MCNP-DSP: a neutron and gamma ray Monte Carlo calculation of source-driven noise-measured parameters

The mCf-source-driven noise analysis measurement method was developed to determine the subcriticality and other properties of configurations of fissile material. The method provides measured parameters that can also be used for nuclear weapons identification, nuclear materials control and accountability, quality assurance, process monitoring, and verification of calculation models and cross section data used for criticality safety analyses. MCNP-DSP was developed to calculate the measured frequency analysis parameters, time analysis quantities such as autocorrelation and cross-correlation functions, and the time distribution of counts after 2S2Cf fission for both neutrons andlor gamma rays using continuous energy cross sections. MCNP-DSP can be used to validate calculational methods and cross section data sets with measured data from subcritical experiments. In most cases the frequency analysis parameters are more sensitive to cross section changes by as much as I or 2 orders of magnitude and thus may be more useful than comparisons of neutron multiplication factors for calculational validation. The use of MCNP-DSP model in place of point kinetics model to interpret subcritical experiments extends the usefulness of this measurement method to systems with much lower neutron multiplication factors. MCNP-DSP can also be used to determine the calculational bias in the neutron multiplication factor (a quantity which is essential to the criticality safety specialist) from in-plant subcritical experiments. This paper describes how MCNP-DSP calculates the measured parameters from the mCf-source-driven time and frequency analysis measurement.