Measurement of prompt neutron decay constant in delayed critical state of heavily reflected reactor

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. (author)