1
0
n
235
92
U
236
92
U
140
55
Cs
93
37
Rb
3
1
0
n
ENERGY RELEASE FROM FISSION
DOE-HDBK-1019/1-93
Atomic and Nuclear Physics
NP-01
Page 56
Rev. 0
ENERGY RELEASE FROM FISSION
Fission of heavy nuclides converts a small amount of mass into an enormous
amount of energy. The amount of energy released by fission can be
determined based on either the change in mass that occurs during the reaction
or by the difference in binding energy per nucleon between the fissile nuclide
and the fission products.
EO 4.8
CHARACTERIZE the fission products in terms of mass
groupings and radioactivity.
EO 4.9
Given the nuclides involved and their masses, CALCULATE
the energy released from fission.
EO 4.10
Given the curve of Binding Energy per nucleon versus mass
number, CALCULATE the energy released from fission.
Calculation of Fission Energy
Nuclear fission results in the release of enormous quantities of energy. It is necessary to be able
to calculate the amount of energy that will be produced. The logical manner in which to pursue
this is to first investigate a typical fission reaction such as the one listed below.
It can be seen that when the compound nucleus splits, it breaks into two fission fragments,
rubidium-93, cesium-140, and some neutrons. Both fission products then decay by multiple -
emissions as a result of the high neutron-to-proton ratio possessed by these nuclides.
In most cases, the resultant fission fragments have masses that vary widely. Figure 21 gives the
percent yield for atomic mass numbers. The most probable pair of fission fragments for the
thermal fission of the fuel uranium-235 have masses of about 95 and 140. Note that the vertical
axis of the fission yield curve is on a logarithmic scale. Therefore, the formation of fission
fragments of mass numbers of about 95 and 140 is highly likely.
