On a various noise source reconstruction algorithms in VVER-1000 reactor core

• A sensitivity analysis of unfolding methods to different parameters is done.
• ISM is proposed to reconstruct the noise source of type vibrating absorber.
• Four algorithms are used to solve the system of equations in the inversion method.
• The neutron noise due to a new defined noise source (ILFAIP) is calculated.
• We find that the scanning method is a reliable algorithm for source reconstruction.

In present study, the neutron noise source is reconstructed using three different unfolding techniques in a typical VVER-1000 reactor core. In first stage, the neutron noise calculation based on Galerkin finite element method (GFEM) is performed; in which the neutron noise in two energy group due to the noise sources of type absorber of variable strength and vibrating absorber is calculated. The neutron noise due to inadvertent loading of a fuel assembly in an improper position (ILFAIP), as a new defined noise source in the neutron noise studies, is calculated as well. In the second stage, the inversion, zoning and scanning methods are applied for reconstruction of the noise source of type absorber of variable strength. Also, improved scanning method (ISM) is used to reconstruct the noise source of type vibrating absorber. To solve the system of equations in the inversion method, four different algorithms are used. The obtained results from various unfolding methods are then compared. Finally, a sensitivity analysis of mentioned methods to different parameters like the location of noise source in the reactor core, number of available detectors and fuel burn up is performed.