[en] A set of nuclear data was calculated for fast reactors based on an ''optimum agreement'' with experimental data. It allows a better approach to a fast reactor project, since both integral and differential data were employed to draw it up. The mathematical method used consists in modifying differential data in view of obtaining a minimum disparity between integral calculated and measured values. The original contribution of the thesis lies in a statistical substantiation of the calculation method. For this purpose, a minimum theorem was demonstrated and the statistical behaviour of the Lagrange multipliers vector as well as the section estimated set were investigated, demonstrating the character of non-biassed estimator. There were also contributions to the formalism for sensitivity coefficients by developing the variational method, generalizing the Swanlake method and writing the sensitivity calculations under a form consistent with the ANISN code. In the last part, the calculation code for the improved nuclear data set is presented using element U²³⁵ as a calculating example. The code was run on IBM-370 and PDP-15 computers (with a limited number of integral data). Section corrections for 2PR-III systems of 400 Kg, 200 Kg and 150 Kg critical mass were calculated. (author)

[en] Scores of critical assemblies were constructed, over a period of about three decades, at the Argonne National Laboratory ZPR-3, ZPR-6, ZPR-9, and zero power plutonium reactor (ZPPR) fast critical assembly facilities. Most of the assemblies were mock-ups of various liquid-metal fast breeder reactor designs. These tended to be complex, containing, for example, mock-ups of control rods and control rod positions. Some assemblies, however, were open-quotes physics benchmarks.close quotes These relatively open-quotes cleanclose quotes assemblies had uniform compositions and simple geometry and were designed to test fast reactor physics data and methods. Assemblies in this last category are well suited to form the basis for new criticality safety benchmarks. The purpose of this paper is to present an overview of some of these benchmark candidates and to describe the strategy being used to create the benchmarks

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[en] Pulsed neutron die-away experiments were performed in three fast critical systems assembled in the Argonne Zero Power Reactor-III (ZPR-III). These experiments were part of a comprehensive study of the mockups of the proposed fast reactors FARET (Fast Reactor Test) and SEFOR (Southwest Experimental Fast Oxide Reactor). The two FARET systems pulsed were Assembly 46-B, a 68 l plutonium-uranium carbide core with stainless steel and sodium reflector; and Assembly 46-C, an 87 l plutonium-uranium oxide core with the same reflector materials. The SEFOR mockup was a 528 l plutonium-depleted uranium oxide core with a reflector of stainless steel, sodium and nickel. In all three cases, an acceptable analysis of the die-away curves required two exponentials plus background. From this data, it was possible to assign, by a two-region transfer function analysis, a prompt neutron lifetime to core neutrons and to the system as a whole. Further, the transfer function model used predicts that the die-away curves in the reflector will contain two exponential terms having the same two exponential decay constants as were found in the core, and that the coefficient of the faster decay will be negative. This was found to be the case within experimental uncertainty. (Auth.)

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[en] This final report covers the Decontamination and Decommissioning (D and D) of the Experimental Breeder Reactor No. 1 (EBR-I) Complex funded under Contract No. AT(10-1)-1375. The major effort consisted of removal and processing of 5500 gallons of sodium/potassium (NaK) coolant from the EBR-I reactor system. Tests were performed to assess the explosive hazards of NaK and KO₂ in various environments and in contact with various contaminants likely to be encountered in the removal and processing operations. A NaK process plant was designed and constructed and the operation was successfully completed. Lesser effort was required for D and D of the Zero Power Reactor (ZPR-III) Facility, the Argonne Fast Source Reactor (AFSR) Shielding, and removal of contaminated NaK from the storage pit. The D and D effort was completed by 13 June 1975, ahead of schedule. (auth)