Modelling of Tarapur BWR lattice and core to estimate the required number of SB-BE startup neutron sources

During the refuelling and criticality of Boiling Water Reactors (BWR), fission counters are used as Source Range neutron Monitors (SRMs) to get the count rates. The study shows that the neutron counts due to spontaneous fission sources are insufficient to meet the SRM's limitations of 3 counts per second (cps). In this work, TAPS fuel assembly is modelled using the lattice transport code DRAGON5, and lattice parameters are generated as a function of fuel depletion. These parameters have been further used to model the reload-2 of the BWR core. 3D diffusion theory code KINFIN is used to simulate the BWR core with external neutron sources to estimate the neutron flux at three SRM locations. Thermal fluxes are then used to compute the neutron count rates using the sensitivity of SRMs for different combinations of five Sb-Be neutron sources.