Neutron noise simulation in the nuclear reactor core based on the average current nodal expansion method

In this work, the zeroth order of average current nodal expansion method (ACNEM) is developed for the neutron noise simulation of nuclear reactors core with two dimensional rectangular fuel assemblies. At first, the static calculation is performed for the forward treatment of diffusion equation. Then the forward neutron noise is earned by solving the diffusion equation in the frequency domain using the zeroth order of ACNEM. For the neutron noise calculation in the domain of reactor core, the noise source is considered as an “absorber with variable strength” type i.e. the absorption cross section can be changed in the selected material. In order to evaluate the accuracy of exploited scheme, the neutron noise simulation is performed for two well-known test cases including 2-D LRA BWR and 2-D BIBLIS PWR. For benchmarking purpose, the adjoint noise calculation is done for comparing results with the forward approach using a conventional relation in an elected non-zero frequency. Also the contrast of results is illustrated between the neutron noise in the zero frequency and the corresponding earned static fluxes. Totally, numerical results of problems validate the accuracy of the neutron noise simulation using the proposed method.