Neutron-neutron Correlations in Spontaneous Fission of ²⁵²Cf

Fission neutrons are correlated because the majority of the neutrons are evaporated from fully accelerated fission fragments. This causes neutrons emitted from the same fragment to have a preference to be emitted in the same direction, while neutrons emitted from different fragments have a preference to be emitted in opposite directions. Several options are available in MCNP for generating correlated neutron events. These options are tested by a comparison to ²⁵²Cf neutron-neutron correlation data recently collected at Los Alamos.