Gareth B Neighbour

Carbon emissions intensity ratio: an indicator for an improved carbon labelling scheme

This letter proposes a new carbon labelling scheme to improve the visibility of products’ life cycle carbon emissions (sometimes defined as carbon footprint). This approach starts by normalizing carbon emissions data on a common scale of ‘carbon emissions intensity’, and a new indicator ‘carbon emissions intensity ratio’ is generated based upon its ratio to the annual national greenhouse gas emission per gross domestic product. Five ranges (extremely low, low, medium, high and extremely high) are used to represent the level of carbon emissions intensity ratio by a simple diagram with colour gradation. Case examples are presented, in which the carbon emissions intensity ratios of various selected products, both distinct and related, are calculated and compared. The limitations of this approach are then discussed, laying a foundation for further work.

Influence of oxidation on toughness parameters for two nuclear grade graphites

Single edge notched beams of two nuclear graphites were oxidized in CO2 at 900°C up to 49% burn-off for IM1-24 graphite and up to 12% burn-off for PGA graphite, and fracture properties KIc, γwof and GIc were measured as a function of oxidation. Property decrements as a function of burn-off were fitted to an exponential decay curve (the Knudsen equation) characterized by a decay parameter, b. For both graphites oxidized to the same extent, the decrements in γwof and GIc are less than for the stress-based parameter KIc. The more severe decrements for KIc are probably because critical flaws of high aspect ratio influence this toughness parameter, whereas the energy-based toughness parameters are influenced by a spectrum of pores of different sizes and shapes. For IM1-24 graphite, crack propagation makes an increasing contribution to the total work of fracture upon oxidation due to growth in the process zone size ahead of the crack tip. The anisotropy of PGA graphite is reflected in the values of Q0 for the three properties parallel and perpendicular to the extrusion direction, but there is no clear evidence for anisotropy in the exponential decay parameter, b. This may indicate that processes that occur in the more isotropic binder phase rather than the anisotropic filler particles dominate fracture.

Controlled crack growth in an oxidized nuclear grade graphite

Curves of the crack growth resistance parameters KR, JR and R as a function of crack length were obtained for IM1-24 nuclear grade graphite subject to oxidation in CO2 at 900°C up to 20% burn-off. For the unoxidized graphite, the curves show three regions: (i) an initial rise attributed to the development of bridging in the crack wake zone, (ii) a plateau region where the process zone ahead of the crack tip and the crack bridging zone reach steady states and (iii) falling R and JR curves (or a rising KR curve) when the crack tip approaches the back of the edge specimen. For oxidation up to ~11% burn-off, the values of R, JR and KR decrease progressively and the plateaux become shorter. At higher burn-off values, the plateau is not found. These trends indicate that the process zone size increases progressively with oxidation, but the length of the crack bridging zone remains unaffected by oxidation at least up to 10% burn-off. The initial values of R and KR, are close to the values of the linear elastic fracture parameters KIc and GIc, respectively.

Plant life management (PLiM) practices for gas-cooled, graphite-moderated nuclear reactors: UK experience

A short review of the united Kingdom’s experience in the design and operation of gas-cooled, graphite-moderated reactors is presented. in particular, the experience of the design and operation of the graphite reactor core is discussed. A brief overview of nuclear graphite manufacture and science is presented with an appreciation of the complexity involved in understanding the effects of the reactor environment on the graphite moderator itself. Further, the context of the UK regulatory regime and the elementary requirements to fulfil a safety case are given. Finally, comments are also given on how this experience will contribute to the development of future reactor designs especially those under Generation IV international Forum.

Automatic code compliance with multi-dimensional data fitting in a BIM context

BIM-based tools can contribute to addressing some of the challenges faced by structural engineering practitioners. A BIM-based framework for the development of components that deliver Automatic Code Compliance (ACC) is presented. The structural design problems that such components solve are categorised as simple, where ACC can be implemented directly, or complex, where more advanced approaches are needed. The mathematical process of Multi-Dimensional Data Fitting (MDDF) is introduced in order for the latter, enabling the compression of complex engineering calculations to a single equation that can be easily implemented into a BIM software engineering package. Proof-of-concept examples are given for both cases: offsite-manufactured structural joists are utilised as a non-recursive example, implementing the results obtained in the manufacturer’s literature; the axial capacity of metal fasteners in axially loaded timber-to-timber connections are utilised as an example of recursive problems. The MDDF analysis and its implementation in a BIM package of those problems are presented. Finally, the concept is generalised for non-structural aspects at a framework level, and the challenges, implications, and prospects of ACC in a BIM context are discussed.

