Silicon oxycarbide glass for the immobilisation of irradiated graphite waste

© 2015 Elsevier B.V. Silicon oxycarbide glass has been investigated as a potential immobilisation medium for irradiated graphite waste from nuclear power generation. The glass was synthesised via sol-gel techniques using alkoxysilane precursors. Attempts to produce a wasteform via conventional sintering were unsuccessful, but dense wasteforms were achieved by spark plasma sintering (SPS). Microstructural investigations showed that the addition of graphite to the glass did not alter the structure of the matrix; no reaction between the graphite and the glass matrix was observed. Silicon oxycarbide glass is a viable candidate for encapsulation of graphite waste prior to disposal

Cost overruns – helping to define what they really mean

Civil engineers are often in the firing line for alleged cost overruns, particularly on major publicly funded infrastructure projects. This usually occurs when the final cost of a project is simply compared with the original estimate, even though this was published a long time ago, in different circumstances and for a quite different project to the one carried out. This paper proposes a systematic approach to ensure that cost overruns, should they occur, are more accurately defined in terms of when the initial and end costs are assessed, from which point of view, at which project stage, and including scope changes and financial assumptions. The paper refers to the UK’s £163 billion nuclear decommissioning programme

Experimental campaign on the HLM loop NACIE-UP with instrumented wire-spaced fuel pin simulator

This work reports post-processed data of the experimental campaign carried out in the HLM-operated NACIE-UP facility in the framework of the HORIZON2020 SESAME project. NACIE-UP is a rectangular loop, where the two vertical pipes, which work as riser and downcomer, are 8 meters long and the two horizontal pipes are 2.4 meters long. A prototypical MYRRHA-like wire-spaced fuel pin bundle simulator (FPS) is installed in the bottom part of the riser, whereas a shell and tubes heat exchanger (HX) is placed in the upper part of the downcomer. The difference in height between the centre of the heating section and the centre of the heat exchanger is about 5.5 m and is essential for the establishment of the natural circulation regime inside the loop. A typical PLOFA test is presented in this paper, from the three fundamental tests performed. Temperatures showed a coherent behaviour with a sharp decrease due to the power decrease from about 100 kW to 10 kW followed by local maximum due to the gas-lift stop. The time trend of the main thermal-hydraulic parameters during the transient are illustrated in detail: among the others, there is the curve of the primary coolant flow rate, measured by a prototypical thermal flow meter. In the FPS, the developing thermal field was experimentally proved, with larger radial differences in the temperature distribution at the outlet monitored sections with respect to the inlet monitored one. Nusselt numbers in the fully developed section exhibited values close to the Kazimi-Carelli correlation and a similar trend. On the initial and final steady states, a statistical analysis was carried out to determine average overall and local values, and the associated uncertainties. The error propagation theory was applied for the derived quantities. Lots of data, both integral and local, were produced and published; the aim is that this information can be used to qualify STH codes, verify CFD codes and coupled STH/CFD methods for HLM systems