Measurement Of Neutron Penetration Standards

A comprehensive study has been made of the neutronic behavior in iron. The research comprised measurements of the neutron angular flux spectrum from approximately 1 keV to 10 MeV in a 76.2-cm-diameter iron sphere, the gamma-ray spectrum from 0.20 to 10.0 MeV in the same bulk assembly, and the gamma-ray time distribution. In addition, the total cross section of iron has been measured from 0.5 MeV to 10 MeV with a 0.035 nsec/m resolution. The neutron angular flux spectra are compared to a series of discrete-ordinates transport calculations using ENDF/B, P3 cross sections in both 29- and 49-group representations. Both calculations indicate that the present ENDF/B data for iron are wrong by as much as fifty percent in some energy regions. (Author).

A comprehensive study has been made of the neutronic behavior in iron. The research comprised measurements of the neutron angular flux spectrum from approximately 1 keV to 10 MeV in a 76.2-cm-diameter iron sphere, the gamma-ray spectrum from 0.20 to 10.0 MeV in the same bulk assembly, and the gamma-ray time distribution. In addition, the total cross section of iron has been measured from 0.5 MeV to 10 MeV with a 0.035 nsec/m resolution. The neutron angular flux spectra are compared to a series of discrete-ordinates transport calculations using ENDF/B, P3 cross sections in both 29- and 49-group representations. Both calculations indicate that the present ENDF/B data for iron are wrong by as much as fifty percent in some energy regions. (Author).

The Committee on Dosimetry for the Radiation Effects Research Foundation (RERF) was set up more than a decade ago at the request of the U.S. Department of Energy. It was charged with monitoring work and experimental results related to the Dosimetry System 1986 (DS86) used by RERF to reconstruct the radiation doses to the survivors in Hiroshima and Nagasaki. At the time it was established, DS86 was believed to be the best available dosimetric system for RERF, but questions have persisted about some features, especially the estimates of neutrons resulting from the Hiroshima bomb. This book describes the current situation, the gamma-ray dosimetry, and such dosimetry issues as thermal-neutron discrepancies between measurement and calculation at various distances in Hiroshima and Nagasaki. It recommends approaches to bring those issues to closure and sets the stage for the recently convened U.S. and Japan Working Groups that will develop a new dosimetry for RERF. The book outlines the changes relating to DS86 in the past 15 years, such as improved numbers that go into, and are part of, more sophisticated calculations for determining the radiations from bombs that reach certain distances in air, and encourages incorporation of the changes into a revised dosimetry system.