New processor for subcritical fissile system measurements for nuclear criticality safety

The 252Cf source-driven noise analysis method can provide a wide variety of measured quantities that can be used to obtain the subcritical neutron multiplication factor (k) and be used to verify Monte Carlo and other transport methods and cross-section data. These measured time and frequency analysis quantities all related to powers of Δk/k up to order 4 and are, therefore, much more sensitive to cross-section changes than the value of k. Calculations with a variety of subcritical systems with k = 0.9 show that some of the frequency analysis quantities are as much as a factor of 50 more sensitive to cross-section data than the value of k. In addition to providing the subcritical neutron multiplication factor for inplant fissile systems, these measurements can provide the bias in calculational methods and data sets, a quantity essential to nuclear criticality safety specialists for criticality safety assessments. In the past, two things have hindered the extensive use of this method: inadequate models for interpretation of measured data and cumbersome hardware. The Monte Carlo models for direct calculation of the measured data, KENO-NR (neutrons only, group cross sections) and MCNP-DSP (neutrons and gamma rays, continuous energy cross sections), have removed the modeling inadequacies. The processor described here has removed the hardware limitations