Chart of the Nuclides -Reply

[Charles Willis <CAW@nrc.gov>]

Robert,

All the information I have about thermal neutron fission of U-235 indicates that
such fission produces more Cs-135 atoms than Ca-137 atoms.  The great difference
in half-lives, 2,300,000 years and 30.07 years respectively, accounts for the
difference in the activities of the two. 

As for the bolded rows and columns on the chart, they indicate the magic numbers,
(i.e. 2, 8, 20, 28, 50, 82, and 126) where the nuclei have closed shells of either
protons or neutrons.  These indicate unusual stability.  For example, there are
about 7 stable nuclides with 82 neutrons in their nuclei whereas there are only 2
stable nuclides with 81 neutrons and only 1 stable nuclide with 83 neutrons.  Of
course, many of the nuclides with 82 neutons, such as Cs-137, are not stable.  

Charlie Willis
caw@nrc.gov