Modelling Porosity in Quasi-Brittle Reactor Core Graphite

2013 ◽  
Vol 577-578 ◽  
pp. 337-340
Author(s):  
G.E. Smith ◽  
Peter E.J. Flewitt ◽  
A. Hodgkins
Keyword(s):  
Nuclear Reactors ◽  
Complex Structure ◽  
Three Dimensional ◽  
Reactor Core ◽  
Virgin Material ◽  
Element Determination ◽  
Mechanical And Physical Properties ◽  
The Uk ◽  
Graphite Moderator

Some designs of nuclear reactors involve a graphite moderator within their core. Different forms of graphite have been adopted in the UK gas-cooled reactors but all have a complex structure of filler particles, matrix and pores. Changes occur in the graphite during service and in particular, porosity increases from that found in the virgin material. As part of a structural assessment, it is important to analyse the effects of this change in porosity. Software has been developed to represent the microstructure of pile grade A (PGA) and Gilsocarbon graphite with a range of porosities, to support finite element determination of material properties. The models are three dimensional geometric and voxel models based on the observed microstructures of these different graphites. Creating a sequence of model specimens with increasing porosities while holding other parameters constant, provides a representative microstructure to test the effect of increasing porosity on mechanical and physical properties.

Ab Initio Determination of a New Complex Structure (55 Non-Hydrogen Atoms) from Synchrotron Powder Data: An Uncommon Nickel Succinate, Ni7(C4H4O4)4(OH)6(H2O)3•7H2O

2004 ◽  
Vol 443-444 ◽  
pp. 333-336
Author(s):  
N. Guillou ◽  
C. Livage ◽  
W. van Beek ◽  
G. Férey
Keyword(s):  
Ab Initio ◽  
Complex Structure ◽  
Three Dimensional ◽  
Free Water ◽  
Hydrogen Atoms ◽  
Monoclinic System ◽  
Synchrotron Powder Diffraction ◽  
Chloride Hexahydrate ◽  
Autogenous Pressure

Ni7(C4H4O4)4(OH)6(H2O)3. 7H2O, a new layered nickel(II) succinate, was prepared hydrothermally (180°C, 48 h, autogenous pressure) from a 1:1.5:4.1:120 mixture of nickel (II) chloride hexahydrate, succinic acid, potassium hydroxide and water. It crystallizes in the monoclinic system (space group P21/c, Z = 4) with the following parameters a = 7.8597(1) Å, b = 18.8154(3)Å, c = 23.4377(4) Å,ϐ = 92.0288(9)°, and V = 3463.9(2) Å3. Its structure, which contains 55 non-hydrogen atoms, was solved ab initio from synchrotron powder diffraction data. It can be described from hybrid organic-inorganic layers, constructed from nickel oxide corrugated chains. These chains are built up from NiO6hexameric units connected via a seventh octahedron. Half of the succinates decorate the chains, and the others connect them to form the layers. The three dimensional arrangement is ensured by hydrogen bonds directly between two adjacent layers and via free water molecules.

scholarly journals Neutronic and thermal-hydraulic coupling for 3D reactor core modeling combining MCB and fluent

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 531-536 ◽  
Author(s):  
Igor P. Królikowski ◽  
Jerzy Cetnar
Keyword(s):  
Cross Sections ◽  
Nuclear Reactions ◽  
Nuclear Reactors ◽  
Input Parameter ◽  
Three Dimensional ◽  
Reactor Core ◽  
Coupled Analysis ◽  
Thermal Hydraulics ◽  
Power Profile ◽  
The Impact

Abstract Three-dimensional simulations of neutronics and thermal hydraulics of nuclear reactors are a tool used to design nuclear reactors. The coupling of MCB and FLUENT is presented, MCB allows to simulate neutronics, whereas FLUENT is computational fluid dynamics (CFD) code. The main purpose of the coupling is to exchange data such as temperature and power profile between both codes. Temperature required as an input parameter for neutronics is significant since cross sections of nuclear reactions depend on temperature. Temperature may be calculated in thermal hydraulics, but this analysis needs as an input the power profile, which is a result from neutronic simulations. Exchange of data between both analyses is required to solve this problem. The coupling is a better solution compared to the assumption of estimated values of the temperatures or the power profiles; therefore the coupled analysis was created. This analysis includes single transient neutronic simulation and several steady-state thermal simulations. The power profile is generated in defined points in time during the neutronic simulation for the thermal analysis to calculate temperature. The coupled simulation gives information about thermal behavior of the reactor, nuclear reactions in the core, and the fuel evolution in time. Results show that there is strong influence of neutronics on thermal hydraulics. This impact is stronger than the impact of thermal hydraulics on neutronics. Influence of the coupling on temperature and neutron multiplication factor is presented. The analysis has been performed for the ELECTRA reactor, which is lead-cooled fast reactor concept, where the coolant fl ow is generated only by natural convection

14C High Concentration Measurements with Relevance for Decommissioning of Nuclear Reactors

Radiocarbon ◽  
2019 ◽  
Vol 61 (2) ◽  
pp. 435-444 ◽  
Author(s):  
M Enachescu ◽  
C Stan-Sion
Keyword(s):  
Mass Spectrometry ◽  
Nuclear Reactor ◽  
Nuclear Reactors ◽  
Isotopic Ratio ◽  
Reactor Core ◽  
High Concentration ◽  
Thermal Column ◽  
Archaeological Artifacts ◽  
Neutron Reactions

