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Nitride nuclear fuel (UN + 10-20% PuN) is considered a promising alternative to the widely used oxide nuclear fuel (UO2). Thermal conductivity and density of nitride fuel are ∼ 7 times and 1.3 times higher than that of oxide fuel, respectively. Nitride fuel demonstrates a good compatibility with the cladding of fuel rods made of stainless steel. Along with the development of new fuel, methods for its subsequent processing are being developed. Various options for the initial opening of nitride spent nuclear fuel (SNF) are considered in this article. The use of gaseous chlorine is technologically inconvenient and dangerous when working with radioactive substances. The electrochemical dissolution of nitride SNF cannot be realized due to the formation of a by-product - UNCl. Uranium nitride chloride is an insulator and it blocks the electrochemical process. It was found that the chlorination of nitride SNF with cadmium or lead chlorides makes it possible to carry out 100% UN → UCl3 conversion. The use of voloxidation (oxidation of nitride SNF to oxides) as the first stage of processing will make the entire technology universal, suitable for processing both nitride and oxide SNF. The choice of the method for opening SNF depends on the choice of the subsequent stages of its processing. [ABSTRACT FROM AUTHOR]

The shortage of ^3He has triggered the search for effective alternative neutron detection technologies for national security applications, including international nuclear safeguards. Any alternative neutron detection technology must meet a neutron detection efficiency requirement while being insensitive to gamma-ray interference at a prescribed level. For nuclear safeguards, a system must perform measurements in the field with a prescribed precision in a specified time. This paper describes an effort to design, model and test an alternatives-based neutron coincidence counter for nuclear safeguards applications. The technology chosen for use in an alternatives-based uranium neutron coincidence collar was boron-lined proportional counters. Extensive modeling was performed of various system configurations and comparisons were made to measurements on a commercial prototype boron-10 based uranium neutron coincidence collar. [ABSTRACT FROM PUBLISHER]

In this brief communication, we describe the Allele Name Translation Tool (antt) and Update NomenCLature (uncl), free programs developed to facilitate the translation of human leukocyte antigen (HLA) allele names recorded using the December 2002 version of the HLA allele nomenclature (e.g. A*01010101) to those recorded using the colon-delimited version of the HLA allele nomenclature (e.g. A*01:01:01:01) that was adopted in April 2010. In addition, theantt anduncl translate specific HLA allele-name changes (e.g. DPB1*0502 is translated to DPB1*104:01), as well as changes to the locus prefix for HLA-C (i.e. Cw* is translated to C*). Theantt anduncl will also translate allele names that have been truncated to two, four, or six digits, as well as ambiguous allele strings. Theantt is a locally installed and run application, whileuncl is a web-based tool that requires only an Internet connection and a modern browser. Theantt accepts a variety of HLA data-presentation and allele-name formats. In addition, theantt can translate using user-defined conversion settings (e.g. the names of alleles that encode identical peptide binding domains can be translated to a common ‘P-code’), and can serve as a preliminary data-sanity tool. Theantt is available for download, anduncl for use, at . [ABSTRACT FROM AUTHOR]

Mutations in two genes, uncoordinated ( unc) and uncoordinated-like ( uncl), lead to a failure of mechanotransduction in Drosophila. UNCL, the human homolog of unc and uncl, is preferentially expressed in periodontal ligament (PDL) fibroblasts compared with gingival fibroblasts. However, the precise role of UNCL in the PDL remains unclear. The aim of the present study has been to examine whether mechanical stimuli modulate the expression of UNCL in the human PDL in vivo and in vitro and to examine the roles of UNCL in the development, regeneration, and repair of the PDL. We have investigated the expression pattern of UNCL during the development of periodontal tissue and the response of PDL fibroblasts to mechanical stress in vivo and in vitro. The expression of UNCL mRNA and protein increases with PDL fibroblast differentiation from the confluent to multilayer stage but slightly decreases on mineralized nodule formation. UNCL has also been localized in ameloblasts and adjacent cells, differentiating cementoblasts, and osteoblasts of the developing tooth. Strong distinct UNCL expression has further been observed in the differentiating cementoblasts of the tooth periodontium at the site of tension after orthodontic tooth movement. Application of cyclic mechanical stress on PDL fibroblasts increases the expression of UNCL mRNA. These results indicate that UNCL plays important roles in the development, differentiation, and maintenance of periodontal tissues and also suggest a potential role of UNCL in the mechanotransduction of PDL fibroblasts. [ABSTRACT FROM AUTHOR]

Verification of the fissile (and fertile) content in fresh nuclear fuel assemblies is conducted by the IAEA to enforce the Nuclear Non-Proliferation Treaty using the UNCL (Uranium Neutron Collar — Light Water Reactor Fuel). The UNCL uses an uncorrelated AmLi neutron source to interrogate the fuel, producing a signal of coincident fission neutrons (Doubles rate) used to assay 235U content of the fuel. The cost of producing calibration assemblies and limited availability of diverse commercial assemblies at any one time historically restricted the ability to explore the full parameter space experimentally. Monte Carlo simulations can overcome this, but introduce additional sources of uncertainty. Here the sensitivity of simulations and measurements to various parameters is assessed for a reference 16 × 16 PWR assembly of uniform 3.2% enrichment. Uncertainty contributions in this evaluation include: simulated AmLi neutron source spectrum, AmLi neutron emission rate, AmLi anisotropicity, high density polyethylene (HDPE) density, the precise position of the fuel assembly within the detector, and experimentally the statistical uncertainty. The overall total systematic uncertainty estimate for the simulation of the absolute/relative Doubles rates responses are estimated to be approximately 2.0%/1.5%, and for experimental measurements systematic uncertainty reduces to 1.1%. This analysis supports further work using the relative Doubles rates in place of measurements for updating and extending the UNCL analysis methodology as systematic uncertainty is reasonably small. [ABSTRACT FROM AUTHOR]

The declared inventory of 235U in fresh, low enriched uranium, nuclear fuel assemblies is routinely verified by nuclear safeguards inspectorates using the UNCL (Uranium Neutron Collar – Light Water Reactor Fuel) nondestructive assay instrument. The trend in modern fuels is towards higher initial enrichment, which in turn requires a larger number of burnable poison pins with higher Gadolinia concentration to hold down the initial reactivity. UNCL assay error for modern fuel assemblies typically exceeds 10%. The traditional algorithm used to correct the response for burnable poison content needs revision to achieve accuracy comparable to the σ R of 4.5% expected for poison-free assemblies. In this paper we review the problem and use a large set of 287 Monte Carlo simulations based on an experimentally benchmarked model corresponding to the 16 × 16 PWR array used in Brazilian Angra type II and III fuel. Simulated relative responses are used to evaluate the functional form of the poison correction and determine parameters optimal for 16 × 16 PWR assemblies. This update is conducted using between 4–24 Gadolinia pins ranging 2–11 wt% Gd 2 O 3 with assemblies having mean enrichments ranging 2.5%–5%. Experimental validation of the updated coefficients using seven measurements shows bias is reduced by an order of magnitude and σ R reduced from 10% to less than 2%. Two updated sets of coefficients are provided, the most accurate of which is directly useable in the existing analysis code (INCC) in use by inspectorate at fuel fabrication facilities. [ABSTRACT FROM AUTHOR]