On the calculation of the bare reactor extrapolation distance by two-group theory

摘要

In the present paper we aim to underline some questions connected with the application of the method of effective boundary condition in the frame of two-group diffusion theory. As well-known, this method permits the evaluation of the extrapolation distance for a bare reactor.nWhen two groups of neutrons are considered, this extrapolation distance is expressed in terms of the two linear extrapolation distances (fast and slow respectively) and obviously it is intermediate between the two. In this way, if the size of the reactor is known, the effective extrapolation distance gives the effective «buckling» in the direction perpendicular to the surface of the reactor, and, hence, it is possible to determine the leakage of fast and slow neutrons in terms of the effective «buckling».nOn the other hand, if the reactor is critical, i.e., the «buckling» is known, from the effective extrapolation distance we will be able to derive, for any geometry, the reactor size in the same direction of the given «buckling».