Criticality of Neptunium-237 and Its Possible Utilization in Nuclear Reactors

The physics parameters of a bare sphere of metallic ²³⁷Np have been investigated. The calculations indicate that a chain reaction can be sustained with fast neutrons. The predicted critical radius is 8.86 cm, and the corresponding critical mass is 59.7 kg. Kinetic parameters such as the prompt neutron lifetime, l, the prompt neutron decay constant at delayed criticality, α_c, and the effective delayed neutron fraction, β_eff, were also calculated. With respect to the last quantity, the phenomenon of the so-called “vanishing dollar” in systems consisting of even-neutron nuclei is discussed. Some remarks concerning the possible utilization of ²³⁷Np, which is produced in nuclear power reactors as a by-product, are appended.