Shielding Design Of The Multi—purpose Reflectometer Instrument Of CSNS And Neutronics Study For ADS

The Multipurpose Reflectometer instruments (MR) is one of the three day one instruments of the Chinese Spallation Neutron Source (CSNS) project. The physical design of the MR shielding is the important basis of the shielding engineering design. In the first part of this paper, the Monte Carlo code of MCNPX2.5.0is employed to carry out the simulation of neutron and photon transportation, and finally achieve the physical design of the MR shielding for the shielding engineering design.The source terms of MCNP shielding model of the reflectometer come from Monte-Carlo neutron transport simulation of target-moderator-reflector model which provide the energy spectra at the entrance of the instrument. Considering the thermo and cold neutron reflection inside the neutron guide, optical simulation package VITESS was used to calculate the thermo and cold neutron intensity along the neutron guide, and serve as source term for MCNPX2.5.0calculation. CSNS Multipurpose Reflectometer is a huge system, one would never get the creditable results without using any variance reduction techniques. So a sphere shielding model was constructed to checkout and select the reasonable variance reduction techniques. A MCNP shielding geometry model was constructed including the neutron guide and shielding materials to conduct the simulation of neutron and photon transport along the neutron guide by MCNPX code.The simulation results provided a space distribution of the radiation dose. And the shielding design along the neutron transport line of MR could be determined accordingly. Geometry and material MCNPX model of the second shutter of MR was constructed to calculate the space dose distribution when the second shutter was closed. And according to the results, physical design of the second shutter of MR could be determined. Geometry and material MCNPX model of the scattering room of MR was constructed to simulate the neutron and photon transport in the shielding of the scattering room. The simulation results give a space distribution of radiation dose rate in the scattering room, so that the physical design of scattering room shielding could be determined.Accelerator-Driven Subcritical system (ADS) is be regarded as a possible ways to transmutate transuranic elements and long-life fission fragments. In ADS project the related neutronics study is one of the critical issues. In the second part of this paper, the Monte Carlo method is employed to carry out the related neutronics study for ADS project, including source neutron efficiency, source proton efficiency, radial power peak ratio, axial power peak ratio and energy gam.Build a Lead-Bismuth Eutectic (LBE) spallation target model and a sub-critical core model. In the study, Set up three kinds of spallation target materials:100%LBE,40%tungsten+LBE (vol%),55%tungsten+LBE (vol%); two reference target radius:10cm and20cm; five proton energy:300MeV,600MeV,1000MeV,1200MeV and1600MeV. After calculating and analyzing various scenarios, gain the information about the proton flux distribution and neutron flux distribution. In the calculating of the source of proton efficiency (ψ*), the result shows that: the proton efficiency was increased linearly with the increase of proton energy; the source proton efficiency of the LBE target is than the source proton efficiency of the40%tungsten+LBE (vol%) target nearly twice as high; the source proton efficiency of the55%tungsten+LBE (vol%) target is than the source proton efficiency of the40%tungsten+LBE (vol%) target nearly high25%. When the target radius increase from10to20cm, the source proton efficiency of the LBE target decreases by about20%, the40%tungsten+LBE (vol%) target decreases by about30%, the source proton efficiency of55%tungsten+LBE (vol%) target decreases by about40%, namely the target with small radius can obtain higher proton efficiency. In the calculating of the radial power peak factor, the result shows that:the radial power peak factor when target radius is10cm, is significantly higher than the radial peak power factor when the target radius is20cm; the radial peak power factor of the LBE target is higher than that of the40%tungsten+LBE (vol%) target and55%tungsten+LBE (vol%) target. Under the same conditions of the target, the radial power peak factor has little relationship with proton energy. In the calculating of the axial power peak factor, the result shows that:the axial peak power factor of the LBE target is higher than that of the40%tungsten+LBE (vol%) target and55%tungsten+LBE (vol%) target. Under the same conditions of the target, the axial power peak factor has little relationship with proton energy. In the calculating of energy gain (G), the result shows that:the result shows that:the energy gain when target radius is10cm, is slightly higher than the energy gain when the target radius is20cm; the energy gain of the LBE target is significantly higher than that of the40%tungsten+LBE (vol%) target and55%tungsten+LBE (vol%) target. Under the same conditions of the target, the energy gain was increased significantly with the increase of proton energy.