Abstract:
Background Delayed neutron, as a key signature of nuclear fission, plays a significant role in nuclear technology and engineering. Major nuclear reactor accidents (e.g., Chernobyl, Fukushima) are often accompanied by explosions, which generated shockwaves that may affece the transport of delayed neutrons and consequently influence the delayed neutron dose assessment. Understanding the influence of the shockwaves on the transport of delayed neutrons is critical for accurate radiological evaluation in such scenarios.
Purpose This study aims to investigate the influence of a shockwave on the transport of delayed neutron released from fission products and to calculate the resulting dose field at ground-level monitoring points.
Methods A correspondence between mass thicknesses and delayed neutron doses was established by using the Monte Carlo method. The LAMBR model, based on a mirroring technique, was used to calculate the complex air density distribution arising by the shockwave at around the delayed neutron source. By combining the mass-thickness equivalent attenuation law with the LAMBR model, the delayed neutron dose fields of typical fission nuclides were calculated.
Results The results indicated that when the strength of the shockwave source is fixed, the enhancing effect of the shockwave on the transport of delayed neutrons becomes more pronounced as the source height increased. Conversely, when the source is close to the ground and the strength of the shockwave source is sufficiently strong, the ground-reflected shockwave may attenuate the transport of delayed neutrons.
Conclusions The transport of delayed neutrons is significantly influenced by the shockwave, and furthermore the influence is closely related to the height and strength of the shockwave source. These findings provide valuable insights for improving dose assessment in accident conditions involving explosions.
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