Year
1997
Abstract
A system for monitoring fissile mass flow in slurries, liquid and gaseous streams has been developed at Oak Ridge National Laboratory. The basis for the measurement is the activation of a fissile stream by neutrons and subsequent detection of delayed radiation produced by fission products resulting from such activation. This development of source modulation correlation measurements for fissile mass flow was first supported by US DOE Nuclear Energy Division in September, 1995, after the concept was proposed earlier in 1995. This paper describes recent simulation measurements with the first prototype of the system for fissile mass flow measurements with HEU UF6 gas for use in blenddown facilities. The theoretical model predictions from basic data for the simulation apparatus were only 15% higher than those actually measured, which is a remarkable agreement considering all of the physical phenomena involved. Thus, the calibration factor for the HEU gas from these simulation measurements is only 0.85 rather than unity which would mean perfect agreement. This amounts to using a completely mathematical based model as a calibration for a nondestructive assay method and having only a 15% difference from measurement. The simulation of HEU gas flow confirms extremely well the understanding of the physical phenomena associated with this measurement system.