Los Alamos Critical Assemblies Facility

Malenfant, R.E.

doi:10.2172/6463833

Cited by 8 publications

(3 citation statements)

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“…There was much interest at the time in thorium as a breeding material for 233 U in place of uranium-toplutonium breeding. 6 The Thor Core is still used to this day at NCERC (Ref.…”

Section: Iia Jemima and Other Early Critical Experiments On Cometmentioning

confidence: 99%

A New Era of Nuclear Criticality Experiments: The First 10 Years of Comet Operations at NCERC

Thompson

Sanchez

Goda

et al. 2021

Nuclear Science and Engineering

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Comet is a general-purpose, heavy-duty, vertical-lift assembly designed for flexibility in conducting a variety of critical experiments. It is currently located at the National Criticality Experiments Research Center (NCERC) in Nevada. In the past, Comet resided at Technical Area-18 in Los Alamos, New Mexico, as part of the Los Alamos Critical Experiments Facility (LACEF). The Comet assembly was relocated to NCERC in 2008 and became fully operational in June of 2011. The first critical experiment performed on Comet at NCERC was a verification of one of the previous configurations of theZeus experiment series. Over the next 10 years, many additional experiments followed including other Zeus configurations as well as completely new designs. This paper discusses the Comet vertical-lift assembly, the transition from LACEF to NCERC, and a selection of experiments that have been performed on Comet during its first 10 years of operation at NCERC.

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“…There was much interest at the time in thorium as a breeding material for 233 U in place of uranium-toplutonium breeding. 6 The Thor Core is still used to this day at NCERC (Ref.…”

Section: Iia Jemima and Other Early Critical Experiments On Cometmentioning

confidence: 99%

A New Era of Nuclear Criticality Experiments: The First 10 Years of Comet Operations at NCERC

Thompson

Sanchez

Goda

et al. 2021

Nuclear Science and Engineering

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“…It was built in the 1950s and has been used for neutron activation studies, reactivity measurements, and calibrations of a variety of elements. 46 Flattop received several safety system upgrades and came back online in 2011. 48 It is essentially a highly enriched uranium (HEU, >90% 235 U) core surrounded by a reflector of natural uranium.…”

Section: Fission -Flattop Critical Assembly Devicementioning

confidence: 99%

“…Combined with the two movable sections of the reflector, these rods act as scrams for the device. 46 There are two other cores that can be used with Flattop -one consists of 240 Pu, and the other of 233 U. The latter has been in storage for several years, as its gamma levels are too high to be safely operated.…”

Section: Fission -Flattop Critical Assembly Devicementioning

confidence: 99%

Synthesis of Actinide Materials for the Study of Basic Actinide Science and Rapid Separation of Fission Products

Dorhout

2017

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This dissertation covers several distinct projects relating to the fields of nuclear forensics and basic actinide science. Post-detonation nuclear forensics, in particular, the study of fission products resulting from a nuclear device to determine device attributes and information, often depends on the comparison of fission products to a library of known ratios. The expansion of this library is imperative as technology advances. Rapid separation of fission products from a target material, without the need to dissolve the target, is an important technique to develop to improve the library and provide a means to develop samples and standards for testing separations. Several materials were studied as a proof-of-concept that fission products can be extracted from a solid target, including microparticulate (< 10 µm diameter) dUO2, porous metal organic frameworks (MOFs) synthesized from depleted uranium (dU), and other organicbased frameworks containing dU. The targets were irradiated with fast neutrons from one of two different neutron sources, contacted with dilute acids to facilitate the separation of fission products, and analyzed via gamma spectroscopy for separation yields. The results indicate that smaller particle sizes of dUO2 in contact with the secondary matrix KBr yield higher separation yields than particles without a secondary matrix. It was also discovered that using 0.1 M HNO3 as a contact acid leads to the dissolution of the target material. Lower concentrations of acid were used for future experiments. In the case of the MOFs, a larger pore size in the framework leads to higher separation yields when contacted with 0.01 M HNO3. Different types of frameworks also yield different results. The second portion of this dissertation describes efforts to better understand electronic structure and bonding of the actinide metals in various environments. One project involved studying thorium and uranium bonding with the soft-donor chalcogenides, specifically sulfur. Results from these studies include the synthesis and characterization of the novel (C5Me5)2Th(SMe)2 complex; the synthesis of (C5Me5)2ThS5 by myriad routes, indicating the product is a thermodynamic sink; and evidence that sulfur is inserted iv into the thorium-carbon bond of (C5Me5)2ThMe2 to form the pentasulfide. The second project involved unique activation of the strong carbon-halide bonds present in benzyl-halides mediated by a uranium-(2,2'-bipyridine) complex. The resultant products include a series of uranium-halide bonds from fluoride to iodide, and the addition of the benzyl group to the bipyridine ring. Studies of the mechanism indicate that the benzyl group is added first to the 6 position of the ring before migrating to its final place at the 4 position. The final project utilized a novel gold-tetrazolate complex that can be tailored to add highnitrogen ligands to actinides in a facile and safe way. This transfer ligand was used to synthesize new uranium-tetrazolate species. A brief exploration into using the transfer ligand to add tetra...

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