Abstract
The measurements of α c the prompt neutron decay constant at delayed critical have been made by pulsed neutron technique in various core configurations of SHE, a graphite-moderated 20% enriched uranium critical assembly. It was confirmed from the results that the value of α c is very strongly dependent on geometrical configurations of the reflector rather than on the atomic ratio of carbon to 235U in the core region. These results are in fairly good agreement with the calculated values obtained directly as the eigenvalue of the characteristic equation on a 34 group P-1 model.