Japan Atomic Energy Research Institute

About: Japan Atomic Energy Research Institute is a based out in . It is known for research contribution in the topics: Neutron & Irradiation. The organization has 7707 authors who have published 14471 publications receiving 207688 citations.

Glass formation at the limit of insufficient network formers.

Abstract: Inorganic glasses normally exhibit a network of interconnected, covalent-bonded, structural elements that has no long-range order. In silicate glasses, the network formers are based on SiO4 tetrahedra interconnected through oxygen atoms at the corners. Conventional wisdom implies that alkaline and alkaline-earth orthosilicate materials cannot be vitrified, because they do not contain sufficient network-forming SiO2 to establish the needed interconnectivity. We studied a bulk magnesium orthosilicate glass obtained by containerless melting and cooling. We found that the role of network former was largely taken on by corner and edge sharing of highly distorted, ionic Mg-O species that adopt 4-, 5-, and 6-coordination with oxygen. The results suggest that similar glassy phases may be found in the containerless environment of interstellar space.

p-Chlorophenoxyisobutyric Acid Impairs Auxin Response in Arabidopsis Root

Abstract: p-Chlorophenoxyisobutyric acid (PCIB) is known as a putative antiauxin and is widely used to inhibit auxin action, although the mechanism of PCIB-mediated inhibition of auxin action is not characterized very well at the molecular level. In the present work, we showed that PCIB inhibited BA::β-glucuronidase (GUS) expression induced by indole-3-acetic acid (IAA), 2,4-dichlorophenoxyacetic acid, and 1-naphthaleneacetic acid. PCIB also inhibited auxin-dependent DR5::GUS expression. RNA hybridization and quantitative reverse transcriptase-polymerase chain reaction analyses suggested that PCIB reduced auxin-induced accumulation of transcripts of Aux/IAA genes. In addition, PCIB relieved the reduction of GUS activity in HS::AXR3NT-GUS transgenic line in which auxin inhibits GUS activity by promoting degradation of the AXR3NT-GUS fusion protein. Physiological analysis revealed that PCIB inhibited lateral root production, gravitropic response of roots, and growth of primary roots. These results suggest that PCIB impairs auxin-signaling pathway by regulating Aux/IAA protein stability and thereby affects the auxin-regulated Arabidopsis root physiology.

Best Practice Guidelines for the use of CFD in Nuclear Reactor Safety Applications

Abstract: In May 2002, an 'Exploratory Meeting of Experts to Define an Action Plan on the Application of Computational Fluid Dynamics (CFD) Codes to Nuclear Reactor Safety Problems' was held at Aix-en-Provence, France. One of three recommended actions was the formation of this writing group to report on the need for guidelines for use of CFD in single phase Nuclear Reactor Safety (NRS) applications. CSNI approved this writing group at the end of 2002, and work began in March 2003. A final report was submitted to GAMA in September 2004, summarizing existing Best Practice Guidelines (BPG) for CFD, and recommending creation of a BPG document for Nuclear Reactor Safety (NRS) applications. The present document is intended to provide an internally complete set of guidelines for a range of single phase applications of CFD to NRS problems. However, it is not meant to be comprehensive; it is recognized that for any specific application a higher level of specificity is possible on questions of nodalization, model selection, and validation. This document should provide direct guidance on the key considerations in known single phase applications, and general directions for resolving remaining details. The intent is that it will serve as a template for further application specific (e.g. PTS, induced break) BPG documents that will provide much more detailed information and examples. The document begins with a summary of NRS related CFD analysis in countries represented by the authors. Chapter 3 deals with definition of the problem and its solution approach. This includes isolation of the portion of the NRS problem most in need of CFD, and use of a classic thermal hydraulic (TH) safety code to provide boundary conditions for the CFD based upon less detailed simulation of the balance of plant. Chapter 4 provides guidance in choosing between various options, and also discusses use of a transient calculation with tightly coupled CFD and TH codes. Chapter 5 discusses selection of physical models available as user options. As is appropriate for single phase CFD, most of the emphasis is on selection of turbulence models. Recommendations are provided for high level selection between Reynolds Averaged Navier Stokes (RANS), Large Eddy Simulation (LES), and hybrid approaches such as Detached Eddy Simulation (DES). Chapter 7 focuses on the numerical approximations available to solve the flow equations. Guidelines are provided for nodalization, and for choice of discrete approximations to the differential equations. Guidance is also given on convergence of iterative solutions, and numerical techniques for following free surfaces. Chapter 7 discusses general assessment strategy. Chapter 8 covers approaches to limiting errors associated with discretization and numerical solution methods (verification). This step is a necessary precursor to quantifying errors associated with physical models (validation) as described in Chapter 9. Guidance on documentation is provided in Chapter 10. Chapter 11 provides some examples of NRS applications; the first two examples are boron dilution and pressurized thermal shock; the third example explores the use of Fluent for simulation of dry cask storage of spent fuel (this example is highly suited to single phase CFD analysis)

Degradation Characteristics of Humic Acid during Photo-Fenton Processes

Abstract: Changes in the molecular and structural characteristics of humic acid (HA) during photo-Fenton processes were studied. When aqueous solutions at pH 5.0, which contained HA, Fe(III), and H2O2, were irradiated (lambda > 370 nm), the concentrations of total organic carbon (TOC) decreased with increasing irradiation time, indicating that a portion of the HA was mineralized to CO2 during this process. To investigate the changes in molecular and structural characteristics, the HA was reisolated from the reaction mixtures after each period of irradiation. The increased elution volumes required for isolation by gel permeation chromatography indicated that the molecular size of HA decreased as a result of the irradiation. In the FTIR spectra, ether and epoxide functional groups were identified, after irradiation. These products could be formed via radical coupling and/or via peroxy radical addition reactions to the unsaturated groups in the HA, such as vinyl and aromatic groups. Moreover, an analysis of structural fragments in HA by pyrolysis-GC/MS showed that the cinnamic acid moieties (CA) disappeared, as a result of irradiation. In the molecular weight fractionated HA, the majority of the iron species were complexed with the high molecular weight HA fraction, and the CA levels of the high molecular weight fraction were larger than those in the low molecular weight fraction. These results are consistent with residues, as the reactive sites in the photo-Fenton systems. Therefore, the degradation of these sites in the high molecular weight fraction may serve as a factor in decreasing the molecular size of HA.

Bystander effect induced by counted high-LET particles in confluent human fibroblasts: a mechanistic study

Abstract: The possible mechanism of a radiation-induced bystander response was investigated by using a high-LET heavy particle microbeam, which allows selected cells to be individually hit with precise numbe...