Study on the off situ reconstruction of the core neutron field based on dual-task hybrid network architecture

The off situ accurate reconstruction of the core neutron field is an important step in realizing real-time reactor monitoring.The existing off situ reconstruction method of the neutron field is only applicable to cases wherein a single region changes at a specified location of the core. However, when the neutron field changes are complex, the accurate identification of the individual changed regions becomes challenging, which seriously affects the accuracy and stability of the neutron field reconstruction. Therefore, this study proposed a dual-task hybrid network architecture(DTHNet) for off situ reconstruction of the core neutron field, which trained the outermost assembly reconstruction task and the core reconstruction task jointly such that the former could assist the latter in the reconstruction of the core neutron field under core complex changes. Furthermore,to exploit the characteristics of the ex-core detection signals, this study designed a global-local feature upsampling module that efficiently distributed the ex-core detection signals to each reconstruction unit to improve the accuracy and stability of reconstruction. Reconstruction experiments were performed on the simulation datasets of the CLEAR-I reactor to verify the accuracy and stability of the proposed method. The results showed that when the location uncertainty of a single region did not exceed nine and the number of multiple changed regions did not exceed five. Further, the reconstructed ARD was within 2%, RDmax was maintained within 17.5%, and the number of RD≥10% was maintained within 10. Furthermore, when the noise interference of the ex-core detection signals was within ±2%, although the average number of RD≥10% increased to 16, the average ARD was still within in 2%, and the average RDmax was within 22%. Collectively, these results show that,theoretically, the DTHNet can accurately and stably reconstruct most of the neutron field under certain complex core changes.