Rapid determination of uranium and plutonium content in mixtures through measurement of the intensity-time curve of delayed neutrons

摘要

The delayed neutron emission of fissile isotopes after irradiation can be described by the six-groups theory. Due to the different half-lives and yields of the fission fragments, the intensity-time curve of delayed neutrons has an individual shape for different fissile isotopes. According to this characteristic, a new rapid analysis method has been developed to determine the concentration of different isotopes in a mixture, such as ~(235)U and ~(239)Pu, without any chemical separation. The intensity-time curve of delayed neutrons is measured by using the multichannel scanning (MCS) method with live ~3He-detectors installed on a fast transfer system at the research reactor Munich (FRM). This method was validated by about 200 measurements with different isotope contents even below the microgram region.