Event By Event Study Of Prompt Neutrons From 239pun F

Employing a recently developed Monte-Carlo model, we study the fission of 24°Pu induced by neutrons with energies from thermal to just below the threshold for second chance fission. Current measurements of the mean number of prompt neutrons emitted in fission, together with less accurate measurements of the neutron energy spectra, place remarkably fine constraints on predictions of microscopic calculations. In particular, the total excitation energy of the nascent fragments must be specified to within 1MeV to avoid disagreement with measurements of the mean neutron multiplicity. The combination of the Monte-Carlo fission model with a statistical likelihood analysis also presents a powerful tool for the evaluation of fission neutron data. Of particular importance is the fission spectrum, which plays a key role in determining reactor criticality. We show that our approach can be used to develop an estimate of the fission spectrum with uncertainties several times smaller than current experimental uncertainties for outgoing neutron energies of less than 2 MeV.

Employing a recently developed Monte Carlo model, we study the fission of 24°Pu induced by neutrons with energies from thermal to just below the threshold for second chance fission. Current measurements of the mean number of prompt neutrons emitted in fission, together with less accurate measurements of the neutron energy spectra, place remarkably fine constraints on predictions of microscopic calculations. In particular, the total excitation energy of the nascent fragments must be specified to within 1 MeV to avoid disagreement with measurements of the mean neutron multiplicity. The combination of the Monte Carlo fission model with a statistical likelihood analysis also presents a powerful tool for the evaluation of fission neutron data. Of particular importance is the fission spectrum, which plays a key role in determining reactor criticality. We show that our approach can be used to develop an estimate of the fission spectrum with uncertainties several times smaller than current experimental uncertainties for outgoing neutron energies of less than 2 MeV.

The Atlas of Neutron Resonances provides detailed information on neutron resonances, thermal neutron cross sections, and average resonance properties which are important to neutron physicist, astrophysicists, solid state physicists, reactor engineers, scientists involved in activation analysis, and evaluators of neutron cross sections. · Compilation and evaluation of the world's thermal neutron cross-sections and resonance parameters for neutron physicists, reactor engineers, and neutron evaluators.· Compilation and evaluation of coherent scattering lengths for solid state physicists and evaluators· Compilation and evaluation of average 30-keV capture cross sections for astrophysicists.· Nuclear level density parameters derived from average spacings of neutron resonances following a new approach (new feature for this edition).· Brief review of sub-threshold fission.· Comparisons of optical model predictions with neutron strength function data and scattering lengths.· Estimation of average E1 radiative widths on the basis of the generalized Landau-Fermi liquid model (a new feature for this edition).

Proceedings of the 4th International Symposium, Smolenice, June 17-21, 1985