No abstract available

[en] 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

[en] Neutron dose rates at several angular locations and at distances out to 0.5 mile have been measured during critical operation of the Little Boy replica. We used modified remmetes and thermoluminescent dosimetry techniques for the measurements. The present status of our analysis is presented including estimates of the neutron-dose-relaxation length in air and the variation of the neutron-to-gamma-ray dose ratio with distance from the replica. These results are preliminary and are subject to detector calibration measurements

[en] 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 distance from the replica. Current experiments and further data analysis will refine these results. 7 references, 8 figures

[en] Survivors of Hiroshima and Nagasaki present a unique problem in dosimetry: the effects of radiation exposure may be inferred although the exposure itself is unknown. Experience with a replica of Little Boy demonstrates the difficulties of measuring dose rates, the problems of comparing measurements with calculations, and the inadequacy of the conventional standards that are used to calibrate dosimeters

[en] To obtain more precise dose-rate measurements, we have taken a commercial gamma-ray dosimeter that uses a Geiger-Mueller (GM) tube as its detector and, by supplying it with an externally regulated high voltage, counted the gamma-ray-induced pulses with suitable scaling and timing circuits. We have now improved the method of calibration by measuring detector response to 13 different sources, each with an independently verified strength, in the energy range from 60 keV to 2.6 MeV. With the use of computer codes, the resulting response curve can be folded into the spectrum of the source to be measured

[en] The design philosophy for the SKUA Burst Assembly Machine, being developed at Los Alamos, is reviewed along with results of supporting calculations. Several novel applications are also discussed to show the unique capabilities available

[en] By determining the response of a Geiger-Muller detector to gamma rays with energies from 0.060 to 2.6 MeV, we are able to provide source-specific calibrations for precise dose-rate measurements

[en] The Los Alamos Critical Experiments Facility (LACEF) has been involved in the testing and evaluation of criticality accident alarm systems since 1980. At that time the solution critical assembly SHEBA was designed and built. The response of the alarms to neutron pulses was done using the GODIVA-IV Burst Assembly. Currently, SHEBA and a new fast assembly, SKUA, are being modified for burst operation

[en] A systematic investigation of heavy isotope behavior in the Pajarito fast-neutron critical assemblies is described. Included will be central reactivity coefficient measurements and fission rate measurements in natural uranium reflected plutonium and 93%-enriched uranium metal assemblies and in Big Ten, a depleted uranium reflected 10%-enriched uranium metal assembly