ABSTRACTS OF JAPANESE ARTICLES

A new approximate method for calculating the effectiveness of multiple control rods fully inserted in a reactor is described. This method is appicable to a bundle of many control rods, regardless of the number of rods, as well as to an array of a limited number of few rods.

Using either the sink model or the well model, a reactor equation of kernel form is obtained. The reactor equation is a two-dimensional diffusion equation with two-group diffusion kernel. In order to facilitate numerical computation of the eigenvalue, the integral equation is reduced to a set of linear homogeneous equations, by dividing the reactor into a large number of unit cells containing at most one control rod.

This method has been programmed for the IBM 7090, the code being given the designation ELC. The iterative procedure used converges much faster than the standard accelerated finite-difference programs. Using the ELC code, the effectiveness of an array of four control rods fully inserted in a cylindrical reactor was calculated. The results are in good agreement with those found by the Scaletter-Nordheim method. In the case of a large number of control rods, there is no alternative method to be compared with.