Effective neutron multiplication factor

Main Question or Discussion Point

Can somebody please explain effective neutron multiplication factor, with example? So when k=1, k>1, k<1 , please give me some example.

$$k=\frac{N_2}{N_1}=\frac{N_3}{N_2}=........=\frac{N_i}{N_i_-_1}$$

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malawi_glenn
Homework Helper
but hey you asked just 4h ago! Remember that the majority of PF-users are from the states and they sleeping at the moment..

Also, again, if this is course work post at approriate subforum. Otherwise, why is this (and other questions that you ask here) urgent??

http://en.wikipedia.org/wiki/Nuclear_chain_reaction

I read that but still can't understand what does it mean to keep constant the neutrons number. Please give me any example.

malawi_glenn
Homework Helper
I read that but still can't understand what does it mean to keep constant the neutrons number. Please give me any example.
I dont understand what you dont understand, please clarify.

Why is it so hard to understand that in order to retain a ciritical chain reaction, k must be equal to 1.

Why should I construct an example for you if you can't even answer my questions:

"Also, again, if this is course work post at approriate subforum. Otherwise, why is this (and other questions that you ask here) urgent??"

So in the first generation must be there 1 neutron, and in the second generation must have 1 neutron.

$$\frac{1}{1}=\frac{2}{2}=\frac{3}{3}=\frac{4}{4}...$$, like this?

But as I know chain reaction goes with 1 neutron, then 3 neutrons, 9, 27....

malawi_glenn
Homework Helper
yes an over-critical chain reaction does that, but an exactly critical has k=1

In my book have same picture like this, and it says, this is http://media.wiley.com/assets/83/12/fg0-7645-5430-1_0503.jpg" [Broken]

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malawi_glenn
Homework Helper
yes, but they have not specidied what KIND of chain reaction it is..

there exists 3kinds of chain reactions:
under critical, cirical & over critical

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or maybe $$\frac{1}{1+0}$$? Probably "neutron production from fission in one generation" means the neutron which is not absorbed nor lost to the system, right?

malawi_glenn