Application Of FLUKA And OpenMC In The ADS Coupling Calculation

Accelerator Driven Subcritical System(ADS)is considered as the most effective disposal method for nuclear waste produced in the nuclear reactor around the world.The study of ADS has been a hot research topic in the field of nuclear energy for years.The main code applied in ADS research is MCNPX,which is developed by Los Alamos National Laboratory.However,to use the MCNPX code we need to get the official authorization of LANL,which is realtively difficult for domestic researchers.To solve this problem,the open-source Monte Carlo codes FLUKA and OpenMC are applied to the ADS coupling calculation.and the accuracy of this method is evaluated by comparing with MCNPX in this paper.The coupling calculation of spallation target and subcritical core can be divided into two steps:the generation of spallation neutrons in the spallation target region and the transport of neutrons in the subcritical core.According to this idea,the FLUKA code is used to simulate the process of high energy proton bombarded with spallation material.And,the information of spallation neutrons like energy,position,direction and weight can be recorded by a user routine called FLUSCW provided by FLUKA.Then these information is written to an external neutron source file in HDF5 format by a convert code,which is requested by the OpenMC calculation.Finally,the fixed source calculation function of OpenMC is applied to simulate the transport of spallation neutrons and obtain the distribution of neutron flux in the core region.During the coupling calculation,some bugs were found in the OpenMC code.The source codes of OpenMC were modified,so that it can be used for our calculation successfully.To validate the feasibility and accuracy of this method,we compare the distribution of neutron flux calculated by FLUKA-OpenMC and MCNPX.The calculations are based on the OECD-ADS benchmark and CIADS(China Initiative Aceelerator Driven System)model.It states that the two methods give the similar distribution of neutron flux.In the OpenMC calculation,the transport of spallation neutrons with energy above 20MeV is ignored due to the upper energy limit of ENDF/B-?.1 database,which results in the flux given by FLUKA-OpenMC is 10?15%smaller than MCNPX.In order to take the high energy spallaion neutron into considerarion,the ADS-HE high energy database released by IAEA(International Atomic Energy Agency)is applied in a simplified ADS model calculation.The result shows that the flux caculations performed by FLUKA-OpenMC and MCNPX are in good agreement with a relative difference of 3%.It demonstrates that the application of FLUKA-OpenMC in the ADS coupling calculation is feasible and the result is of similar accurary with MCNPX.