Effect of the Choice of Scattering Data, Bound or Unbound, and the Energy Group Structure on the Calculated Absorptions in the 1 eV Pu-240 Resonance

摘要

The effect of using free gas or molecular bound scattering data in calculating the absorption of neutrons in 1 eV resonance of Pu-240 was investigated. In the lattice studied, using the data for the bound H and D atoms gave about 12 percent more absorption in the resonance than using the data for the free gas at rest. This is due to differences in the downscattering cross sections. Upscattering is not important. The use of transport corrected in-group scattering cross sections was found to allow for the non-isotropic scattering in calculating the absorption in the resonance as well as the inclusion of P1 Legendre scattering terms. The energy group structure used with the WIMS and RAHAB codes over the 1 eV resonance is adequate. Use of a finer mesh only decreases the calculated absorption by 1 percent. (Atomindex citation 16:076675)