Build Up and Characterization of Ultraslow Nuclear Burn-Up Wave in Epithermal Neutron Multiplying Medium

A study is carried out on the build-up and characterization of ultraslow nuclear burn-up wave in epithermal neutron multiplying medium for slab geometry. Uranium-plutonium fissile medium is considered for the calculation. Transient part of the wave is characterized by transient time (TT), transient length (TL), and TT and TL are defined as the time and distance required to develop asymptotic neutron flux propagating through the media. Steady-state part of the wave is characterized with wave velocity and reaction zone width (full width half maximum (FWHM) and fill width 10% of maximum (FW10M)). Parametric studies are carried out for different enrichment of U-235 and different values of external source of neutron. It is observed that TT, TL, FWHM, and FW10M decrease with the increase in enrichment. The velocity of the wave increases with the enrichment of U-235. This study is beneficial for understanding the characteristics of nuclear burn-up wave in epithermal region as it will help in further researches in this area.