/library/oar/handle/123456789/930 Thu, 06 Nov 2025 07:49:29 GMT 2025-11-06T07:49:29Z /library/oar/handle/123456789/139105 Title: RCC-MRx type P damage assessment methodologies for the design of nuclear fusion reactor components Authors: Degiorgio, Kevin; Muscat, Martin; Mollicone, Pierluigi Abstract: The RCC-MRx (Design and Construction Rules for mechanical components of nuclear installations: high-temperature, research and fusion reactors) code is developed by the French Association for Design, Construction and Surveillance Rules of Nuclear Power Plant Components (AFCEN). RCC-MRx differentiates between the different type of component damage depending on the type of load set. A constant steady load results in Type P damage while a cyclic time varying load results in Type S damage. The work presented here deals with Type P damages. Two failure modes are of interest: immediate excessive deformation and immediate plastic instability. To prevent these failure modes, RCC-MRx presents an elastic, limit analysis and an elastoplastic approach. The elastic approach is guaranteed to give a safe but highly conservative design. The limit and elastoplastic approach require more computational effort and requires the availability of the relevant material properties. The latter approach leads to less conservative but still safe designs. Having a structurally safe and less conservative design is most of the time preferred because of issues of sustainability and cost. RCC-MRx has primarily been written for fission type nuclear reactors and process pressure vessels rather than for nuclear fusion reactors. Fusion reactors differ from fission ones both in the type of loading and also in the type of geometry. Some fusion reactor components have a box type shape rather than cylindrical or spherical as in fission type reactors and process pressure vessels. RCC-MRx has a section dedicated to the assessment of box type of structures. This paper considers the Type P damage rules for negligible creep and negligible irradiation applied to a simple hollow box section, modelled in cantilever mode under the action of various load sets. The results indicate that elastic analysis is the most conservative. Also, depending on overall deformation of the structure, the results show that the elastoplastic plastic instability rule limit may be reached before that of the elastoplastic excessive deformation rule. The elastoplastic rule for excessive deformation presents several challenges in its application and is discussed in more detail together with a methodology to overcome these difficulties. The finite element software Ansys® Academic Research Mechanical, Release 2023 R2 is used as the analysis tool. Wed, 01 Jan 2025 00:00:00 GMT /library/oar/handle/123456789/139105 2025-01-01T00:00:00Z /library/oar/handle/123456789/139024 Title: Countergradient turbulent transport in a plume with a crossflow Authors: Fenton, Daniel; Cimarelli, Andrea; Mollicone, Jean-Paul; van Reeuwijk, Maarten; De Angelis, Elisabetta Abstract: Direct numerical simulation of a turbulent forced buoyant plume in a crossflow is performed at a source Reynolds number , Richardson number , Prandtl number and source-to-crossflow velocity ratio . The instantaneous and temporally averaged flow fields are assessed in detail, providing an overview of the flow dynamics. The velocity, temperature and pressure fields are used together with enstrophy fields to describe qualitatively the evolution of the plume as it is swept downstream by the crossflow, and the mechanisms involved in its evolution are outlined. The plume trajectory is determined quantitatively in a number of ways, and it is shown that the central streamline and the centre of buoyancy of the plume differ significantly—as with jets in crossflow, the central streamline is seen to follow the top of the plume, whereas the centre of buoyancy, by definition, describes the plume as a whole. We then investigate the turbulence properties inside the plume; in particular the eddy viscosity and diffusivity are presented, which are significant parameters in turbulence modelling. Assessment of turbulence production demonstrates the presence of regions where turbulence kinetic energy is redistributed to the kinetic energy of the mean flow, implying a negative eddy viscosity within certain regions of the domain. Similarly, the observation that the buoyancy flux and buoyancy gradient are anti-parallel in specific regions of the flow implies a negative eddy diffusivity in said regions, which must be realised in models of such flows in order to capture the countergradient transport of thermal properties. A characteristic eddy viscosity and diffusivity are presented, and shown to