Neutronic Simulation Of The ADS Target-reactor Coupled System Using Geant4

The development of nuclear power has three important issues:1.The supply of nuclear fuel;2.The safety of nuclear reactors;3.The treatment of nuclear waste.Accelerator Driven Sub-critical System?ADS?is considered as a clean and safe advanced nuclear energy system which can effectively solve the difficulties faced by nuclear power development.ADS mainly composes high-current proton accelerators,spallation targets and subcritical reactor.The proton beam induced the heavy metal target,and a large number of neutrons produced by the spallation reaction are used as neutron source to drive and maintain the subcritical reactor working,so it has inherent safety.The ADS system has a neutron spectrum which is hard,high flux and has a wide energy distribution.It is capable of nuclear waste transmutation,nuclear fuel reproducing and producing energy.In 2011,the Chinese Academy of Sciences carried on a strategic project?Class A?"Future Advanced Nuclear Fission Energy-ADS Transmutation System".The new ADS system which has tungsten pebble bed spallation target is proposed by the Chinese Academy of Sciences,it consists of a new spallation target and a particle/helium mixed cooling reactor.For the ADS new target-reactor coupled system,neutron research is very important.The neutron study of the ADS target-reactor coupled system is based on the new target reactor system.The neutrons in the system are derived from the reaction in the spallation target and the fuel fission reaction in the core,respectively.The distribution of neutron spectrum shows very strongly spatial anisotropy.Since the core structure and the cooling medium in the new target reactor system are different from the known cores,there must be a differences in the sub-transport process.The neutron simulation of the ADS target-reactor coupled system has a very important influence on the design of system,especially on the target coupling optimization,is directly related to its safety and economy.It is necessary to carry out systematic neutron studies through a special experimental platform.This work will carry out the neutron simulation study of ADS target-reactor coupled system.This dissertation will carry out the neutron simulation study of ADS target-reactor coupled system.The main contents include:?1?Theoretical simulation of proton induced spallation reaction:The neutron energy spectrum,fission fragments,etc.of the proton induced spallation reaction were simulated using various theoretical models of spallation reactions?INCLXX,BERT,BIC etc.?.Comparing with the existing experimental data,the best spallation reaction theoretical model is given;?2?ADS subcritical critical target reactor coupling system neutron simulation:ADS subcritical critical target-reactor coupled system is constructed using MCNPX and GEANT4 software package.The theoretical model of the system includes spallation targets,U-238 cladding,graphite reflectors,polyethylene moderated layers,and so on.At the same time,the model was used to carry out neutron simulation of the ADS target coupled system:Impact of incident proton energy and spallation target size on spallation neutron yield,neutron energy spectrum,yield and spatial distribution of leakage neutron from tungsten ball granule target,influence of layout of outer layers of target area on target area neutron,the neutron transport in each layer around the target area,and Geant4 used in the k_eff calculation method.Overall,the neutronic calculations with the Geant4 code for the ADS target-reactor coupled is reasonable and reliable.This study provides a reference for the design of the ADS target-reactor coupled system.