Second order of average current nodal expansion method for the neutron noise simulation

• Main Authors: N. Poursalehi, A. Abed
• Format: Article
• Language: English
• Published: Elsevier 2021-05-01
• Series: Nuclear Engineering and Technology
• Subjects: Frequency dependent diffusion equation; Neutron noise; Average current nodal expansion approach; Second order of solution
• Online Access: http://www.sciencedirect.com/science/article/pii/S1738573320309189

The aim of this work is to prepare a neutron noise calculator based on the second order of average current nodal expansion method (ACNEM). Generally, nodal methods have the ability to fulfill the neutronic analysis with adequate precision using coarse meshes as large as a fuel assembly size. But, for the zeroth order of ACNEM, the accuracy of neutronic simulations may not be sufficient when coarse meshes are employed in the reactor core modeling. In this work, the capability of second order ACNEM is extended for solving the neutron diffusion equation in the frequency domain using coarse meshes. For this purpose, two problems are modeled and checked including a slab reactor and 2D BIBLIS PWR. For validating of results, a semi-analytical solution is utilized for 1D test case, and for 2D problem, the results of both forward and adjoint neutron noise calculations are exploited. Numerical results indicate that by increasing the order of method, the errors of frequency dependent coarse mesh solutions are considerably decreased in comparison to the reference. Accordingly, the accuracy of second order ACNEM can be acceptable for the neutron noise calculations by using coarse meshes in the nuclear reactor core.