title: Hiroshima-like neutrons from A-bomb replica: physical basis for their use in biological experiments.
abstract: The lineal energy distribution and several other dosimetric parameters were measured for the neutrons emitted from a replica of the Hiroshima bomb to determine their usefulness in biological experiments designed to estimate the effectiveness of actual Hiroshima neutrons. The "Little-Boy" replica (LBR) was constructed at the Los Alamos National Laboratory in support of the recent atomic-bomb dose reevaluation and was made of identical materials and had nearly identical dimensions and geometry as the Hiroshima bomb. However, the LBR was operated as a steady-state nuclear reactor, which permitted measurements under controlled conditions. Detailed dosimetric measurements and calculations were made at distances of up to 2.1 m from the center of the LBR uranium core. At these distances, the in-air kerma was approximately 97% from neutrons and kerma rates were shown to be particularly useful for biological experiments (up to approximately 7 Gy/h was possible). Quantitative intercomparisons of neutron energy spectra, lineal energy distributions, and measured cytogenetic results for several fission-neutron sources indicate that Hiroshima and LBR neutrons should be of similar biological effectiveness. Based on these evaluations, and cytogenetic results for LBR neutrons reported in a companion paper (this issue), it is estimated that Hiroshima neutrons were 20 to 30% more effective than the fission neutrons commonly used in radiobiology.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550.
authors.forename: T
authors.initials: T
authors.lastname: Straume
authors.forename: J C
authors.initials: JC
authors.lastname: McDonald
authors.forename: R A
authors.initials: RA
authors.lastname: Pederson
authors.forename: D J
authors.initials: DJ
authors.lastname: Brenner
authors.forename: R L
authors.initials: RL
authors.lastname: Dobson
mesh_terms: D009502:Neutrons; D009689:Nuclear Warfare; D011829:Radiation Dosage; D011853:Radiobiology