Nuclear II PREFLIGHT

Please type your (first) name: Please type your LAST NAME and LAST FOUR SS# digits: IN:

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. The Fusion Faceoff

Since fusion of deuterium or tritium plasmas must occur at very high temperatures, finding a bottle to hold the plasma during its "fusing" has been difficult. In the early 50's, it was thought that magnetic confinement in a "magnetic bottle" would solve the problem. We have learned a great deal about plasmas in the 50 years since those first "Sherwood" conferences, but magnetic confined fusion still appears to be always 10 years in the future. In the 80's, an alternative approach became popular, called inertial confinement, where a pellet is heated so fast, it doesn't have time to fly apart before fusing. Calculate the Lawson criterion for the two processes, and suggest what the limiting factors are for both processes.




2. Biophysics

In your body, are there:

More protons than there are neutrons.

More neutrons than there are protons.

An approximately equal number of each.

Depends on how many electrons there are.


3. Nuclear Reactions

This java applet simulates a nuclear reaction in which 235U is the fissile isotope. The chain reaction can be controlled by moving the "neutron absorbers" slider up and down. This slider dynamically changes the number of neutron absorbers present as the applet is running, just like an operator at a nuclear power plant lowers and raises the control rods. When a neutron hits the fissile 235U, an average of 2.5 neutrons are released; sometimes 2, sometimes 3. You can also specify the inital amount of 235U; but you must hit the RESET button for this change to take effect.

Start - Starts the reaction

Stop - Pauses the reaction

Reset - Reconfigures reaction

Enable Sound - Actives sound which occurrs everytime a U235 atom fissions (the simulation may not produce the sound 100% of time due to large amount of atoms). This option may slow down the speed of the applet.

NOTE: When the applet is paused (STOP or RESET has been hit), moving the slider up and down does not have its desired effect. You can move it while the reaction is running. In addition, you must hit RESET for the change in initial 235U amount to take effect.



What is the minimum absorber needed to prevent the reaction from going nuclear? (As in bomb.) You can calculate this without the applet, and use the applet to verify your answer.




honors extra

In a nuclear bomb, a chain reaction leads to rapid release of energy. The same process occurs in a a supernovae, when a star suddenly releases enormous amounts of energy. The Crab nebula is the remnant of a star that exploded in 1054 AD, as recorded by Chinese astronomers, it was so bright it was visible in the daytime. If a star can explode, why are most stars quite stable? What is the determining factor that decides whether our sun will explode in the near future?





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.