1. Phys 150 Lecture 71 Please sit together in pairs: –Onyema and Dian –Alejandra and Michael –Chris and Honglu –Ryan and Matt –John F. and Lin –Walter and Anwen –Max and Mengyue –Amanda and Melissa –Pauline and Zhongyun –John W. and Erich –Jennifer and Irfan –Alexandra and Jason –David and Jiayuna –Abigael and Erica –Jake and

2. Phys 150 Lecture 92 Announcements Exam 1 is Thursday, February 28, in class. Multiple choice and written-answer questions and an essay. Exam covers Chapters 1-5. Practice Exam is on Phys 150 web page Homework 6 is due on Sunday at midnight There is no reading assignment for next week and no Quiz on Tuesday.

3. Phys 150 Lecture 103 Nuclear Reactors and Bombs Chain reaction –n + 235 U  2 fission fragments + 2 n + Energy Basic reaction for a nuclear bomb or a nuclear reactor –Bomb: explosive chain reaction –Reactor: controlled chain reaction

4. Phys 150 Lecture 104 i>clicker question 235 U is more likely to fission when it is hit with A.a slow neutron B.a fast neutron C.deuterium D.tritium

5. Phys 150 Lecture 105 i>clicker question 235 U is more likely to fission when it is hit with A.a slow neutron B.a fast neutron C.deuterium D.tritium -A slow neutron is easier to absorb to make 236 U, which then fissions spontaneously

6. Phys 150 Lecture 106 i>clicker question A neutron released from 235 U fission is fast. To slow it down in a nuclear reactor, we use A. 238 U B.a control rod C.a moderator D.All of the above

7. Phys 150 Lecture 107 i>clicker question A neutron released from 235 U fission is fast. To slow it down in a nuclear reactor, we use A. 238 U – absorbs neutrons B.a control rod – absorbs neutrons C.a moderator – slows neutrons – H 2 O, D 2 O, C D.All of the above

8. Phys 150 Lecture 108 i>clicker question Uranium enriched to 3% 235 U is enough to sustain a controlled chain reaction because A.you only need one neutron to sustain the reaction B.slow neutrons are preferentially absorbed on 238 U C.of the control rods D.the enriched Uranium has more energy

9. Phys 150 Lecture 109 i>clicker question Uranium enriched to 3% 235 U is enough to sustain a controlled chain reaction because A.you only need one neutron to sustain the reaction – don’t want doubling! B.slow neutrons are preferentially absorbed on 238 U – actually, on 235 U C.of the control rods D.the enriched Uranium has more energy

10. Phys 150 Lecture 1010 i>clicker question A Uranium-based nuclear reactor cannot explode like a nuclear bomb because A.there is not enough fuel B.if the fuel heats up, the chain reaction stops C.of the control rods D.All of the above

11. Phys 150 Lecture 1011 i>clicker question A Uranium-based nuclear reactor cannot explode like a nuclear bomb because A.there is not enough fuel B.if the fuel heats up, the chain reaction stops - fission depends on slow neutrons A.of the control rods B.All of the above Cooling towers Containment building

12. Phys 150 Lecture 1012 i>clicker question In one year, a Gigawatt nuclear power plant consumes about A.1 cubic foot of 235 U B.10 cubic yards of 235 U C.100 cubic yards of 235 U D.1000 cubic yards of 235 U

13. Phys 150 Lecture 1013 i>clicker question In one year, a Gigawatt nuclear power plant consumes about A.1 cubic foot of 235 U ≈ 1 cubic yard of 3% enriched Uranium B.10 cubic yards of 235 U C.100 cubic yards of 235 U D.1000 cubic yards of 235 U

14. Phys 150 Lecture 1014 i>clicker question Reprocessing of nuclear waste allows for A.the enrichment of Uranium B.the recycling of 238 U C.the recycling of 235 U D.the production of 239 Pu

15. Phys 150 Lecture 1015 i>clicker question Reprocessing of nuclear waste allows for A.the enrichment of Uranium B.the recycling of 238 U C.the recycling of 235 U D.the production of 239 Pu: n + 238 U  239 U 239 Np β β 239 Pu Breeder reactor

16. Phys 150 Lecture 1016 i>clicker question Depleted Uranium A.is not radioactive B.is a very soft metal C.is mostly 238 U D.All of the above

17. Phys 150 Lecture 1017 i>clicker question Depleted Uranium A.is not radioactive – about ½ as much B.is a very soft metal – used for artillery shells C.is mostly 238 U - it’s depleted of 235 U D.All of the above

18. Phys 150 Lecture 1018 i>clicker question The Candu reactor in Canada A.uses Beryllium control rods B.uses natural Uranium as fuel C.uses Lithium as a moderator D.uses Helium as a coolant

19. Phys 150 Lecture 1019 i>clicker question The Candu reactor in Canada A.uses Beryllium control rods B.uses natural Uranium as fuel C.uses Lithium as a moderator – D 2 O D.uses Helium as a coolant -D 2 O (heavy water) is a better moderator than ordinary water, so you don’t need to enrich the Uranium