Quanzhi Yu

Study of shielding design for SANS at CSNS

The small angle neutron scattering (SANS) instrument is presently being constructed at Chinese Spallation Neutron Source (CSNS) in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open TO chopper. The basic design scheme of the beam stop is discussed. The size of the TO chopper rotor is also estimated.

Validation of source biasing method for its use in CSNS beamline shielding calculation

The Chinese spallation neutron source (CSNS) is a high-performance pulsed neutron source, having 20 neutron beamlines for neutron scattering instruments. The shielding design of these beamlines is usually needed for Monte Carlo (MC) calculation, and the use of variance reduction methods is critical to carrying out an efficient, reliable MC shielding calculation. This paper discusses the source biasing method based on actual source term and geometry model of a CSNS neutron beamline. Dose distribution throughout the geometry model was calculated with the FLUKA MC code. Full analogue calculation and biased calculation were compared, and it was validated that the source biasing method can effectively promote the calculation efficiency.

Shielding calculation for the CSNS target station

In this paper we firstly calculate the one-dimension shielding models to give the basic data for the Chinese Spallation Neutron Source (CSNS) target station. Then the three-dimensional shielding calculations have been performed for the detailed design of the CSNS target station. The gaps and void spaces in the CSNS target station are considered for precise estimation. We find that 4.8-meter-radius steel adding 1.2-meter-thick magnetite concrete can satisfy the shielding requirement in the horizontal direction. The dose rate on the top of the ceiling is a little higher than 2.5μSv/h due to streaming effect, which originates from the moderator transfer lines. A thin sandwich structure will be adopted for decreasing residual radioactivity dose rate on the altitude directions after considering the engineering cost and maintenance. All these calculations lie on the Monte Carlo simulation code MCNPX2.5.0.