Differences in the Use of Nuclide x Vectors Demonstrated with an Analytic k_∞ Problem

摘要

This paper came about from the observation that MCNP's KSEN (a Monte Carlo code) and SENSMG/PARTISN (a deterministic code) computed very different sensitivities of k_∞ to the same input nuclide fission x vectors. This paper shows that the differences are due to the way each code uses the nuclide fission x vectors.None of the differences arise if the test material has only one nuclide or if PARTISN uses a fission x matrix. The differences may also be masked if different nuclear data are used in the comparison, such as "continuous energy" vs. multigroup. Some combination of these probably explains why previous comparisons of Monte Carlo and deterministic sensitivities to x did not seem to find this effect.