Validation of the Fast Neutron Multiplicity Counting System for <sup>252</sup>Cf Mass Measurement

Background: Nuclear material accountancy is essential for nuclear security and non-proliferation, requiring fast and accurate measurement methods. To overcome the limitations of conventional thermal neutron multiplicity counting, this study developed a fast neutron multiplicity counting (FNMC) system using organic scintillators.Materials and Methods: An FNMC system was constructed using a pixelated trans-stilbene array and a silicon photomultiplier (SiPM) array. Performance was evaluated through Monte Carlo N-Particle Extended (MCNPX)-PoliMi simulations and experiments at 50 keVee and 100 keVee energy thresholds, analyzing detection efficiency, crosstalk, and singles (<i>S</i>), doubles (<i>D</i>), and triples (<i>T</i>) rates.Results and Discussion: The FNMC system showed a linear relationship between <i>S</i>, <i>D</i>, and <i>T</i> values and mass, with mass estimation errors of 0.4% at 50 keVee and 2.2% at 100 keVee threshold. Lower energy thresholds provided higher detection efficiency and accuracy. The system effectively minimized crosstalk and pile-up errors.Conclusion: The FNMC system provides a precise and reliable method for rapid nuclear material verification. It demonstrates strong potential for non-destructive analysis and nuclear safeguards applications, offering improved efficiency and accuracy compared to conventional methods.