Nuclear Chain Reaction

Based on the last slide, you can guess that a nuclear chain reaction is the behind what we know as a nuclear bomb.

However, nuclear chain of reaction can not only be destructive, but constructive as well.

We don’t a full understanding of it yet, as it has only been discovered within the century, but it has proved to be an essential in today’s world of weapon technology and the production of energy.

What is a nuclear chain reaction?

1) Absorbs a neutron, and fissions into two new atoms.

2) One of those neutrons is absorbed by an atom of uranium-238, and does not continue the reaction. Another neutron is simply lost and does not collide with anything, also not continuing the reaction. However one neutron does collide with an atom of uranium-235, which then fissions and releases two neutrons and some binding energy.

3) Both of those neutrons collide with uranium-235 atoms, each of which fission and release between one and three neutrons, and so on.

How does this correlate to what we have been learning?

• The effective multiplication factor, k, is given as

If k is greater than 1, the chain reaction is supercritical, and the neutron population will grow exponentially.

If k is less than 1, the chain reaction is subcritical, and the neutron population will exponentially decay.

If k = 1, the chain reaction is critical and the neutron population will remain constant.Nuclear power plants operate under this condition (controlled)

Nuclear weapons are designed to operate under this state

The Six Factors used determine to k 1

2

3

456

Example of a

“classic

Explosion”

Important points of nuclear chain reaction:

• A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. (Exponential)

• Can be destructive under uncontrollable environment (nuclear weapons)

• Can be used to produce high amounts of energy at a lower cost (nuclear power plants operate under this state with k = 1)

• With each reaction, it produces several millions times more energy per a chemical reaction

Questions?