Nuclear II PREFLIGHT

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The following three questions refer to the material you were to read in preparation for the lesson. Questions one and three require you to write a three or four sentence response. Number two is a multiple choice question. Click in the appropriate circle.

You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button at the bottom of this page. Don't submit more than once. (If you absolutely HAVE to resubmit it, put a note on the end to that effect.)




1. Power Plant Problems

The control-room operators of the Kärnobyl nuclear power plant are telecommuting and are running the plant through the Web. However, the mean time between failure for the components of Kärnobyl is not great. Try to keep the reactor stable when component failures occur! Use sequence buttons 1-3 to run a failure-simulation sequence. The randomize button starts a random failure sequence. When a simulation sequence is running, you can control the state of valves and pumps by clicking on them. The moderator rods in the reactor can be moved by mouse dragging them.

(More information at: http://www.ida.liu.se/~her/npp/demo.html)
To prevent the release of radioactive material, what is the most critical variable to control? What must you do to prevent melt-down?




2. Cold Fusion

Which of the following reactions will NOT release any extra energy?

4He + 4He.

8Be + 8Be.

16O + 16O.

32S + 32S.


3. Nuclear Bombs


How much 239Pu do you need to make a bomb? Halliday and Resnick did not include this calculation in their text. Nor did they include it in the problems. If you want my paranoid opinion, they were discouraged from putting it in the book by.... Well, we should be able to figure that out. Say Pu fissions and produces 2.11 fast neutrons. Suppose that the cross section (the target area that a neutron has to hit to score a fission) is somewhere around 748 barns. (Back in the early days of atomic physics, they would say "that was as easy as hitting the broad side of a barn". The table at the end of the book has the conversion factor=10-28m2) How big a sphere of 239Pu would you need to be sure that one of those 2.11 neutrons from a random decay scores a hit before it escapes and thereby sustains the chain reaction? How much would that sphere weigh?




honors extra

Nearly all the nuclear reactors in America were Light Water (rather than Deuterated or Heavy Water) Reactors, most of them employing double heat exchangers and pressurized water (to keep it from boiling). However, several other countries, notably France, have opted for a "Breeder Reactor" that is cooled, not directly by water, but by liquid Na. What is so special about Breeders, why do they use liquid Na for coolant, and why hasn't the United States adopted this technology?





Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):




You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button.

I received no help from anyone on this assignment.