• Energy Research
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Plutonium mononitride is one of the main fuels for Generation IV reactors and can be prepared from nitrogenation of plutonium hydride. We investigated the adsorption and dissociation of nitrogen on PuH2 (111) surface to elaborate the initial stage of nitrogenation. The adsorption energies varied greatly with respect to the adsorption sites and orientations of the adsorbed molecule. The nitrogen exhibited preferential adsorption above the ccp site, where the molecular nitrogen was nearly parallel to the PuH2 surface and pointed to the nearest Pu atom. The orbital hybridization and the electrostatic attraction between the Pu and N weakened the N-N bond in the adsorbed molecule. The mechanism of the dissociation process was investigated within transition state theory, and the analysis of the activation barrier indicated that dissociation of nitrogen is not the rate-determining step of nitrogenation. These findings can contribute to a better understanding of the nuclear fuel cycle.

We present a systematic attempt to fit the Viking lander surface pressure cycle using a Mars General Circulation Model, MarsWRF. Following the earlier study by Wood and Paige (1992) using a one‐dimensional model, high‐precision fitting was achieved by tuning five time‐independent parameters: the albedo and emissivity of the seasonal caps of the two hemispheres and the total CO2 inventory in the atmosphere frost system. We used a linear iterative method to derive the best fit parameters: albedo of the northern cap = 0.795, emissivity of the northern cap = 0.485, albedo of the southern cap = 0.461, emissivity of the southern cap = 0.785, and total CO2 mass = 2.83 × 1016 kg. If these parameters are used in MarsWRF, the smoothed surface pressure residual at the VL1 site is always smaller than several Pascal through a year. As in other similar studies, the best fit parameters do not match well with the current estimation of the seasonal cap radiative properties, suggesting that important physics contributing to the energy balance not explicitly included in MarsWRF have been effectively aliased into the derived parameters. One such effect is likely the variation of thermal conductivity with depth in the regolith due to the presence of water ice. Including such a parameterization in the fitting process improves the reasonableness of the best fit cap properties, mostly improving the emissivities. The conductivities required in the north to provide the best fit are higher than those required in the south. A completely physically reasonable set of fit parameters could still not be attained. Like all prior published GCM simulations, none of the cases considered are capable of predicting a residual southern CO2 cap.

Oscillating point absorber buoys may rise out of the water and be subjected to bottom slamming upon re-entering the water. Numerical simulations are performed to estimate the power absorption, the impact velocities and the corresponding slamming forces for various slamming constraints. Three buoy shapes are considered: a hemisphere and two conical shapes with deadrise angles of 30° and 45°, with a waterline diameter of 5 m. The simulations indicate that the risk of rising out of the water is largely dependent on the buoy draft and sea state. Although associated with power losses, emergence occurrence probabilities can be significantly reduced by adapting the control parameters. The magnitude of the slamming load is severely influenced by the buoy shape. The ratio between the peak impact load on the hemisphere and that on the 45° cone is approximately 2, whereas the power absorption is only 4–8% higher for the 45° cone. This work illustrates the need to include slamming considerations aside from power absorption criteria in the buoy shape design process and the control strategy.

Pollution flashover occurs when soluble and nonsoluble materials cover the surface of an insulator, and this may ultimately cause a reduction in its performance. In this paper, the common type of sodium chloride (NaCl) was used as a soluble pollutant (ESDD) and kaolin as a nonsoluble pollutant (NSDD). Samples of silicone rubber (SiR) insulators were selected for this study and fabricated at the Advanced High Voltage Engineering Research Centre (AHIVEC) at Cardiff University. The samples were preconditioned and polluted according to standard specifications. Additionally, the AC voltage ramp technique was used to achieve flashover (FOV) voltage with different pollution levels. The aim of this work was to investigate the effect of nonsoluble materials on flashover characteristics to understand their interaction with dry-band arcs by using FOV electrical equations and experimental data. The test results show that the FOV voltage of the silicone rubber insulator substantially decreased with the increase in both ESDD and NSDD values. It was also identified from these results that the dry-band arcs were considerably influenced by both ESDD and NSDD levels. This impact can be quantified by determining the variation of discharge parameters (N, n). Based on the FOV equations and experimental data, a mathematical model was suggested, taking into account the effect of both ESDD and NSDD.

