The Pulsed Neutron Source (PNS) experiment on the Fast-thermal Coupled sub-critical core VENUS-1# has been performed in CIAE with 14MeV accelerator neutron source. The preliminary experimental data indicated spatial dependence of prompt neutron attenuation constant a, which is conflict to traditional theories. To re-evaluate the experiment and probe possible special features of the Fast-thermal Coupled core, a Monte-Carlo simulation of PNS experiment has been performed in this paper. Considering Contamination of harmonics mode of prompt neutrons, a data-processing technique, e.g. harmonics filtering, is used to obtain the fundamental mode decay. The simulated results indicate that, the influence of harmonics and external source are mainly in the time region 0～500μs after pulsed neutron injection; by harmonics filtering, spatially independent α values are obtained and verified. By the method above, the experimental data are re-processed, however, the problem of the spatially dependence of a is not improved at all, the α value indicated by detector R is still quite different from others'. The works performed in this paper suggest that, some future PNS experiments should be deployed to confirm the experimental phenomenon.
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