Download 25.3 section summary

SECTION SUMMARY
25.3 Fission and fusion of atomic nuclei Summary:
Nuclear fission occurs when fissionable isotopes are bombarded with neutrons.
The fissionable atom breaks into two fragments of about the same size, and in the
process they release more neutrons and energy.
Neutron moderation is the process that reduces the speed of neutrons. Sometimes
water is used as a moderator in nuclear reactors. Neutron absorption is the process
that decreases the number of slow-moving neutrons. In nuclear fusion, nuclei
combine to make nuclei of greater mass. The sun’s energy is produced when
hydrogen nuclei fuse to make helium nuclei. Fusion releases even more energy than
fission. Fusion only occurs at very high temperature- in the excess of 40, 000oC, and
it is not easy produced under laboratory conditions.
25.3 Fission and fusion of atomic nuclei Vocabulary Terms:
fission:
the splitting of a nucleus into smaller fragments,
accompanied by the release of neutrons and a large
amount of energy
neutron moderation:
a process used in nuclear reactors to slow down
neutrons so the reactor fuel captures them to
continue the chain reaction
neutron absorption:
a process that decreases the number of slow-moving
neutrons in a nuclear reactor; this is accomplished
by using control rods made of a material such as
cadmium, which absorbs neutrons
fusion:
the process of combining nuclei to produce a
nucleus of greater mass
uranium-253:
isotope capable of fission
The End of the Summary