Page 229 - A Life - my Live - my path

Appendix

Fission products
This is "radioactive waste".
The fission of 92uranium 235 produces 93krypton and
36
56.
140barium
Each fission product decays into other products with half-
lives ranging from a few milliseconds to several thousand
years.

Neutrons
These neutrons will generate - each in turn - another fission
reaction.
If this cascade of reactions is not controlled, the result is a
chain reaction used in atomic bombs.
For a chain reaction to take place, there must initially be
sufficient fissile material (e.g. plutonium 239 ) - this is known as
critical mass. This fissile material must also be confined to a
small volume and highly enriched (90%) to sustain a chain
reaction.

In nuclear reactors, the level of chain reaction is controlled
by neutron-absorbing control rods. These rods are generally
made of silver, indium and cadmium. They are inserted into
the reactor’s core to a greater or lesser extent, depending on
the power required. The fissile material used in a reactor is
enriched to 4 or 5% and contained in a large volume.

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