THE Be$sup 9$ (n,2n) Be$sup 8$ REACTION AND ITS INFLUENCE ON THE INFINITE MULTIPLICATION FACTOR FOR BERYLLIUM MODERATED HETEROGENEOUS THERMAL REACTORS

The influence of the Be/sup 9/ (n,2n)Be/sup 8/ reaction on the infinite multiplication factor of heterogenrous thermal reactors using beryllium as moderator is considered. The distortion of the fission neutron spectrum due to collisions either in the natural uranium bars or in the moderator is taken into account. The estimate of the effect is made using the differential cross section for the ues of the order of 7% are obtained. (auth)