Energy. on this world and elsewhere. Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434)

Transcription

1 Energy on this world and elsewhere Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434) Course web site available at click on classes and find Physics or at Lecture #22 November 9, 2017

2 Announcements The Superquiz/midterm will be returned on Tuesday, my apologies for the delay. Read Chapter 12 of Richter s book. You are not responsible for the Technical Notes unless otherwise indicated. A problem set will be posted by Friday evening (uh this time I mean it). - Help session Tuesday and Wednesday evenings of next week at 6:30 pm.

3 Next-generation nuclear reactors

4 Next-generation reactors are designed to be more robust in the event of an emergency Existing designs in the event of loss of offsite power: - - Control rods immediately drop into place Residual heat carried away by pumping system driven by emergency diesel generators. Next generation designs when losing offsite power: - - Control rods immediately drop ito place Residual heat carried away by pumping system driven by emergency diesel generators. - If emergency generators are not available, passive cooling kicks in.

5 A new generation of reactors: Westinghouse AP-1000 with passive safety measures Note: the AP stands for Advanced Passive Four two being built in the US. First new plants in decades. At least four units in China nearing completion. Plans for building, but not, I believe, construction, for many more being built throughout the world..

6 Westinghouse AP-1000 with passive safety measures

7 Westinghouse AP-1000 with passive safety measures

8 Westinghouse AP-1000 with passive safety measures

9 Westinghouse AP-1000 with passive safety measures

10 Sanmen 1 and Sanmen 2 nearing completion

11 Article from Bloomberg News (Feb. 20, 2017) I see no indication that the numbers of reactors shown above are a realistic projection, but maybe this will change when the first new units start coming online.

12 Article from Bloomberg News (Feb. 20, 2017)

13 Westinghouse AP-1000 with passive safety measures These were all under construction, although construction on V C summer 2 and 3 has been halted or abandoned.

14 Dealing with nuclear waste To quote Richter, Spent Fuel: Love It or hate It, we have It.

15 The concept of the half-life of an isotope The half-life of a nucleus is the time it takes for one half of the original amount of that substance to decay. Radioactive decay is an exponential process.

16 All waste is not equal. With the exception of technetium, the byproducts of fission are relatively short lived. The actinides, however, that result from neutron capture and subsequent decay, are very long lived.

17 Calculating what s left If you are interested in an integral number of half-lives, it is particularly easy. Let us say that you want to know what is left after n half-lives. You simply take the initial quantity of the substance and multiply by (1/2) n For example, consider 137 Cs, a fission fragment with a half-life of 30 years. How much would be left after 90 years? First we note that 90/30=3 Further assume we have a quantity of 137 Cs N 0 at t=0 N(t=90 years) =(1/2)(1/2)(1/2) N 0 = (1/2) n N 0 = (1/8) N 0

18 Calculating what s left If you prefer, you can also use the equation: N(t) =N 0 e ( ln 2 t 1/2 ) t In this way, you can also deal with an arbitrary time period.

19 One approach to dealing with waste Separate out the fission products, and store all but the technetium in vitrified form (turned into a glass). Either store the actinides (including plutonium) or burn/transmute them in some type of fast reactor. - - One variant of this approach is separating out some of the actinides, such as plutonium, and plowing them back into new fuel rods. France is closest to making this a reality, and I am not sure how it is going.

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