Novel Bonner Sphere Spectrometer Response Functions Using MCNP6

Bonner Sphere Spectrometer response functions were computed using MCNP6 and compared to response functions calculated by Mares and Schraube (1994) using MCNP4. The simulated environment exposed a LiI(Eu) scintillator crystal to neutrons of discrete energy levels from thermal through 25 MeV, with energy resolution identical to that documented by Mares and Schraube. The shapes of the response functions were found to be in excellent agreement with previous data, but the MCNP6-calculated functions differed consistently from the Mares and Schraube data by a factor of two, which is possibly due to ambiguity within their published methodology. Regardless, a comparison of the response functions calculated from MCNP6 and MCNP4 were assessed as > 99% significant using a chi-squared test with 25 degrees of freedom.