No abstract available

No abstract available

[en] Eleven irradiations of foil packs located in the central region of Big Ten were made for the Interlaboratory Reaction Rate Program. Each irradiation was at a nominal 10¹⁵ fluence and the principal fluence monitor was the National Bureau of Standards' double fission chamber containing ²³⁵U and ²³⁸U deposits and located at the center of Big Ten. Secondary monitors consisted of three external fission chambers and two internal foil sets containing Au, In, and Al. Activities of one set were counted at the LASL and the other at the Hanford Engineering Developement Laboratory. The uncertainty in relative fluence for each irradiation was +-0.3%

[en] Foils of various fissile and nonfissile materials commonly used in neutron dosimetry have been irradiated in the CFRMF, Idaho and Big-10 Los Alamos. Following these irradiations quantitative γ-ray counting was undertaken by five separate groups at four laboratories. Each group used independently calibrated γ-ray detectors; either Ge(Li) or NaI(Tl). These measurements were made as a part of the Interlaboratory Reaction Rate (ILRR) program. Intercomparison of the reaction rate values obtained by each group show good consistency, with individual variations from the average reaction rates generally being less than +-2%. Based upon this consistency and the estimated uncertainties in the nuclear decay parameters the absolute accuracies of these reaction rates are estimated at +-2% (1 sigma). Integral cross section values have been deduced for these reactions in CFRMF and Big-10

No abstract available

[en] The central neutron-flux spectrum of the Los Alamos Scientific Laboratory's critical assembly, Big Ten, was measured with a ⁶Li spectrometer and techniques developed at the Centre d'Etude de L'Energie Nucleaire, Mol, as part of an experimental program to establish the characteristics of Big Ten

[en] The central neutron-flux spectrum of the Los Alamos Scientific Laboratory's critical assembly, Big Ten, was measured with a ⁶Li spectrometer and techniques developed at the Centre d'Etude de l'Energie Nucleaire, Mol, as part of an experimental program to establish the characteristics of Big Ten

[en] The Critical Assemblies Facility of the Los Alamos National Laboratory has been in existence for thirty-five years. In that period, many thousands of measurements have been made on assemblies of ²³⁵U, ²³³U, and ²³⁹Pu in various configurations, including the nitrate, sulfate, fluoride, carbide, and oxide chemical compositions and the solid, liquid, and gaseous states. The present complex of eleven operating machines is described, and typical applications are presented

[en] Big Ten is described in the detail appropriate for a benchmark critical assembly. Characteristics provided are spectral indexes and a detailed neutron flux spectrum, Rossi-α on a reactivity scale established by positive periods, and reactivity coefficients of a variety of isotopes, including the fissionable materials. The observed characteristics are compared with values calculated with ENDF/B-IV cross sections

[en] Measured fission product yields are reported for three benchmark neutron fields--the BIG-10 fast critical assembly at Los Alamos, the CFRMF fast neutron cavity at INEL, and the thermal column of the NBS Research Reactor. These measurements were carried out by participants in the Interlaboratory LMFBR Reaction Rates (ILRR) program. Fission product generation rates were determined by post-irradiation analysis of gamma-ray emission from fission activation foils. The gamma counting was performed by Ge(Li) spectrometry at INEL, ANL, and HEDL; the sample sent to INEL was also analyzed by NaI(Tl) spectrometry for Ba-140 content. The fission rates were determined by means of the NBS Double Fission Ionization Chamber using thin deposits of each of the fissionable isotopes. Four fissionable isotopes were included in the fast neutron field measurements; these were U-235, U-238, Pu-239, and Np-237. Only U-235 was included in the thermal neutron yield measurements. For the fast neutron fields, consensus yields were determined for three fission product isotopes--Zr-95, Ru-103, and Ba-140. For these fission product isotopes, a separately activated foil was analyzed by each of the three gamma counting laboratories. The experimental standard deviation of the three independent results was typically +- 1.5%. For the thermal neutron field, a consensus value for the Cs-137 yield was also obtained. Subsidiary fission yields are also reported for other isotopes which were studied less intensively (usually by only one of the participating laboratories). Comparisons with EBR-II fast reactor yields from destructive analysis and with ENDF/B recommended values are given