Calculation of Thermal Neutron Diffusion Length in a Light Water Media using MCNP Code

Abstract

One of the key parameters of neutron diffusing media is the thermal neutron diffusion length. The popular calculational method is founded on utilizing MCNP code and curve fitting of a mathematical function to the neutron flux distribution in the media. In this investigation, a novel method based on the PTRAC card is proposed. The thermal neutron diffusion length parameter for light and water is calculated based on the above methods. The results are compared with the reported values and significant agreement is seen. The advantage of the above method is its independence from curve fitting to calculate the neutron flux distribution. In addition, in the curve fitting method, it is assumed that there is enough distance from the source location. This affects the error of the results because the neutron flux distribution function is correct everywhere except at the neutron source location. In the present investigation, the correctness of the proposed method in light water media is evaluated numerically.

Keywords

• mcnp code
• neutron diffusion length
• neutron flux