Criticality Studies for a Neutron Multiplier

Critical experiments were performed on an annular assembly of 93.2 wt% 235U enriched U-Al alloy fuel elements in light water to provide data for the design and operation of a subcritical neutron multiplier of a 252Cf neutron source. The various factors affecting criticality were determined. In addition to measurement of the critical fuel rod loading under various conditions, values of keff were determined as a function of fuel rod loading by means of pulsed neutron source experiments. The data provide the design basis for operation of the neutron multiplier, yielding a maximum flux value in the internal irradiation column consistent with maintaining a degree of subcriticality in operation.