Prompt Neutron Emission Multiplicity Distribution and Average Values (Nubar) at 2200 m/s for the Fissile Nuclides

The prompt neutron emission multiplicity distribution P_v and its average value ⟨v⟩ (i.e., nubar) have been determined at the standard neutron energy of 0.0253 eV for the neutron-induced fission of the four fissile nuclides ^233,235 U and ^239,241Pu. Revised values of ⟨v⟩ have been obtained by reevaluating ⟨v⟩ experiments measured at 2200 m/s relative to the ⟨v⟩ from the spontaneous fission of ²⁵²Cf. These revised values of ⟨v⟩ have been used to renormalize the measured P_v values. The revised values of (v) are all ∼0.25 to 0.5% smaller than the corresponding values of ENDF/B-V.