Neutron total cross section of 240Pu below 6 eV and the parameters of the 1.0-eV resonance

Measurements of the low-energy neutron transmission of five different 240Pu samples have been made using the Oak Ridge Electron Linear Accelerator (ORELA) pulsed-neutron source and the time-of-flight technique in an attempt to resolve discrepancies between the evaluated low-energy cross section of this nuclide and the observed production of heavier Pu isotopes in light-water reactors (LWRs). Three ''thin'' samples consisting of Pu metal foils containing 0.73 at. % 240Pu were measured above 0.4 eV in order to derive the parameters of the 1.056-eV resonance, which is responsible for most of the observed 2200-m/s cross section. Two ''thick'' samples of 99.97 at. % 240Pu metal were measured from 0.003 eV to about 6 eV to obtain the 2200-m/s cross section and the cross-section shape in the low-energy region. A consistent set of resonance parameters was derived from the above data sets