Question

Why does a nuclear fission reaction generally not result in an uncontrolled chain reaction?
please help!

Answer 1

That's not a math question...

Answer 2

mhmm

Answer 3

A nuclear fission reaction generally does not result in an uncontrolled chain reaction because of the release of binding energy. This contributes heat and energy into the reaction, which tends to reduce the density of the fissile material, i.e. making it larger, and thus making it subcritical.

The hard part in creating an uncontrolled fission reaction is in holding the fissile material in a supercritical geometry long enough to convert all of it. This requires enormous pressure and high technology.

Also, the result of a fission reaction includes neutrons that are often too energetic to properly go on and create subsequent reactions. In a controlled reaction, a moderator is required to "slow down" the neutrons. In an uncontrolled reaction, the dynamics are such that only prompt neutrons are needed to support the chain reaction, a state we call super prompt criticality, but in order to sustain this, the enrichment of the fuel must be above a certain level, typically greater than 20 percent U-235. Modern weapons are in the high 80's and 90's percent.

Read more: http://wiki.answers.com/Q/Why_does_a_nuclear_fission_reaction_generally_not_result_in_an_uncontrolled_chain_reaction#ixzz1wYwwLhEN

Answer 4

In another form of radioactivity, nuclear fission, the unstable nucleus of a large atom splits into two roughly equal smaller nuclei, losing several spare neutrons in the process and releasing energy. The fast-moving free neutrons usually pass through matter, but each one can be captured more easily by another nucleus after the neutron loses some energy and slows down. If a free neutron hits a large nucleus, such as that of uranium, the nucleus can capture it and become unstable. Each new unstable nucleus splits into two roughly equal smaller nuclei and creates more spare neutrons and more energy. Those spare neutrons can then strike more large nuclei to repeat the process in a chain reaction

Answer 5

so is it because matter is converted to energy during the reaction?

Answer 6

yes

Answer 7

okay thank you