Fissionability and criticality: from protactinium to californium and beyond

An empirical correlation of k∞ of a nucleus with the difference between its neutron binding energy and activation energy for fission, based on available data, suggests the possibility of providing estimates of k∞ of other heavy even-neutron nuclides. Calculated values of the activation and binding energies for nuclides ranging from to 2 tabulated together with the known critical (fissionability) parameters. The evidence also suggests that it is possible to achieve criticality with the naturally occurring protactinium isotope, .