Measurements of the Epicadmium Capture-to-Fission Cross-Section Ratio in U²³⁵

The epicadmium capture-to-fission cross-section ratio in U²³⁵ is obtained from post-irradiation measurements on bare and cadmium-covered samples exposed in the beryllium reflector of the Materials Testing Reactor. Relative capture-to-fission rates are determined from measurements of the quantities of U²³⁶ and of fission product Cs¹³⁷ produced. The bare experiment measurements are used in combination with the cadmium-covered measurements to eliminate the need to know the yield and half-life of Cs¹³⁷. For the irradiation spectrum, the experiment gives a value of 0.51 ± 0.03 for the U²³⁵ epicadmium α(above 0.51 eV).