ABSTRACTDecommissioning of nuclear reactors requires determination of all remnant long-lived isotopes that were produced during their long functioning time of the respective facilities. Radiocarbon (14C) is such an isotope (T1/2 = 5730 yr), widely produced by neutron reactions in a thermal column of a nuclear reactor. Accelerator mass spectrometry (AMS) uses 14C for precise dating of up to 50,000 years old archaeological artifacts. This study presents a premier AMS measurement of high concentrated 14C samples that are strictly forbidden in laboratories dedicated to perform 14C dating. The determined 14C activities range from the natural level (isotopic ratio 14C/12C = 1.2 × 10–12) up to values of 10,000 times higher. 14C bulk and depth profile concentrations were measured in the thermal column disks of a decommissioned nuclear reactor. Results have shown that the 14C concentration in the thermal column, close the reactor core is about 75 kBq/g and decreases to 0.7 Bq/g and the end of the column. Such AMS measurements are applicable for decommissioning and waste management of nuclear reactors.

scholarly journals Optimization of method for simultaneous multi-element determination of trace elements by Inductively Coupled Plasma-Optical Emission Spectrometry: Chemometric approach

2006 ◽  
Vol 52 ◽  
pp. 3-8
Author(s):  
Rumenka Petkovska ◽  
Aneta Dimitrovska
Keyword(s):  
Inductively Coupled Plasma ◽  
Three Dimensional ◽  
Optical Emission ◽  
Response Surfaces ◽  
Operating Conditions ◽  
Emission Spectrometry ◽  
Objective Functions ◽  
Element Determination ◽  
Inductively Coupled

Two objective functions for multi-element optimization in ICP-OES were used and compared using signal-to-background ratios as a figure of merit. Three dimensional response surfaces were generated for a number of elements (Fe, Zn, Cu, Se, Mn, Cr, Ni and Co) to evaluate the performance of both objective functions in locating the optimum compromise instrumental operating conditions in multielement determinations. IEC technique was used for correction of spectral interferences. Validation of the applied method was carried out by determination of linearity (1 to 100 μg/l), accuracy, precision, detection and quantification limit for each element. Detection limit was calculated using SBR-RSD approach. Both objective functions gave the same set of instrumental operating conditions for simultaneous multi-element determination as the best compromise.

scholarly journals Determination of the crystal lattice parameters based on the fast Fourier transform

2021 ◽  
Vol 24 (2) ◽  
pp. 41-48
Author(s):  
Maxim Yu. Ponamarev
Keyword(s):  
Light Field ◽  
Complex Structure ◽  
Three Dimensional ◽  
Coherent Radiation ◽  
Dimensional Image ◽  
Propagation Axis ◽  
Characteristic Features ◽  
3D Scene ◽  
Crystal Lattice Parameters

In this work, it is shown that the image formed as a result of the passage of coherent radiation through the crystal has certain characteristic features. When the crystal is rotated with respect to the propagation axis of the investigated beam, the formation of the intensity distribution of a complex structure associated with the transformation of the flat image into volumetric was detected at the output. Crystalline plates can be used to form the distribution of a continuous flat light field in the implementation of a real 3D scene, which can provide a three-dimensional image on a television screen, as well as on a computer monitor screen. It can also be used in billboards. The three-dimensional image obtained in this way can be observed directly with the eyes of a person (without using special glasses. Thus, the information capacity of the image on the screen increases, and the perception of the picture approaches real conditions.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

Thromboplastin Related Differences in the Determination of International Normalised Ratio: A Cause for Concern?

1994 ◽  
Vol 72 (03) ◽  
pp. 426-429 ◽  
Author(s):  
S Kitchen ◽  
I D Walker ◽  
T A L Woods ◽  
F E Preston
Keyword(s):  
Patient Management ◽  
External Quality Assessment ◽  
Oral Anticoagulant Therapy ◽  
Warfarin Dosage ◽  
External Quality ◽  
External Quality Assessment Scheme ◽  
International Normalised Ratio ◽  
The Uk ◽  
The Relationship

SummaryWhen the International Normalised Ratio (INR) is used for control of oral anticoagulant therapy the same result should be obtained irrespective of the laboratory reagent used. However, in the UK National External Quality Assessment Scheme (NEQAS) for Blood Coagulation INRs determined using different reagents have been significantly different.For 18 NEQAS samples Manchester Reagent (MR) was associated with significantly lower INRs than those obtained using Diagen Activated (DA, p = 0.0004) or Instrumentation Laboratory PT-Fib HS (IL, p = 0.0001). Mean INRs for this group were 3.15, 3.61, and 3.65 for MR, DA, and IL respectively. For 61 fresh samples from warfarin-ised patients with INRs of greater than 3.0 the relationship between thromboplastins in respect of INR was similar to that observed for NEQAS data. Thus INRs obtained with MR were significantly lower than with DA or IL (p <0.0001). Mean INRs for this group were 4.01, 4.40, and 4.59 for MR, DA, and IL respectively.We conclude that the differences between INRs measured with the thromboplastins studied here are sufficiently great to influence patient management through warfarin dosage schedules, particularly in the upper therapeutic range of INR. There is clearly a need to address the issues responsible for the observed discrepancies.

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