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Title: Neutron and gamma-ray measurements on the LANL Little Boy Comet Assembly

Abstract

We measured the neutron and gamma-ray dose rates at various distances from the Little Boy Comet Assembly at Los Alamos National Laboratory (LANL), Los Alamos, New Mexico on April 28 and 29, 1983. The distances selected varied from 350 ft to 1860 ft from the assembly, with the latter point being located at the edge of the mesa overlooking Pajarito Canyon. We varied the power levels for the various runs but we have normalized all of them to a single power-level. We also made corrections for the variations in the power-level indicators of the assembly using data provided by LANL.

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (USA)
OSTI Identifier:
5492667
Report Number(s):
UCRL-89797; CONF-8309153-2
ON: DE84002469
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Seminar on measurements and calculations on the replica of Little Boy, Los Alamos, NM, USA, 13 Sep 1983
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; ZERO POWER REACTORS; GAMMA DOSIMETRY; NEUTRON DOSIMETRY; DOSE RATES; SPECTRAL RESPONSE; DOSIMETRY; EXPERIMENTAL REACTORS; REACTORS; RESEARCH AND TEST REACTORS; 220600* - Nuclear Reactor Technology- Research, Test & Experimental Reactors

Citation Formats

Hankins, D.E.. Neutron and gamma-ray measurements on the LANL Little Boy Comet Assembly. United States: N. p., 1983. Web.
Hankins, D.E.. Neutron and gamma-ray measurements on the LANL Little Boy Comet Assembly. United States.
Hankins, D.E.. Thu . "Neutron and gamma-ray measurements on the LANL Little Boy Comet Assembly". United States. doi:. https://www.osti.gov/servlets/purl/5492667.
@article{osti_5492667,
title = {Neutron and gamma-ray measurements on the LANL Little Boy Comet Assembly},
author = {Hankins, D.E.},
abstractNote = {We measured the neutron and gamma-ray dose rates at various distances from the Little Boy Comet Assembly at Los Alamos National Laboratory (LANL), Los Alamos, New Mexico on April 28 and 29, 1983. The distances selected varied from 350 ft to 1860 ft from the assembly, with the latter point being located at the edge of the mesa overlooking Pajarito Canyon. We varied the power levels for the various runs but we have normalized all of them to a single power-level. We also made corrections for the variations in the power-level indicators of the assembly using data provided by LANL.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Sep 01 00:00:00 EDT 1983},
month = {Thu Sep 01 00:00:00 EDT 1983}
}

Conference:
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  • We measured neutron and gamma-ray dose rates at various distances from the Little Boy-Comet Critical Assembly at Los Alamos National Laboratory (LANL) in April of 1983. The Little Boy-Comet Assembly is a replica of the atomic weapon detonated over Hiroshima, designed to be operated at various steady-state power levels. The selected distances for measurement ranged from 107 m to 567 m. Gamma-ray measurements were made with a Reuter-Stokes environmental ionization chamber which has a sensitivity of 1.0 ..mu..R/hour. Neutron measurements were made with a pulsed-source remmeter which has a sensitivity of 0.1 ..mu..rem/hour, designed and built at Lawrence Livermore Nationalmore » Laboratory (LLNL). 12 references, 7 figures, 6 tables.« less
  • The radiation-measurement team of the Weapons Engineering Division at Lawrence Livermore National Laboratory (LLNL) measured neutron and gamma dose and spectra on the Little Boy replica at Los Alamos National Laboratory (LANL) in April 1983. This assembly is a replica of the gun-type atomic bomb exploded over Hiroshima in 1945. These measurements support the National Academy of Sciences Program to reassess the radiation doses due to atomic bomb explosions in Japan. Specifically, the following types of information were important: neutron spectra as a function of geometry, gamma to neutron dose ratios out to 1.5 km, and neutron attenuation in themore » atmosphere. We measured neutron and gamma dose/fission from close-in to a kilometer out, and neutron and gamma spectra at 90 and 30/sup 0/ close-in. This paper describes these measurements and the results. 12 references, 13 figures, 5 tables.« less
  • We present the current status of our gamma-ray dosimetry results for the Little Boy replica. Both Geiger-Mueller and thermoluminescent detectors were used in the measurements. Future work is needed to test assumptions made in data analysis.
  • We report dose-rate information obtained at many locations in the near vicinity of, and at distances out to 0.64 km from, the Little Boy replica while it was operated as a critical assembly. The measurements were made with modified conventional dosimetry instruments that used an Anderson-Braun detector for neutrons and a Geiger-Mueller tube for gamma rays with suitable electronic modules to count particle-induced pulses. Thermoluminescent dosimetry methods provide corroborative data. Our analysis gives estimates of both neutron and gamma-ray relaxation lengths in air for comparison with earlier calculations. We also show the neutron-to-gamma-ray dose ratio as a function of distancemore » from the replica. Current experiments and further data analysis will refine these results. 7 references, 8 figures.« less
  • This report presents integral measurements of neutron and gamma-ray leakage fluxes from a critical mockup of the Hiroshima bomb Little Boy at Los Alamos National Laobratory with detector systems developed by Oak Ridge National Laboratory. Bonner ball detectors were used to map the neutron fluxes in the horizontal midplane at various distances from the mockup and for selected polar angles, keeping the source-detector separation constant. Gamma-ray energy deposition measurements were made with thermoluminescent detectors at several locations on the iron shell of the source mockup. The measurements were performed as part of a larger progam to provide benchmark data formore » testing the methods used to calculate the radiation released from the Little Boy bomb over Hiroshima. 3 references, 10 figures.« less