A Nuclear Cross Section Data Handbook
A Nuclear Cross Section Data Handbook
A Nuclear Cross Section Data Handbook
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Density Values<br />
APPENDIX A<br />
EXPLANATORY NOTES<br />
Density values are given in units of grams/cm3 and were obtained from the<br />
1988-89 Edition of the CRC <strong>Handbook</strong> of Mathematics and Physics (Ref. 18).<br />
In the case of the T!ransuranium Elements, the density value was gleaned from<br />
the most recent publication in the literature for the best known isotope. The<br />
ratio-of-masses principle was subsequently applied to obtain the density values<br />
for the remaining isotopes (please see Refs. 19 and 20). The density value of<br />
12.44 grams/cm3 was used for all of the average fission product pairs. There<br />
is absolutely nothing magical about this value. It was chosen for the sake<br />
of thoroughness and completeness of the data presented and because it is a<br />
good average representation of the density, based upon the masses of the fission<br />
products. In every case, the density value quoted is that value used to calculate<br />
the mean free paths given with the plots.<br />
Abundance Values<br />
The isotopic abundances were taken from the Table of the Isotopes compiled by<br />
Russell L. Heath, found on pages B-227 through B-448 of the 1988-1989 edition<br />
of the CRC <strong>Handbook</strong> of Chemistry and Physics. The abundances for the<br />
uranium isotopes were taken from the 13th edition of the Chart of the Nuclides<br />
(Ref. 21).<br />
Q-Values<br />
Note that in the tabular data for any given nuclide, two Q-Values are listed for<br />
a specified reaction, QhFand QR. QR is the Reaction Q-value. It is obtained<br />
by taking the difference between the nm.sses of the constituent particles of a<br />
reaction before and after the occurrence of that reaction. QK is the Kinematic<br />
Q-value. For discrete-level inelastic scattering, QIf differs from QR. It is the<br />
negative of the energy of the discrete level excited in the target nucleus. QK is<br />
used in the formula for calculating the secondary energy from discrete-inelastic<br />
scattering. As a matter of fact, it is the Kinematic Q-value that is carried on<br />
the —.. A C E files for a particular reaction on the MCNP Library, not the Reaction<br />
Q-value. l%rtherrnore, it is only for discrete-inelastic reactions that the Q value<br />
is used explicitly in MCNP calculations. The Reaction Q-value is used when<br />
the heating numbers are calculated in the NJOY processing code (Ref. 9)<br />
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