The occurrence and properties of subsea permafrost near Prudhoe Bay, Alaska, were investigated by drilling and probing. Nine holes were drilled and 27 sites were probed with a cone penetrometer. The deepest drill hole was 65.1 m below the seabed, while a depth of 14.1 m was reached with the cone penetrometer. Engineering and chemical properties were determined from core samples and point penetration resistance data were obtained with the penetrometer. Thermal profiles were acquired at both the drill and probe sites. Temperatures below 0° C were observed in all the drill and penetrometer holes logged, although frozen sediments were encountered only occasionally. Seasonally frozen sediments were observed near the seabed at each site. The degree of ice bonding, or strength, could be related to seabed temperature and was greatest in shallow water (<2 m). The penetrometer resistance and thermal data indicated that deeper ice-bonded sediments occur, for example approximately 12.7 m below the seabed in 2 m of water off the Sagavanirktok delta. Of eight holes drilled offshore, it appeared that four encountered bonded permafrost. In general, the position of the ice-bonded permafrost interface was extremely irregular. The depth below the seabed to this interface at various distances from shore along the line studied was 28.8 m at 1 km, 65.1 m at 3.5 km, 44.1 m at 6.8 km, and 29.5 m at 17.2 km. Shallow, over-consolidated marine sediments were found in the upper fine-grained section at all of the drill sites investigated; the degree of over-consolidation varied considerably among the sites. This fine-grained section was up to 10 m thick and covered sands and coarse gravels.

Abstract With the plan to increase nuclear generating capacity to 58 GWe and more than 30GWe under construction by 2020, China would have to confront the challenge from the transportation safety of nuclear material. In this paper, based on the analysis of transportation systems and the accident scenarios, the safety evaluation index system of spent fuel road transportation was established by using analytic hierarchy process (AHP), and the transportation safety evaluation model was constructed by weighted nearest neighbor method. By using the model, the safety evaluation of spent fuel road transportation in DaYa Bay nuclear power plant was carried out. The evaluation results showed that the whole transportation was safe, though it has safety risk caused by the weather and the junctions of the bridges and tunnels. In addition, the results from the fuzzy comprehensive evaluation method and the weighted nearest neighbor method are compared, which indicated that the weighted nearest neighbor method supplied a better decision support during the spent fuel road transportation.

AbstractThe present study documents noise pollution levels measured for the most common cars used by people in Saudi Arabia. The noise levels were measured following standard procedure by using calibrated sound pressure level meter at all sides of the car front, rear, right and left sides. This investigation has been conducted to measure the noise pollution level from Toyota car Model 2002 because it used for most Saudi people. Measurements of the noise level from this car at stationary and motion situation have been carried out. The noise levels produced by variable engine speed ranged from750 to 4000rpm were recorded. The sound level found to be 59.45 dBA when the vehicle in motion at normal speed. When the vehicle at idle speed 750rpm the maximum noise level measured at the back exhaust 50.4 dBA where the minimum level recorded at the right side 40.8dBA. When the car parked or at stationary state and the engine at 2500rpm the maximum noise level at the back exhaust is 53dB A whereas the minimum level showed from the left side. For maximum engine speed 4000rpm the back exhaust area has a maximum noise level58.2 dBA where as the right side at 51.2 dBA. The maximum sound level recorded near the engine at speed of 4000rpm was 57 dBA but the minimum level recorded at 1000rpm. From the recorded results it can be seen these measured noise level are under the acceptable ranges due to the progress and development of vehicles emission reduction and the environment protection issues. Based on the study findings it can be inferred that there is an urgent need to set up noise standards in the country to control the noise pollution level from vehicles as well as to keep clean environment.

Bio-based polymers are increasingly attracting attention as a solution to reducing the consumption of non-renewable resources and curbing the accumulation of fossil-based plastic waste. In this study, we analyze the economics of a new packaging film based on a polylactic acid-polyhydroxybutyrate blend (PLA-PHB), with PHB obtained from agro-industrial residues (potato peels). We model various sizes of biorefineries using the new biotechnology in Europe. For a four-year payback period, which is generally accepted in the industry, the calculated minimum product selling price ranges from 9.7 euros per kilogram to 37.2 euros per kilogram, depending, among other factors, on the production capacity of the biorefinery. We have incorporated the uncertainty over the model parameters in a Monte Carlo simulation and investigated the relative impact of individual factors on the minimum product selling price. Overall, the results indicate that the bio-based feedstock availability is the most influential factor on the profitability of the new biotechnology.