Verification of the on-the-fly global variance reduction technique on Monte Carlo global coupled neutron photon shielding calculations

Highlights: • A new feature of on-the-fly global variance reduction (OTF) to accelerate the MC global coupled neutron photon transportation has been developed. • ITER C model and IFMIF-DONES (International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source) had been chosen as test cases and calculated with OTF and analogue. • The results of OTF had been compared to analogue • OTF has shown to result in substantial reduction of computational time for global coupled neutron photon shielding calculation. Using Monte Carlo (MC) transport codes for fusion device shielding calculation is very challenging due to the complexity and heavy shielding of a fusion reactor. An effective on-the-fly (OTF) global variance reduction method was developed and verified before. The OTF method is designed to speed up the general-purpose MC global total neutron distribution by generating and updating the global weight window mesh (WWM) internally in the MC code. In this work, this method has been further extended for accelerating global coupled neutron photon transportation calculation. The goal of this paper is to evaluate the applicability of OTF to enhance the efficiency of the global total neutron and photon fluxes calculation of challenging problems. For verification purposes, the ITER C-model and IFMIF-DONES have been chosen as test cases. The OTF has achieved a substantial reduction in computational time comparing with analogue method.