a fast neutron • deuterium • tritium Phys 150 Lecture 10

9. i>clicker question 235U is more likely to fission when it is hit with • a slow neutron • a fast neutron • deuterium • tritium - A slow neutron is easier to absorb to make 236U, which then fissions spontaneously Phys 150 Lecture 10

10. i>clicker question A neutron released from 235U fission is fast. To slow it down in a nuclear reactor, we use • 238U • a control rod • a moderator • All of the above Phys 150 Lecture 10

11. i>clicker question A neutron released from 235U fission is fast. To slow it down in a nuclear reactor, we use • 238U – absorbs neutrons • a control rod – absorbs neutrons • a moderator –slows neutrons –H2O, D2O, C • All of the above Phys 150 Lecture 10

12. i>clicker question Uranium enriched to 3% 235U is enough to sustain a controlled chain reaction because • you only need one neutron to sustain the reaction • slow neutrons are preferentially absorbed on 238U • of the control rods • the enriched Uranium has more energy Phys 150 Lecture 10

13. i>clicker question Uranium enriched to 3% 235U is enough to sustain a controlled chain reaction because • you only need one neutron to sustain the reaction – don’t want doubling! • slow neutrons are preferentially absorbed on 238U – actually, on 235U • of the control rods • the enriched Uranium has more energy Phys 150 Lecture 10

14. i>clicker question A Uranium-based nuclear reactor cannot explode like a nuclear bomb because • there is not enough fuel • if the fuel heats up, the chain reaction stops • of the control rods • All of the above Phys 150 Lecture 10

15. i>clicker question A Uranium-based nuclear reactor cannot explode like a nuclear bomb because • there is not enough fuel • if the fuel heats up, the chain reaction stops - fission depends on slow neutrons • of the control rods • All of the above Cooling towers Containment building Phys 150 Lecture 10

16. i>clicker question In one year, a Gigawatt nuclear power plant consumes about • 1 cubic foot of 235U • 10 cubic yards of 235U • 100 cubic yards of 235U • 1000 cubic yards of 235U Phys 150 Lecture 10

17. i>clicker question In one year, a Gigawatt nuclear power plant consumes about • 1 cubic foot of 235U≈ 1 cubic yard of 3% enriched Uranium • 10 cubic yards of 235U • 100 cubic yards of 235U • 1000 cubic yards of 235U Phys 150 Lecture 10

18. i>clicker question Uranium reprocessing refers to • the enrichment of Uranium • the recycling of 238U • the recycling of 235U • the production of 239Pu Phys 150 Lecture 10

19. i>clicker question Uranium reprocessing refers to • the enrichment of Uranium • the recycling of 238U • the recycling of 235U • the production of 239Pu:n + 238U  239U β 239Np β Breeder reactor • 239Pu Phys 150 Lecture 10

20. i>clicker question Depleted Uranium • is not radioactive • is a very soft metal • is mostly 238U • All of the above Phys 150 Lecture 10

21. i>clicker question Depleted Uranium • is not radioactive – about ½ as much • is a very soft metal – used for artillery shells • is mostly 238U - it’s depleted of 235U • All of the above Phys 150 Lecture 10

22. i>clicker question The Candu reactor in Canada • uses Beryllium control rods • uses natural Uranium as fuel • uses Lithium as a moderator • uses Helium as a coolant Phys 150 Lecture 10

23. i>clicker question The Candu reactor in Canada • uses Beryllium control rods • uses natural Uranium as fuel • uses Lithium as a moderator – D2O • uses Helium as a coolant - D2O (heavy water) is a better moderator than ordinary water, so you don’t need to enrich the Uranium Phys 150 Lecture 10