To correctly predict the neutron behavior based on diffusion calculations, it is necessary to adopt well-specified boundary conditions using suitable diffusion approximations to transport boundary conditions. Boundary conditions such as the zero net-current, the Marshak, the Mark, the zero scalar flux, and the Albedo condition have been used extensively in diffusion theory to approximate the reflective and vacuum conditions in transport theory. In this paper, we derive and analyze these conditions to prove their mathematical validity and to understand their physical implications, as well as their relationships with one another. To show the validity of these diffusion boundary conditions, we solve a sample problem. The results show that solutions of the diffusion equation with these well-formulated boundary conditions are very close to the solution of the transport equation with transport boundary conditions.

1. Introduction
 2. Transport Equation and TransportBoundary Conditions
  2.1 Transport Equation
  2.2 Transport Boundary Conditions
 3. Diffusion Equation and Diffusion BoundaryConditions
  3.1 Diffusion Equation
  3.2 Diffusion Boundary Conditions
 4. Numerical Results
 5. Discussion
 REFERENCES

• Taewan Noh(홍익대학교) | 노태완 Corresponding Author