A Nuclear Cross Section Data Handbook

A. Tabular Data
There are 129 sets of tabular data contained in this volume, one for each of
the elements or isotopes on the MCNP library. The tabular data module contains
relevant explanatory information which was detailed in the previous section. The
tabular data or text has encoded T@Ccommands to facilitate the formatting of the
pie charts and text on a single page.
B. Graphics Data
The Handbook contains two graphics data modules, the pie-chart data module,
and the graph or plot data module. The pie-chart module consists of individual
pie charts which have been generated at three different energies. The individual
pie charts are then ordered and formatted so as to be cent ained in a single file and
subsequently combined with the tabular data.
The graph or plot data module consists of a series of curves which characterize
the reactions or ENDF/B MT’s. These curves are grouped into various categories
which form a single graph. For each graph the cross section in barns on the ordinate
is plotted versus the energy in MeV along the abscissa. On the upper right hand side
of each graph the date the plot was generated is given, followed by the ZAID, the
chemical symbol for the element or isotope, the library upon which the evaluat ion is
listed, and the MT’s being plotted. The graphs of curves are subsequently formatted
so that all categories of curves are contained on a single page. It is understood that
not all categories of plots appear for every evaluation. In fact, each page may
contain as few as two or as many as six graphs of plots or curves.
IV. Heating Numbers
Included among the plots for each each nuclide (page two of each evaluation) is a
plot labeled “Heating Numbers” in units of MeV/collision. On the first page under
evaluation information these numbers are detailed as either local or total heating
numbers. Generally, the heating numbers are one of the leas~derstood items of
data available to the user; as such, they merit special attention.
By heating or heating numbers one is actually referring to the local energy
deposition resulting from the production of charged particle motion by neutrons
and gammas. The heating number is simply a means of quantizing or calculating
this effect. The heating number H(E) is a function of incident neutron energy E,
and is a measure of the energy deposited per collision. In local heating the energy
of the secondary neutrons and photons is assumed to be carried away from the
site of the reaction. Local neutron heating is therefore due to the kinetic energy
of the recoil nucleus, of the emitted charged particles, and of the charged particles
produced by radioactive decay of the residual nucleus. Total neutron heating is
the sum of the energy carried away by the photons and the energy deposited in
the collision. Other processes such as internal conversion also contribute to local
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