Subcriticality Measurements for Two Coupled Uranyl Nitrate Solution Tanks Using Sup 252 Cf-Source-Driven Neutron Noise Analysis Methods

摘要

The subcriticality of two interacting solution tanks was determined using sup 252 Cf-source-driven neutron noise analysis methods. These experiments were the first test of this method for an interacting system with materials (in this case, uranyl nitrate) typical of nuclear materials in processing plants. The experiments were performed to test the conclusions from previous interaction experiments with uranium metal discs for a fissile system with moderation, and to provide data to test theoretical models for coupled systems. The uranium metal experiments showed that the subcritical neutron multiplication factor, k/sub eff/, could be determined using point kinetics without any correction for spatial effects from measurements with the source and detectors located adjacent to the same cylinder, whereas for source-detector configurations with either the source and/or detectors adjacent to different cylinders, a model which incorporates the coupling is required to obtain subcriticality. In the previous experiments with two coupled uranium metal cylinders, the measurements were performed at frequencies (1 MHz) for the metal discs. Thus, many aspects of the theory relating to the relationships between various spatial models could not be verified in previous experiments. These measurements and their interpretation have shown that (1) point kinetics interpretation of the measured ratios of spectral densities yields the subcritical neutron multiplication factor when the source and detectors are located in or adjacent to one of the cylinders of uranyl nitrate, and (2) the coupling reactivity can be obtained by incorporating a third neutron detector adjacent to the cylinder without the source using the kinetics model of Difilippo, which includes one additional spatial mode in the direction of the coupling. (ERA citation 11:030335)