be approximately constant in the fully developed regime, resulting in a constant characteristic turbulent Prandtl number, in turn signifying self-similarity. Mon, 01 Jan 2024 00:00:00 GMT /library/oar/handle/123456789/139024 2024-01-01T00:00:00Z /library/oar/handle/123456789/137819 Title: Subsea long-duration energy storage for integration with offshore wind farms Authors: Cutajar, Charise; Sant, Tonio; Aquilina, Luke; Buhagiar, Daniel; Baldacchino, Daniel Abstract: Aim: Disinfection products and protocols have been devised to provide safe blood and blood derivatives for transfusion; however, sepsis is still the leading cause of transfusion reaction fatalities. This raises the question whether disinfection on its own is sufficient for preventing such outcomes and whether cleaning of the arm prior to disinfection can further reduce the amount of skin commensals responsible for the contamination of blood products. Methodology: One of the blood donor’s arms was disinfected according to the standard protocol and swabs were taken before and after disinfection (Scenario 1). The other arm was cleaned with a hypoallergenic soap-free and alcohol-free wipe and then disinfected (Scenario 2). Swabs from this arm were taken before cleaning, after cleaning and after disinfection. Tryptone soya agar plates were inoculated and incubated at a temperature which facilitates bacterial and fungal growth. Results: A rate reduction was set and plates that failed this criterion were due to coagulase negative staphylococci. The commonest bacteria identified was Staphylococcus epidermidis. Less fungi were isolated on the after-disinfection plates that failed disinfection and these were Penicillium sp. and Cladosporium sp. Resultant colony counts from both Scenarios were statistically analysed and resulted in a significant reduction of bacterial colony counts post disinfection; however, the after disinfection plates of Scenario 2 had a lower average of colony counts than Scenario 1. Cleaning the skin prior disinfection resulted in a significant reduction of bacterial colony count and leading to a higher average of bacterial reduction in Scenario 2 than Scenario 1. Although Scenario 2 had a reduction rate of 98.3% which was more than that of Scenario 1 which had a reduction rate of 97.5%, there was no statistically significant difference (P=0.293) between the outcomes. Conclusion: Cleaning the skin prior to disinfection reduces the bacterial load on the skin which makes the disinfection process more effective and reduces the probability of contamination of blood products. Mon, 01 Jan 2024 00:00:00 GMT /library/oar/handle/123456789/137819 2024-01-01T00:00:00Z /library/oar/handle/123456789/136894 Title: Numerical simulation method of hydraulic power take-off of point-absorbing wave energy device based on simulink Authors: Jing, Fengmei; Wang, Song; Sant, Tonio; Micallef, Christopher; Mollicone, Jean-Paul Abstract: Wave energy has a high energy density and strong predictability, presenting encouraging prospects for development. So far, there are dozens of different wave energy devices (WECs), but the mechanism that ultimately converts wave energy into electrical energy in these devices has always been the focus of research by scholars from various countries. The energy conversion mechanism in wave energy devices is called PTO (power take-off). According to different working principles, PTOs can be classified into the linear motor type, hydraulic type, and mechanical type. Hydraulic PTOs are characterized by their high efficiency, low cost, and simple installation. They are widely used in the energy conversion links of various wave energy devices. However, apart from experimental methods, there is currently almost no concise numerical method to predict and evaluate the power generation performance of hydraulic PTO. Therefore, based on the working principle of hydraulic PTO, this paper proposes a numerical method to simulate the performance of a hydraulic PTO using MATLAB(2018b) Simulink®. Using a point-absorption wave energy device as a carrier, a float hydraulic system power-generation numerical model is built. The method is validated by comparison with previous experimental results. The predicted power generation and conversion efficiency of the point-absorption wave energy device under different regular and irregular wave conditions are compared. Key factors affecting the power generation performance of the device were investigated, providing insight for the subsequent optimal design of the device, which is of great significance to the development and utilization of wave energy resources. Mon, 01 Jan 2024 00:00:00 GMT /library/oar/handle/123456789/136894 2024-01-01T00:00:00Z