Strategies for ideal indoor environments towards low/zero carbon buildings through a biomimetic approach

ABSTRACT Biomimicry is a relatively new discipline of applied science that seeks inspiration from natural systems for innovative solutions to human problems. Taking nature as ‘model, mentor and measure’ receives wide acceptance in the field of architecture but predominantly in conceptualising novel forms. The biomimicry concept is comprehensively analysed for its ability to provide more sustainable and possibly even regenerative built environments. As part of this study, first, various frameworks for approaching ‘biomimicry’ in general are discussed and then relevant examples pertaining to architecture are evaluated. Case studies are critiqued with respect to varied levels of sustainability achieved and its causative factors. In the second part, an approach model for ‘biomimetic architecture’ in the context of Mumbai is presented and applicable strategies based on climatic adaptation are suggested using local biodiversity as a library of organisms. The generic example of ‘human skin’ addressing the same adaptation is analysed and complemented by a state-of-the-art case study on similar lines. The results achieved clearly reveal that biomimicry is a successful approach to design and operate the sustainable built environments for the buildings of the future.

Quantitative Microstructure Characterisation of Advanced Carbons Using Image Analysis

The complex structures and widespread industrial uses of advanced carbons, such as nuclear graphite, make it necessary to accurately characterise the material. Bulk properties of a material may be determined using mechanical testing, however, when dealing with a highly heterogeneous material with an irregular pore / flaw distribution, microstructural characterisation is advantageous. Image analysis provides a very powerful tool to determine and quantify microstructural features such as particle sizes, porosity, etc. This paper presents a novel characterisation methodology applied to advanced carbon materials using computational processes in conjunction with micrographs. In addition, the accuracy of the image data obtained is discussed in relation to validation.

Modelling and measuring reactor core graphite properties and performance

Gas-cooled, graphite-moderated nuclear reactors suffer ageing and degradation to the graphite during service posing a threat to the functionality of the core, and potentially, the safe operation of the reactor. Thus, the importance of modelling and measuring reactor core graphite properties and performance increases especially as continued use beyond the designed life time becomes significant. This book captures the proceedings from the third in a series of meetings addressing the extensive research and analysis performed to ensure the continuing safe performance of the graphite cores. Covering four broad themes: mechanistic; statistical; empirical; and, plant performance, this book should appeal to a wide range of readers from engineers and reactor operators to policy makers.

Securing the safe performance of graphite reactor cores

Papers included address the following general topic areas: Assessment methodologies (including the development of test methods for collection of data) Surveillance and Test methods (including in-core methods, e.g. monitoring and inspection, and out-of-core methods, e.g. irradiation experiments in a materials test reactor) Prediction of the performance of the graphite core (including fundamental material properties, modelling graphite component behaviour and modelling whole-core behaviour) Plant modifications (such as diverse shut down systems) Graphite decommissioning (including on safe disposal of the graphite core) Regulatory requirements Future reactor designs

Biaxial Testing: Appropriate for Mechanical Characterisation?

Material properties are often described as being characteristic and are quoted as such irrespective of scale. However, although the testing of materials is sometimes assumed to be a mature field, there are issues related to the appropriateness of the test, the inherent suitability of the assumptions in determining the material property value, and indeed inherent microstructure of the material concerned. Quasi-brittle materials by their very character show deviation from a truly elastic material and so challenge some of the assumptions being made; and this is true for nuclear graphites. Polygranular graphite is used in Advanced Gas-cooled Reactors (AGRs) primarily as a means of providing moderation for the nuclear reaction, but also as a major structural component in the form of the core bricks. At present, in the nuclear industry, the prediction of when cracked graphite bricks will occur in a nuclear core is largely based on the measurement of mechanical properties from small samples, even though the volume of a typical brick is a factor of 104 greater than that of a typical flexural test sample. For polygranular graphites, many models to predict the probability of failure have been generated and these are usually related to a uniaxial value and indeed most tests conducted determine uniaxial values. If sample size restrictions apply, particularly for engineering ceramics, a biaxial stress geometry is sometimes used. This is especially true if the material is used in applications that impose multi-axial stress fields and so to some extent better resemble the engineering duty and reflect the real performance criterion. As an illustration, this paper will also discuss the evaluation and choice of different designs of biaxial test apparatus. Further, for the preferred biaxial testing system, results will be presented that demonstrates the issues discussed above and shows the complexities involved in the small-scale dependence of geometry upon strength.