Optimization study of China advanced research reactor CNS using MCNP

A Cold Neutron Source (CNS) for China Advanced Research Reactor (CARR) was designed and optimized using the MCNP code. Many factors including moderator and material of moderator cell, which would greatly affect the nuclear heating and gain factor, have been optimized. Liquid hydrogen at 23K and 6061 aluminum alloy are selected as the cold moderator and moderator material. The shape of moderator cell, which impact the performance effectively, is optimized from cylindrical annulus to crescent by analyzing the neutron flux inside it. These parameters, such as the thickness of and ortho/para ratio in liquid hydrogen, cold neutron spectrum and neutron temperature, have been also evaluated. The cold neuron gain factor and brightness at the entrance of horizontal channel are showed and compared with other facilities. The result indicates that a good performance had been gained for developing CARR CNS