Neutronics calculation of a reactor cold neutron source

The construction of a reactor cold neutron source(CNS) will be completed in the near future.To evaluate performance of the CNS,a neutronics calculation using MCNP4C code has been carried out.The results show that the average neutron flux in the moderator is 6.69×1013/cm2.s,and the cold neutron gain factors corresponding to 4- and 6- wavelengths are 16 and 32,respectively.The results also indicate that different ratios of ortho-H2/para-H2 have an obvious impact on cold neutron spectrum in the moderator,but within 3 K of the moderator temperature changes,the spectrum varies slightly.