Absolute Subcriticality Measurement without Calibration and Detection Efficiency Dependence by the 252Cf Source-Driven Noise Method

The 252Cf-source-driven noise analysis method determines the subcriticality of a system containing fissionable material from the ratio of cross power spectral densities between the detectors that detect particles from the fission process and between these detectors and an ionization chamber containing a spontaneously fissioning neutron source which provides neutrons to induce fission in the system. This method has two advantages: (a) a calibration is not required and thus subcriticality can be determined from measurements only on the subcritical system of interest, and (b) the subcriticality is independent of the type of detector or its efficiency. These properties of this technique are illustrated by measurements.