Effect of Photo-Reactions on the Effective Yield of Delayed Neutrons in the Pressure Tube Type Heavy Water Reactor

Abstract

A theoretical study with use made of the collision probability method has been undertaken on the effect of photo-reactions brought upon the effective yield β of delayed neutrons in a pressure tube type heavy water reactor loaded with ²³⁵U. It is concluded that the shielding effect of the reactor structural materials for the hard γ-rays emitted from fission products reduces the contribution of the photo-neutrons to β from the currently used value of 1.00×10^-3 to 2.2×10^-4.