Development of quick neutron spectrum reconstruction module based on POD for burnup calculation of fast reactor

Aizawa, Naoto*; Watanabe, Tomoaki  ; Chiba, Go*; Tada, Kenichi   ; Fujita, Tatsuya*; Yamamoto, Akio*

A quick neutron spectrum reconstruction module based on proper orthogonal decomposition (POD) and a regression model for fast reactors is developed for the general-purpose burnup calculation code SWAT-X. This module enables burnup calculations to be performed quickly for arbitrary conditions based on a few parameters, eliminating the need for computationally intensive calculation codes. Reduced-order and regression models are constructed by applying the POD technique to the snapshot data of the multi-group neutron fluxes calculated using randomly-sampled parameter sets for a single hexagonal pin-cell of a sodium-cooled fast reactor. The neutron spectrum is reconstructed using a linear combination of POD basis vectors with the coefficients obtained from the regression model. The applicability of a pin-cell model, the accuracy of the reconstruction module itself, and its integration with SWAT-X are verified by comparing with the calculation results from the reactor physics code system CBZ.